2011 ASHRAE Handbook - Heating, Ventilating, and Air-Conditioning Applications (SI Edition) 978-1-61344-665-2, 978-1-936504-07-7

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2011 ASHRAE" HANDBOOK

Heating, Ventilating, and Air-conditioning APPLICATIONS SI Edition

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American Society of Heating, Refrigerating and Air-conditioning Engineers, Inc. 1791 Tullie Circle, N.E., Atlanta, GA 30329

(404) 636-8400

http://www .ashrae.org

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020 11 American Society of Heating, Refrigerating and Air-conditioning Engineers, Inc. All rights reserved. DEDICATED TO THE ADVANCEMENT OF THE PROFESSION AND ITS ALLIED INDUSTRIES

No part of this book may be reproduced without permission in writing from ASHRAE, except by a reviewer who may quote brief passages or reproduce illustrations in a review with appropriate credit; nor may any part of this book be reproduced, stored in a retrieval system, or transmitted in any form or by any means-lectronic, photocopying, recording, or other-without permission in writing from ASHRAE. Volunteer members of ASHRAE Technical Committees and others compiled the information in this handbook, and it is generally reviewed and updated every four years. Comments, criticisms, and suggestions regarding the subject matter are invited. Any errors or omissions in the data should be brought to the attention of the Editor. Additions and corrections to Handbook volumes in print will be published in the Handbook published the year following their verification and, as soon as verified, on the ASHRAE Internet Web site.

DISCLAIMER ASHRAE has compiled this publication with care, but ASHRAE has not investigated, and ASHRAE expressly disclaims any duty to investigate, any product, service, process, procedure, design, or the like that may be described herein. The appearance of any technical data or editorial material in this publication does not constitute endorsement, warranty, or guaranty by ASHRAE of any product, service, process, procedure, design, or the like. ASHRAE does not warrant that the information in this publication is free of errors. The entire risk of the use of any information in this publication is assumed by the user. ISBN 978-1-936504-07-7 ISSN 1078-6082

The paper for this book was manufactured in an acid- and elemental-chlorine-fee process with pulp obtained from sources using sustainable forestry practices. The printing used soy-based inks.

ASHRAE Research: Improving the Quality of Life The American Society of Heating, Refrigerating and AirConditioning Engineers is the world’s foremost technical society in the fields of heating, ventilation, air conditioning, and refrigeration. Its members worldwide are individuals who share ideas, identify needs, support research, and write the industry’s standards for testing and practice. The result is that engineers are better able to keep indoor environments safe and productive while protecting and preserving the outdoors for generations to come. One of the ways that ASHRAE supports its members’ and industry’s need for information is through ASHRAE Research. Thousands of individuals and companies support ASHRAE Research

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annually, enabling ASHRAE to report new data about material properties and building physics and to promote the application of innovative technologies. Chapters in the ASHRAE Handbook are updated through the experience of members of ASHRAE Technical Committees and through results of ASHRAE Research reported at ASHRAE conferences and published in ASHRAE special publications and in ASHRAE Transactions. For information about ASHRAE Research or to become a member, contact ASHRAE, 1791 Tullie Circle, Atlanta, GA 30329; telephone: 404-636-8400; www.ashrae.org.

Preface The 201 1 ASHRAE Handbook-HVAC Applications comprises over 60 chapters covering a broad range of facilities and topics, and is written to help engineers design and use equipment and systems described in other Handbook volumes. ASHRAE Technical Committees have revised nearly every chapter to cover current requirements, technology, and design practice. An accompanying CDROM contains all the volume’s chapters in both I-P and SI units. This edition includes two new chapters: Chapter 4, Tall Buildings, focuses on HVAC issues unique to tall buildings, including stack effect, system selection, mechanical room location, water distribution, vertical transportation, and life safety. Chapter 60, Ultraviolet Air and Surface Treatment, covers ultraviolet germicidal irradiation (UVGI) systems and relevant guidelines, standards, and practices, as well as energy use and economic considerations. Here are selected highlights of the other revisions and additions: Chapter 3, Commercial and Public Buildings, now covers office buildings, transportation centers, and warehouses and distribution centers, with new sections on commissioning, sustainability, energy efficiency, energy benchmarking, renewable energy, value engineering, and life-cycle cost analysis. Chapter 7, Educational Facilities, has added content on higher education facilities, commissioning, dedicated outdoor air systems (DOAS), combined heat and power (CHP), and sustainability and energy efficiency. Chapter 8, Health-Care Facilities, has been updated to reflect ASHRAE Standard 170-2008 and has revised discussion on design criteria for pharmacies. Chapter 18, Clean Spaces, has updated content on standards, filters, barrier technology, and sustainability plus a new section on installation and test procedures. Chapter 19, Data Processing and Telecommunication Facilities, has a new title and revised andor new content on design temperatures, change rate, humidity, power usage effectiveness (PUE), aisle containment, economizer cycles, and computer room airhandling (CRAH) units. Chapter 33, Kitchen Ventilation, largely rewritten, covers key sustainability impacts and recent research results. Chapter 34, Geothermal Energy, has updated tables and graphs, with new, step-by-step design guidance on vertical systems, and expanded content on hybrid systems, I S 0 rating, and system efficiency. Chapter 36, Energy Use and Management, has updates on ASHRAE’s Building Energy Quotient (eQ) labeling program.

Chapter 40, Computer Applications, updated throughout, has new content on building information modeling (BIM) and wireless applications. Chapter 41, Building Energy Monitoring, has a new section on simplifying methodology for small projects. Chapter 42, Supervisory Control Strategies and Optimization, has been reorganized, with new content on thermal storage and thermally active building systems (TABS), hybrid cooling plants, and predictive control. Chapter 43, HVAC Commissioning, has been updated throughout to reflect ASHRAE Guideline 1.l-2007. Chapter 44, Building Envelopes, has reorganized and expanded content on nonresidential and existing buildings, durability, and common building envelope assemblies. Chapter 48, Noise and Vibration Control, has a new title plus reorganized and new content on noise criteria, chiller noise, and vibration measurement. Chapter 50, Service Water Heating, has expanded content on sizing tankless water heaters plus new data on piping heat loss. Chapter 55, Seismic- and Wind-Resistant Design, has a new title and reflects changes to building codes, standards for anchor bolt design, and other new requirements. Chapter 57, Room Air Distribution, has extensive new application guidelines plus new content on indoor air quality (IAQ), sustainability, and chilled beams. Chapter 59, HVAC Security, has a new title, with updates from ASHRAE Guideline 29-2009 and new sections on risk evaluation, requirements analysis, and system design. This volume is nublished. both as a bound nrint volume and in electronic format on a CD-ROM, in two editions: one using inchpound (I-P) units of measurement, the other using the International System of Units (SI). Corrections to the 2008,2009, and 201 0 Handbook volumes can be found on the ASHRAE Web site at http:llwww.ashrae.org and in the Additions and Corrections section of this volume. Corrections for this volume will be listed in subsequent volumes and on the ASHRAE Web site. Reader comments are enthusiastically invited. To suggest improvements for a chapter, please comment using the form on the ASHRAE Web site or, using the cutout pages at the end of this volume’s index, write to Handbook Editor, ASHRAE, 1791 Tullie Circle, Atlanta, GA 30329, or fax 678-539-2187, or e-mail mo wenaashrae .org. Mark S. Owen Editor

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CONTENTS Contributors

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ASHRAE Technical Committees, Task Groups, and Technical Resource Groups ASHRAE Research: Improving the Quality of Life Preface COMFORT APPLICATIONS Chapter

1. Residences (TC 8.1 1, Unitary and Room Air Conditioners and Heat Pumps) 2. Retail Facilities (TC 9.8, Large-Building Air-conditioning Applications) 3. Commercial and Public Buildings (TC 9.8) 4. Tall Buildings (TC 9.12, Tall Buildings) 5. Places of Assembly (TC 9.8) 6. Hotels, Motels, and Dormitories (TC 9.8) 7. Educational Facilities (TC 9.7) 8. Health-Care Facilities (TC 9.6, Health-Care Facilities) 9. Justice Facilities (TG9.JF, Justice Facilities) 10. Automobiles (TC 9.3, Transportation Air Conditioning) 11. Mass Transit (TC 9.3) 12. Aircraft (TC 9.3) 13. Ships (TC 9.3)

INDUSTRIAL APPLICATIONS Chapter

14. Industrial Air Conditioning (TC 9.2, Industrial Air Conditioning) 15. Enclosed Vehicular Facilities (TC 5.9, Enclosed Vehicular Facilities) 16. Laboratories (TC 9.10, Laboratory Systems) 17. Engine Test Facilities (TC 9.2) 18. Clean Spaces (TC 9.1 1, Clean Spaces) 19. Data Processing and Telecommunication Facilities (TC 9.9, Mission-Critical Facilities, Technology Spaces, and Electronic Equipment) 20. Printing Plants (TC 9.2) 21. Textile Processing Plants (TC 9.2) 22. Photographic Material Facilities (TC 9.2) 23. Museums, Galleries, Archives, and Libraries (TC 9.8) 24. Environmental Control for Animals and Plants (TC 2.2, Plant and Animal Environment) 25. Drying and Storing Selected Farm Crops (TC 2.2) 26. Air Conditioning of Wood and Paper Product Facilities (TC 9.2) 27. Power Plants (TC 9.2) 28. Nuclear Facilities (TC 9.2) 29. Mine Air Conditioning and Ventilation (TC 9.2) 30. Industrial Drying (TC 9.2) 3 1. Ventilation of the Industrial Environment (TC 5.8, Industrial Ventilation Systems) 32. Industrial Local Exhaust (TC 5.8) 33. Kitchen Ventilation (TC 5.10, Kitchen Ventilation)

ENERGY-RELATED APPLICATIONS Chapter

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34. Geothermal Energy (TC 6.8, Geothermal Heat Pump and Energy Recovery Applications) 35. Solar Energy Use (TC 6.7, Solar Energy Utilization)

BUILDING OPERATIONS AND MANAGEMENT Chapter

36. 37. 38. 39. 40. 41. 42. 43.

Energy Use and Management (TC 7.6, Building Energy Performance) Owning and Operating Costs (TC 7.8, Owning and Operating Costs) Testing, Adjusting, and Balancing (TC 7.7, Testing and Balancing) Operation and Maintenance Management (TC 7.3, Operation and Maintenance Management) Computer Applications (TC 1.5, Computer Applications) Building Energy Monitoring (TC 7.6) Supervisory Control Strategies and Optimization (TC 7.5, Smart Building Systems) HVAC Commissioning (TC 7.9, Building Commissioning)

GENERAL APPLICATIONS Chapter

44. Building Envelopes (TC 4.4, Building Materials and Building Envelope Performance) 45. Building Air Intake and Exhaust Design (TC 4.3, Ventilation Requirements and Infiltration) 46. Control of Gaseous Indoor Air Contaminants (TC 2.3, Gaseous Air Contaminants and Gas Contaminant Removal Equipment) 47. Design and Application of Controls (TC 1.4, Control Theory and Application) 48. Noise and Vibration Control (TC 2.6, Sound and Vibration Control) 49. Water Treatment (TC 3.6, Water Treatment) 50. Service Water Heating (TC 6.6, Service Water Heating) 5 1. Snow Melting and Freeze Protection (TC 6.5, Radiant Heating and Cooling) 52. Evaporative Cooling (TC 5.7, Evaporative Cooling) 53. Fire and Smoke Management (TC 5.6, Control of Fire and Smoke) 54. Radiant Heating and Cooling (TC 6.5) 55. Seismic- and Wind-Resistant Design (TC 2.7, Seismic and Wind Restraint Design) 56. Electrical Considerations (TC 1.9, Electrical Systems) 57. Room Air Distribution (TC 5.3, Room Air Distribution) 58. Integrated Building Design (TC 7.1, Integrated Building Design) 59. HVAC Security (TG2.HVAC, Heating, Ventilation, and Air-conditioning Security) 60. Ultraviolet Air and Surface Treatment (TC 2.9, Ultraviolet Air and Surface Treatment) 61. Codes and Standards

Additions and Corrections Index Composite index to the 2008 HVAC Systems and Equipment, 2009 Fundamentals, 2010 Refrigeration, and 201 1 HVAC Applications volumes

Comment Pages

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RESIDENCES

Systems ............................................................................................................................................ Equipment Sizing ............................................................................................................................. Single-Family Residences ............................................................................................................... Multifamily Residences Manufactured Homes ......................................................................................................................

S

1.1 1.2 1.3 1.6 1.7

systems usually dehumidify air as well as lowering its temperature. Typical forced-air residential installations are shown in Figures 1 and 2. Figure 1 shows a gas furnace, split-system air conditioner, humidifier, and air filter. Air from the space enters the equipment through a return air duct. It passes initially through the air filter. The circulating blower is an integral part of the furnace, which supplies heat during winter. An optional humidifier adds moisture to the heated air, which is distributed throughout the home via the supply duct. When cooling is required, heat and moisture are removed from the circulating air as it passes across the evaporator coil. Refrigerant lines connect the evaporator coil to a remote condensing unit located outdoors. Condensate from the evaporator is removed through a drainline with a trap. Figure 2 shows a split-system heat pump, supplemental electric resistance heaters, humidifier, and air filter. The system functions as follows: Air from the space enters the equipment through the return air duct, and passes through a filter. The circulating blower is an integral part ofthe indoor air-handling portion ofthe heat pump system, which supplies heat through the indoor coil during the heating season. Optional electric heaters supplement heat from the heat pump during periods of low outdoor temperature and counteract indoor airstream cooling during periodic defrost cycles. An optional

PACE-CONDITIONING systems for residential use vary with both local and application factors. Local factors include energy source availability (present and projected) and price; climate; socioeconomic circumstances; and availability of installation and maintenance skills. Application factors include housing type, construction characteristics, and building codes. As a result, many different systems are selected to provide combinations of heating, cooling, humidification, dehumidification, ventilation, and air filtering. This chapter emphasizes the more common systems for space conditioning of both single-family (i.e., traditional site-built and modular or manufactured homes) and multifamily residences. Lowrise multifamily buildings generally follow single-family practice because constraints favor compact designs; HVAC systems in highrise apartment, condominium, and dormitory buildings are often of commercial types similar to those used in hotels. Retrofit and remodeling construction also adopt the same systems as those for new construction, but site-specific circumstances may call for unique designs.

SYSTEMS Common residential systems are listed in Table 1. Three generally recognized groups are central forced air, central hydronic, and zoned systems. System selection and design involve such key decisions as (1) source(s) of energy, (2) means of distribution and delivery, and (3) terminal device(s). Climate determines the services needed. Heating and cooling are generally required. Air cleaning, by filtration or electrostatic devices, is present in most systems. Humidification, which is commonly added to all but the most basic systems, is provided in heating systems for thermal comfort (as defmed in ASHRAE Standard 5 5 ) , health, and reduction of static electricity discharges. Cooling

Table 1 Residential Heating and Cooling Systems Central Forced Air

Central Hvdronic

Most common energy sources

Gas Oil Electricity

Gas Oil Electricity

Gas Electricity

Distribution medium

Air

Water Steam

Air Water Refrigerant

Distribution system

Ducting

Piping

Ducting Piping or Free delively

Terminal devices

Diffusers Registers Grilles

Radiators Radiant panels Fan-coil units

Included with product or same as forced-air or hydronic systems

Zoned

Fig. 1 Typical Residential Installation of Heating, Cooling, Humidifying, and Air Filtering System

The preparation of this chapter is assigned to TC 8.11, Unitary and Room Air Conditioners and Heat Pumps.

1.1

201 1 ASHRAE Handbook-HVAC Applications (SI)

1.2

and in areas such as the southwestern United States, where rooftopmounted packages connect to attic duct systems. Central hydronic heating systems are popular both in Europe and in parts of North America where central cooling has not normally been provided. New construction, especially in multistory homes, now typically includes forced-air cooling. Zoned systems are designed to condition only part of a home at any one time. They may consist of individual room units or central systems with zoned distribution networks. Multiple central systems that serve individual floors or the sleeping and common portions of a home separately are sometimes used in large single-family residences. The energy source is a major consideration in system selection. For heating, natural gas and electricity are most widely used in North America, followed by fuel oil, propane, wood, corn, solar energy, geothermal energy, waste heat, coal, district thermal energy, and others. Relative prices, safety, and environmental concerns (both indoor and outdoor) are further factors in heating energy source selection. Where various sources are available, economics strongly influence the selection. Electricity is the dominant energy source for cooling.

Fig. 2

Fig. 3

Typical Residential Installation of Air-Coupled Heat Pump

EQUIPMENT SIZING The heat loss and gain of each conditioned room and of ductwork or piping run through unconditioned spaces in the structure must be accurately calculated to select equipment with the proper heating and cooling capacity. To determine heat loss and gain accurately, the floor plan and construction details, including information on wall, ceiling, and floor construction as well as the type and thickness of insulation, must be known. Window design and exterior door details are also needed. With this information, heat loss and gain can be calculated using the Air-conditioning Contractors of America (ACCA) Manual Ja or similar calculation procedures. To conserve energy, many jurisdictions require that the building be designed to meet or exceed the requirements of ASHRAE Standard 90.2 or similar requirements. Proper matching of equipment capacity to the building heat loss and gain is essential. The heating capacity of air-source heat pumps is usually supplemented by auxiliary heaters, most often of the electric resistance type; in some cases, however, fossil fuel furnaces or solar systems are used. Undersized equipment will be unable to maintain the intended indoor temperature under conditions of extreme outdoor temperatures. Some oversizing may be desirable to enable recovery from setback and to maintain indoor comfort during outdoor conditions that are more extreme than the nominal design conditions. Grossly oversized equipment can cause discomfort because of short ontimes, wide indoor temperature swings, and inadequate dehumidification when cooling. Gross oversizing may also contribute to higher energy use by increasing cyclic thermal losses and off-cycle losses. Variable-capacity equipment (heat pumps, air conditioners, and furnaces) can more closely match building loads over broad ambient temperature ranges, usually reducing these losses and improving comfort levels; in the case of heat pumps, supplemental heat needs may also be reduced. Residences of tight construction may have high indoor humidity and a build-up of indoor air contaminants at times. Air-to-air heat recovery equipment may be used to provide tempered ventilation air to tightly constructed houses. Outdoor air intakes connected to the return duct of central systems may also be used when reducing installed costs is the most important task. Simple exhaust systems with or without passive air intakes are also popular. Natural ventilation by operable windows is also popular in some climates. Excessive accumulation of radon is of concern in all buildings; lower-level spaces should not be depressurized, which causes increased migration of soil gases into buildings. All ventilation schemes increase

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Example of Two-Zone, Ductless Minisplit System in Typical Residential Installation

humidifier adds moisture to the heated air, which is distributed throughout the home through the supply duct. When cooling is required, heat and moisture are removed from the circulating air as it passes across the evaporator coil. Refrigerant lines connect the indoor coil to the outdoor unit. Condensate from the indoor coil is removed through a drainline with a trap. Minisplit systems, which are similar to split systems but are typically ductless, are increasingly popular worldwide. A typical two-zone, ductless minisplit system is shown in Figure 3. In this example, the minisplit system consists mainly of two parts: an outdoor condensing unit, which is installed outside, and two indoor airhandling units that are usually installed on perimeter walls of the house. Each indoor air handler serves one zone and is controlled independently from the other indoor unit. Unitary systems, such as window-mounted, through-the-wall, or rooftop units where all equipment is contained in one cabinet, are also popular. Ducted versions are used extensively in regions where residences have duct systems in crawlspaces beneath the main floor

Residences

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heating and cooling loads and thus the required system capacity, thereby resulting in greater energy consumption. In all cases, minimum ventilation rates, as described in ASHRAE Standards 62.1 and 62.2, should be maintained.

SINGLE-FAMILY RESIDENCES Heat Pumps Heat pumps for single-family houses are normally unitary or split systems, as illustrated in Figures 2 and 3. Most commercially available heat pumps, particularly in North America, are electrically powered, air-source systems. Supplemental heat is generally required at low outdoor temperatures or during defrost. In most cases, supplemental or back-up heat is provided by electric resistance heating elements. Heat pumps may be classified by thermal source and distribution medium in the heating mode as well as the type of fuel used. The most commonly used classes of heat pump equipment are air-to-air and water-to-air. Air-to-water and water-to-water types are also used. Heat pump systems are generally described as air-source or ground-source. The thermal s l n k for cooling is generally assumed to be the same as the thermal source for heating. Air-source systems using ambient air as the heat sourceisink are generally the least costly to install and thus the most commonly used. Ground-source systems usually use water-to-air heat pumps to extract heat from the ground using groundwater or a buried heat exchanger. Ground-Source (Geothermal) Systems. As a heat sourceislnk, groundwater (from individual wells or supplied as a utility from community wells) offers the following advantages over ambient air: (1) heat pump capacity is independent of ambient air temperature, reducing supplementary heating requirements; (2) no defrost cycle is required; (3) although operating conditions for establishing rated efficiency are not the same as for air-source systems, seasonal efficiency is usually higher for heating and for cooling; and (4) peak heating energy consumption is usually lower. Two other system types are ground-coupled and surface-water-coupled systems. Ground-coupled systems offer the same advantages, but because surface water temperatures track fluctuations in air temperature, surface-water-coupled systems may not offer the same benefits as other ground-source systems. Both system types circulate brine or water in a buried or submerged heat exchanger to transfer heat from the ground or water. Direct-expansion, ground-source systems, with evaporators buried in the ground, also are available but are seldom used. Water-source systems that extract heat from surface water (e.g., lakes or rivers) or city (tap) water are sometimes used where local conditions allow. Further information may be found in Chapter 48 of the 2008 ASHRAE Handbook-HVAC Systems and Equipment. Water supply, quality, and disposal must be considered for groundwater systems. Caneta Research (1995) and Kavanaugh and Rafferty (1997) provide detailed information on these subjects. Secondary coolants for ground-coupled systems are discussed in Caneta Research (1995) and in Chapter 31 of the 2009 ASHRAE Handbook-Fundamentals. Buried heat exchanger configurations may be horizontal or vertical, with the vertical including both multiple-shallow- and single-deep-well configurations. Groundcoupled systems avoid water quality, quantity, and disposal concerns but are sometimes more expensive than groundwater systems. However, ground-coupled systems are usually more efficient, especially when pumping power for the groundwater system is considered. Proper installation of the ground coil(s) is critical to success. Add-on Heat Pumps. In add-on systems, a heat pump is added (often as a retrofit) to an existing furnace or boilerifan-coil system. The heat pump and combustion device are operated in one of two ways: (1) alternately, depending on which is most cost-effective, or (2) in parallel. In unitary bivalent heat pumps, the heat pump and

combustion device are grouped in a common chassis and cabinets to provide similar benefits at lower installation costs. Fuel-Fired Heat Pumps. Extensive research and development has been conducted to develop fuel-fred heat pumps. They have been marketed in North America. More information may be found in Chapter 48 of the 2008 ASHRAE Handbook-HVACSystems and Equipment. Water-Heating Options. Heat pumps may be equipped with desuperheaters (either integral or field-installed) to reclaim heat for domestic water heating when operated in cooling mode. Integrated space-conditioning and water-heating heat pumps with an additional full-size condenser for water heating are also available.

Furnaces Furnaces are fueled by gas (natural or propane), electricity, oil, wood, or other combustibles. Gas, oil, and wood furnaces may draw combustion air from the house or from outdoors. If the furnace space is located such that combustion air is drawn from the outdoors, the arrangement is called an isolated combustion system (ICS). Furnaces are generally rated on an ICS basis. Outdoor air is ducted to the combustion chamber (a direct-vent system) for manufactured home applications and some mid- and high-efficiency equipment designs. Using outside air for combustion eliminates both infiltration losses associated with using indoor air for combustion and stack losses associated with atmospherically induced drafthood-equipped furnaces. Two available types of high-efficiency gas furnaces are noncondensing and condensing. Both increase efficiency by adding or improving heat exchanger surface area and reducing heat loss during furnace off-times. The higher-efficiency condensing type also recovers more energy by condensing water vapor from combustion products. Condensate is formed in a corrosion resistant heat exchanger and is disposed of through a drain line. Care must be taken to prevent freezing the condensate when the furnace is installed in an unheated space such as an attic. Condensing furnaces generally use PVC for vent pipes and condensate drains. Wood-, corn-, and coal-fueled furnaces are used in some areas as either the primary or supplemental heating unit. These furnaces may have catalytic converters to enhance the combustion process, increasing furnace efficiency and producing cleaner exhaust. Chapters 30 and 32 of the 2008 ASHRAE Handbook-HVAC Systems and Equipment include more detailed information on furnaces and furnace efficiency.

zyxwvutsrq Hydronic Heating Systems With the growth of demand for central cooling systems, hydronic systems have declined in popularity in new construction, but still account for a significant portion of existing systems in colder climates. The fluid is heated in a central boiler and distributed by piping to terminal units in each room. Terminal units are typically either radiators or baseboard convectors. Other terminal units include fan-coils and radiant panels. Most recently installed residential systems use a forced-circulation, multiple-zone hot-water system with a series-loop piping arrangement. Chapters 12 and 35 of the 2008 ASHRAE Handbook-HVAC Systems and Equipment have more information on hydronics. Design water temperature is based on economic and comfort considerations. Generally, higher temperatures result in lower frst costs because smaller terminal units are needed. However, losses tend to be greater, resulting in higher operating costs and reduced comfort because of the concentrated heat source. Typical design temperatures range from 80 to 95°C. For radiant panel systems, design temperatures range from 45 to 75°C. The preferred control method allows the water temperature to decrease as outdoor temperatures rise. Provisions for expansion and contraction of piping and heat distributing units and for eliminating air from the hydronic system are essential for quiet, leak-tight operation.

201 1 ASHRAE Handbook-HVAC

1.4 Fossil fuel systems that condense water vapor from the flue gases must be designed for return water temperatures in the range of 50 to 55°C for most of the heating season. Noncondensing systems must maintain high enough water temperatures in the boiler to prevent this condensation. If rapid heating is required, both terminal unit and boiler size must be increased, although gross oversizing should be avoided. Another concept for multi- or single-family dwellings is a combined water-heatinglspace-heatingsystem that uses water from the domestic hot-water storage tank to provide space heating. Water circulates from the storage tank to a hydronic coil in the system air handler. Space heating is provided by circulating indoor air across the coil. A split-system central air conditioner with the evaporator located in the system air handler can be included to provide space cooling.

Zoned Heating Systems Most moderate-cost residences in North America have singlethermal-zone HVAC systems with one thermostat. Multizoned systems, however, offer the potential for improved thermal comfort. Lower operating costs are possible with zoned systems because unoccupied areas (e.g., common areas at night, sleeping areas during the day) can be kept at lower temperatures in the winter. One form of this system consists of individual heaters located in each room. These heaters are usually electric or gas-fred. Electric heaters are available in the following types: baseboard free-convection, wall insert (free-convection or forced-fan), radiant panels for walls and ceilings, and radiant cables for walls, ceilings, and floors. Matching equipment capacity to heating requirements is critical for individual room systems. Heating delivery cannot be adjusted by adjusting air or water flow, so greater precision in room-by-room sizing is needed. Most individual heaters have integral thermostats that limit the ability to optimize unit control without continuous fan operation. Individual heat pumps for each room or group of rooms (zone) are another form of zoned electric heating. For example, two or more small unitary heat pumps can be installed in two-story or large one-story homes. The multisplit heat pump consists of a central compressor and an outdoor heat exchanger to service multiple indoor zones. Each zone uses one or more fan-coils, with separate thermostatic controls for each zone. Such systems are used in both new and retrofit construction. A method for zoned heating in central ducted systems is the zone-damper system. This consists of individual zone dampers and thermostats combined with a zone control system. Both variableair-volume (damper position proportional to zone demand) and on/ off (damper fully open or fully closed in response to thermostat) types are available. These systems sometimes include a provision to modulate to lower capacities when only a few zones require heating.

Applications (SI)

Some form of back-up heating is generally needed with solar thermal energy systems. Solar electric systems are not normally used for space heating because of the high energy densities required and the economics of photovoltaics. However, hybrid collectors, which combine electric and thermal capabilities, are available. Chapter 35 has information on sizing solar heating equipment.

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Unitary Air Conditioners In forced-air systems, the same air distribution duct system can be used for both heating and cooling. Split-system central cooling, as illustrated in Figure 1, is the most widely used forced-air system. Upflow, downflow, and horizontal-airflow indoor units are available. Condensing units are installed on a noncombustible pad outside and contain a motor- or engine-driven compressor, condenser, condenser fan and fan motor, and controls. The condensing unit and evaporator coil are connected by refrigerant tubing that is normally field-supplied. However, precharged, factory-supplied tubing with quick-connect couplings is also common where the distance between components is not excessive. A distinct advantage of split-system central cooling is that it can readily be added to existing forced-air heating systems. Airflow rates are generally set by the cooling requirements to achieve good performance, but most existing heating duct systems are adaptable to cooling. Airflow rates of 45 to 60 Lls per kilowatt of refrigeration are normally recommended for good cooling performance. As with heat pumps, these systems may be fitted with desuperheaters for domestic water heating. Some cooling equipment includes forced-air heating as an integral part of the product. Year-round heating and cooling packages with a gas, oil, or electric furnace for heating and a vapor-compression system for cooling are available. Air-to-air and water-source heat pumps provide cooling and heating by reversing the flow of refrigerant. Distribution. Duct systems for cooling (and heating) should be designed and installed in accordance with accepted practice. Useful information is found in ACCA Manuals Da and Sa.Chapter 9 of the 2008 ASHRAE Handbook-HVAC Systems and Equipment also discusses air distribution design for small heating and cooling systems. Because weather is the primary influence on the load, the cooling and heating load in each room changes from hour to hour. Therefore, the owner or occupant should be able to make seasonal or more frequent adjustments to the air distribution system to improve comfort. Adjustments may involve opening additional outlets in secondfloor rooms during summer and throttling or closing heating outlets in some rooms during winter. Manually adjustable balancing dampers may be provided to facilitate these adjustments. Other possible refinements are installing a heating and cooling system sized to meet heating requirements, with additional self-contained cooling units serving rooms with high summer loads, or separate central systems for the upper and lower floors of a house. On deluxe applications, zone-damper systems can be used. Another way of balancing cooling and heating loads is to use variable-capacity compressors in heat pump systems. Operating characteristics of both heating and cooling equipment must be considered when zoning is used. For example, a reduction in air quantity to one or more rooms may reduce airflow across the evaporator to such a degree that frost forms on the fms. Reduced airflow on heat pumps during the heating season can cause overloading if airflow across the indoor coil is not maintained above 45 Lls per kilowatt. Reduced air volume to a given room reduces the air velocity from the supply outlet and might cause unsatisfactory air distribution in the room. Manufacturers of zoned systems normally provide guidelines for avoiding such situations. Special Considerations. In residences with more than one story, cooling and heating are complicated by air buoyancy, also known as the stack effect. In many such houses, especially with single-zone

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Solar Heating Both active and passive solar thermal energy systems are sometimes used to heat residences. In typical active systems, flat-plate collectors heat air or water. Air systems distribute heated air either to the living space for immediate use or to a thermal storage medium (e.g., a rock pile). Water systems pass heated water from the collectors through a heat exchanger and store heat in a water tank. Because of low delivered-water temperatures, radiant floor panels requiring moderate temperatures are often used. A water-source heat pump between the water storage tank and the load can be used to increase temperature differentials. Trombe walls, direct-gain, and greenhouse-like sunspaces are common passive solar thermal systems. Glazing facing south (in the northern hemisphere), with overhangs to reduce solar gains in the summer, and movable night insulation panels reduce heating requirements.

1.5

Residences systems, the upper level tends to overheat in winter and undercool in summer. Multiple air outlets, some near the floor and others near the ceiling, have been used with some success on all levels. To control airflow, the homeowner opens some outlets and closes others from season to season. Free air circulation between floors can be reduced by locating returns high in each room and keeping doors closed. In existing homes, the cooling that can be added is limited by the air-handling capacity of the existing duct system. Although the existing duct system is usually satisfactory for normal occupancy, it may be inadequate during large gatherings. In all cases where new cooling (or heating) equipment is installed in existing homes, supply air ducts and outlets must be checked for acceptable airhandling capacity and air distribution. Maintaining upward airflow at an effective velocity is important when converting existing heating systems with floor or baseboard outlets to both heat and cool. It is not necessary to change the deflection from summer to winter for registers located at the perimeter of a residence. Registers located near the floor on the inside walls of rooms may operate unsatisfactorily if the deflection is not changed from summer to winter. Occupants of air-conditioned spaces usually prefer minimum perceptible air motion. Perimeter baseboard outlets with multiple slots or orifices directing air upwards effectively meet this requirement. Ceiling outlets with multidirectional vanes are also satisfactory. A residence without a forced-air heating system may be cooled by one or more central systems with separate duct systems, by individual room air conditioners (window-mounted or through-thewall), or by minisplit room air conditioners. Cooling equipment must be located carefully. Because cooling systems require higher indoor airflow rates than most heating systems, sound levels generated indoors are usually higher. Thus, indoor air-handling units located near sleeping areas may require sound attenuation. Outdoor noise levels should also be considered when locating the equipment. Many communities have ordinances regulating the sound level of mechanical devices, including cooling equipment. Manufacturers of unitary air conditioners often rate the sound level of their products according to an industry standard (AHRI Standard 270). AHRI Standard 275 gives information on how to predict the dBA sound level when the AHRI sound rating number, the equipment location relative to reflective surfaces, and the distance to the property line are known. An effective and inexpensive way to reduce noise is to put distance and natural barriers between sound source and listener. However, airflow to and from air-cooled condensing units must not be obstructed; for example, plantings and screens must be porous and placed away from units so as not to restrict intake or discharge of air. Most manufacturers provide recommendations regarding acceptable distances between condensing units and natural barriers. Outdoor units should be placed as far as is practical from porches and patios, which may be used while the house is being cooled. Locations near bedroom windows and neighboring homes should also be avoided. In high-crime areas, consider placing units on roofs or other semisecure areas.

and return duct systems. When applying supply-to-return duct humidifiers on heat pump systems, care should be taken to maintain proper airflow across the indoor coil. Self-contained portable or tabletop humidifiers can be used in any residence. Even though this type of humidifier introduces all the moisture to one area of the home, moisture migrates and raises humidity levels in other rooms. Overhumidification should be avoided it can cause condensate to form on the coldest surfaces in the living space (usually windows). Also, because moisture migrates through all structural materials, vapor retarders should be installed near the wanner inside surface of insulated walls, ceilings, and floors in most temperature climates. Lack of attention to this construction detail allows moisture to migrate from inside to outside, causing damp insulation, mold, possible structural damage, and exterior paint blistering. Central humidifiers may be rated in accordance with AHRI Standard 610. This rating is expressed in the number of litres per day evaporated by 60°C entering air. Some manufacturers certify the performance of their product to the AHRI standard. Selecting the proper size humidifier is important and is outlined in AHRI Guideline F. Humidifier cleaning and maintenance schedules must be followed to maintain efficient operation and prevent bacteria build-up. Chapter 21 ofthe 2008 ASHRAE Handbook-HVACSystems and Equipment contains more information on residential humidifiers.

Evaporative Coolers

Most comfort conditioning systems that circulate air incorporate some form of air filter. Usually, they are disposable or cleanable filters that have relatively low air-cleaning efficiency. Higherefficiency alternatives include pleated media filters and electronic air filters. These high-efficiency filters may have high static pressure drops. The air distribution system should be carefully evaluated before installing such filters so that airflow rates are not overly reduced with their use. Airflow must be evaluated both when the filter is new and when it is in need of replacement or cleaning. Air filters are mounted in the return air duct or plenum and operate whenever air circulates through the duct system. Air filters are rated in accordance with AHRI Standard 680, which was based on ASHRAE Standard 52.1. Atmospheric dust spot efficiency levels are

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Dehumidifiers Many homes also use dehumidifiers to remove moisture and control indoor humidity levels. In cold climates, dehumidification is sometimes required during the summer in basement areas to control mold and mildew growth and to reduce zone humidity levels. Traditionally, portable dehumidifiers have been used to control humidity in this application. Although these portable units are not always as efficient as central systems, their low frst cost and ability to serve a single zone make them appropriate in many circumstances. In hot, humid climates, providing sufficient dehumidification with sensible cooling is important. Although conventional airconditioning units provide some dehumidification as a consequence of sensible cooling, in some cases space humidity levels can still exceed comfortable levels. Several dehumidification enhancements to conventional airconditioning systems are possible to improve moisture removal characteristics and lower the space humidity level. Some simple improvements include lowering the supply airflow rate and eliminating off-cycle fan operation. Additional equipment options such as condenserireheat coils, sensible-heat-exchanger-assisted evaporators (e.g., heat pipes), and subcoolingireheat coils can further improve dehumidification performance. Desiccants, applied as either thermally activated units or heat recovery systems (e.g., enthalpy wheels), can also increase dehumidification capacity and lower the indoor humidity level. Some dehumidification options add heat to the conditioned zone that, in some cases, increases the load on the sensible cooling equipment.

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In climates that are dry throughout the entire cooling season, evaporative coolers can be used to cool residences. They must be installed and maintained carefully to reduce the potential for water and thus air quality problems. Further details on evaporative coolers can be found in Chapter 40 of the 2008 ASHRAE Handbook-HVAC Systems and Equipment and in Chapter 52 of this volume.

Humidifiers For improved winter comfort, equipment that increases indoor relative humidity may be needed. In a ducted heating system, a central whole-house humidifier can be attached to or installed within a supply plenum or main supply duct, or installed between the supply

Air Filters

z zyxwvutsrq 201 1 ASHRAE Handbook-HVAC

1.6

generally less than 20% for disposable filters and vary from 60 to 90% for electronic air filters. However, increasingly, the minimum efficiency rating value (MERV) from ASHRAE Standard 52.2 is given instead; a higher MERV implies greater particulate removal, but also typically increased air pressure drop across the filter. To maintain optimum performance, the collector cells of electronic air filters must be cleaned periodically. Automatic indicators are often used to signal the need for cleaning. Electronic air filters have higher initial costs than disposable or pleated filters, but generally last the life of the air-conditioning system. Also available are gas-phase filters such as those that use activated carbon. Chapter 28 of the 2008 ASHRAE Handbook-HVAC Systems and Equipment covers the design of residential air filters in more detail. Ultraviolet (UV) germicidal light as an air filtration system for residential applications has become popular recently. UV light has been successfully used in health care facilities, food-processing plants, schools, and laboratories. It can break organic molecular bonds, which translates into cellular or genetic damages for microorganisms. Single or multiple UV lamps are usually installed in the return duct or downstream of indoor coils in the supply duct. Direct exposure of occupants to UV light is avoided because UV light does not pass through metal, glass, or plastic. This air purification method effectively reduces the transmission of airborne germs, bacteria, molds, viruses, and fungi in the air streams without increasing duct pressure losses. The power required by each UV lamp might range between 30 and 100 W, depending on the intensity and exposure time required to kill the various microorganisms. Chapter 16 of the 2008 ASHRAE Handbook-HVAC Systems and Equipment and Chapter 60 of this volume cover the design and application of UV lamp systems in more detail.

Controls Historically, residential heating and cooling equipment has been controlled by a wall thermostat. Today, simple wall thermostats with bimetallic strips are often replaced by programmable microelectronic models that can set heating and cooling equipment at different temperature levels, depending on the time of day or week. This has led to night setback, workday, and vacation control to reduce energy demand and operating costs. For heat pump equipment, electronic thermostats can incorporate night setback with an appropriate scheme to limit use of resistance heat during recovery. Chapter 47 contains more details about automatic control systems.

MULTIFAMILY RESIDENCES Attached homes and low-rise multifamily apartments generally use heating and cooling equipment comparable to that used in single-family dwellings. Separate systems for each unit allow individual control to suit the occupant and facilitate individual metering of energy use; separate metering and direct billing of occupants encourages energy conservation.

Forced-Air Systems High-rise multifamily structures may also use unitary or minisplit heating and cooling equipment comparable to that used in single-family dwellings. Equipment may be installed in a separate mechanical equipment room in the apartment, in a soffit or above a dropped ceiling over a hallway or closet, or wall-mounted. Split systems’ condensing or heat pump units are often placed on roofs, balconies, or the ground. Small residential warm-air furnaces may also be used, but a means of providing combustion air and venting combustion products from gas- or oil-fred furnaces is required. It may be necessary to use a multiple-vent chimney or a manifold-type vent system. Local codes must be consulted. Direct-vent furnaces that are placed near or on an outside wall are also available for apartments.

Applications (SI)

Hydronic Systems

Individual heating and cooling units are not always possible or practical in high-rise structures. In this case, applied central systems are used. Two- or four-pipe hydronic central systems are widely used in high-rise apartments. Each dwelling unit has either individual room units or ducted fan-coil units. The most flexible hydronic system with usually the lowest operating costs is the four-pipe type, which provides heating or cooling for each apartment dweller. The two-pipe system is less flexible because it cannot provide heating and cooling simultaneously. This limitation causes problems during the spring and fall when some apartments in a complex require heating while others require cooling because of solar or internal loads. This springifall problem may be overcome by operating the two-pipe system in a cooling mode and providing the relatively low amount of heating that may be required by means of individual electric resistance heaters. See the section on Hydronic Heating Systems for description of a combined water-heatingispace-heatingsystem for multi- or single-family dwellings. Chapter 12 ofthe 2008 ASHRAEHandbookHVAC Systems and Equipment discusses hydronic design in more detail.

Through-the-Wall Units Through-the-wall room air conditioners, packaged terminal air conditioners (PTACs), and packaged terminal heat pumps (PTHPs) can be used for conditioning single rooms. Each room with an outside wall may have such a unit. These units are used extensively in renovation of old buildings because they are self-contained and typically do not require complex piping or ductwork renovation. Room air conditioners have integral controls and may include resistance or heat pump heating. PTACs and PTHPs have special indoor and outdoor appearance treatments, making them adaptable to a wider range of architectural needs. PTACs can include gas, electric resistance, hot water, or steam heat. Integral or remote wallmounted controls are used for both PTACs and PTHPs. Further information may be found in Chapter 49 of the 2008 ASHRAE Handbook-HVAC Systems and Equipment and in AHRI Standard 3 lOi380.

Water-Loop Heat Pumps Any mid- or high-rise structure having interior zones with high internal heat gains that require year-round cooling can efficiently use a water-loop heat pump. Such systems have the flexibility and control of a four-pipe system but use only two pipes. Water-source heat pumps allow individual metering of each apartment. The building owner pays only the utility cost for the circulating pump, cooling tower, and supplemental boiler heat. Existing buildings can be retrofitted with heat flow meters and timers on fan motors for individual metering. Economics permitting, solar or ground heat energy can provide the supplementary heat in lieu of a boiler. The ground can also provide a heat sit&, which in some cases can eliminate the cooling tower. In areas where the water table is continuously high and the soil is porous, groundwater from wells can be used.

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Special Concerns for Apartment Buildings Many ventilation systems are used in apartment buildings. Local building codes generally govern outdoor air quantities. ASHRAE Standard 62.1-2004 requires minimum outdoor air quantities of 24 Lis intermittent or 10 Lis continuous or operable windows for baths and toilets, and 48 Lis intermittent or 12 Lis continuous or operable windows for kitchens. In some buildings with centrally controlled exhaust and supply systems, the systems are operated on time clocks for certain periods of the day. In other cases, the outside air is reduced or shut off during extremely cold periods. If known, these factors should be considered when estimating heating load.

Residences

1.7

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Another important load, frequently overlooked, is heat gain from piping for hot-water services. Buildings using exhaust and supply air systems 24 Wday may benefit from air-to-air heat recovery devices (see Chapter 25 of the 2008 ASHRAE Handbook-HVAC Systems and Equipment). Such recovery devices can reduce energy consumption by transferring 40 to 80% of the sensible and latent heat between the exhaust air and supply air streams. Infiltration loads in high-rise buildings without ventilation openings for perimeter units are not controllable year-round by general building pressurization. When outer walls are penetrated to supply outdoor air to unitary or fan-coil equipment, combined wind and thermal stack effects create other infiltration problems. Interior public corridors in apartment buildings need conditioning and smoke management to meet their ventilation and thermal needs, and to meet the requirements of f r e and life safety codes. Stair towers, however, are normally kept separate from hallways to maintain fre-safe egress routes and, if needed, to serve as safe havens until rescue. Therefore, great care is needed when designing buildings with interior hallways and stair towers. Chapter 53 provides further information. Air-conditioning equipment must be isolated to reduce noise generation or transmission. The design and location of cooling towers must be chosen to avoid disturbing occupants within the building and neighbors in adjacent buildings. Also, for cooling towers, prevention of Legionella is a serious concern. Further information on cooling towers is in Chapter 39 of the 2008 ASHRAE HandbookHVAC Systems and Equipment. In large apartment houses, a central building energy management system may allow individual apartment air-conditioning systems or units to be monitored for maintenance and operating purposes.

Fig. 4

Typical Installation of Heating and Cooling Equipment for Manufactured Home

MANUFACTURED HOMES Manufactured homes are constructed in factories rather than site-built, and in 2001 constituted over 6.4% of all housing units and about 11% of all new single-family homes sold in the United States (DOE 2005). Heating and cooling systems in manufactured homes, as well as other facets of construction such as insulation levels, are regulated in the United States by HUD Manufactured Home Construction and Safety Standards. Each complete home or home section is assembled on a transportation frame (a chassis with wheels and axles) for transport. Manufactured homes vary in size from small, single-floor section units starting at 37 m2 to large, multiple sections, which when joined together can provide over 230 m2 and have an appearance similar to site-constructed homes. Heating systems are factory-installed and are primarily forcedair downflow units feeding main supply ducts built into the subfloor, with floor registers located throughout the home. A small percentage of homes in the far southern and southwestern United States use upflow units feeding overhead ducts in the attic space. Typically, there is no return duct system. Air returns to the air handler from each room through door undercuts, hallways, and a grilled door or louvered panel. The complete heating system is a reduced-clearance type with the air-handling unit installed in a small closet or alcove, usually in a hallway. Sound control measures may be required if large forced-air systems are installed close to sleeping areas. Gas, oil, and electric furnaces or heat pumps may be installed by the home manufacturer to satisfy market requirements. Gas and oil furnaces are compact direct-vent types approved for installation in a manufactured home. The special venting arrangement used is a vertical through-the-roof concentric pipe-in-pipe system that draws all air for combustion directly from the outdoors and discharges combustion products through a windproof vent terminal. Gas furnaces must be easily convertible from liquefied petroleum to natural gas and back as required at the final site.

Manufactured homes may be cooled with add-on split or singlepackage air-conditioning systems when supply ducts are adequately sized and rated for that purpose according to HUD requirements. The split-system evaporator coil may be installed in the integral coil cavity provided with the furnace. A high-static-pressure blower is used to overcome resistance through the furnace, evaporator coil, and compact air distribution system. Single-package air conditioners are connected with flexible air ducts to feed existing factory in-floor or overhead ducts. Dampers or other means are required to prevent the cooled, conditioned air from backflowing through a furnace cabinet. A typical installation of a downflow gas or oil furnace with a split-system air conditioner is illustrated in Figure 4. Air enters the furnace from the hallway, passing through a louvered door on the front of the furnace. The air then passes through air filters and is drawn into the top-mounted blower, which during winter forces air down over the heat exchanger, where it picks up heat. For summer cooling, the blower forces air through the furnace heat exchanger and then through the split-system evaporator coil, which removes heat and moisture from the passing air. During heating and cooling, conditioned air then passes through a combustible floor base via a duct connector before flowing into the floor air distribution duct. The evaporator coil is connected with quick-connect refrigerant lines to a remote air-cooled condensing unit. The condensate collected at the evaporator is drained by a flexible hose, routed to the exterior through the floor construction, and connected to a suitable drain.

REFERENCES ACCA. 2009. Residential duct systems, 3rd ed. ANSI/ACCA 1 Manual D@. Air Conditioning Contractors of America, Shirlington, VA ACCA. 2006. Residential load calculation, 8th ed., v. 2. ANSI/ACCA 2 Manual [email protected] Conditioning Contractors of America, Shirlington, VA

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ACCA. 2004. Residential equipment selection. ANSI/ACCA 3 Manual S@. Air Conditioning Contractors of America, Shirlington, VA AHRI. 1997. Selection, installation and servicing of residential humidifiers. Cuideline F-1997. Air Conditioning, Heating, and Refrigeration Institute, Arlington, VA. AHRI. 1995. Sound rating of outdoor unitary equipment. Standard 2702008. Air Conditioning, Heating, and Refrigeration Institute, Arlington, VA. AHRI. 1997. Application of sound rating levels of outdoor unitary equipment. Standard 275-97. Air Conditioning, Heating, and Refrigeration Institute, Arlington, VA. AHRI. 2004. Packaged terminal air-conditioners and heat pumps. Standard 3 10/380-2004. Air Conditioning, Heating, and Refrigeration Institute, Arlington, VA. AHRI. 2004. Central system humidifiers for residential applications. Standard 610-2004. Air Conditioning, Heating, and Refrigeration Institute, Arlington, VA. AHRI. 2004. Residential air filter equipment. Standard 680-2004. Air Conditioning, Heating, and Refrigeration Institute, Arlington, VA.

201 1 ASHRAE Handbook-HVAC Applications (SI)

ASHRAE. 1992. Gravimetric and dust spot procedures for testing aircleaning devices used in general ventilation for removing particulate matter. Standard 52.1-1992. ASHRAE. 20 10. Thermal environmental conditions for human occupancy. A N W A S H M E Standard 55-2010. ASHRAE. 2010. Ventilation for acceptable indoor air quality. ANSI/ ASHRAE Standard 62.1-2010. ASHRAE. 2010. Ventilation and acceptable indoor air quality in low-rise residential buildings. Standard 62.2-20 10. ASHRAE. 2007. Energy-efficient design of low-rise residential buildings. A N W A S H M E Standard 90.2-2007. Caneta Research. 1995. Commercial/institutional ground-source heat pump engineering manual. ASHRAE. DOE. 2005. Buildings energy databook. U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Washington, D.C. Kavanaugh, S.P. and K. Rafferty. 1997. Ground source heatpumps-Design of geothermal systems for commercial and institutional buildings. ASHRAE.

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zyx zyxwvutsrqp zyxwvut CHAPTER 2

RETAIL FACILITIES

General Criteria......................................................................... Small Stores ............................................................................... Discount, Big-Box, and Supercenter Stores Supermarkets..............................................................................

Department Stores ...................................................................... Convenience Centers .................................................................. Regional Shopping Centers Multiple-Use Complexes ............................................................

2.1 2.1 2.2 2.3

T

HIS chapter covers design and application of air-conditioning and heating systems for various retail merchandising facilities. Load calculations, systems, and equipment are covered elsewhere in the Handbook series.

2.5 2.6 2.6 2.7

latent heat removal demand at the equipment. The high latent heat removal requirement may also occur at outdoor dry-bulb temperatures below design. Unitary HVAC equipment and HVAC systems should be designed and selected to provide the necessary sensible and latent heat removal. The equipment, systems, and controls should be designed to provide the necessary temperature, ventilation, filtration, and humidity conditions. HVAC system selection and design for retail facilities are normally determined by economics. First cost is usually the determining factor for small stores. For large retail facilities, owning, operating, and maintenance costs are also considered. Decisions about mechanical systems for retail facilities are typically based on a cash flow analysis rather than on a full life-cycle analysis.

GENERAL CRITERIA To apply equipment properly, the construction of the space to be conditioned, its use and occupancy, the time of day in which greatest occupancy occurs, physical building characteristics, and lighting layout must be known. The following must also be considered: Electric power-size of service Heating-availability of steam, hot water, gas, oil, or electricity Cooling-availability of chilled water, well water, city water, and water conservation equipment Internal heat gains Equipment locations Structural considerations Rigging and delivery of equipment Obstructions Ventilation-opening through roof or wall for outdoor air duct Exposures and number of doors Orientation of store Code requirements Utility rates and regulations Building standards

SMALL STORES Small stores are typically located in convenience centers and may have at least the store front exposed to outdoor weather, although some are free standing. Large glass areas found at the front of many small stores may cause high peak solar heat gain unless they have northern exposures or large overhanging canopies. High heat loss may be experienced on cold, cloudy days in the front of these stores. The HVAC system for this portion of the small store should be designed to offset the greater cooling and heating requirements. Entrance vestibules, entry heaters, andor air curtains may be needed in some climates.

Design Considerations System Design. Single-zone unitary rooftop equipment is common in store air conditioning. Using multiple units to condition the store involves less ductwork and can maintain comfort in the event of partial equipment failure. Prefabricated and matching curbs simplify installation and ensure compatibility with roof materials. Air to air heat pumps, offered as packaged equipment, are readily adaptable to small-store applications. Ground-source and other closed-loop heat pump systems have been provided for small stores where the requirements of several users may be combined. Winter design conditions, utility rates, maintenance costs, and operating costs should be compared to those of conventional heating HVAC systems before this type of system is chosen. Water-cooled unitary equipment is available for small-store air conditioning. However, many communities restrict the use of city water and groundwater for condensing purposes and may require installation of a cooling tower. Water-cooled equipment generally operates efficiently and economically. Air Distribution. External static pressures available in smallstore air-conditioning units are limited, and air distribution should be designed to keep duct resistances low. Duct velocities should not exceed 6 d s , and pressure drop should not exceed 0.8 Paim. Average air quantities, typically range from 47 to 60 Lis per kilowatt of cooling in accordance with the calculated internal sensible heat load. Attention should be paid to suspended obstacles (e.g., lights, soffits, ceiling recesses, displays) that interfere with proper air distribution.

Specific design requirements, such as the increase in outdoor air required to make up for kitchen exhaust, must be considered. Ventilation requirements of ASHRAE Standard 62.1 must be followed. Objectionable odors may necessitate special filtering, exhaust, and additional outdoor air intake. Security requirements must be considered and included in the overall design and application. Minimum considerations require secure equipment rooms, secure air-handling systems, and outdoor air intakes located on the top of facilities. More extensive security measures should be developed based on overall facility design, owner requirements, and local authorities. Load calculations should be made using the procedures outlined in Chapter 18 of the ASHRAE Handbook-Fundamentals. Almost all localities have some form of energy code in effect that establishes strict requirements for insulation, equipment efficiencies, system designs, etc., and places strict limits on fenestration and lighting. The requirements of ASHRAE Standard 90.1 must be met as a minimum guideline for retail facilities. The Advanced Energy Design Guidef o r Small Retail Buildings (ASHRAE 2006) provides additional energy savings suggestions. Retail facilities often have a high internal sensible heat gain relative to the total heat gain. However, the quantity of outdoor air required by ventilation codes and standards may result in a high The preparation of this chapter is assigned to TC 9.8, Large-Building AirConditioning Applications.

2.1

201 1 ASHRAE Handbook-HVAC

2.2 The duct system should contain enough dampers for air balancing. Volume dampers should be installed in takeoffs from the main supply duct to balance air to the branch ducts. Dampers should be installed in the return and outdoor air ducts for proper outdoor air/ return air balance and for economizer operation. Control. Controls for small stores should be kept as simple as possible while still providing the required functions. Unitary equipment is typically available with manufacturer-supplied controls for easy installation and operation. Automatic dampers should be placed in outdoor air inlets and in exhausts to prevent air entering when the fan is turned off. Heating controls vary with the nature of the heating medium. Duct heaters are generally furnished with manufacturer-installed safety controls. Steam or hot-water heating coils require a motorized valve for heating control. Time clock control can limit unnecessary HVAC operation. Unoccupied reset controls should be provided in conjunction with timed control. Maintenance. To protect the initial investment and ensure maximum efficiency, maintenance of air-conditioning units in small stores should be provided by a reliable service company on a yearly basis. The maintenance agreement should clearly specify responsibility for filter replacements, lubrication, belts, coil cleaning, adjustment of controls, refrigeration cycle maintenance, replacement of refrigerant, pump repairs, electrical maintenance, winterizing, system start-up, and extra labor required for repairs. Improving Operating Cost. Outdoor air economizers can reduce the operating cost of cooling in most climates. They are generally available as factory options or accessories with roof-mounted units. Increased exterior insulation generally reduces operating energy requirements and may in some cases allow the size of installed equipment to be reduced. Most codes now include minimum requirements for insulation and fenestration materials. The Advanced Energy Design Guide for Small Retail Buildings (ASHRAE 2006) provides additional energy savings suggestions.

Applications (SI)

equipment size while providing the desired inside temperature most of the time. Heat gain from lighting is not uniform throughout the entire area. For example, jewelry and other specialty displays typically have lighting heat gains of 65 to 85 W per square metre of floor area, whereas the typical sales area has an average value of 20 to 40 W/m2. For stockrooms and receiving, marking, toilet, and rest room areas, a value of 20 W/m2 may be used. When available, actual lighting layouts rather than average values should be used for load computation. ASHRAE Standards 62.1 and 90.1 provide data and population density information to be used for load determination. Chapter 33 of this volume has specific information on ventilation systems for kitchens and food service areas. Ventilation and outdoor air must be provided as required in ASHRAE Standard 62.1 and local codes. Data on the heat released by special merchandising equipment, such as amusement rides for children or equipment used for preparing speciality food items (e.g., popcorn, pizza, frankfurters, hamburgers, doughnuts, roasted chickens, cooked nuts, etc.), should be obtained from the equipment manufacturers.

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Design Considerations Heat released by installed lighting is often sufficient to offset the design roof heat loss. Therefore, interior areas of these stores need cooling during business hours throughout the year. Perimeter areas, especially the storefront and entrance areas, may have highly variable heating and cooling requirements. Proper zone control and HVAC design are essential. Location of checkout lanes in the storefront or entrance areas makes proper environmental zone control even more important. System Design. The important factors in selecting discount, bigbox, and supercenter store air-conditioning systems are (1) installation costs, (2) floor space required for equipment, (3) maintenance requirements, (4) equipment reliability, and (5) simplicity of control. Roof-mounted units are most commonly used. Air Distribution. The air supply for large interior sales areas should generally be designed to satisfy the primary cooling requirement. For perimeter areas, the variable heating and cooling requirements must be considered. Because these stores require high, clear areas for display and restocking, air is generally distributed from heights of 4.3 m and greater. Air distribution at these heights requires high discharge velocities in the heating season to overcome the buoyancy of hot air. This discharge air velocity creates turbulence in the space and induces airflow from the ceiling area to promote complete mixing. Space-mounted fans, and radiant heating at the perimeter, entrance heaters, and air curtains may be required. Control. Because the controls are usually operated by personnel who have little knowledge of air conditioning, systems should be kept as simple as possible while still providing the required functions. Unitary equipment is typically available with manufacturersupplied controls for easy installation and operation. Automatic dampers should be placed in outdoor air inlets and in exhausts to prevent air entering when the fan is turned off. Heating controls vary with the nature of the heating medium. Duct heaters are generally furnished with manufacturer-installed safety controls. Steam or hot-water heating coils require a motorized valve for heating control. Time clock control can limit unnecessary HVAC operation. Unoccupied reset controls should be provided in conjunction with timed control. Maintenance. Most stores do not employ trained HVAC maintenance personnel; they rely instead on service contracts with either the installer or a local service company. (See the section on Small Stores). Improving Operating Cost. See the section on Small Stores.

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DISCOUNT, BIG-BOX, AND SWERCENTER STORES Large discount, big-box, and supercenter stores attract customers with discount prices. These stores typically have high-bay fixture displays and usually store merchandise in the sales area. They feature a wide range of merchandise and may include such diverse areas as a food service area, auto service area, supermarket, pharmacy, bank, and garden shop. Some stores sell pets, including fish and birds. This variety of activity must be considered in designing the HVAC systems. The design and application suggestions for small stores also apply to discount stores. Each specific area is typically treated as a traditional stand-alone facility would be. Conditioning outdoor air for all areas must be considered to limit the introduction of excess moisture that will migrate to the freezer aisles of a grocery area. Hardware, lumber, furniture, etc., is also sold in big-box facilities. A particular concern in this type of facility is ventilation for merchandise and material-handling equipment, such as forklift trucks. In addition, areas such as stockrooms, rest rooms, break rooms, offices, and special storage rooms for perishable merchandise may require separate HVAC systems or refrigeration.

Load Determination Operating economics and the spaces served often dictate inside design conditions. Some stores may base summer load calculations on a higher inside temperature (e.g., 27°C db) but then set the thermostats to control at 22 to 24°C db. This reduces the installed

2.3

Retail Facilities

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Table 1 Refrigerating Effect (RE) Produced by Open Refrigerated Display Fixtures

RE on Building Per Unit Length of Fixture"

Display Fixture Types

Latent Heat, Wlrn

toTotal RE

Heat, Wlrn

Total RE, Wlrn

15 15 20 20 20

199 384 554 1238 1538

235 45 1 692 1548 1922

62 67

15 15

352 384

414 45 1

50 21 1 188

15 20 20

286 842 754

336 1053 942

35 184

15 20

196 738

23 1 922

Low-temperature (frozen food) Single-deck 36 Single-decwdouble-island 67 2-deck 138 3-deck 310 4- or 5-deck 384 Ice cream Single-deck Single-decwdouble-island Standard-temperature Meats Single-deck Multideck Dairy, multideck Produce Single-deck Multideck

% Latent Sensible

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Fig. 1 Refrigerated Case Load Variation with Store Air Humidity

*These figures are general magnitudes for fixtures adjusted for average desired product temperatures and apply to store ambients in front of display cases of 22.2 to 23.3"C with 50 to 55% rh. Raising the dry bulb only 2 to 3 K and the humidity to 5 to 10% can increase loads (heat removal) 25% or more. Lower temperatures and humidities, as in winter, have an equally marked effect on lowering loads and heat removal from the space. Consult display case manufacturer's data for the particular equipment to be used.

SUPERMARKETS Load Determination

Heating and cooling loads should be calculated using the methods outlined in Chapter 18 of the 2009 ASHRAE Handbook-Fundamentals. In supermarkets, space conditioning is required both for human comfort and for proper operation of refrigerated display cases. The air-conditioning unit should introduce a minimum quantity of outdoor air, either the volume required for ventilation based on ASHRAE Standard 62.1 or the volume required to maintain slightly positive pressure in the space, whichever is larger. Many supermarkets are units of a large chain owned or operated by a single company. The standardized construction, layout, and equipment used in designing many similar stores simplify load calculations. It is important that the final air-conditioning load be correctly determined. Refer to manufacturers' data for information on total heat extraction, sensible heat, latent heat, and percentage of latent to total load for display cases. Engineers report considerable fixture heat removal (case load) variation as the relative humidity and temperature vary in comparatively small increments. Relative humidity above 55% substantially increases the load; reduced absolute humidity substantially decreases the load, as shown in Figure 1. Trends in store design, which include more food refrigeration and more efficient lighting, reduce the sensible component of the load even further. To calculate the total load and percentage of latent and sensible heat that the air conditioning must handle, the refrigerating effect imposed by the display fixtures must be subtracted from the building's gross air-conditioning requirements (Table 1). Modern supermarket designs have a high percentage of closed refrigerated display fixtures. These vertical cases have large glass display doors and greatly reduce the problem of latent and sensible heat removal from the occupied space. The doors do, however, require heaters to minimize condensation and fogging. These heaters should cycle by automatic control. For more information on supermarkets, see Chapter 15 in the 2010 ASHRAE Handbook-Refrigeration.

Design Considerations

Store owners and operators frequently complain about cold aisles, heaters that operate even when the outdoor temperature is above 21"C, and air conditioners that operate infrequently. These problems are usually attributed to spillover of cold air from open refrigerated display equipment. Although refrigerated display equipment may cause cold stores, the problem is not excessive spillover or improperly operating equipment. Heating and air-conditioning systems must compensate for the effects of open refrigerated display equipment. Design considerations include the following: Increased heating requirement because of removal of large quantities of heat, even in summer. Net air-conditioning load after deducting the latent and sensible refrigeration effect. The load reduction and change in sensiblelatent load ratio have a major effect on equipment selection. Need for special air circulation and distribution to offset the heat removed by open refrigerating equipment. Need for independent temperature and humidity control.

Each of these problems is present to some degree in every supermarket, although situations vary with climate and store layout. Methods of overcoming these problems are discussed in the following sections. Energy costs may be extremely high if the year-round air-conditioning system has not been designed to compensate for the effects of refrigerated display equipment. Heat Removed by Refrigerated Displays. The display refrigerator not only cools a displayed product but also envelops it in a blanket of cold air that absorbs heat from the room air in contact with it. Approximately 80 to 90% of the heat removed from the room by vertical refrigerators is absorbed through the display opening. Thus, the open refrigerator acts as a large air cooler, absorbing heat from the room and rejecting it via the condensers outside the building. Occasionally, this conditioning effect can be greater than the design air-conditioning capacity of the store. The heat removed by the refrigeration equipment must be considered in the design of the air-conditioning and heating systems because this heat is being

201 1 ASHRAE Handbook-HVAC

2.4 removed constantly, day and night, summer and winter, regardless of the store temperature. Display cases increase the building heating requirement such that heat is often required at unexpected times. The following example illustrates the extent of this cooling effect. The desired store temperature is 24°C. Store heat loss or gain is assumed to be 8 kW1"C of temperature difference between outdoor and store temperature. (This value varies with store size, location, and exposure.) The heat removed by refrigeration equipment is 56 kW. (This value varies with the number of refrigerators.) The latent heat removed is assumed to be 19% of the total, leaving 81% or 45.4 kW sensible heat removed, which cools the store 45.418 = 5.7"C. By constantly removing sensible heat from its environment, the refrigeration equipment in this store will cool the store 5.7"C below outdoor temperature in winter and in summer. Thus, in mild climates, heat must be added to the store to maintain comfort conditions. The designer can either discard or reclaim the heat removed by refrigeration. If economics and store heat data indicate that the heat should be discarded, heat extraction from the space must be included in the heating load calculation. If this internal heat loss is not included, the heating system may not have sufficient capacity to maintain design temperature under peak conditions. The additional sensible heat removed by the cases may change the air-conditioning latent load ratio from 32% to as much as 50% of the net heat load. Removing a 50% latent load by refrigeration alone is very difficult. Normally, it requires specially designed equipment with reheat or chemical adsorption. Multishelf refrigerated display equipment requires 55% rh or less. In the dry-bulb temperature ranges of average stores, humidity in excess of 55% can cause heavy coil frosting, product zone frosting in low-temperature cases, fixture sweating, and substantially increased refrigeration power consumption. A humidistat can be used during summer cooling to control humidity by transferring heat from the condenser to a heating coil in the airstream. The store thermostat maintains proper summer temperature conditions. Override controls prevent conflict between the humidistat and the thermostat. The equivalent result can be accomplished with a conventional air-conditioning system by using three- or four-way valves and reheat condensers in the ducts. This system borrows heat from the standard condenser and is controlled by a humidistat. For higher energy efficiency, specially designed equipment should be considered. Desiccant dehumidifiers and heat pipes have also been used. Humidity. Cooling from refrigeration equipment does not preclude the need for air conditioning. On the contrary, it increases the need for humidity control. With increases in store humidity, heavier loads are imposed on the refrigeration equipment, operating costs rise, more defrost periods are required, and the display life of products is shortened. The dew point rises with relative humidity, and sweating can become so profuse that even nonrefrigerated items such as shelving superstructures, canned products, mirrors, and walls may sweat. Lower humidity results in lower operating costs for refrigerated cases. There are three methods to reduce the humidity level: (1) standard air conditioning, which may overcool the space when the latent load is high and sensible load is low; (2) mechanical dehumidification, which removes moisture by lowering the air temperature to its dew point, and uses hot-gas reheat when needed to discharge at any desired temperature; and (3) desiccant dehumidification, which removes moisture independent of temperature, supplying warm air to the space unless postcooling is provided to discharge at any desired temperature. Each method provides different dew-point temperatures at different energy consumption and capital expenditures. The designer should evaluate and consider all consequential tradeoffs. Standard air conditioning requires no additional investment but reduces the

Applications (SI)

space dew-point temperature only to 16 to 18°C. At 24°C space temperature this results in 60 to 70% rh at best. Mechanical dehumidifiers can provide humidity levels of 40 to 50% at 24°C. Supply air temperature can be controlled with hot-gas reheat between 10 and 32°C. Desiccant dehumidification can provide levels of 35 to 40% rh at 24°C. Postcooling supply air may be required, depending on internal sensible loads. A desiccant is reactivated by passing hot air at 80 to 121°C through the desiccant base. System Design. The same air-handling equipment and distribution system are generally used for both cooling and heating. The entrance area is the most difficult section to heat. Many supermarkets in the northern United States are built with vestibules provided with separate heating equipment to temper the cold air entering from the outdoors. Auxiliary heat may also be provided at the checkout area, which is usually close to the front entrance. Methods of heating entrance areas include the use of (1) air curtains, (2) gasfired or electric infrared radiant heaters, and (3) waste heat from the refrigeration condensers. Air-cooled condensing units are the most commonly used in supermarkets. Typically, a central air handler conditions the entire sales area. Specialty areas like bakeries, computer rooms, or warehouses are better served with a separate air handler because the loads in these areas vary and require different control than the sales area. Most installations are made on the roof of the supermarket. If aircooled condensers are located on the ground outside the store, they must be protected against vandalism as well as truck and customer traffic. If water-cooled condensers are used on the air-conditioning equipment and a cooling tower is required, provisions should be made to prevent freezing during winter operation. Air Distribution. Designers overcome the concentrated load at the front of a supermarket by discharging a large portion of the total air supply into the front third of the sales area. The air supply to the space with a standard air-conditioning system is typically 5 L1s per square metre of sales area. This value should be calculated based on the sensible and latent internal loads. The desiccant system typically requires less air supply because of its high moisture removal rate, typically 2.5 L1s per square metre. Mechanical dehumidification can fall within these parameters, depending on required dew point and suction pressure limitations. Being denser, air cooled by the refrigerators settles to the floor and becomes increasingly colder, especially in the first 900 mm above the floor. If this cold air remains still, it causes discomfort and does not help to cool other areas of the store that need more cooling. Cold floors or areas in the store cannot be eliminated by the simple addition of heat. Reduction of air-conditioning capacity without circulation of localized cold air is analogous to installing an air conditioner without a fan. To take advantage of the cooling effect of the refrigerators and provide an even temperature in the store, the cold air must be mixed with the general store air. To accomplish the necessary mixing, air returns should be located at floor level; they should also be strategically placed to remove the cold air near concentrations of refrigerated fixtures. Returns should be designed and located to avoid creating drafts. There are two general solutions to this problem:

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Return Ducts in Floor. This is the preferred method and can be accomplished in two ways. The floor area in front of the refrigerated display cases is the coolest area. Refrigerant lines are run to all of these cases, usually in tubes or trenches. If the trenches or tubes are enlarged and made to open under the cases for air return, air can be drawn in from the cold area (Figure 2). The air is returned to the air-handling unit through a tee connection to the trench before it enters the back room area. The opening through which the refrigerant lines enter the back room should be sealed. If refrigerant line conduits are not used, air can be returned through inexpensive underfloor ducts. If refrigerators have insufficient undercase air passage, the manufacturer should be

Retail Facilities

Fig. 2

2.5

Floor Return Ducts

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Fig. 3 Air Mixing Using Fans Behind Cases

Heat Reclaiming Systems

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consulted. Often they can be raised off the floor approximately 40 mm. Floor trenches can also be used as ducts for tubing, electrical supply, and so forth. Floor-level return relieves the problem of localized cold areas and cold aisles and uses the cooling effect for store cooling, or increases the heating efficiency by distributing the air to areas that need it most. Fans Behind Cases. If ducts cannot be placed in the floor, circulating fans can draw air from the floor and discharge it above the cases (Figure 3). Although this approach prevents objectionable cold aisles in front of the refrigerated display cases, it does not prevent an area with a concentration of refrigerated fixtures from remaining colder than the rest of the store.

Control. Store personnel should only be required to change the position of a selector switch to start or stop the system or to change from heating to cooling or from cooling to heating. Control systems for heat recovery applications are more complex and should be coordinated with the equipment manufacturer. Maintenance and Heat Reclamation. Most supermarkets, except large chains, do not employ trained maintenance personnel, but rather rely on service contracts with either the installer or a local service company. This relieves store management of the responsibility of keeping the air conditioning operating properly. Heat extracted from the store and heat of compression may be reclaimed for heating cost saving. One method of reclaiming rejected heat is to use a separate condenser coil located in the air conditioner’s air handler, either alternately or in conjunction with the main refrigeration condensers, to provide heat as required (Figure

Fig. 5 Machine Room with Automatic Temperature Control Interlocked with Store Temperature Control

4). Another system uses water-cooled condensers and delivers its rejected heat to a water coil in the air handler. The heat rejected by conventional machines using air-cooled condensers may be reclaimed by proper duct and damper design (Figure 5 ) . Automatic controls can either reject this heat to the outdoors or recirculate it through the store.

DEPARTMENT STORES Department stores vary in size, type, and location, so airconditioning design should be specific to each store. Essential features of a quality system include (1) an automatic control system properly designed to compensate for load fluctuations, (2) zoned air distribution to maintain uniform conditions under shifting loads, and (3) use of outdoor air for cooling during favorable conditions. It is also desirable to adjust inside temperature for variations in outdoor temperature. Although close control of humidity is not necessary, a properly designed system should operate to maintain relative humidity at 50% or below. This humidity limit eliminates musty odors and retards perspiration, particularly in fitting rooms.

Load Determination Because the occupancy (except store personnel) is transient, inside conditions are commonly set not to exceed 26°C db and 50% rh at outdoor summer design conditions, and 21°C db at outdoor winter design conditions. Winter humidification is seldom used in store air conditioning.

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2.6

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Table 2 Approximate Lighting Load for Older Department Stores Wlm2

Area

Basement First floor Upper floors, women’s wear Upper floors, house furnishings

Applications (SI)

30 to 50 40 to 70 30 to 50 20 to 30

various departments should be considered. Flexibility must be left in the duct design to allow for future movement of departments. It may be necessary to design separate air systems for entrances, particularly in northern areas. This is also true for storage areas where cooling is not contemplated. Air curtains may be installed at entrance doorways to limit infiltration of unconditioned air, at the same time providing greater ease of entry. Control. Space temperature controls are usually operated by personnel who have little knowledge of air conditioning. Therefore, exposed sensors and controls should be kept as simple as possible while still providing the required functions. Control must be such that correctly conditioned air is delivered to each zone. Outdoor air intake should be automatically controlled to operate at minimum cost while providing required airflow. Partial or full automatic control should be provided for cooling to compensate for load fluctuations. Completely automatic refrigeration plants should be considered. Heating controls vary with the nature of the heating medium. Duct heaters are generally furnished with manufacturer-installed safety controls. Steam or hot-water heating coils require a motorized valve for heating control. Time clock control can limit unnecessary HVAC operation. Unoccupied reset controls should be provided in conjunction with timed control. Automatic dampers should be placed in outdoor air inlets and in exhausts to prevent air entering when the fan is turned off. Maintenance. Most department stores employ personnel for routine housekeeping, operation, and minor maintenance, but rely on service and preventive maintenance contracts for refrigeration cycles, chemical treatment, central plant systems, and repairs. Improving Operating Cost. An outdoor air economizer can reduce the operating cost of cooling in most climates. These are generally available as factory options or accessories with the airhandling units or control systems. Heat recovery and desiccant dehumidification should also be analyzed.

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ASHRAE Standard 62.1 provides population density information for load determination purposes. Energy codes and standards restrict installed lighting watt density for newly constructed facilities. However, older facilities may have increased lighting watt densities. Values in Table 2 are approximations for older facilities. Other loads, such as those from motors, beauty parlor, restaurant equipment, and any special display or merchandising equipment, should be determined. Minimum outdoor air requirements should be as defined in ASHRAE Standard 62.1 or local codes. Paint shops, alteration rooms, rest rooms, eating places, and locker rooms should be provided with positive exhaust ventilation, and their requirements must be checked against local codes.

Design Considerations Before performing load calculations, the designer should examine the store arrangement to determine what will affect the load and the system design. For existing buildings, actual construction, floor arrangement, and load sources can be surveyed. For new buildings, examination of the drawings and discussion with the architect or owner is required. Larger stores may contain beauty parlors, food service areas, extensive office areas, auditoriums, warehouse space, etc. Some of these special areas may operate during hours in addition to the normal store-open hours. If present or future operation could be compromised by such a strategy, these spaces should be served by separate HVAC systems. Because of the concentrated load and exhaust requirements, beauty parlors and food service areas should be provided with separate ventilation and air distribution. Future plans for the store must be ascertained because they can have a great effect on the type of air conditioning and refrigeration to be used. System Design. Air conditioning systems for department stores may use unitary or central station equipment. Selection should be based on owning and operating costs as well as special considerations for the particular store, such as store hours, load variations, and size of load. Large department stores have often used central-station systems consisting of air-handling units having chilled-water cooling coils, hot-water heating coils, fans, and filters. Some department stores now use large unitary units. Air systems must have adequate zoning for varying loads, occupancy, and usage. Wide variations in people loads may justify considering variable-volume air distribution systems. Water chilling and heating plants distribute water to the various air handlers and zones and may take advantage of some load diversity throughout the building. Air-conditioning equipment should not be placed in the sales area; instead, it should be located in mechanical equipment room areas or on the roof whenever practicable. Ease of maintenance and operation must be considered in the design of equipment rooms and locations. Many locations require provisions for smoke removal. This is normally accommodated through the roof and may be integrated with the HVAC system. Air Distribution. All buildings must be studied for orientation, wind exposure, construction, and floor arrangement. These factors affect not only load calculations, but also zone arrangements and duct locations. In addition to entrances, wall areas with significant glass, roof areas, and population densities, the expected locations of

CONVENIENCE CENTERS Many small stores, discount stores, supermarkets, drugstores, theaters, and even department stores are located in convenience centers. The space for an individual store is usually leased. Arrangements for installing air conditioning in leased space vary. Typically, the developer builds a shell structure and provides the tenant with an allowance for usual heating and cooling and other minimum interior fmish work. The tenant must then install an HVAC system. In another arrangement, developers install HVAC units in the small stores with the shell construction, often before the space is leased or the occupancy is known. Larger stores typically provide their own HVAC design and installation.

Design Considerations The developer or owner may establish standards for typical heating and cooling that may or may not be sufficient for the tenant’s specific requirements. The tenant may therefore have to install systems of different sizes and types than originally allowed for by the developer. The tenant must ascertain that power and other services will be available for the total intended requirements. The use of party walls in convenience centers tends to reduce heating and cooling loads. However, the effect an unoccupied adjacent space has on the partition load must be considered.

REGIONAL SHOPPING CENTERS Regional shopping centers generally incorporate an enclosed, heated and air-conditioned mall. These centers are normally owned by a developer, who may be an independent party, a financial institution, or one of the major tenants in the center.

2.7

Retail Facilities Some regional shopping centers are designed with an open pedestrian mall between rows of stores. This open-air concept results in tenant spaces similar to those in a convenience center. Storefronts and other perimeters of the tenant spaces are exposed to exterior weather conditions. Major department stores in shopping centers are typically considered separate buildings, although they are attached to the mall. The space for individual small stores is usually leased. Arrangements for installing air conditioning in the individually leased spaces vary, but are similar to those for small stores in convenience centers. Table 3 presents typical data that can be used as check figures and field estimates. However, this table should not be used for final determination of load, because the values are only averages.

Design Considerations The owner or developer provides the HVAC system for an enclosed mall. The regional shopping center may use a central plant or unitary equipment. The owner generally requires that the individual tenant stores connect to a central plant and includes charges for heating and cooling services. Where unitary systems are used, the owner generally requires that the individual tenant install a unitary system of similar design. The owner may establish standards for typical heating and cooling systems that may or may not be sufficient for the tenant’s specific requirements. Therefore, the tenant may have to install systems of different sizes than originally allowed for by the developer. Leasing arrangements may include provisions that have a detrimental effect on conservation (such as allowing excessive lighting and outdoor air or deleting requirements for economizer systems). The designer of HVAC for tenants in a shopping center must be well aware of the lease requirements and work closely with leasing agents to guide these systems toward better energy efficiency. Many regional shopping centers contain specialty food court areas that require special considerations for odor control, outdoor air requirements, kitchen exhaust, heat removal, and refrigeration equipment. System Design. Regional shopping centers vary widely in physical arrangement and architectural design. Single-level and smaller centers usually use unitary systems for mall and tenant air conditioning; multilevel and larger centers usually use a central system. The owner sets the design of the mall and generally requires that similar systems be installed for tenant stores. A typical central system may distribute chilled air to individual tenant stores and to the mall air-conditioning system and use variable-volume control and electric heating at the local use point. Some plants distribute both hot and chilled water. Some all-air systems

Table 3 Typical Installed Cooling Capacity and Lighting Levels-Midwestern United States

Type of Space

Dry retailb Restaurant Fast food food court tenant area food court seating area Mall common area Total

Area per Unit of Installed Cooling m2/kW

Installed Cooling per Unit of Area, W/m2

Lighting Density of Area, W/m2

Annual Lighting Energy Use,a kWh/m2

9.69 3.59

104.1 277.6

43.1 21.5

174.4 87.2

4.23 3.88 7.61 6.97

236.6 258.7 135.6 142.0

32.3 32.3 32.3 38.8

131.3 131.3 131.3c 157.2

also distribute heated air. Central plant systems typically provide improved efficiency and better overall economics of operation. Central systems may also provide the basic components required for smoke removal. Air Distribution. Air distribution in individual stores should be designed for the particular space occupancy. Some tenant stores maintain a negative pressure relative to the public mall for odor control. The total facility HVAC system should maintain a slight positive pressure relative to atmospheric pressure and a neutral pressure relative between most of the individual tenant stores. Exterior entrances should have vestibules. Smoke management is required by many building codes, so air distribution should be designed to easily accommodate smoke control requirements. Maintenance. Methods for ensuring the operation and maintenance of HVAC systems in regional shopping centers are similar to those used in department stores. Individual tenant stores may have to provide their own maintenance. Improving Operating Cost. Methods for lowering operating costs in shopping centers are similar to those used in department stores. Some shopping centers have successfully used cooling tower heat exchanger economizers. Central plant systems for regional shopping centers typically have lower operating costs than unitary systems. However, the initial cost of the central plant system is typically higher.

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MULTIPLE-USE COMPLEXES Multiple-use complexes are being developed in many metropolitan areas. These complexes generally combine retail fac other facilities such as offices, hotels, residences, or other commercial space into a single site. This consolidation of facilities into a single site or structure provides benefits such as improved land use; structural savings; more efficient parking; utility savings; and opportunities for more efficient electrical, fire protection, and mechanical systems.

Load Determination The various occupancies may have peak HVAC demands that occur at different times of the day or year. Therefore, the HVAC loads of these occupancies should be determined independently. Where a combined central plant is considered. a block load should also be determined.

Design Considerations Retail facilities are generally located on the lower levels of multiple-use complexes, and other commercial facilities are on upper levels. Generally, the perimeter loads of the retail portion differ from those of the other commercial spaces. Greater lighting and population densities also make HVAC demands for the retail space different from those for the other commercial space. The differences in HVAC characteristics for various occupancies within a multiple-use complex indicate that separate air handling and distribution should be used for the separate spaces. However, combining the heating and cooling requirements of various fac into a central plant can achieve a substantial saving. A combined central heating and cooling plant for a multiple-use complex also provides good opportunities for heat recovery, thermal storage, and other similar functions that may not be economical in a single-use facility. Many multiple-use complexes have atriums. The stack effect created by atriums requires special design considerations for tenants and space on the main floor. Areas near entrances require special measures to prevent drafts and accommodate extra heating requirements. System Design. Individual air-handling and distribution systems should be designed for the various occupancies. The central heating

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Source: Based on 2001 Data-Midwestern United States. aHours of operating lighting assumes 12 ldday and 6.5 dayslweek. bJewelly, high-end lingerie, and some other occupancy lighting levels are typically 65 to 85 120 W/m2 and can range to 120 Wlm2. Cooling requirements for these spaces are higher. c62.4 kWh/m2 for centers that shut off lighting during daylight, assuming 6 ldday and 6.2 dayslweek.

2.8 and cooling plant may be sized for the block load requirements, which may be less than the sum of each occupancy’s demand. control. ~ ~ l ~complexes i ~ typically l ~ require - ~ centralized ~ ~ control. It may be dictated by requirements for fire and smoke control, security, remote monitoring, billing for central facilities use, maintenance Control, building operations Control, and energy management.

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Applications (SI)

REFERENCES

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ASHRAE. 2006. Advanced energy design guide for small retail buildings.

ASHRAE. 2010. Ventilation for acceptable indoor air quality. ANSI/ASHRAE Standard 62.1-2010.

ASHRAE. 2007. Energy standard for buildings except low-rise residential buildings. ANSI/ASHRAE/IES Standard 90.1-2007.

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COMMERCIAL AND PUBLIC BUILDINGS

Office Buildings. .............................................................................................................................. 3.1 Transportation Centers ................................................................................................................... 3.6 Warehouses and Distribution Centers ............................................................................................ 3.8 Sustainability and Energy Efficiency 3.9 Commissioning and Retrocommissioning ..................................................................................... 3.12 Seismic and Wind Restraint Considerations 3.13

T

buildings), or businesshndustrial park (typically one- to threestory buildings). Floorplate (Floor Space Area). Size typically ranges from 1670 to 2800 m2 and averages from 1860 to 2320 m2. Use and Ownership. Office buildings can be single tenant or multitenant. A single-tenant building can be owned by the tenant or leased from a landlord. From an HVAC&R systems standpoint, a single tenantlowner is more cautious considering issues such as lifecycle cost and energy conservation. In many cases, the systems are not selected based on the lowest first cost but on life-cycle cost. Sometimes, the developer may wish to select a system that allows individual tenants to pay directly for the energy they consume. Building Features and Amenities. Examples include typically parking, telecommunications, HVAC&R, energy management, restaurants, security, retail outlets, health club, etc.

HIS chapter contains technical, environmental, and design considerations to assist the design engineer in the proper application of HVAC systems and equipment for commercial and public buildings.

OFFICE BUILDINGS General Design Considerations Despite cyclical market fluctuations, office buildings are considered the most complex and competitive segments of real estate development. Survey data of 824 000 office buildings (EIA 2003) demonstrate the distribution of the U.S. office buildings by the numbers and the area, as shown in Table 1. According to Gause (1998), an office building can be divided into the following categories:

Typical areas that can be found in office buildings are:

Class. The most basic feature, class represents the building’s quality by taking into account variables such as age, location, building materials, building systems, amenities, lease rates, etc. Office buildings are of three classes: A, B, and C. Class A is generally the most desirable building, located in the most desirable locations, and offering first-rate design, building systems, and amenities. Class B buildings are located in good locations, have little chance of functional obsolescence, and have reasonable management. Class C buildings are typically older, have not been modernized, are often functionally obsolete, and may contain asbestos. These low standards make Class C buildings potential candidates for demolition or conversion to another use. Size and Flexibility. Office buildings are typically grouped into three categories: high rise (16 stories and above), mid rise (four to 15 stories), and low rise (one to three stories). Location. An office building is typically in one of three locations: downtown (usually high rises), suburban (low- to mid-rise

Offices Offices: (private or semiprivate acoustically andor visually). Conference rooms

EmployeeNisitor Support Spaces Convenience store, kiosk, or vending machines Lobby: central location for building directory, schedules, and general information Atria or common space: informal, multipurpose recreation and social gathering space Cafeteria or dining hall Private toilets or restrooms Child care centers Physical fitness area Interior or surface parking areas

Administrative Support Spaces Table 1 Data for U.S. Office Buildings

May be private or semiprivate acoustically and/or visually.

Percent of Total Floor Number of Total Space Percent of Buildings Number of (Million Total Floor (Thousands) Buildings m2) Space Total 93 to 465 m2 466 to 929 m2 930 to 2323 m2 2324 to 4647 m2 4648 to 9264 m2 9265 to 18 587 m2 18 588 to 46 468 m2 >46 468 m2

824 503 127 116 43 17 11 5 2

100.0 61.0 15.4 14.1 5.2 2.1 1.3 0.6 0.2

1135 128 87 175 140 112 133 139 220

Operation and Maintenance Spaces General storage: for items such as stationery, equipment, and instructional materials. Food preparation area or kitchen Computedinformation technology (IT) closets Maintenance closets Mechanical and electrical rooms

100.0 11.32 7.68 15.46 12.34 9.90 11.70 12.23 19.37

A well-designed and functioning HVAC system should provide the following: Comfortable and consistent temperature and humidity Adequate amounts of outdoor air at all time to satisfy ventilation requirements Remove odors and contaminates from circulated air

Source: EM (2003)

The major factors affecting sizing and selection of the HVAC systems are as follows:

The preparation of this chapter is assigned to TC 9.8, Large-Building AirConditioning Applications.

3.1

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3.2

Applications (SI)

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Building size, shape and number of floors Amount of exterior glass Orientation, envelope Internal loads, occupants, lighting Thermal zoning (number of zones, private offices, open areas, etc .) Office HVAC systems generally range from small, unitary, decentralized cooling and heating up to large systems comprising central plants (chillers, cooling towers, boilers, etc.) and large air-handling systems. Often, several types of HVAC systems are applied in one building because of special requirements such as continuous operation, supplementary cooling, etc. In office buildings, the class ofthe building also affects selection ofthe HVAC systems. For example, in a class A office building, the HVAC&R systems must meet more stringent criteria, including individual thermal control, noise, and flexibility; HVAC systems such as single-zone constant-volume, water-source heat pump, and packaged terminal air conditioners (PTACs) might be inapplicable to this class, whereas properly designedvariable-air-volume (VAV) systems canmeet these requirements.

recommendations for ventilation design based on the ventilation rate procedure method and filtration criteria for office buildings. Acceptable noise levels in office buildings are important for office personnel; see Table 4 and Chapter 48.

Load Characteristics

Office buildings usually include both peripheral and interior zone spaces. The peripheral zone extends 3 to 3.6 m inward from the outer wall toward the interior of the building, and frequently has a large window area. These zones may be extensively subdivided. Peripheral zones have variable loads because of changing sun position and weather. These zones typically require heating in winter. During intermediate seasons, one side of the building may require Table 3 Typical Recommended Design Criteria for Ventilation and Filtration for Office Buildings Ventilation and Exhausta,b Combined Occupant Outdoor Air Outdoor Air Density: (Defaultvalue) per L/s per L/s per Person 100 m2 L/(s.m2) Unit

Minimum Filtration Efficiency, MERVC

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Design Criteria

A typical HVAC design criteria covers parameters required for thermal comfort, indoor air quality (IAQ), and sound. Thermal comfort parameters (temperature and humidity) are discussed in ASHRAE Standard 55-2010 and Chapter 9 of the 2009 ASHRAE Handbook-Fundamentals. Ventilation and IAQ are covered by ASHRAE Standard 62.1-2010, the user’s manual for that standard (ASHRAE 2010), and Chapter 16 of the 2009 ASHRAE Handbook-Fundamentals. Sound and vibration are discussed in Chapter 48 of this volume and Chapter 8 of the 2009 ASHRAE HandbookFundamentals. Thermal comfort is affected by air temperature, humidity, air velocity, and mean radiant temperature (MRT), as well as nonenvironmental factors such as clothing, gender, age, and physical activity. These variables and how they correlate to thermal comfort can be evaluated by the Thermal Comfort Tool CD (ASHRAE 1997) in conjunction with ASHRAE Standard 55. General guidelines for temperature and humidity applicable for areas in office buildings are shown in Table 2. All office, administration, and support areas need outdoor air for ventilation, Outdoor air is introduced to occupied areas and then exhausted by fans or exhaust openings, removing indoor air pollutants generated by occupants and any other building-related sources. ASHRAE Standard 62.1 is used as the basis for many building codes. To defme the ventilation and exhaust design criteria, consult local applicable ventilation and exhaust standards. Table 3 provides Table 2

Typical Recommended Indoor Temperature and Humidity in Office Buildings Indoor Design Conditions Temperature, OC/ Relative Humidity, %

Area

Winter

Offices, conference 20.3 to 24.2 rooms, common areas 20 to 30% Cafeteria 21.1 to 23.3 20to30% Kitchen 21.1 to 23.3 Toilets 22.2 Storage Mechanical rooms

17.8 16.1

Summer

Comments

23.3 to 26.7 50 to 60% 25.8 50% 28.9 to 31.1 No humidity control Usually not conditioned No humidity control Usually not conditioned

Category

Office areas Reception areas Main entry lobbies Telephone/data entry Cafeteria Kitchend,e

8.5 3.5 5.5

5 30 10

6 to 8 6 to 8 6 to 8

3.0

60

6 to 8

4.7

100

6 to 8 NA

3.5 (exhaust)

Toilets

35 (exhaust)

Storages

0.6

NA

1 to 4

Notes: aBased on ASHRAE Standard 62.1-2010, Tables 6-1 and 6-4. For systems seming multiple zones, apply multiple-zone calculations procedure. IfDCV is considered, see the section on Demand Control Ventilation (DCV). bThis table should not be used as the only source for design criteria. Governing local codes, design guidelines, ANSJJASHRAE Standard 62.1-2010 and user’s manual, (ASHRAE 2010) must be consulted. %ERV = minimum efficiency reporting values, based on ASHRAE Standard 52.2-2007. dSee Chapter 33 for additional information on kitchen ventilation. For kitchenette use 1.5 L/(s.m2) eConsult local codes for kitchen exhaust requirements. default occupancy density when actual occupant density is not known. gThis recommendation for storage might not be sufficient when the materials stored have harmful emissions.

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Table 4 Typical Recommended Design Guidelines for HVACRelated Background Sound for Areas in Office Buildings Sound Criteriaa’

Category

Executive and private office Conference rooms Teleconference rooms Open-plan office space Corridors and lobbies Cafeteria Kitchen Storage Mechanical rooms

RC 0; QAI < 5 dB

Comments

25 to 35 25 to 35 2 with replaceable wear plates (wear backs) in the heel are often used where particulate loading is extremely heavy or the particles are very abrasive. When corrosive material is present, alternatives such as special coatings or different duct materials (fibrous glass or stainless steel) can be used. Cleanout openings should be located to allow access to the duct interior in the event of a blockage. Certain contaminants may require washdown systems andor fire detection and suppression systems to comply with safety or fire prevention codes. These requirements should be verified with local code officials and insurance underwriters. NFPA standards provide guidance on fire safety. Industrial duct construction is described in Chapter 18 of the 2008 ASHRAE Handbook-HVAC Systems and Equipment, and in Sheet Metal and Air Conditioning Contractors' National Association (SMACNA) Standard 005-1999.

32.8 Air Cleaners

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Air-cleaning equipment is usually selected to (1) conform to federal, state, or local emissions standards and regulations; (2) prevent reentrainment of contaminants to work areas; (3) reclaim usable materials; (4) allow cleaned air to recirculate to work spaces andor processes; (5) prevent physical damage to adjacent properties; and (6) protect neighbors from contaminants. Factors to consider when selecting air-cleaning equipment include the type of contaminant (number of components, particulate versus gaseous, moisture and heat in the airstream, and pollutant concentration), contaminant characteristics (e.g. volatility, reactivity), required contaminant removal efficiency, disposal method, and air or gas stream characteristics. Auxiliary systems such as instrument-grade compressed air, electricity, or water may be required and should be considered in equipment selection. Specific hazards such as explosions, fire, or toxicity must be considered in equipment selection, design, and location. See Chapters 28 and 29 of the 2008 ASHRAE Handbook-HVAC Systems and Equipment for information on equipment for removing airborne contaminants. An applications engineer should be consulted when selecting equipment. The cleaner’s pressure loss must be added to overall system pressure calculations. In some cleaners, specifically some fabric filters, loss increases as operation time increases. System design should incorporate the maximum pressure drop of the cleaner, or hood flow rates will be lower than designed during most of the duty cycle. Also, fabric collector losses are usually given only for a clean air plenum. A reacceleration to the duct velocity, with the associated entry losses, must be calculated during design. Most other cleaners are rated flange-to-flange with reacceleration included in the loss.

Air-Moving Devices The type of air-moving device selected depends on the type and concentration of contaminant, the pressure rise required, and allowable noise levels. Fans are usually used. Chapter 20 of the 2008 ASHRAE Handbook-HVAC Systems and Equipment describes available fans; Air Movement and Control Association Publication 201 (AMCA 2002) describes proper connection of the fan(s) to the system. The fan should be located downstream of the air cleaner whenever possible to (1) reduce possible abrasion of the fan wheel blades and (2) create negative pressure within the air cleaner and the entire length of dirty duct so that air leaks into the exhaust system throughout its dirty side and control of the contaminant is maintained. Fans handling flammable or explosive dusts should be specified as spark-resistant. AMCA provides three different spark-resistant fan construction specifications. The fan manufacturer should be consulted when handling these materials. Multiple NFPA standards give fire safety requirements for fans and systems handling explosive or flammable materials. When possible, devices such as fans and pollution-control equipment should be located outside classified areas, andor outside the building, to reduce the risk of f r e or explosion. In some instances, the fan is located upstream from the cleaner to help remove dust. This is especially true with cyclone collectors, for example, which are used in the woodworking industry. If explosive, corrosive, flammable, or sticky materials are handled, an injector (also known as an eductor) can transport the material to the aircleaning equipment. Injectors create a shear layer that induces airflow into the duct. Injectors should be the last choice because their efficiency seldom exceeds 10%.

201 1 ASHRAE Handbook-HVAC

Applications (SI)

(3) nature of the contaminants being exhausted. Heat transfer efficiency depends on the type of heat recovery system used. If exhausted air contains particulate matter (e.g., dust, lint) or oil mist, the exhausted air should be filtered to prevent fouling the heat exchanger. If exhausted air contains gaseous and vaporous or volatile contaminants, such as hydrocarbons and water-soluble chemicals, their effect on the heat recovery device should be investigated. Chapter 25 of the 2008 ASHRAE Handbook-HVAC Systems and Equipment discusses air-to-air energy recovery systems. When selecting energy recovery equipment for industrial exhaust systems, cross-contamination from the energy recovery device must be considered. Some types of energy recovery equipment may allow considerable cross-contamination (e.g., some heat wheels) from the exhaust into the supply airstream, whereas other types (e.g., runaround coils) do not. The exhaust side of the energy recovery device should be negatively pressured compared to the supply side, so that any leakage will be from the clean side into the contaminated side. This is not acceptable for some applications. The material of the energy recovery device must be compatible with the pollutants being exhausted. If the exhaust airstream destroys the heat exchanger, contamination can enter the supply airstream and cause additional equipment damage as well as increase exposure to workers.

zyxwvuts Exhaust Stacks The exhaust stack must be designed and located to prevent reentraining discharged air into supply system inlets. The building’s shape and surroundings determine the atmospheric airflow over it. Chapter 24 of the 2009 ASHRAE Handbook-Fundamentals and Chapter 45 of this volume cover exhaust stack design. The typical code-required minimum stack height is intended to provide protection for workers near the stack, so discharged air will be above their breathing zone. The minimum required stack height does not protect against reentrainment of contaminated exhaust into any outside air intakes. If rain protection is important, a no-loss stack head design (ACGIH 2007; SMACNAStandard 005) is recommended. Weather caps deflect air downward, increasing the chance that contaminants will recirculate into air inlets, have high friction losses, and provide less rain protection than a properly designed stack head. Weather caps should never be used with a contaminated or hazardous exhaust stream. Figure 12 contrasts flow patterns of weather caps and stack heads. Loss data for stack heads are presented in the Duct Fitting Database CD-ROM (ASHRAE 2008). Losses in straight-duct stack heads are balanced by the pressure regain at the expansion to the larger-diameter stack head.

Energy Recovery to Increase Sustainability Energy transfer from exhausted air to replacement air may be economically feasible, depending on the (1) location of the exhaust and replacement air ducts, (2) temperature of the exhausted gas, and

Fig. 12 Comparison of Flow Pattern for Stack Heads and Weather Caps

Industrial Local Exhaust Instrumentation and Controls

zyxwvutsr 32.9

Some industrial exhaust systems may require positive verification of system airflow. Indicators of performance failure may require both audible and visual warning indicators. Other instrumentation, such as dust collector level indication, rotary lock valve operation, or fire detection, may be required. Selection of electronic monitoring instruments should consider durability expectations, maintenance, and calibration requirements. Interfaces may be required with the process control system or with the balance of the plant ventilation system. Electrical devices in systems conveying flammable or explosive materials or in a hazardous location may need to meet certain electrical safety and code requirements. These requirements are determined by the owner, process equipment manufacturer, federal and state regulations, local codes, andor insurance requirements.

OPERATION System Testing and Balancing After installation, an exhaust system should be tested and balanced to ensure that it operates properly, with the required flow rates through each hood. If actual flow rates are different from design values, they should be corrected before the system is used. Testing is also necessary to obtain and document baseline data to determine (1) compliance with federal, state, and local codes; (2) by periodic inspections or real-time monitoring, whether maintenance on the system is needed to ensure design operation; (3) whether a system has sufficient capacity for additional airflow; (4) whether system leakage is acceptable; and ( 5 ) compliance with testing, adjusting, and balancing (TAB) standards. AMCA (1990) and Chapter 5 of ACGIH (2007) contain detailed information on preferred methods for testing systems.

AMCA. 2002. Fans and systems. Publication 201-02. Air Movement and Control Association International, Arlington Heights, IL. ASHRAE. 2010. Ventilation for acceptable indoor air quality. ANSI/ ASHRAE Standard 62.1-2010. ASHRAE. 2008. Ductfitting database. Bill, R.G. and B. Gebhart. 1975. The transition of plane plumes. International Journal ofHeat andMass Transfer 18:513-526. Brooks, P. 2001. Designing industrial exhaust systems. ASHRAE Journal 43(4):1-5. Caplan, K.J. and G.W. Knutson. 1977. The effect of room air challenge on the efficiency of laboratory fume hoods. ASHRAE Transactions 83(1):141-156. Caplan, K.J. and G.W. Knutson. 1978. Laboratory fume hoods: Influence of room air supply. ASHRAE Transactions 82( 1):522-537. DallaValle, J.M. 1952. Exhaust hoods, 2nd ed. Industrial Press, New York. Goodfellow, H. 1985. Design of ventilation systems for fume control. In Advanced design of ventilation systemsfor contaminant control,pp. 359438. Elsevier, New York. Goodfellow, H. and E. Tahti, eds. 200 1. Industrial ventilation design guidebook. Academic Press, New York. Hemeon, W.C.L. 1963. Exhaust for hot processes. Ch. 8 in Plant andprocess ventilation, 2nd ed., pp. 160-196. Industrial Press, New York. Hemeon, W.C.L. 1999. Exhaust for hot processes. Ch. 8 in Hemeon’splant andprocess ventilation, 3rd ed., pp. 117-147, D.J. Burton, ed. Lewis, New York. McKernan, J.L. and M.J. Ellenbecker. 2007. Ventilation equations for improved exothermic process control. Annals of Occupational Hygiene 51:269-279. McKernan, J.L., M.J. Ellenbecker, C.A Holcroft, and M.R. Petersen. 2007a. Evaluation of a proposed area equation for improved exothermic process control. Annals of Occupational Hygiene 5 1:725-738. McKernan, J.L., M.J. Ellenbecker, C.A. Holcroft, andM.R. Petersen. 2007b. Evaluation of a proposed velocity equation for improved exothermic process control. Annals of Occupational Hygiene 5 1:357-369. NFPA. 2003. Ovens and furnaces. ANSI/NFPA Standard 8603. National Fire Protection Association, Quincy, MA. Nielsen, P.V. 1993. Displacement ventilation: Theory and design. Aalborg University, Aalborg, Denmark. SMACNA. 1999. Round industrial duct construction standards, 2nd ed. ANSI/SMACNA/BSR Standard 005-1999. Sheet Metal and Air Conditioning Contractors’ National Association, Chantilly, VA. U.S. Public Health Service. 1973. Air pollution engineering manual. Publication 999-AP-40.

zyxwvutsrqp

Operation and Maintenance Periodic inspection and maintenance are required for proper operation of exhaust systems. System designers should keep this requirement in mind and account for it through the installation of clean-outiinspection doors and through strategic placement of equipment that ensures access for maintenance activities. Systems are often changed or damaged after installation, resulting in low duct velocities andor incorrect volumetric flow rates. Low duct velocities can cause contaminants to settle and plug the duct, reducing flow rates at affected hoods. Adding hoods to an existing system can change volumetric flow at the original hoods. In both cases, changed hood volumes can increase worker exposure and health risks. The maintenance program should include (1) inspecting ductwork for particulate accumulation and damage by erosion or physical abuse, (2) checking exhaust hoods for proper volumetric flow rates and physical condition, (3) checking fan drives, (4) maintaining air-cleaning equipment according to manufacturers’ guidelines, and ( 5 ) confirming that the system continues to meet compliance with worker exposure and environmental pollution requirements.

REFERENCES

BIBLIOGRAPHY Bastress, E., J. Niedzwocki, and A. Nugent. 1974. Ventilation required for grinding, buffing, and polishing operations. Publication 75107. U.S. Department of Health, Education, and Welfare. National Institute for Occupational Safety and Health, Washington, D.C. Baturin, V.V. 1972. Fundamentals of industrial ventilation, 3rd English ed. Pergamon, New York. Braconnier, R. 1988. Bibliographic review ofvelocity field in the vicinity of local exhaust hood openings. American Industrial Hygiene Association Journal 49(4):185-198. Brandt, A.D., R.J. Steffy, and R.G Huebscher. 1947. Nature of airflow at suction openings. ASHVE Transactions 53:5576. British Occupational Hygiene Society (BOHS). 1987. Controlling airborne contaminants in the workplace. Technical Guide 7. Science Review Ltd. and H&H Scientific Consultants, Leeds, U.K. Burgess, W.A., M.J. Ellenbecker, and R.D. Treitman. 1989. Ventilationfor control of the work environment. John Wiley & Sons, New York. Chambers, D.T. 1993. Local exhaust ventilation: A philosophical review of the current state-of-the-art with particular emphasis on improved worker protection. DCE, Leicester, U.K. Flynn, M.R. and M.J. Ellenbecker. 1985. The potential flow solution for airflow into a flanged circular hood. American Industrial Hygiene Journal 46(6):3 18-322. Fuller, F.H. and A.W. Etchells. 1979. The rating of laboratory hood performance. ASHRAE Journal 2 1(10):49-53. Garrison, R.P. 1977. Nozzle performance and design for high-velocitynowvolume exhaust ventilation. Ph.D. dissertation. University of Michigan, Ann Arbor. Goodfellow, H.D. 1986. Ventilation ’85(ConferenceProceedings). Elsevier, Amsterdam.

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ACGIH. 2007. Industrial ventilation: A manual of recommended practice for Operation and Maintenance. Committee on Industrial Ventilation, American Conference of Governmental Industrial Hygienists, Cincinnati, OH. ACGIH. 20 10. Industrial ventilation: A manual of recommended practice forDesign, 27th ed. Committee on Industrial Ventilation, American Conference of Governmental Industrial Hygienists, Cincinnati, OH. Alden, J.L. and J.M. Kane. 1982. Design of industrial ventilation systems, 5th ed. Industrial Press, New York. AMCA. 1990. Field performance measurement of fan systems. Publication 203-90. Air Movement and Control Association International, Arlington Heights, IL.

32.10

z zyxwvutsrqponm 201 1 ASHRAE Handbook-HVAC

Hagopian, J.H. and E.K. Bastress. 1976. Recommended industrial ventilation guidelines. Publication 76162. U.S. Department of Health, Education, and Welfare, National Institute for Occupational Safety and Health, Washington, D.C. Heinsohn, R.J. 1991. Industrial ventilation: Engineering principles. John Wiley & Sons, New York. Heinsohn, R.J., K.C. Hsieh, and C.L. Merkle. 1985. Lateral ventilation systems for open vessels. ASHRAE Transactions 91( lB):361-382. Hinds, W. 1982. Aerosol technology: Properties, behavior, and measurement of airborneparticles. John Wiley & Sons, New York. Huebener, D.J. and R.T. Hughes. 1985. Development of push-pull ventilation. American Industrial Hygiene Association Journal 46(5):262-267. Kofoed, P. and P.V. Nielsen. 1991. Thermal plumes in ventilated roomsVertical volume flux influenced by enclosing walls. Presented at 12th Air Infiltration and Ventilation Centre Conference, Ottawa. Ljungqvist, B. and C. Waering. 1988. Some observations on “modern” design of fume cupboards. Proceedings of the 2nd International Symposium on Ventilationfor Contaminant Control, Ventilation ’88.Pergamon, U.K. Morton, B.R., G. Taylor, and J.S. Turner. 1956. Turbulent gravitational convection from maintained and instantaneous sources. Proceedings of Royal Society 234A: 1. Posokhin, V.N. and A.M. Zhivov 1997. Principles of local exhaust design. Proceedings of the 5th International Symposium on Ventilationfor Contaminant Control, vol. 1. Canadian Environment Industry Association (CEIA), Ottawa.

Applications (SI)

Qiang, Y.L. 1984. The effectiveness ofhoods in windy conditions. Kungliga Tekniska Hoggskolan, Stockholm. Safemazandarani, P. and H.D. Goodfellow. 1989. Analysis of remote receptor hoods under the influence of cross-drafts. ASHRAE Transactions 95(1):465-471. Sciola, V. 1993. The practical application of reduced flow push-pull plating tank exhaust systems. Presented at 3rd International Symposium on Ventilation for Contaminant Control, Ventilation ’9 1, Cincinnati, OH. Sepsy, C.F. and D.B. Pies. 1973. An experimental study of the pressure losses in converging flow fittings used in exhaust systems. Document PB 221 130. Prepared by Ohio State University for National Institute for Occupational Health. Shibata, M., R.H. Howell, and T. Hayashi 1982. Characteristics and design method for push-pull hoods: Part I-Cooperation theory on airflow; Part 2-Streamline analysis of push-pull flows. ASHRAE Transactions 88( 1): 535-570. Silverman,L. 1942. Velocity characteristics of narrow exhaust slots. Journal of Industrial Hygiene and Toxicology 24 (November):267. Sutton, O.G. 1950. The dispersion of hot gases in the atmosphere. Journal oj Meteorology 7(5):307. Zarouri, M.D., R.J. Heinsohn, and C.L. Merkle. 1983. Computer-aided design of a grinding booth for large castings. ASHRAE Transactions 89(2A):95-118. Zarouri, M.D., R.J. Heinsohn, and C.L. Merkle. 1983. Numerical computation of trajectories and concentrations of particles in a grinding booth. ASHRAE Transactions 89(2A):119-135.

zyxwvutsrqpon

zyx zyxwvut CHAPTER 33

KITCHEN VENTILATION Commercial Kitchen Ventilation Energy Considerations.. System Integration and Design Cooking Efluent Generation and Control ............................... Heat Gain Calculations Exhaust Systems ..................................................................... Commercial Exhaust Hoods ................................................... Duct Systems ..........................................................................

33.5

33.10 33.10 33.18

K

ITCHEN ventilation is a complex web of interconnected HVAC systems. The main components typically include (1) cooling to address heat from cooking appliances, (2) makeup air to provide proper pressurization during cooking operations, and (3) exhaust to remove heat and effluent generated by cooking appliances. System design includes aspects of air conditioning, f r e safety, ventilation, building pressurization, refrigeration, air distribution, and food service equipment. Kitchens are in many buildings, including restaurants, hotels, hospitals, retail malls, single- and multifamily dwellings, and correctional facilities. Each building type has special requirements for its kitchens, but many basic needs are common to all. This chapter provides an understanding of the different components of kitchen ventilation systems and where they can be applied. Additionally, background information is included to provide an understanding of the history and rationale behind these design decisions. Kitchen ventilation has at least two purposes: (1) to provide a comfortable environment in the kitchen and (2) to ensure the safety of personnel working in the kitchen and of other building occupants. Comfort criteria often depend on the local climate, because some kitchens are not air conditioned. Kitchen ventilation ensures safety by providing a means to remove the heat, smoke, and grease (cooking effluent) produced during normal cooking operations. HVAC system designers are most frequently involved in commercial kitchen applications, in which cooking effluent contains large amounts of grease or water vapor. Residential kitchens typically use a totally different type of hood. The amount of grease produced in residential applications is significantly less than in commercial applications, so the health and f r e hazard is much lower. The centerpiece of almost any kitchen ventilation system is an exhaust hood(s), used primarily to remove cooking effluent from kitchens. Effluent includes gaseous, liquid, and solid contaminants produced by the cooking process, and may also include products of fuel and even food combustion. These contaminants must be removed for both comfort and safety; effluent can be potentially life-threatening and, under certain conditions, flammable. Finally, it should be noted that the arrangement of food service equipment and its coordination with the hood(s) can greatly affect the energy used by these systems, which in turn affects kitchen operating costs. Quite often, the hood selection and appliance layout is determined by a kitchen facility designer. To minimize energy use and ensure a properly designed kitchen ventilation system, the HVAC engineer should reach out to the kitchen designer and share the practices and ideas presented in this chapter.

Sustainability Impact Kitchens are some of the most intensive users of energy for a given area compared to other commercial or institutional occupancies. In The preparation of this chapter is assigned to TC 5.10, Kitchen Ventilation,

Replacement (Makeup) Air Systems Air Balancing ......................................................................... Operations and Maintenance Residential Kitchen Ventilation.............................................. Exhaust Systems ..................................................................... Research .................................................................................

33.27 33.29 33.30 33.31

addition to energy used during cooking, the kitchen ventilation system must address the large amount of heat emitted or convected into the kitchen from the cooking equipment, and supply and condition the ventilation air needed as part of the cooking effluent exhaust system. Given these factors, it is imperative that the kitchen ventilation system be designed with careful consideration of both frst cost and operating costs. An additional factor to be considered is the cooking effluent, and any treatments that may be required before it is discharged into the atmosphere.

COMMERCIAL KITCHEN VENTILATION ENERGY CONSIDERATIONS Restaurants and commercial kitchens are the largest consumers of energy per unit of floor area when compared to other commercial or institutional occupancies (Itron and California Energy Commission 2006). Primary drivers of commercial kitchen energy use are the cooking appliances and the HVAC system. The kitchen exhaust ventilation system is often the largest energy-consuming component in a commercial food service facility. However, energy consumption associated with commercial kitchen ventilation (CKV) and HVAC systems, as well the conservation potential, can vary significantly (Fisher 2003). Beyond the design exhaust ventilation rate itself, the magnitude of energy consumption and cost of a CKV system is affected by factors such as geographic location (i.e., climate), system operating hours, static pressure and fan efficiencies, makeup air heating and cooling set points and level of dehumidification, efficiency of heating and cooling systems, level of interaction between kitchen and building HVAC system, appliances under the hood and associated radiant heat gain to space, and applied utility rates. Minimizing the exhaust airflow needed for cooking appliances and reducing radiant load from the appliances are primary considerations in optimizing CKV system design. Because climatic zones vary dramatically in temperature and humidity, energy-efficient designs have widely varying rates of returns on the investment. In new facilities, the designer can select conservation measures suitable for the climatic zone and the HVAC system to maximize the economic benefits. The operating cost burden has stimulated energy efficiency design concepts and operating strategies discussed in this section and detailed in industry design guidelines (PG&E 2004). It has also impacted changes to ASHRAE Standard 90.1. The updated Kitchen Exhaust Systems section of ASHRAE Standard 90.1 states that if a CKV system has a total exhaust airflow rate greater than 2.4 m3/s, the design must adhere to maximum exhaust rates specified for the different hood types. These rates apply to listed hoods, and are set 30% below the minimum values

33.1

33.2

z zyxwvutsrqp

for unlisted hoods dictated by the International Mechanical Code@ (IMC) (ICC 2009a); refer to Table 3 in this chapter for minimum unlisted hood airflow rates. If a kitchen or dining facility has a total kitchen hood exhaust airflow rate greater than 2.4 m3/s, it must have one of the following: At least 50% of all replacement air is transfer air that would otherwise be exhausted Demand ventilation system(s) on at least 75% of the exhaust air, capable of at least 50% reduction in exhaust and replacement air system airflow rates, including controls necessary to modulate airflow in response to appliance operation and to maintain full capture and containment of smoke, effluent, and combustion products during cooking and idle Listed energy recovery devices with a sensible heat recovery effectiveness of not less than 40% on at least 50% of the total exhaust airflow

Energy Conservation Strategies Specifying Exhaust Hoods for Reduced Airflow. The type and style of exhaust hood selected depends on factors such as restaurant type, restaurant menu, and food service equipment installed, as well as flexibility for future kitchen upgrades. Exhaust flow rates are largely determined by the food service equipment and hood style. Wall-mounted canopy hoods function effectively at lower exhaust flow rates than single-island hoods. Single- and double-island canopy hoods are more sensitive to makeup air (MUA) supply and cross drafts than wall mounted canopy hoods (Swierczyna et al. 2009). Engineered backshelf (proximity) hoods may exhibit the lowest capture and containment flow rates. In some cases, a backshelf hood performs the same job as a wall-mounted canopy hood at one-third the exhaust rate. Cooking appliance type and duty rating must be included in the specification process, because not all hoods (particularly backshelf hoods) are rated or designed for all cooking appliance types or duty ratings. Threshold exhaust rates for a specific hood and appliance configuration may be determined by laboratory testing under the specifications of ASTM Standard F1704-09. Similar in concept to the listed airflow rates derived from UL Standard 710, the threshold of containment and capture (C&C) for an ASTM Standard F1704 test is established under ideal laboratory conditions and is only a reference point for specifying the exhaust airflow rate for a CKV system. Side Panels and Overhang. In many cases, side (or end) panels allow a reduced exhaust rate because they direct replacement airflow to the front of the hood and cooking equipment. They are a relatively inexpensive way to improve capture and containment and reduce the total exhaust rate. It is important to know that partial side panels can provide almost the same benefit as full panels. Although tending to defy its definition as an “island” canopy, end panels can improve the performance of a double- or single-island canopy hood. A significant benefit of end panels, when hoods are exposed to cross drafts, is mitigation of the negative effect those drafts have on hood performance. However, air distribution designs that eliminate cross drafts are preferred. Increasing overhang is another specification detail that can improve the hood’s ability to capture and allow reduced exhaust rates. It is important that the engineer and food service designers work closely on appliance placement size and type, because they impact hood sizing, which in turn impacts lighting, HVAC, and most importantly hood performance. A hood that is too small (i.e., little or no overhang) may often not be capable of working properly at any airflow rate, whereas those with generous overhang may operate well at airflow rates reduced by 30% or more. Custom-Designed Hoods. Hoods can be custom designed for specific cooking appliances or cooking processes. Customization often reduces exhaust and replacement air quantities and consequently reduces fan sizes, energy use, and energy costs. To operate at flow rates lower than required by code, custom-designed hoods

201 1 ASHRAE Handbook-HVAC

Applications (SI)

must be either listed or approved by the local code official. The cost involved with custom design makes the process more applicable to chain restaurants, such as quick service, where a specific design may be installed repeatedly. Some single-site establishments may have architectural restrictions that demand a custom solution. Transfer Air. ASHRAE Standard 62.1 specifies the quantity of outdoor air that must be provided to ventilate public spaces, such as dining rooms, in food service establishments. Standard 62.1 allows this ventilation air be reused by transfer from the ventilated public spaces to the kitchen, where it can be used to replace air exhausted by the hood system and assist kitchen comfort. By maximizing transfer of air from adjoining public spaces to the kitchen, the designer is able to minimize the quantity of dedicated outdoor air supplied to the kitchen as replacement air. This can reduce the energy load on the replacement air system, as well as improve thermal comfort in the kitchen. Most quick-service and fast-casual restaurants do not physically segregate the kitchen from the dining room, so conditioned air can be easily transferred from the dining area to the kitchen. In restaurants where the kitchen and dining room are physically segregated, ducts between the two areas may be required for proper flow of replacement air into the kitchen. Transfer fans may be required to overcome duct losses, because the differential pressure between spaces may be very low ( 4 . 2 5 Pa). This design can reduce kitchen replacement air requirements and enhance employee comfort, especially if the kitchen is not air conditioned. Codes may restrict transfer of air from adjoining spaces, other than public dining areas, in buildings such as hospitals. Adjoining spaces should not be overventilated to increase transfer airflow, because the heating and cooling conditions for dining and other public spaces are more energy-intense than for conditioning replacement air introduced directly into the kitchen.

Demand-Controlled Ventilation Demand-controlled ventilation (DCV) refers to any engineered, automated method of modulating (i.e., variable reduction) the amount of air exhausted for a specific cooking operation in response to a part-load or no-load condition. In conjunction with this, the amount of replacement air (consisting of makeup, transfer, and outside air) is also modulated to maintain the same relative air ratios, airflow patterns, and pressurizations. Use of DCV must be accounted for in the design of all involved ventilation systems to create a fully integrated system. Complete capture and containment of all smoke and greasy vapor must be maintained when an exhaust system equipped with DCV is operated at less than 100% of design airflow. Selection of all components, and design of the DCV system, must be such that stable operation can be maintained at all modulated and full-flow conditions. When DCV is used as the method of compliance with ASHRAE Standard 90.1 (section 6.5.7.1.4 part b), it must meet all requirements of that section. The exhaust system configuration and equipment to be served by a DCV system must be evaluated to determine the feasibility and cost benefits resulting from its use. An example of a situation where a DCV system may not be appropriate is when gas-underfred broilers are present. Evaporative Cooling. Direct evaporative coolers are an alternative to mechanical cooling (or, for that matter, no cooling) of replacement air only in dry climates where dehumidification is not required. Indirect evaporative cooling has a wider range in geographical applications. Water costs, availability, and use restrictions should be considered. Heat Recovery from Exhaust Hood Ventilation Air. Hightemperature effluent, often in excess of 200°C, from the cooking equipment mixes with replacement room air, resulting in exhaust air temperatures well over 35°C. It is frequently assumed that this heated exhaust air is suitable for heat recovery; however, over time,

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33.3

Kitchen Ventilation smoke and grease in the exhaust air can foul the heat transfer surfaces. Under these conditions, the heat exchangers require regular maintenance (e.g., automatic washdown) to maintain heat recovery effectiveness and mitigate risk of fre. Because heat recovery systems are expensive, food service facilities with large ventilation rates and relatively light-duty cooking equipment are the best candidates for this equipment. Hospitals are a good example, with large exhaust rates and very low levels of grease production from the cooking equipment. An exhaust hood equipped with heat recovery is more likely to be cost-effective where the climate is extreme. A mild climate is not conducive to use of this conservation measure. Optimized Heating and Cooling Set Points. IMC (ICC 2009a) requires that makeup air be conditioned to within 5.6 K of the kitchen space, except when makeup air is part of the air-conditioning system and does not adversely affect comfort conditions in the occupied space. The exception is important because it allows the design to be optimized to take advantage of the typically lower heating balance points of commercial kitchens. A commercial kitchen may be considered comfortable at temperatures of up to 29°C when space humidity is 160%. During heating seasons, space humidity is typically not an issue if the kitchen exhaust systems are properly designed and operated. During the heating season, space gains from unhooded appliances and radiant gains from hooded appliances, lighting, refrigeration units, and staff make it possible to maintain comfort using lower supply air temperatures. During cooling seasons, in climatic areas that require dehumidification, consideration must be given to all sources that may introduce moisture into commercial kitchens, including internal cooking, holding, and washing as well as local MUA systems or kitchen HVAC systems not designed for continuous dehumidification. Humidity control (160%) allows optimization of cooling set points at higher temperatures while maintaining a comfortable working environment. A dedicated outdoor air system (DOAS) providing conditioned outdoor for kitchen heating, cooling and dehumidification also optimizes set points by using economizer operation when outdoor air alone (no conditioning) can maintain kitchen set points. The use of dedicated outdoor air to heat, cool, and dehumidify outdoor air to control space comfort and humidity and replace air exhausted through the hood has been demonstrated to be an energy-effective design for optimizing heating and cooling set points (Brown 2007). Accordingly, when local MUA systems are used, it is essential that the heating set point of those units not be set higher than the forecasted heatingicooling balance point (e.g., 13°C) to avoid simultaneous replacement air heating and HVAC cooling. It may be more difficult to control comfort when local MUA (e.g., at 13°C) is introduced into a kitchen being heated by a conventional HVAC system introducing kitchen supply air at temperatures 227°C.

Reduced Exhaust and Associated Duct Velocities Tempering outside replacement air can account for a large part of a food service facility’s heating and cooling costs. By reducing exhaust flow rates (and the corresponding replacement air quantity) when little or no product is being cooked, energy cost can be significantly reduced when combined with a DVC system. Field evaluations by one large restaurant chain suggest that cooking appliances may operate under no-load conditions for 75% or more of an average business day (Spata and Turgeon 1995). However, it has been difficult to reduce exhaust flow rates in a retrofit situation because of the minimum duct velocity restriction. National Fire Protection Association (NFPA) Standard 96 had historically required a minimum duct velocity of 7.62 d s . The common belief was that, if duct velocity were lowered, a higher percentage of grease would accumulate on the ductwork, which would then require more frequent duct cleaning. However, no data or research could be identified to support this assumption. Therefore, ASHRAE research project RP-1033 (Kuehn 2000) was undertaken to determine the true effect of duct velocity on grease deposition.

The project analyzed grease deposition as a function of mean duct velocity, using octanoic acid (commonly found in cooking oils and other foods). The results showed that, for design duct velocities below the traditional 7.5 d s threshold, grease deposition was not increased; in fact, in isothermal conditions, as duct velocity decreased, grease deposition on all internal sides of the duct also decreased. These results led to NFPA Standard 96 and the IMC changing their minimum duct velocity requirements from 7.62 mis to 2.54 d s . Another significant finding in the study was that, if there is a large temperature gradient between exhaust air inside the duct and the external duct wall, the rate of grease deposition increases significantly. Therefore, duct insulation should be considered where there are large temperature variations. The primary benefit of these code-approved duct velocity changes is the potential for reduced food service energy consumption. By reducing excessive exhaust airflows, while maintaining necessary capture and containment, energy for fans as well as for heating, cooling andor dehumidifying air that was previously wasted may now be saved. Previously, if a restaurant remodeled their cooking operation and the remodel resulted in reduced exhaust airflows, the owner had to install new, smaller-diameter ductwork to comply with the 7.62 d s duct velocity requirement. This is often too costly, if not also physically impractical. Now, if a system designed for heavy-duty equipment upgrades to more energy-efficient, lighter-duty equipment, exhaust airflows can be reduced without the expense of modifying ductwork. Reduced code-approved duct velocity also facilitates the application of DVC systems with less resistance from local code authorities. From a new-facility design perspective, it is recommended that most kitchens be designed for an in-duct velocity between 7.62 and 9.1 d s . This allows for reducing the airflows to 2.5 mis if needed in the future or as part of a demand-ventilation control strategy.

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SYSTEM INTEGRATION AND DESIGN Ideally, system integration and balancing bring the many ventilation components together to provide the most comfortable, efficient, and economical performance of each component and of the entire system. In commercial kitchen ventilation, the replacement air system(s) must integrate and balance with the exhaust system andor facility HVAC system(s). Even optimal system designs require field testing and balancing once installed. It is important to verify compliance with design, and equally important to c o n f m that the design meets the needs of the operating facility. Air balance is a critical step in any CKV commissioning process. The following fundamentals should be considered and applied to all food service facilities, including restaurants, within the constraints of the particular facility and its location, equipment, and systems.

Principles Although there are exceptions, the following are the fundamental principles of integrating and balancing food service facility systems for both comfort control and economical operation:

zyxwvutsrq In a freestanding building, the overall building should always be slightly positively pressurized (e.g. +1.25 Pa) compared to atmosphere to minimize infiltration of unconditioned andor unfiltered outdoor air. This pressurization helps prevent outdoor contamination such as dust and odors entering the building. In multiple-occupancy buildings, maintain the food preparation areas slightly negative to the dining and other adjacent areas but positive to atmosphere. This requires that the adjacent areas be maintained correspondingly higher to atmosphere. This helps prevent odor migration. Every kitchen should always be slightly negative (-0.25 Pa) to adjacent rooms or areas immediately surrounding it to help contain

201 1 ASHRAE Handbook-HVAC Applications (SI)

33.4 odors in the kitchen and to isolate the kitchen environment from the dining or customer environment. System HVAC design should limit cross-zoning airflow that would allow airflow supplied to food preparation areas being returned and resupplied to customer or other non-food-preparation areas. Odor contamination is an obvious potential problem. In addition, in conditions such as seasonal transitions, when adjacent zones may be in different modes (e.g., economizer versus air conditioning or heating), comfort may be adversely affected. Ideally, the kitchen HVAC system should be separate from all other zones’ HVAC systems. Three situations to consider are the following: During seasonal transitions, the kitchen zone may require air conditioning or may be served by ventilation air only, while dining areas require heating. Even in hot kitchens that may require cooling when the adjacent dining areas require heating, it is still important to maintain the pressure differential between these spaces and continue transfer of heated dining-area air into the kitchen. If dedicated kitchen makeup air is heated, thermostatic control of the heating source should ideally be based on kitchen temperature rather than outside temperature. To limit kitchen personnel discomfort, it is important to control the low-temperature MUA set point and prevent drastic temperature variations between the kitchen space and MUA being introduced. Makeup air heating should be interlocked with kitchen HVAC cooling to prevent simultaneous heating and cooling. HVAC thermostat locations in kitchens must consider the potential conflicting temperatures. Ideally, there should be no perceptible drafts in dining areas, with temperature variations ofno more than 0.6 K. Kitchens might not be draft-free; however, velocities at or near exhaust hoods should be no greater than 0.4 d s . Kitchen comfort is greatly impacted by radiant heat in work areas, but it is desirable to maintain sensible temperatures within 3 K. These conditions can be achieved with even distribution and thorough circulation of air in each zone by an adequate number of registers sized to preclude high air velocities. If there are noticeable drafts or temperature differences, dining customers will be uncomfortable and facility personnel are generally less comfortable and less productive.

with single-hoodductifan systems. Air balance is one of the main challenges. These systems may be designed with bleed ducts andor balancing dampers. These dampers must be listed for this application. Additionally, most filters come in varying sizes to allow pressure loss equalization at varying airflows. Adjustable filters are available, but should not be used when they can be interchanged between hoods or within the same hood, because this interchange can disrupt the previously achieved balance. Balancing can also be accomplished by changing the number andor size of filters in some hoods. In some multitenant installations, the duct design may be completed and installed before the tenants have been identified. In cases such as master kitchen-exhaust systems, which are sometimes used in shopping center food courts, no single group is responsible for the entire design. The base building designer typically lays out ductwork to (or through) each tenant space, and each tenant selects a hood and lays out connecting ductwork. Often, the base building designer has incomplete information on tenant exhaust requirements. Therefore, one engineer must be responsible for defming criteria for each tenant’s design and for evaluating proposed tenant work to ensure that tenant designs match the system’s capacity. The engineer should also evaluate any proposed changes to the system, such as changing tenancy. Rudimentary computer modeling of the exhaust system may be helpful (Elovitz 1992). Given the unpredictability and volatility of tenant requirements, it may not be possible to balance the entire system perfectly. However, without adequate supervision, it is very probable the system will not achieve proper balance. For greatest success with multiple-hood exhaust systems, minimize pressure losses in ducts by keeping velocities low, minimizing sharp transitions, and using hoods with relatively high pressure drops. When pressure loss in the ducts is low compared to the loss through the hood, changes in pressure loss in the ductwork because of field conditions or changes in design airflow have a smaller effect on total pressure loss and thus on actual airflow. Minimum code-required air velocity (2.5 d s ) must be maintained in all parts of the exhaust ductwork at all times. If fewer or smaller hoods are installed than the design anticipated, resulting in low velocity in portions of the ductwork, the velocity must be brought up to the minimum. One way is to introduce outdoor air, preferably untempered, through a bleed duct system directly into the exhaust duct (Figure 1). The bypass duct should connect to the top or sides (at least 50 mm from the bottom) of the exhaust duct to prevent backflow of water or grease through the bypass duct when fans are off. This arrangement is also shown in NFPA Standard 96 and should be discussed with the authority having jurisdiction. A f r e damper is required in the bleed duct, located close to the exhaust duct. Bypass duct construction should be the same as the exhaust duct construction, including enclosure and clearance requirements, for at least a metre beyond the fire damper or as required by the local authority having jurisdiction (AHJ). Means to adjust the

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Both design concepts and operating principles for proper integration and balance are involved in achieving desired results under varying conditions. The same principles are important in almost every aspect of food service ventilation. In restaurants with multiple exhaust hoods, or hoods with demand control systems, exhaust airflow volume may vary throughout the day. Replacement air must be controlled to maintain proper building and kitchen differential pressures to ensure the kitchen remains negative to adjacent areas at all operating points. The more variable the exhaust, or the more numerous and smaller the zones involved, the more complex the design, but the overall pressure relationship principles must be maintained to provide optimum comfort, efficiency, and economy. A different application is a kitchen with one side exposed to a larger building with common or remote dining. Examples are a food court in a mall or a small restaurant in a hospital, airport, or similar building. Positive pressure at the front of the kitchen might cause some cooking grease, vapor, and odors to spread into the common building space, which would be undesirable. In such a case, the kitchen area is held at a negative pressure relative to other common building areas as well as to its own back room storage or office space. Such spaces that include direct-vent appliances, such as gas-fired water heaters, must maintain the pressure required for safe appliance operation.

Multiple-Hood Systems Single kitchen exhaust ductifan systems serving multiple hoods present unique design and balancing challenges not encountered

Fig. 1 Bleed Method of Introducing Outdoor Air Directly into Exhaust Duct (Brohard et al. 2003)

33.5

Kitchen Ventilation bleed airflow must be provided upstream of the f r e damper. All dampers must be in the clean bleed air duct so they are not exposed to grease-laden exhaust air. The difference in pressure between bleed and exhaust air duct may be great; the balancing device must be able to make a fine airflow adjustment against this pressure difference. It is best to provide two balancing devices in series, such as an orifice plate or blast gate for coarse adjustment followed by an opposed-blade damper for fme adjustment. Directly measuring air velocities in the exhaust ductwork to assess exhaust system performance may be desirable. Velocity (pitot-tube) traverses may be performed in kitchen exhaust systems, but holes drilled for the pitot tube must be liquidtight to maintain the fire-safe integrity of the ductwork, per NFPA Standard 96. Holes should never be drilled in the bottom of a duct, where they may collect grease. Velocity traverses should not be performed when cooking is in progress because grease collects on the instrumentation.

Table 1 Recommended Duct Cleaning Schedules Type or Volume of Cooking

Inspection Frequency

Solid fuel High-volume cooking (gas charbroiler or wok cooking) Moderate-volume Low-volume (churches. dav camus. seasonal businesses)

Monthly Quarterly Semiannually Annuallv

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Dynamic Volumetric Flow Rate Effects Minimum exhaust flow rates for kitchen hoods are determined either by laboratory tests or by building code requirements. Energy codes specify maximum airflow rates. In either case, the installed system must ensure proper capture and containment under maximum cooking load conditions. The majority of kitchen exhaust systems use fixed-speed fans, which move the same volume of air at a given speed regardless of air density. Although the air volume remains constant, heat and moisture generated by the cooking process affect mass flow. Exhaust fans for kitchen ventilation systems, like for other hightemperature exhaust processes, must be selected to provide adequate airflow at standard conditions to meet the mass flow needs of the actual cooking process. Testing for hood listing in accordance with UL Standard 710, for example, requires capture and containment testing using actual cooking, with cooking appliance heated to controlled surface temperatures and food product cooked, including flare-ups, to determine airflow. This airflow must be converted to standard air conditions to provide proper design ratings for fan selections.

COOKING EFFLUENT GENERATION AND CONTROL Air quality, fire safety, labor cost, and maintenance costs are important concerns about emissions from a commercial cooking operation. Cooking emissions have also been identified as a major component of smog particulate. This has led to regulation in some major cities, requiring reduction of emissions from specific cooking operations. In a fre, grease deposits in duct act as fuel. Reducing this grease can help prevent a small kitchen f r e from becoming a major structural fre. In the past, the only control of grease build-up in exhaust ducts was frequent duct cleaning, which is expensive and disruptive to kitchen operation. It also depends on frequent duct inspections and regular cleaning. Grease build-up on fans, f r e nozzles, roofs, and other ventilation equipment can be costly in additional maintenance and replacement costs. From an energy and sustainability perspective, it is desirable to reduce the atmospheric emissions and achieve the highest grease extraction or destruction with the lowest energy costs possible. For mechanical extractors, the pressure drop of the filters is the predominant driver for energy usage, whereas for other control systems there may be electrical components or water use that needs to be evaluated. Figure 2 presents some design guidance for what filtration may be desirable under various exhaust temperature andor duty level situations. Another issue that commonly comes up during kitchen design and operation is how often ductwork needs to be cleaned in restaurants. Table 1 presents inspection schedules adapted from Table 11.4 of NFPA Standard 96.

Source: NFPA Standard 96. Table 11.4.

Effluent Generation

During cooking operations on appliances, effluent is generated. This effluent includes water vapor and organic material (in both particulate and vapor form) released from the food. If the energy source for the appliance involves combustion additional contaminants may also be released. Particle Size Comparisons (from Exhaust Systems). Effluent from five types of commercial cooking equipment has been measured under a typical exhaust hood (Kuehn et al. 1999). Foods that emit relatively large amounts of grease were selected. Figures 3A and 3B shows the measured amount of grease in the plume entering the hood above different appliances and the amount in the vapor phase, particles below 2.5 pm in size (PM 2.5), particles less than 10 pm in size (PM lo), and the total amount of particulate grease. Ovens and fryers generate little or no grease particulate emissions, whereas other processes generate significant amounts. However, gas underfred broilers (referred to as “gas broilers” in Figures 3A and 3B) generate much smaller particulates compared to the griddles and ranges, and these emissions depend on the broiler design. The amount of grease in the vapor phase is significant and varies from 30% to over 90% by mass; this affects the design approach for grease removal systems. Carbon monoxide (CO) and carbon dioxide (CO,) emissions are present in solid fuel and natural gas combustion processes but not in processes from electrical appliances. Additional CO and CO, emissions may be generated by gas underfred boilers when grease drippings land on extremely hot surfaces and burn. Nitrogen oxide (NO,) emissions appear to be exclusively associated with gas appliances and related to total gas consumption. Figure 3C shows the measured plume volumetric flow rate entering the hood. In general, gas appliances have slightly larger flow rates than electric because additional products of combustion must be vented. Gas underfred and electric broilers have plume flow rates considerably larger than the other appliances shown. Effluent flow rates from gas underfired and electric broilers are approximately 100 times larger than the actual volumetric flow rate created by vaporizing moisture and grease from food. The difference is caused by ambient air entrained into the effluent plume before it reaches the exhaust hood.

Thermal Plume Behavior The most common method of contaminant control is to install an air inlet device (a hood) where the plume can enter it and be conveyed away by an exhaust system. The hood is generally located above or behind the heated surface to intercept normal upward flow. Understanding plume behavior is central to designing effective ventilation systems. Effluent released from a noncooking cold process, such as metal grinding, is captured and removed by placing air inlets so that they catch forcibly ejected material, or by creating airstreams with sufficient velocity to induce the flow of effluent into an inlet. This technique has led to an empirical concept of capture velocity that is often misapplied to hot processes. Effluent (such as grease and smoke from cooking) released from a hot process and contained in a plume may be captured by locating an inlet hood so that the plume flows into it by buoyancy. Hood exhaust rate must equal or slightly exceed plume volumetric flow rate, but the hood need

201 1 ASHRAE Handbook-HVAC Applications (SI)

33.6

Fig. 2

Typical Filter Guidelines Versus Appliance Duty and Exhaust Temperature

not actively induce capture of the effluent if the hood is large enough at its height above the cooking operation to encompass the plume as it expands during its rise. Additional exhaust airflow may be needed to resist cross currents that carry the plume away from the hood. A heated plume, without cross currents or other interference, rises vertically, entraining additional air, which causes the plume to enlarge and its average velocity and temperature to decrease. If a surface parallel to the plume centerline (e.g., a back wall) is nearby, the plume will be drawn toward the surface by the Coanda effect. This tendency may also help direct the plume into the hood. Figure 4 illustrates a heated plume with and without cooking effluent as it rises from heated cooking appliances. Figure 4A shows two gas underfired broilers cooking hamburgers under a wall-mounted, exhaust-only, canopy hood. Note that the hood is mounted against a clear back wall to improve experimental observation. Figures 4B and 4C show the hot-air plume without cooking, visualized using a schlieren optical system, under full capture and spillage conditions, respectively.

Effluent Control Effluents generated by cooking include grease in particulate (solid or liquid) and vapor states, smoke particles, and volatile

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Fig. 3A Grease in Particulate and Vapor Phases for Commercial Cooking Appliances with Total Emissions Less Than 50 kg/lOOO kg of Food Cooked

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Kitchen Ventilation organic compounds (VOCs or low-carbon aromatics, which are significant contributors to odor). Grease vapor is condensable and may condense into grease particulate in the exhaust airstream when diluted with room-temperature air or when it is exhausted into the cooler outdoor atmosphere. Effluent controls in the vast majority of kitchen ventilation systems are limited to removing solid and liquid grease particles by mechanical grease removal devices in the hood. More effective devices reduce grease build-up downstream of the hood, lowering the frequency of duct cleaning and reducing the f r e hazard. The reported grease extraction efficiency of mechanical filtration systems (e.g., baffle filters and slot cartridge filters) may reflect the particulate removal performance of these devices. These devices are listed for their ability to limit flame penetration into the plenum and duct. Grease extraction performance can be evaluated using ASTM Standard F2519. Smaller aerodynamic particles (150°C) electric power production, intermediate- and low-temperature ( 4 50°C) direct-use applications, and ground-source heat pump applications (generally 50 mgikg at 93"C, titanium would be used. At lower temperatures, much higher chloride exposure can be tolerated (see Figure 4). Downhole Heat Exchangers. The downhole heat exchanger (DHE) is an arrangement of pipes or tubes suspended in a wellbore (Culver and Reistad 1978). A secondary fluid circulates from the load through the exchanger and back to the load in a closed loop. The primary advantage of a DHE is that only heat is extracted from the earth, which eliminates the need to dispose of spent fluids. Other advantages are the elimination of (1) well pumps with their initial operating and maintenance costs, (2) the potential for depletion of groundwater, and (3) environmental and institutional restrictions on surface disposal. One disadvantage of a DHE is the limited amount of heat that can be extracted from or rejected to the well. The amount of heat extracted depends on the hydraulic conductivity of the aquifer and well design. Because of the limitations of natural convection, only about 10% of the heat output of the well is available from a DHE in comparison to pumping and using surface heat exchange (Reistad et al. 1979). With wells of approximately 95°C and depths of 150 m, output under favorable conditions is sufficient to serve the needs of up to five homes. The DHE in low- to moderate-temperature geothermal wells is installed in a casing, as shown in Figure 5. Downhole heat exchangers with higher outputs rely on water circulation within the well, whereas lower-output DHEs rely on earth conduction. Circulation in the well can be accomplished by two methods: (1) undersized casing and (2) convection tube. Both methods rely on the difference in density between the water surrounding the DHE and that in the aquifer. Circulation provides the following advantages: Water circulates around the DHE at velocities that, in optimum conditions, can approach those in the shell of a shell-and-tube exchanger. Hot water moving up the annulus heats the upper rocks and the well becomes nearly isothermal.

Some of the cool water, being denser than the water in the aquifer, slnks into the aquifer and is replaced by hotter water, which flows up the annulus. Figure 5 shows well construction in competent formation (i.e., where the wellbore will stand open without a casing). An undersized casing with perforations at the lowest producing zone (usually near the bottom) and just below the static water level is installed. A packer near the top of the competent formation allows installation of an annular seal between it and the surface. When the DHE is installed and heat extracted, thermosiphoning causes cooler water inside the casing to move to the bottom, and hotter water moves up the annulus outside the casing. Because most DHEs are used for space heating (an intermittent operation), heated rocks in the upper portion of the well store heat for the next cycle. Where the well will not stand open without casing, a convection tube can be used. This is a pipe one-half the diameter of the casing either hung with its lower end above the well bottom and its upper end below the surface or set on the bottom with perforations at the bottom and below the static water level. If a U-bend DHE is used, it can be either inside or outside the convection tube. DHEs operate best in aquifers with a high hydraulic conductivity and that provide water movement for heat and mass transfer.

Valves In large (>65 mm) pipe sizes, resilient-lined butterfly valves are preferred for geothermal applications. The lining material protects the valve body from exposure to the geothermal fluid. The rotary rather than reciprocating motion of the stem makes the valve less susceptible to leakage and build-up of scale deposits. For many direct-use applications, these valves are composed of Buna-N or EPDM seats, stainless steel shafts, and bronze or stainless steel disks. Where oil-lubricated well pumps are used, a seat material of oil-resistant material is recommended. Gate valves have been used in some larger geothermal systems but have been subject to stem leakage and seizure. After several years of use, they are no longer capable of 100% shutoff.

Piping

Fig. 5

Typical Connection of Downhole Heat Exchanger for Space and Domestic Hot-Water Heating (Reistad et al. 1979)

Piping in geothermal systems can be divided into two broad groups: pipes used inside buildings and those used outside, typically buried. Indoor piping carrying geothermal water is usually limited to the mechanical room. Carbon steel with grooved end joining is the most common material. For buried piping, many existing systems use some form of nonmetallic piping, particularly asbestos cement (which is no longer available) and glass fiber. With the cost of glass fiber for larger sizes (>150 mm) sometimes prohibitive, ductile iron is frequently used. Available in sizes >50 mm, ductile iron offers several positive characteristics: low cost, familiarity to installation crews, and wide availability. It requires no allowances for thermal expansion if pushon fittings are used. Most larger-diameter buried piping is preinsulated. The basic ductile iron pipe is surrounded by a layer of insulation (typically polyurethane), which is protected by an outer jacket of PVC or PE. Standard ductile iron used for municipal water systems is sometimes modified for geothermal use. The seal coat used to protect the cement lining of the pipe is not suitable for the temperature of most geothermal applications; in applications where the geothermal water is especially soft or low in pH, the cement lining should be omitted, as well. Special high-temperature gaskets (usually EPDM) are used in geothermal applications. Few problems have been encountered in using ferrous piping with low-temperature geothermal fluids unless high chloride concentration, low (35 kW) and in areas with high electric rates and high cooling requirements (>2000 full-load hours) would this type of equipment offer an attractive investment to the owner (Rafferty 1989a).

INDUSTRIAL APPLICATIONS Design philosophy for the use of geothermal energy in industrial applications, including agricultural facilities, is similar to that for space conditioning. However, these applications have the potential for much more economical use of the geothermal resource, primarily because they (1) operate year-round, which gives them greater load factors than possible with space-conditioning applications; (2) do not require extensive (and expensive) distribution to dispersed energy consumers, as is common in district heating; and (3) often require various temperatures and, consequently, may be able to make greater use of a particular resource than space conditioning, which is restricted to a specific temperature. In the United States, the primary non-space-heating applications of direct-use geothermal resources are dehydration (primarily vegetables), gold mining, and aquaculture.

GROUND-SOURCE HEAT PUMPS Ground-source heat pumps were originally developed in the residential arena and are now widely applied in the commercial sector. Many of the installation recommendations and design guides appropriate to residential design must be amended for large buildings. Kavanaugh and Rafferty (1997) provide a more complete overview of design of ground-source heat pump systems. Kavanaugh (1991) and OSU (1988a, 1988b) provide a more detailed treatment of the

201 1 ASHRAE Handbook-HVAC

34.10 design and installation of ground-source heat pumps, but their focus is primarily residential and light commercial applications. Comprehensive coverage of commercial and institutional design and construction of ground-source heat pump systems is provided in CSA Standard C448.2.

TERMINOLOGY The term ground-source heat pump (GSHP) is applied to a variety of systems that use the ground, groundwater, or surface water as a heat source and sink. The general terms include groundcoupled (GCHP), groundwater (GWHP), and surface-water (SWHP) heat pumps. Many parallel terms exist [e.g., geothermal heat pumps (GHP), geo-exchange, and ground-source (GS) systems] and are used to meet a variety of marketing or institutional needs (Kavanaugh 1992). See Chapter 8 ofthe 2008 ASHRAE Handbook-HVAC Systems and Equipment for a discussion of the merits of various other nongeothermal heat sourcesislnks. This chapter focuses primarily on the ground-loop portion of GSHP systems, although the heat pump units used in these systems are unique to GSHP technology as well. GSHP systems typically use extended-range water-source heat pump units, in most cases of water-to-air configuration. Extended-range units are specifically designed for operation at entering water temperatures between -5°C in heating mode and 40°C in cooling mode. Units not meeting the extended-range criteria are not suitable for use in GSHP systems. Some applications can include a free-cooling mode when waterloop temperatures fall near or below 13°C. This includes groundwater loops, deep-surface-water loops, and interior core zones of ground-coupled loops when perimeter zones require heating. This is typically accomplished by inserting a water coil in the return air stream before the refrigerant coil.

Ground-Coupled Heat Pump Systems The GCHP is a subset of the GSHP and is often called a closedloop heat pump. A GCHP system consists of a reversible vapor compression cycle that is llnked to a closed ground heat exchanger buried in soil (Figure 9). The most widely used unit is a water-to-air heat pump, which circulates a water or a wateriantifreeze solution

Applications (SI)

zyxwvuts through a liquid-to-reftigerant heat exchanger and a buried thermoplastic piping network. Heat pump units often include desuperheater heat exchangers (shown on the left in Figure 9). These devices use hot refrigerant at the compressor outlet to heat water. A second type of GCHP is the direct-expansion (DX) GCHP, which uses a buried copper piping network through which reftigerant is circulated. The GCHP is further subdivided according to ground heat exchanger design: vertical and horizontal. Vertical GCHPs (Figure 10) generally consist of two small-diameter, high-density polyethylene (HDPE) tubes placed in a vertical borehole that is subsequently filled with a solid medium. The tubes are thermally fused at the bottom of the bore to a close return U-bend. Vertical tubes range from 20 to 40 mm nominal diameter. Bore depths range from 15 to 180 m, depending on local drilling conditions and available equipment. Boreholes are typically 100 to 150 mm in diameter. To reduce thermal interference between individual bores, a minimum borehole separation distance of 6 m is recommended when loops are placed in a grid pattern. This distance may be reduced when bores are placed in a single row, the annual ground load is balanced (i.e., energy released in the ground is approximately equal to the energy extracted on an annual basis), or water movement or evaporation and subsequent recharge mitigates the effect of heat build-up in the loop field. Advantages of the vertical GCHP are that it (1) requires relatively small plots of ground, (2) is in contact with soil that varies very little in temperature and thermal properties, (3) requires the smallest amount of pipe and pumping energy, and (4) can yield the most efficient GCHP system performance. Disadvantages are (1) typically higher cost because of expensive equipment needed to drill the borehole and (2) the limited availability of contractors to perform such work. Hybrid systems are a variation of ground-coupled systems in which a smaller ground loop is used, augmented in cooling mode by a fluid cooler or a cooling tower. This approach can have merit in large cooling-dominated applications. The ground loop is sized to meet the heating requirements. The downsized loop is used in conjunction with the fluid cooler or cooling tower with an isolation heat

Fig. 9 Vertical Closed-Loop Ground-Coupled Heat Pump System (Kavanaugh 1985)

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Fig. 10 Vertical Ground-Coupled Heat Pump Piping

34.11

Geothermal Energy exchanger to meet the heat rejection load. Using the cooler reduces the capital cost of the ground loop in such applications, but somewhat increases maintenance requirements. For heavily heatingdominant applications, a downsized loop also can be augmented with an auxiliary heat source such as electric resistance, solar collectors, or fossil fuel. Horizontal GCHPs (Figure 11) canbe dividedinto several subgroups, including single-pipe, multiple-pipe, spiral, and horizontally bored. Single-pipe horizontal GCHPs were initially placed in narrow trenches at least 1.2 m deep. These designs require the greatest amount of ground area. Multiple pipes (usually two, four, or six), placed in a single trench, can reduce the amount of required ground area. Trench length is reduced with multiple-pipe GCHPs, but total pipe length must be increased to overcome thermal interference from adjacent pipes. The spiral coil is reported to further reduce required ground area. These horizontal ground heat exchangers are made by stretching small-diameter polyethylene tubing from the tight coil in which it is shipped into an extended coil that can be placed vertically in a narrow trench or laid flat at the bottom of a wide trench. Recommended trench lengths are much shorter than those of single-pipe horizontal GCHPs, but pipe lengths must be much longer to achieve equivalent thermal performance. When horizontally bored loops are grouted and placed in the deep earth, as shown in Figure 11, design lengths are near those for vertical systems, because annual temperature and moisture content variations approach deep-earth values. Advantages of horizontal GCHPs are that (1) they are typically less expensive than vertical GCHPs because relatively low-cost installation equipment is widely available, (2) many residential applications have adequate ground area, and (3) trained equipment

Fig. 11 Trenched Horizontal and Horizontally Bored Ground-Coupled Heat Pump Piping

operators are more widely available. Disadvantages include, in addition to a larger ground area requirement, (1) greater adverse variations in performance because ground temperatures and thermal properties fluctuate with season, rainfall, and burial depth; (2) slightly higher pumping-energy requirements; and (3) lower system efficiencies. OSU (1988a, 1988b) and Svec (1990) cover the design and installation of horizontal GCHPs.

Groundwater Heat Pump Systems The second subset of GSHPs is groundwater heat pumps (Figure 12). Until the development of GCHPs, they were the most widely used type of GSHP. In the commercial sector, GWHPs can be an attractive alternative because large quantities of water can be delivered from and returned to relatively inexpensive wells that require very little ground area. Whereas the cost per unit capacity of the ground heat exchanger is relatively constant for GCHPs, the cost per unit capacity of a well water system is much lower for a large GWHP system. A single pair of high-volume wells can serve an entire building. Properly designed groundwater loops with correctly developed water wells require no more maintenance than conventional air and water central HVAC. When groundwater is injected back into the aquifer by a second well, net water use is zero. One widely used design places a central water-to-water heat exchanger between the groundwater and a closed water loop, which is connected to water-to-air heat pumps located in the building. A second possibility is to circulate groundwater through a heat recovery chiller (isolated with a heat exchanger), and to heat and cool the building with a distributed hydronic loop. Both types and other variations may be suited for direct preconditioning in much of the United States. Groundwater below 15°C can be circulated directly through hydronic coils in series or in parallel with heat pumps. The cool groundwater can displace a large amount of energy that would otherwise have to be generated by mechanical refrigeration. Advantages of GWHPs under suitable conditions are (1) they cost less than GCHP equipment, (2) the space required for the water well is very compact, (3) water well contractors are widely available, and

Fig. 12 Unitary Groundwater Heat Pump System

z

201 1 ASHRAE Handbook-HVAC

34.12 (4) the technology has been used for decades in some of the largest commercial systems. Disadvantages are that (1) local environmental regulations may be restrictive, (2) water availability may be limited, (3) fouling precautions may be necessary if groundwater is used directly in the heat pumps and water quality is poor, and (4) pumping energy may be high if the system is poorly designed or draws from a deep aquifer.

Surface Water Heat Pump Systems Surface water heat pumps have been included as a subset of GSHPs because of the similarities in applications and installation methods. SWHPs can be either closed-loop systems similar to GCHPs or open-loop systems similar to GWHPs. However, the thermal characteristics of surface water bodies are quite different than those of the ground or groundwater. Some unique applications are possible, though special precautions may be warranted. Closed-loop SWHPs (Figure 13) consist of water-to-air or waterto-water heat pumps connected to a piping network placed in a lake, river, or other open body of water. A pump circulates water or a wateriantifreeze solution through the heat pump water-to-refrigerant heat exchanger and the submerged piping loop, which transfers heat to or from the body of water. The recommended piping material is thermally fused HDPE tubing with ultraviolet (UV) radiation protection. Advantages of closed-loop SWHPs are (1) relatively low cost (compared to GCHPs) because of reduced excavation costs, (2) low pumping-energy requirements, (3) low maintenance requirements, and (4) low operating cost. Disadvantages are (1) the possibility of coil damage in public lakes and (2) wide variation in water temperature with outdoor conditions if lakes are small andor shallow. Such variation in water temperature would cause undesirable variations in efficiency and capacity, though not as severe as with air-source heat pumps. Open-loop SWHPs can use surface water bodies the way cooling towers are used, but without the need for fan energy or frequent maintenance. In wann climates, lakes can also serve as heat sources during winter heating mode, but in colder climates where water temperatures drop below 7"C, closed-loop systems are the only viable option for heating. Lake water can be pumped directly to water-to-air or water-towater heat pumps or through an intermediate heat exchanger that is connected to the units with a closed piping loop. Direct systems tend to be smaller, having only a few heat pumps. In deep lakes (12 m or more), there is often enough thermal stratification throughout the

Applications (SI)

year that direct cooling or precooling is possible. Water can be pumped from the bottom of deep lakes through a coil in the return air duct. Total cooling is possible if water is 10°C or below. Precooling is possible with wanner water, which can then be circulated through the heat pump units. Large-scale cooling-only systems have been deployed successfully in some locations, including Cornell University and the city ofToronto [Cornell University 2006; Enwave (no date)].

z

Site Characterization Site characteristics influence the type of GSHP system most suitable for a particular location. Site characterization is the evaluation of a site's geology and hydrogeology with respect to its effect on GSHP system design. Important issues include presence or absence of water, depth to water, water (or soilirock) temperature, depth to rock, rock type, and the nature and thickness of unconsolidated materials overlying the rock. Information about the nature of water resources at the site helps to determine whether an open-loop system may be possible. Depth to water affects pumping energy for an open-loop system and possibly the type of rig used for drilling closed-loop boreholes. Groundwater temperature in most locations is the same as the undisturbed ground temperature. These temperatures are key inputs to the design of GSHP systems. The types of soil and rock allow a preliminary evaluation of the range of thermal conductivity/diffusivity that might be expected. The thickness and nature of the unconsolidated (soil, gravel, sand, clay, etc.) materials overlying the rock influence whether casing is required in the upper portion of boreholes for closed-loop systems, a factor which increases drilling cost. After the GSHP system type has been decided, specific details about the subsurface materials' (rockisoil) thermal conductivity and diffusivity, water well static and pumping levels, drawdown, etc., are necessary to design the system. Ways to obtain these more detailed data are discussed in other parts of this chapter. There are many sources for gathering site characterization information, such as geologic and hydrologic maps, state geology and water regulatory agencies, the U.S. Geological Survey (USGS 2000), and any information that may be available from geotechnical studies of the site. Among the best sources of information are completion reports for nearby water wells. These reports are filed by the driller upon completion of a water well and provide a great deal of information of interest for both open- and closed-loop designs. The most thorough versions of well completion reports (level of detail varies by state) cover all of the issues of interest listed at the beginning of this section. Information about access to and interpretation of these reports and other sources of information for site characterization is included in Rafferty (2000a) and Sachs (2002). Once the type of system has been selected, more site-specific tests (ground thermal properties test for GCHP or well flow test for GWHP) can be used to determine the parameters necessary for system design.

zyxwv

Commissioning GSHP Systems

Fig. 13 Lake Loop Piping

The design phase of GSHP commissioning requires a thorough site survey and characterization, accurate load modeling, and ensuring that the design chosen (and its documentation) meets the design intent. The construction phase is dominated by observation of installation and verification of prefunctional checks and tests. It also involves planning, training development, and other activities to help future building operators understand the HVAC system. The acceptance phase starts with functional tests and verification of all test results. It continues with full documentation: completing the commission report to include records of design changes and all as-built plans and documents, and completing the operations and maintenance manual and system manual. Finally, after system testing and balancing is complete, the owner's operating staff are

34.13

Geothermal Energy

zyxwvutsr

Table 3 Example of GSHP Commissioning Process for Mechanical Design System

Function

Performed By

Witnessed BY

Heat pump piping Ground source piping Pumps Heat recovery unit

Pressure test, clean, and fill Pressure test, clean, fill, and purge air Inspect, test, and start up Inspect, test, and start up; provide clean set of filters, staff instruction Inspect, test, and start up; provide clean filters, staff instruction Flushing and cleaning, chemical treatment, staff instruction

Contractor

ME

Contractor Contractor Contractor Manufacturer Contractor Manufacturer Manufacturer Contractor Manufacturer Contractor Contractor/ manufacturer Manufacturer TAB contractor TAB contractor TAB contractor Contractor CA CA CA

ME

Heat pump units Chemical treatment

Balancing

Controls

Balancing, spot checking, follow-up site visits Installation/commissioning, staff instruction, performance testing, seasonal testing

Source: Caneta (2001). ME = Architectlengineer

CA ~

CMowner ~

~

CMowner ME and CA ~

CMowner ~

ME and CA CA

7. Conduct site survey to determine ground thermal properties and drilling conditions (see following recommendations). 8. Determine and evaluate possible loop field arrangements that are likely to be optimum for the building and site (bore depth, separation distance, completion methods, annulus groutifill, and header arrangements); include subheader circuits (typically 5 to 15 U-tubes on each) with isolation valves to allow air and debris flushing of sections of loop field through a set of full-port purge valves. 9. Determine optimum ground heat exchanger dimensions with Equations (2) to (5) or software; one or more alternatives (depth, number of bores, groutifill material, etc.) that provide equivalent performance may yield more competitive bids. 10. Iterate to determine optimum operating temperatures, flows, loop field arrangement, depth, bores, groutifill materials, etc. 11. Lay out interior piping and compute head loss through critical path. 12. Select pumps and control method, determine system efficiency, and consider modifying water distribution system if pump demand exceeds 8% of the system total demand or air distribution system if fan demand exceeds 12% of the system total.

Documents necessary to adequately describe a GCHP installation include, as a minimum,

~

CMowner

Heat pump specifications at rated conditions

~

~

Pump(s) specifications, expansion tank size, and air separator zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA

CA = Commissioning authority TAB = Testing, adjusting, and balancing

trained. The acceptance phase ends when “substantial completion” is reached. The warranty period begins from this date. Table 3 provides information on tasks and participants involved in the GSHP commissioning process. Additional details on this topic, along with preventive maintenance and troubleshooting information, are included in Caneta (2001).

GROUND-COUPLED HEAT PUMPS Vertical Design This section provides an overview of a suggested design procedure; related information and equations are discussed in more detail in Kavanaugh and Rafferty (1997). Several public software programs are available for performing the repetitive computations necessary for system optimization. Shonder et al. (1999, 2000) tested the accuracy of these programs and found that only one program matched the results of field-measured data in the initial test. However, closer agreement was attained with several programs in subsequent evaluations. A more recent publication (Kavanaugh 2008) updates the design recommendations for GCHP systems: 1. Calculate peak zone cooling and heating loads, and estimate off-peak loads. 2. Estimate annual heat rejection into and absorption from loop field to account for potential ground temperature change (see Tables 7 and 8). 3. Select preliminary loop operating temperatures and flow rate to begin optimization of first cost and efficiency (selecting temperatures near normal ground temperature results in high efficiencies but larger and more costly ground loops). 4. Correct heat pump performance at rated conditions to actual design conditions (see Table 13). 5. Select heat pumps to meet cooling and heating loads, and locate units to minimize duct cost and fan power and noise. 6. Arrange heat pump into ground loop circuits to minimize system cost, pump energy and electrical demand (see Figures 18 to 20).

Fluid specifications: system volume, Inhibitors, antifreeze concentration (if required), water quality, etc. Design operating conditions: entering and leaving ground loop temperatures, return air temperatures (including wet bulb in cooling), airflow rates, and liquid flow rates Pipe header details with ground loop layout, including pipe diameters, spacing, and clearance from building and ut Bore depth and approximate bore diameter Piping material specifications, and visual inspection and pressure testing requirements Groutifill specifications: thermal conductivity and acceptable placement methods to eliminate voids Purge provisions and flow requirements to ensure removal of air and debris without reinjecting air when switching to adjacent subheader circuits Instructions on connecting to building loop(s) and coordinating building and ground loop flushing Sequence of operation for controls In the design of vertical GCHPs, accurate knowledge of soilirock formation thermal properties is critical. These properties can be estimated in the field by installing a loop of approximately the same size and depth as the heat exchangers planned for the site. Heat is added in a water loop at a constant rate, and data are collected as shown in Figure 14. Inverse methods are applied to find thermal conductivity, diffusivity, and temperature of the formation. These methods are based on the either the line source (Gehlin 1998; Mogensen 1983; Witte et al. 2002), the cylindrical heat source (Ingersoll and Zobel 1954), or a numerical algorithm (Austin et al. 2000; Shonder and Beck 1999; Spitler et al. 1999). More than one of these methods should be applied, when possible, to enhance reported accuracy. Recommended test specifications are as follows (Kavanaugh 2000,2001): Thermal property tests should be performed for 36 to 48 h. Heat rate should be 50 to 80 Wim of bore, which are the expected peak loads on the U-tubes for an actual heat pump system. Standard deviation of input power should be less than *1.5% of the average value and peaks less than *lo% of average, or resulting temperature variation should be less than *0.3 K from a straight trend line of a log (time) versus average loop temperature.

zyxwvu

201 1 ASHRAE Handbook-HVAC

34.14

Applications (SI)

The method of Ingersoll and Zobel(l954) can be used to handle these shorter-term variations. It uses the following steady-state heat transfer equation:

where q L

= =

tg = tw =

R

=

zyxw

heat transfer rate, kW required bore length, m ground temperature, "C liquid temperature, "C effective thermal resistance of ground, (mK)/kW

The equation is rearranged to solve for the required bore length L. The steady-state equation is modified to represent the variable heat rate of a ground heat exchanger by using a series of constantheat-rate "pulses." Thermal resistance of the ground per unit length is calculated as a function of time corresponding to the time span over which a particular heat pulse occurs. A term is also included to account for thermal resistance of the pipe wall and interfaces between the pipe and fluid and the pipe and the ground. The resulting equation takes the following form for cooling:

zyxwvuts zyxwvutsrqpon Fig. 14 Thermal Properties Test Apparatus

Accuracy of temperature measurement and recording devices should be *0.3 K. Combined accuracy of the power transducer and recording device should be *2% of the reading. Flow rates should be sufficient to provide a differential loop temperature of 3.7 to 7.0 K. This is the temperature differential for an actual heat pump system. A waiting period of five days is suggested for low-conductivity soils [ k < 1.7 W/(m.K)] after the ground loop has been installed and grouted (or filled) before the thermal conductivity test is initiated. A delay of three days is recommended for higherconductivity formations [ k > 1.7 W/(m.K)]. The initial ground temperature measurement should be made at the end of the waiting period by directly inserting a probe inside a liquid-filled ground heat exchanger at three locations, representing the average, or by temperature measurement as liquid exits the loop during the period immediately after start-up. Data collection should be at least once every 10 min. All aboveground piping should be insulated with a minimum of 13 mm closed-cell insulation or equivalent. Test rigs should be enclosed in a sealed cabinet that is insulated with a minimum of 25 mm fiberglass insulation or equivalent. If retesting a bore is necessary, loop temperature should be allowed to return to within 0.3 K of the pretest initial ground temperature. This typically requires a 10 to 12 day delay in mid- to high-conductivity formations and 14 days in low-conductivity formations if a comnlete 48 h test has been conducted. Waitinnv periods can be proportionally reduced if tests were shorter.

The required length for heating is

where F,, = short-circuit heat loss factor L, = required bore length for cooling, m L, = required bore length for heating, m PLF, = part-load factor during design month qa = net annual average heat transfer to ground, kW qlc =building design cooling block load, kW qlh =building design heating block load, kW Rga = effective thermal resistance of ground (annual pulse),(mK)/kW Rgd = effective thermal resistance of ground (peak daily pulse: 1 h minimum, 4 to 6 h recommended), (mK)/kW R, = effective thermal resistance of ground (monthly pulse), (mK)/kW R, =thermal resistance ofbore, (mK)/kW tg =undisturbed ground temperature, "C =temperature penalty for interference of adJacent bores, "C tm = liquid temperature at heat pump inlet, "C t,,,, = liquid temperature at heat . pump . outlet, "C W, = system power input at design cooling load, kW W, = system power input at design heating load, kW

zyxw zyxwvu

The ground-loop design method uses a limited amount of information from commercial systems. A major missing component is long-term, field-monitored data, which are needed to further validate the design method so that the effects of water movement and long-term heat storage are more fully addressed. The conservative designer can assume no benefit from water movement; designers who assume maximum benefit must ignore annual imbalances in heat rejection and absorption. One design method is based on the solution of the equation for heat transfer from a cylinder buried in the earth. This equation was developed and evaluated by Carslaw and Jaeger (1947) and was suggested by Ingersoll and Zobel (1954) as an appropriate method of sizing ground heat exchangers. Kavanaugh (1985) adjusted the method to account for the U-bend arrangement and hourly heat rate variations. Alternative design methods are described by Eskilson (1987), Morrison (1997), Spitler (2000), and Spitler et al. (2000).

6

Note: Heat transfer rate, building loads, and temperature penalties are positive for heating and negative for cooling.

Equations (2) and (3) consider three different pulses of heat to account for long-term heat imbalances qa, average monthly heat rates during the design month, and maximum heat rates for a shortterm period during a design day. This period could be as short as 1 h, but a 4 to 6 h block is recommended. The required bore is the larger of the two lengths L, and Lh found from Equations (2) and (3). If L, is larger than Lh, an oversized coil could be beneficial during the heating season. A second option is to install the smaller heating length along with a cooling tower to compensate for the undersized coil. If Lh is larger, the designer should

34.15

Geothermal Energy Table 4

zyxwvuts zyxwvutsrq zy

Summary of Potential Completion Methods for Different Geological Regime Types Grout

0.6 < k s 1.4 W/(m.K)

Geological Regime Type

Clay or low-permeability rock, no aquifer single-aquifer multiple-aquifer Permeable rock, no shallow aquifers single-aquifer multiple-aquifers Karst terrains with secondarv oermeabilitv Fractured terrains with secondary permeability

Two-Fill with

1.4 < k s 2.1 W/(m.K)

k > 2.1 W/(m.K)

Yes Yes Yes

Yes Yes Yes

Yes

Yes

Yes Yes Yes

Yes Yes Yes Yes Yes

Yes Yes Yes Yes Yes

Yes Yes Yes Yes Yes

Yes Yes

Yes Yes

~

~

Yes ~

Backfill Cuttings Below Other" Below with Cutting Aquifers Aquifers

Yes

~

~ ~

zyxwvutsrqp ~

~

~

~

*Use ofbackfill material that has thermal conductivity o f k 2 2.4 W/(m.K)

install this length, and during cooling mode the efficiency benefits of an oversized ground coil could be used to compensate for the higher first cost. Selection of the fill material for the borehole is a function of thermal, regulatory, and economic considerations. Historically, a relatively low-thermal-conductivity bentonite grout commonly used in the water well industry and, in some cases, drill cuttings have been used as fill. More recently, thermally enhanced materials have been developed. Nutter et al. (2001) contains a detailed evaluation of potential fills and grouts for vertical boreholes. Table 4 summarizes potential completion methods for various geological conditions. "Two-fill" refers to the practice of placing a low-permeability material in the upper portion of the hole andor in intervals where it is required to separate individual aquifers, and a more thermally advantageous material in the remaining intervals. Thermal resistance of the ground is calculated from ground properties, pipe dimensions, and operating periods of the representative heat rate pulses. Table 5 lists typical thermal properties for soils and fills for the annular region ofthe bore holes. Table 6 gives equivalent thermal resistance of the vertical high-density polyethylene (HDPE) U-tubes for two bore hole diameters db. Alternative methods of computing the thermal borehole resistance are presented by Bernier (2006), Hellstrom (1991), and Remund (1999). The most difficult parameters to evaluate in Equations (2) and (3) are the equivalent thermal resistances of the ground. The solutions of Carslaw and Jaeger (1947) require that the time of operation, bore diameter, and thermal diffusivity of the ground be related in the dimensionless Fourier number (Fo):

Yes

=

~

~

Yes

Yes

Recommended potentially viable backfill methods

Table 5

Thermal Properties of Selected Soils, Rocks, and Bore Grouts/Fills Dry Density, Conductivity, kg/m3 W/(m.K)

soils Heavy clay, 15% water 5% water Light clay, 15% water 5% water Heavy sand, 15% water 5% water Light sand, 15% water 5% water Rocks Granite Limestone Sandstone Shale, wet k Y

Diffusivity, m2/day

1925 1925 1285 1285 1925 1925 1285 1285

1.4 to 1.9 1.0 to 1.4 0.7 to 1.0 0.5 to 0.9 2.8 to 3.8 2.1 to 2.3 1.0 to 2.1 0.9 to 1.9

0.042 to 0.061 0.047 to 0.061 0.055 to 0.047 0.056 to 0.056 0.084 to 0.1 1 0.093 to 0.14 0.047 to 0.093 0.055 to 0.12

2650 2400 to 2800

2.3 to 3.7 2.4 to 3.8 2.1 to 3.5 1.4 to 2.4 1.0 to 2.1

0.084 to 0.13 0.084 to 0.13 0.65 to 0.1 1 0.065 to 0.084 0.055 to 0.074

2570 to 2730

Grouts/Backfills Bentonite (20 to 30% solids) Neat cement (not recommended) 20% bentonite/80% SiO, sand 15% bentonite/85% SiO, sand 10% bentonite/90% SiO, sand 30% concrete/70% SiO? sand, s. plasticizer

0.73 to 0.75 0.69 to 0.78 1.47 to 1.64 1.00 to 1.10 2.08 to 2.42 2.08 to 2.42

Source: Kavanaugh and Rafferty (1997).

Table 6 Thermal Resistance of Bores R, for High-Density Polyethylene U-Tube Vertical Ground Heat Exchangers

where ag = thermal diffusivity of the ground, m2/day 7 = time of operation, days db = bore diameter, m

The method may be modified to permit calculation of equivalent thermal resistances for varying heatpulses. A system can be modeled by three heat pulses, a 10 year (3650 day) pulse of qa, a 1 month (30 day) pulse of qm, and a 6 h (0.25 day) pulse of qd Three times are defined as 71 = 3650 days Tf

150 mm Diameter Bore

100 mm Diameter Bore 0.86 1.73 2.60

0.86

1.73

2.60

0.33 0.29 0.26

0.40 0.35 0.31

0.19 0.17 0.16

0.14 0.12 0.10

z

zyxwvutsr

+ 30 = 3680 days = 3650 + 30 +0.25 = 3680.25 days

T~ = 3650

Bore Fill Conductivity,* W/(m.K) U-Tube Diameter, mm

The Fourier number is then computed with the following values: Fof =4a.rfld;

20 25 30

0.16 0.14 0.14

0.10 0.10 0.08

*Based on DR 11, HDPE tubing with turbulent flow

Corrections for Other Tubes and Flows DR 9 Tubing

Re = 4000

Re = 1500

+0.03 W/(m.K)

+0.014 W/(m.K)

+0.004 W/(m.K)

Sources: Kavanaugh (2001) and Remund and Paul (2000).

201 1 ASHRAE Handbook-HVAC Applications (SI)

34.16 2

F o ~= 4 0 , ( ~ fzyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA T1)idb

z

~

2

F o ~= 4 0 , ( ~ f " ) i d , ~

An intermediate step in computing the ground's thermal resistance using the methods of Ingersoll and Zobel(l954) is to identify a G-factor, which is then determined from Figure 15 for each Fourier value. Rga

= (Gf

Rg"

= (GI

GJk,

~

~

(5a)

G2)ikg

(5b)

Rgd = G2/kg

(5c)

Ranges of the ground thermal conductivity kg are given in Table 6. State geological surveys are a good source of soil and rock data. However, geotechnical site surveys are highly recommended to determine load soil, rock types, and drilling conditions. Performance degrades somewhat because of short-circuiting heat losses between the upward- and downward-flowing legs of a conventional U-bend loop. This degradation can be accounted for by introducing the short-circuit heat loss factor [F,, in Equations (2) and (3)] in the table below. Normally U-tubes are piped in parallel to the supply and return headers. Occasionally, when bore depths are shallow, two or three loops can be piped in series. In these cases, short-circuit heat loss is reduced; thus, the values for F,, are smaller than for a single bore piped in series.

zyxwvutsrq Fsc

Bores per Loop

36 mL/(s.kW)

54 mL/(s.kW)

1 2 3

1.06 1.03 1.02

1.04 1.02 1.01

Temperature. The remaining terms in Equations (2) and (3) are temperatures. The local deep-ground temperature tg can best be obtained from local water well logs and geological surveys. A second, less accurate source is a temperature contour map, similar to Figure 16, prepared by state geological surveys. A third source, which can yield ground temperatures within 2 K, is a map with contours, such as Figure 17. Comparison of Figures 16 and 17 indicates the complex variations that would not be accounted for without detailed contour maps. Selecting the temperature twi of water entering the unit is critical in the design process. Choosing a value close to ground temperature results in higher system efficiency, but makes the required ground coil length very long and thus unreasonably expensive. Choosing a value far from tgallows selection of a small, inexpensive ground coil, but the system's heat pumps will have both greatly reduced capacity during heating and high demand when cooling. Selecting t, to be 11 to 17 K higher than tgin cooling and 6 to 11 K lower than tg heating is a good compromise between frst cost and efficiency m many regions of the United States. A final temperature to consider is the temperature penalty tp resulting from thermal interferences from adjacent bores. The designer must select a reasonable separation distance to minimize required land area without causing large increases in the required bore length (L,, Lh).Table 7 presents the temperature penalty for a 10 by 10 vertical grid of bores for various operating conditions after 10 years of operation in a nonporous soil where cooling effects from moisture evaporation or water movement do not mitigate temperature change (Kavanaugh 2003; Kavanaugh and Rafferty 1997). Correction factors are included to find the temperature penalty for four other grid patterns. Note that the higher the number of internal bores, the larger the correction factor. In the table, adjustments are made to the number of equivalent full-load hours (EFLHs) in cooling and heating that correspond to

Fig. 15 Fourier/G-Factor Graph for Ground Thermal Resistance (Kavanaugh and Rafferty 1997)

values consistent with the local ground temperature. To mitigate long-term heat build-up for small separation distances, the required heat exchanger length is extended to maintain good system efficiencies. Larger separation distances result in shorter required lengths and smaller temperature changes, because there is greater thermal capacity available and greater area to diffuse heat to the far field. The table applies only to a limited number of specific cases and is not intended for application to actual designs. It is intended to demonstrate trends for various ground temperatures, hours of operation in heating and cooling, and bore separation distances. Note that values of tp in the table are significantly different from those obtained using the approach presented by Bemier et al. (2008) Smaller bore lengths per kilowatt of peak block load result in larger temperature changes; the relationship between bore length and temperature change is inverse and linear. Values in this table represent worst-case scenarios, and the temperature change is usually mitigated by groundwater recharge (vertical flow), groundwater movement (horizontal flow), and evaporation (and condensation) of water in the soil. Groundwater movement strongly affects the long-term temperature change in a densely packed ground loop field (Chiasson et al. 2000). A related factor is the evaporative cooling effect experienced with heat addition to the ground. Although thermal conductivity is somewhat reduced with lower moisture content (see Table 5), the net effect is beneficial in porous soils when water movement recharges the ground to original moisture levels. A similar effect may be experienced in cold climates when soil moisture freezes and the heat of solidification mitigates excessive temperature decline. Because these effects have not been thoroughly studied, the design engineer must establish a range of design lengths between one based on minimal groundwater movement, as in very tight clay soils with

zyxwvutsr zyxwvu +

Geothermal Energy

zyxw zy 34.17

Table 7 Long-Term Temperature Penalty for Worst-case Nonporous Formations for 10 x 10 grid and 350 kW Load EFLH,, EFLH,

MY^

MY^

250

1250

500

Bore Bore Tg, Separation, Length, Tpex,l@, COPcoolixg COP,eatixg OC m m OC

,

1000

750

750

1000

500

1250

250

3.6

4.5

70

-0.7

3.6

6

6.1

67

-0.4

5.2

3.6

7.6

66

-0.2

4.9

3.7

4.5

66

-0.8

4.9

3.7

6.1

64

-0.4

4.9

3.7

7.6

63

-0.2

4.2

4.0

4.5

63

1.9

4.2

4.0

6.1

59

1.0

4.2

4.0

7.6

58

0.6

3.9

4.4

4.5

87

3.8

3.9

4.4

6.1

76

2.1

3.9

4.4

7.6

70

1.1

3.8

4.6

4.5

110

7

13

18

20

5.6

zyxwvu zyxwvutsrq

Fig. 16 Water and Ground Temperatures in Alabama at 15 and 45 m Depth

3.8

4.6

6.1

88

3.2

3.8

4.6

7.6

78

1.7

0

1500

Not recommended without solar or thermal regeneration

1500

0

Not recommended without fluid cooler or cooling tower assist

Note: kg = 2.4 W/(mK), k,,

(Chandler 1987)

5.2

5.2

=

1.5 W/(mK), rated COP,,,,,$COP,,,,

=

5.9/4.2 (GLHP).

Correction Factors for Other Grid Patterns:

1 x 10 gnd

2

Cf= 0.36

Cf= 0.45

x

10 gnd

5 x 5 gnd Cf= 0.75

Fig. 17 Approximate Groundwater Temperatures (“C) in the Continental United States

20

x

20 gnd

Cf= 1.14

201 1 ASHRAE Handbook-HVAC Applications (SI)

34.18 poor percolation rates, and a second based on the higher rates characteristic of porous aquifers. The long-term temperature change table and a commonly used software for GCHP system design both use EFLH calculations. To the extent that annual loads are proportional to peak loads, the equivalent full-load hours method provides a simple estimate of a n n u l loads frompeak loads. The EFLHs in Table 8 provide a quick means to estimate annual loads needed to size ground heat exchangers at the initial feasibility study phase of a project. Because EFLHs vary with changes in both annual loads and peak loads, not all building parameters effects are included in EFLHs. For instance, building operating hours change annual loads by increasing the amount of time that internal gains are at elevated levels, but they do not change the peak load. Occupancy hours can add load without increasing the installed capacity, thereby changing the EFLHs. Furthermore, changes in other parameters, such as internal gains, do not necessarily scale with system capacity in the same proportion as annual load,

Table 8

again leading to changing EFLHs. Potential users of EFLHs must understand these sources of variability to use them effectively (Carlson 2001).

z

Hybrid System Design As indicated in Table 7, the required length of the heat exchanger and the resulting temperature penalty in climates with severe imbalances in cooling and heating operating hours lead to high costs and/or long-term performance degradation. This is exacerbated in coolingdominated applications, because the power input to compressors, fans, and pumps must be rejected through the ground exchanger. In heating mode, this heat is delivered to the building; thus, less heat is required from the ground. To achieve thermal balance, the heat pumps must operate in heating mode 1.6 to 1.8 h for every hour in cooling. Kavanaugh and Rafferty (1997) suggest that heat exchanger length for heating L, be determined using Equation (3) with heating-

zyxwvu

Equivalent Full-Load Hours (EFLH) for Typical Occupancy with Constant-Temperature Set Points EFLH Occupancy School

Office

Retail

Hospital

Location

Heating

Cooling

Heating

Cooling

Heating

Cooling

Heating

Cooling

Atlanta, GA Baltimore, MD Bismarck, ND Boston, MA Charleston, WV Charlotte, NC Chicago, IL Dallas, TX Detroit, MI Fairbanks, AK Great Falls, MT Hilo, HI Houston, TX Indianapolis, IN Los Angeles, CA Louisville, KY Madison, WI Memphis, TN Miami, FL Minneapolis, MN Montgomery, AL Nashville, TN New Orleans, LA New York, NY Omaha, NE Phoenix, AZ Pittsburgh, PA Portland, ME Richmond, VA Sacramento, CA Salt Lake City, UT Seattle, WA St. Louis, MO Tampa, FL Tulsa, OK

290-200 460-320 500-460 520-450 440-3 10 320-200 470-390 200-120 480-400 630-560 430-360 1-0 130-90 480-400 160-80 430-290 470-390 240-170 12-6 500-420 180-120 320-250 110-67 440-350 400-330 110-65 500-470 480-400 410-270 360-220 540-520 650-460 400-280 58-35 300-240

690-830 500-610 150-250 300-510 430-570 650-730 280-410 830-890 230-360 26-54 130-220 1360-1390 940-1000 3 80-560 780-910 550-670 210-310 700-830 1260-1300 200-300 840-910 570-740 920-990 360-550 310-440 950-1020 300-530 190-300 630-730 680-850 410-710 260-460 460-550 1050-1110 580-770

690-480 890-720 990-950 1000-960 840-770 780-530 920-820 520-340 1020-970 1170-1050 890-820 23-13 350-250 920-840 580-370 830-710 900-840 600-420 46-34 950-860 470-330 680-590 320-230 870-790 800-720 290-210 950-910 980-880 820-660 990-640 1060-1040 1370-1270 800-710 190-140 620-560

1080-1360 690-1080 250-540 450-970 620-1140 1060-1340 420-780 1350-1580 390-820 64-200 210-490 2440-2580 1550-1770 560-1000 1280-1670 770-1250 320-640 1090-1350 1980-2150 320-610 1260-15 10 830-1280 1500-1720 540-1040 480-820 1340-1610 440-920 310-630 880-1310 1080-1430 5 10-1090 440-1200 680-1100 1800-2000 830-1300

600-380 770-570 900-810 870- 760 730-620 670-420 810-670 440-280 900-790 1090-930 800-680 14-8 300-190 820-690 440-250 720-570 800-700 510-330 37-25 860-720 400-250 590-470 260-160 760-630 720-600 250-170 840-750 870-710 710-520 830-480 930-830 1170-960 700-570 160-100 540-450

1380-1860 880-1480 340-780 610-1380 820-1600 1350-1830 550-1090 1660-2090 530-1 170 110-320 290-710 2990-3370 1870-2290 730-1410 1740-2350 1000-1720 420-900 1350-1780 2350-2740 430-870 1550-1990 1030-1710 1820-2240 720- 1480 610-1130 1630-2090 600-13 10 410-900 1110-1770 1460-2020 660-1520 710-1860 850-1500 2170-2580 1030-1730

430-160 590-300 730-530 680-420 550-320 490-180 640-400 310-100 710-460 930-690 640-420 0-0 200-70 640-390 180-20 550-300 640-440 370- 140 12-1 700-470 260-90 450-240 160-46 590-330 570-360 140-34 650-420 690-420 530-250 540- 120 720-440 850-360 550-320 90-22 410-220

2010-2850 1340-2340 540-1290 1020-2330 1260-2560 1990-2820 870-1780 2320-3100 870-1950 210-600 500-1210 4060-49 10 2540-3320 1120-2250 2740-3770 1480-2690 680-1490 1910-2680 3110-3890 680-1420 2170-2950 1490-2620 2500-3280 1160-2440 920-1780 2220-3040 960-2160 700-1520 1650-2760 2250-3180 1060-2470 1340-3270 1260-2330 2910-3710 1470-2630

zyxwvutsrqp

Notes: 1. The ranges in values are from internal gains at 6.5 and 21 Wm2. 2. Operating with large temperature setbacks during unoccupied periods (effectively turning offthe system) reduces heating EFLHs by 20% and cooling EFLHs by 5%.

Equations relating EFLH to Heating and Cooling Degree Days allowing calculation of EFLH for locations other than those listed here can be found in Carlson (2001).

z zyxwvutsrqpo 34.19

Geothermal Energy

mode loop temperatures twiand twoas low as possible to minimize L,. A fluid cooler or cooling tower with an isolation heat exchanger is sized to meet the capacity difference between the required cooling length L, from Equation (2) and the heating length L,:

This strategy does not completely eliminate long-term ground temperature change. However, the fluid cooler or cooling tower can operate additional hours during off-peak periods to ensure no temperature change occurs. It is suggested that operation during periods of lower outdoor-air wet-bulb temperature substantially reduces the operating hours and energy required to achieve this balance. A more detailed study (Hackel et al. 2009) included assumptions about typical installation and operating costs to demonstrate an optimized design strategy. A variety of cases were considered, and the simplified best-fit regression for the hybrid ground heat exchanger length Lhyb was found to be

Hackel et al. (2009) explored the balance between theoretical installation and operating costs to find an optimized hybrid design strategy. Various cooling-dominated scenarios were considered, and the simplified best-fit regression for a theoretically optimal hybrid ground heat exchanger length L,?,, was found to be proportional to heating load:

Ltot

qpeak,heat = Cl

Atground

where Cl=147 (m.K)/kW at k=2.4 W/(m.K). For other groundconductivities, the change in ground heat exchanger size is approximately inversely proportional to the change in conductivity. This basic strategy of sizing hybrids was found to be valid for a wide range of economic scenarios. Results of this study suggest that in most cases it is economically optimal to include antifreeze in the system and allow the entering fluid temperature to drop to 2°C or lower. If a cooling tower is used, its optimal size can be found according to the following equation. The tower should be controlled according to the At between the fluid temperature and the ambient (wet or dry bulb, depending on whether a tower or cooler is used).

smaller, dedicated subsystem such as dedicated ventilation preheat, baseboard perimeter heating, or unit heaters. If the heat is not expected to operate often, another effective option is electric duct heaters placed at the heat pumps; in this case, ensure that controls do not leave this auxiliary heat on for extended periods. In some situations, it may only be cost-effective to provide indirect heat through a supplemental heat coil on the geothermal fluid loop. Coil energy could be supplied by gas boiler, solar panels, electric resistance, or another source. However, there are several drawbacks to this approach: The heat coil’s high potential temperatures are not covered by typical ground loop warranties and pose a danger to the loop. If controls are not maintained correctly, the boiler may dump heat to the ground, and only a fraction of that rejected heat would be recovered. The heat pumps operate whenever heating is needed, even though a high-temperature coil is also operating. This, coupled with the need for a heat exchanger in most of these systems, adds significant and unnecessary energy consumption to the system.

Pump and Piping System Options Loop design can have a substantial effect on both pumping power requirements and system installed cost. A GSHP survey (Caneta 1995) reported that installed pumping power varied from 0.0085 to 0.045 kWelect/kWtherm of heat pump power. This represents 4 to 21% of the total demand of typical GSHP systems and up to 50% of the total energy for some pump control schemes. Table 9 gives a recommended set of guidelines for minimizing the power of closedloop GSHPs and maximizing system efficiency. Good Table 9 grades can be obtained by minimizing extensive piping arrangements with long interior and exterior piping runs, high-head-loss fittings, valves, and control devices. Designers must compare the costs and advantages of large central piping loops and larger pumps with those of multiple smaller loops and smaller pumps. Pumping rates greater than 0.05 L/s.kW in closed-loop systems result in marginal equipment capacity gains in modern waterto-air heat pumps, and typically decrease overall system efficiency. Kavanaugh et al. (2002) found the total cost of vertical GCHP ground-loop systems (including headers) ranged from $10 to $55 per metre of vertical bore. The cost of headers is a significant portion of the total and in many cases exceeded the cost of the vertical bore. The savings in vertical loop costs because of central systems’ load diversity often is not warranted because ofthe increased cost of large-diameter piping networks connecting equipment inside the building and below-grade circuits connecting exterior ground loops. In low-rise buildings with large footprints, such as a school, multiple unitary loop systems (Figure 18) are recommended to offset the high cost of central interior piping and ground-loop header costs. Although the total length of vertical bore for unitary systems is greater than for central loop systems, the high cost of interior piping, exterior headers, and valve vaults often offsets the bore cost savings. Additionally, pump demand is substantially reduced in the unitary system because of the short header runs, so low-wattage o d off circulator pumps are suggested.

zyxwvutsrq

where C, = 0.736 m/(kW.K) and to = -18°C. Heating-Dominated Hybrids. Heating-dominated hybrids are needed in only the most severe cold climates, partially because of the constant heat creation of compressors. Most commercial buildings throughout the United States are cooling-dominated and would not benefit from supplemental heat, especially when ventilation heat recovery is used to temper cold winter air. In severely heatingdominated climates (i.e., approximately twice as much annual heating load as cooling load), however, a heating-dominated hybrid could decrease the size of the ground heat exchanger and balance the ground load. In an optimal system, the ground heat exchanger is sized to meet the cooling load and a supplemental device meets the remaining heating load. A robust, efficient solution to a heating hybrid uses the heat sources to heat air or fluid directly (because boilers, electricity, and solar all provide high enough temperatures for this) and avoid operating the heat pump unnecessarily. Delivering this supplemental heat by coils separate from the geothermal fluid system increases system efficiency and eliminates the problems posed in the indirect approach. The separate heat source should be delivered through a

Table 9

Guidelines for Pump Power for GSHP Ground Loops

Installed Pump Power k w , , m p o kWcool

Grade

< 1.6 1.1 to 1.6 1.6 to 2.1 2.1 to 3.2 > 3.2

A B C D F

Source: Kavanaugh and Rafferty (1997).

0.05 L/s.kWCoo1, kPa < 138 138 to 206 206 to 275 275 to 413 > 413

Next Page

201 1 ASHRAE Handbook-HVAC

34.20

Applications (SI)

Fig. 18 Unitary GCHP Loops with On/Off Circulator Pumps

zyxwvutsrqpo Fig. 19

Subcentral GCHP Loop with OdOff Circulator Pumps

A compromise in applications with significant load diversity is to group ground loops into multiple smaller subcentral loops in different areas of the building (Figure 19). Subcentral loops can be served by odoff circulator pumps located on each heat pump if a check valve is installed on each heat pump to prevent reverse water circulation through idle units. Figure 20 is an example of a central loop that can effectively reduce the cost of the required vertical bore in buildings with higher load diversities. The central ground loop consists of several

subheader sets, each having 6 to 20 vertical U-tube heat exchangers. The subheaders are gathered into a valve manifold located either near the center of the loop field in a below-grade vault or in the building equipment room. Each subheader set has isolation valves for independent purging of air and debris. Interior piping is similar to conventional water-source heat pump systems in which interior piping is routed to individual water-to-air heat pumps in each zone andor heat pump water heaters and water-to-water heat pumps.

zyxw zyx zyxwvut CHAPTER 35

SOLAR ENERGY USE Quality and Quantity of Solar Energy ..................................... Solar Energy Collection ........................................................... Components ........................................................................... Water Heating ........................................................................ Solar Heating and Cooling Systems ...................................... Cooling by Nocturnal Radiation and Evaporation ........................................................................

35.1 35.6 35.11 35.13 35.15 35.17

T

HE sun radiates considerable energy onto the earth. Putting that diffuse, rarely over 950 W/m2 energy to work has lead to the creation of many types of devices to convert that energy into useful forms, mainly heat and electricity. How that energy is valued economically drives the ebb and flow of the global solar industry. This chapter discusses several different types of solar equipment and system designs for various HVAC applications, as well as methods to determine the solar resource. Worldwide, solar energy use varies in application and degree. In China and, to a lesser extent, Australasia, solar energy is widely used, particularly for water heating. In Europe, government incentives have fostered use of photovoltaic and thermal systems for both domestic hot-water and space heating. In the Middle East, solar power is used for desalination and absorption air conditioning. Solar energy use in the United States is relatively modest, driven by tax policy and utility programs that generally react to energy shortages or the price of oil. Recent interest in sustainability and green buildings has led to an increased focus on solar energy devices for their nonpolluting and renewable qualities; replacing fossil fuel with domestic, renewable energy sources can also enhance national security by reducing dependence on imported energy. For more information on the use of solar and other energy sources, see the Energy Information Administration (EAI) of the U.S. Department of Energy (www.eai.doe.gov) and the International Energy Agency (www.iea.org).

Cooling by Solar Energy ........................................................ Sizing Solar Heating and Cooling Systems: Energy Requirements .......................................................... Installation Guidelines ........................................................... Design, Installation, and Operation Checklist....................... Photovoltaic Applications Symbols ..................................................................................

35.18 35.19 35.23 35.25 35.26 35.27

between the earth-sun line and the earth's equatorial plane, called the solar declination 6. This angle varies with the date, as shown in Table 1 for the year 1964 and in Table 2 for 1977. For other dates, the declination may be estimated by the following equation:

6

=

[

23.45 sin 360" x 365

where N = year day, with January 1 = 1. For values of N, see Tables 1 and2. The relationship between 6 and the date from year to year varies to an insignificant degree. The daily change in the declination is the primary reason for the changing seasons, with their variation in the distribution of solar radiation over the earth's surface and the varying number of hours of daylight and darkness. Note that the following sections are based in the northern hemisphere; sites in the southern hemisphere will be 180" from the examples (e.g., a solar panel should face north). The earth's rotation causes the sun's apparent motion (Figure 1). The position of the sun can be defmed in terms of its altitude p above the horizon (angle HOQ) and its azimuth 4,measured as angle HOS in the horizontal plane. At solar noon, the sun is exactly on the meridian, which contains the south-north line. Consequently, the solar azimuth 4 is 0". The noon altitude pN is given by the following equation as

zyx

QUALITY AND QUANTITY OF SOLAR ENERGY Solar Constant Solar energy approaches the earth as electromagnetic radiation, with wavelengths ranging from 0.1 pm (x-rays) to 100 m (radio waves). The earth maintains a thermal equilibrium between the m u a l input of shortwave radiation (0.3 to 2.0 pm) from the sun and the outward flux of longwave radiation (3.0 to 30 pm). Only a limited band need be considered in terrestrial applications, because 99% of the sun's radiant energy has wavelengths between 0.28 and 4.96 pm. The current value of the solar constant (which is defmed as the intensity of solar radiation on a surface normal to the sun's rays, just beyond the earth's atmosphere at the average earth-sun distance) is 1367 W/m2. Chapter 15 ofthe2009ASHRAEHandbookFundamentals has further information on this topic.

where LAT = latitude. Because the earth's daily rotation and its annual orbit around the sun are regular and predictable, the solar altitude and azimuth may be readily calculated for any desired time of day when the latitude, longitude, and date (declination) are specified. Apparent solar time (AST) must be used, expressed in terms of the hour angle H , where

Solar Angles

Solar Time

zyxw zyxwvuts

The axis about which the earth rotates is tilted at an angle of 23.45' to the plane of the earth's orbital plane and the sun's equator. The earth's tilted axis results in a day-by-day variation of the angle The preparation of this chapter is assigned to TC 6.7, Solar Energy Utilization.

H

= ~

(Number of hours from solar noon) x 15O

Number of minutes from solar noon

(3)

A

Apparent solar time (AST) generally differs from local standard time (LST) or daylight saving time (DST), and the difference can be significant, particularly when DST is in effect. Because the sun appears to move at the rate of 360" in 24 h, its apparent rate of motion is 4 min per degree of longitude. The AST can be determined from the following equation:

35.1

zyx zy

201 1 ASHRAE Handbook-HVAC Applications (SI)

35.2

Table 1 Date, Declination, and Equation of Time for the 21st Day of Each Month of 1964, with Data (A, B, C) Used to Calculate Direct Normal Radiation Intensity at the Earth's Surface Year Day Declination 6, degrees Equationoftime, minutes Solar noon A, W/m2 B. dimensionless C, dimensionless

Jan

Feb

Mar

21 -19.9 -11.2

52 -10.6 -13.9 late 1215 0.144 0.060

80 0.0 -7.5

1230 0.142 0.058

1186 0.156 0.071

Apr

May

June

July

Aug

Sept

111 141 +11.9 +20.3 +1.1 +3.3 early 1136 1104 0.180 0.196 0.097 0.121

172 +23.45 -1.4

202 +20.5 -6.2 late 1085 0.207 0.136

233 +12.1 -2.4

264 0.0 +7.5

1107 0.201 0.122

1152 0.177 0.092

1088 0.205 0.134

Oct

Dec

Nov

294 325 -10.7 -19.9 +15.4 +13.8 early 1193 1221 0.160 0.149 0.073 0.063

I I

Table 2

Solar Position Data for 1977

Date

Jan

Feb

Mar

Apr

1

1 -23.0 -3.6 6 -22.4 -5.9 11 -21.7 -8.0 16 -20.8 -9.8 21 -19.6 -1 1.4 26 -18.6 -12.6

32 -17.0 -13.7 37 -15.5 -14.2 42 -13.9 -14.4 47 -12.2 -14.2 52 -10.4 -13.8 57 -8.6 -13.1

60 -7.4 -12.5 65 -5.5 -11.4 70 -3.5 -10.2 75 -1.6 -8.8 80 +0.4 -7.4 85 +2.4 -5.8

91 +4.7 -4.0 96 +6.6 -2.5 101 -8.5 -1.1

May 121 +15.2 +2.9 126 +16.6 +3.5 131 +17.9 +3.7

June 152 +22.1 +2.4 157 +22.7 +1.6 162 +23.1 +0.6

+10.3 106 +0.1

+19.2 136 +3.8

+23.3 167 -0.4

+12.0 111 +1.2 116 +13.6 +2.2

+20.3 141 +3.6 146 +21.2 +3.2

+23.4 172 -1.5 177 +23.3 -2.6

6 11 16 21 26

YearDay Declination 6 Eq of Time YearDay Declination 6 Eq of Time YearDay Declination 6 Eq of Time YearDay Declination 6 Eq of Time Year Day Declination 6 Eq of Time YearDay Declination 6 Eq of Time

1234 0.142 0.057

C = ratio of diffuse radiation on horizontal surface to direct normal irradiation.

A = avvarent solar irradiation at air mass zero for each month. B = atmospheric extinction coefficient.

zy zy

355 -23.45 +1.6

July 182 +23.1 -3.6 187 +22.7 -4.5 192 +22.1 -5.3 197 +2 1.3 -5.9 202 +20.6 -6.2 207 +19.3 -6.4

Aug 213 +17.9 -6.2 218 +16.6 -5.8 223 +15.2 -5.1 228 +13.6 -4.3 233 +12.0 -3.1

Sept 244 +8.2

249 +6.7 +1.6 254 +4.4 +3.3 259 +2.5 +5.0 264 +0.5 +6.8

Oct 274 -3.3 +10.2 279 -5.3 +11.8 284 -7.2 +13.1 289 -8.7 +14.3 294 -10.8 +15.3

Nov 305 -14.6 +16.3 310 -16.1 +16.3 315 -17.5 +15.9 320 -18.8 +15.2 325 -20.0 +14.1

Dec 335 -21.9 +11.0 340 -22.5 +9.0 345 -23.0 +6.8 350 -23.3 +4.4 355 -23.4 +2.0

238 +10.3 -1.8

269 -1.4 +8.6

299 -12.6 +15.9

330 -21.0 +12.7

360 -23.4 -0.5

+o.o

Source: ASHRAE Standard93-1986 (RA91). Notes: Units for declination are angular degrees; units for equation of time are minutes. Values of declination and equation of time valy slightly for specific dates in other years.

AST

=

LST + Equation of time

+ (4 min) (LST meridian - Local longitude)

(4)

The longitudes of the seven standard time meridians that affect North America are Atlantic ST, 60"; Eastern ST, 75"; Central ST, 90"; Mountain ST, 105"; Pacific ST, 120"; Yukon ST, 135"; and Alaska-Hawaii ST, 150". The equation of time is the measure, in minutes, of the extent by which solar time, as determined by a sundial, runs faster or slower than local standard time (LST), as determined by a clock that runs at a uniform rate. Table 1 gives values of the declination of the sun and the equation of time for the 21 st day of each month for the year 1964 (when the ASHRAE solar radiation tables were frst calculated), and Table 2 gives values of 6 and the equation of time for six days each month for the year 1977.

Fig. 1 Apparent Daily Path of the Sun Showing Solar Altitude (p) and Solar Azimuth (4)

Example 1. Find AST at noon DST on July 21 for Washington, D.C., longitude = 77", and for Chicago, longitude = 87.6". Solution: Noon DST is actually 11:OO AM LST. Washington is in the eastern time zone, and the LST meridian is 75". From Table 1, the equation of time for July 21 is -6.2 min. Thus, from Equation (4), noon DST for Washington is actually AST = 11:OO 6.2 + 4(75 -

-

To fmd the solar altitude p and the azimuth 4 when the hour angle H, latitude LAT, and declination 6 are known, the following equations may be used: sin p

77) = 10:45.8 AST = 10.76 h

or 11:03.4AST= 11.06h

The hour angles H for these two examples (see Figure 2) are for Washington, H = (12.00 for Chicago, H = (12.00

-

10.76) 15" = 18.6" east 11.06) 15" = 14.10" east

cos 6 cos H

+ sin(LAT) sin 6

sin 4 = cos 6 sin Hlcos p

Chicago is in the central time zone, and the LST meridian is 90". Thus, from Equation (4), noon central DST is AST= 11:OO-6.2+4(90-87.6)=

= cos(LAT)

cos 4 = (cos Hcos 6 sin LAT

~

sin 6 cos LAT)Icos p

(5) (6) (7)

Tables 15 through 21 in Chapter 29 of the 1997 ASHRAE Handbook-Fundamentals give values for latitudes from 16 to 64" north. For any other date or latitude, interpolation between the tabulated values will give sufficiently accurate results.

35.3

Solar Energy Use

ASHRAE Standard 93-2010 provides tabulated values of 0 for horizontal and vertical surfaces and for south-facing surfaces tilted upward at angles equal to the latitude minus 1O", the latitude, the latitude plus lo", and the latitude plus 20". These tables cover the latitudes from 24" to 64" north, in 8" intervals.

Solar Spectrum Beyond the earth's atmosphere, the effective blackbody temperature of the sun is 5760 K. The maximum spectral intensity occurs at 0.48 pm in the green portion of the visible spectrum. Thekaekara (1973) presents tables and charts of the sun's extraterrestrial spectral irradiance from 0.120 to 100 pm, the range in which most of the sun's radiant energy is contained. The ultraviolet portion of the spectrum below 0.40 pm contains 8.73% of the total, another 38.15% is containedin thevisible region between 0.40 and 0.70 pm, and the infrared region contains the remaining 53.12%.

Fig. 2

zyxwvutsrq

Solar Angles with Respect to a Tilted Surface

Incident Angle

Solar Radiation at the Earth's Surface

The angle between the line normal to the irradiated surface (OP' in Figure 2) and the earth-sun line OQ is called the incident angle 0. It is important in solar technology because it affects the intensity of the direct component of solar radiation striking the surface and the surface's ability to absorb, transmit, or reflect the sun's rays. To determine 0, the surface azimuth v and the surface-solar azimuth y must be known. The surface azimuth (angle POS in Figure 2) is the angle between the south-north line SO and the normal PO to the intersection of the irradiated surface with the horizontal plane, shown as line OM. The surface-solar azimuth, angle HOP, is designated by y and is the angular difference between the solar azimuth 4 and the surface azimuth v. For surfaces facing east of south, y = 4 v in the morning and y = 4 + v in the afternoon. For surfaces facing west of south, y = 4 + v in the morning and y = 4 v in the afternoon. For south-facing surfaces, v = O", so v = 4 for all conditions. The angles 6 , p, and 4 are always positive. For a surface with a tilt angle C (measured from the horizontal), the angle of incidence 0 between the direct solar beam and the normal to the surface (angle QOP' in Figure 2) is given by ~

In passing through the earth's atmosphere, some of the sun's direct radiation ID is scattered by nitrogen, oxygen, and other molecules, which are small compared to the wavelengths of the radiation; and by aerosols, water droplets, dust, and other particles with diameters comparable to the wavelengths (Gates 1966). This scattered radiation causes the sky to appear blue on clear days, and some of it reaches the earth as diffuse radiation I. Attenuation of the solar rays is also caused by absorption, first by the ozone in the outer atmosphere, which causes a sharp cutoff at 0.29 pm of the ultraviolet radiation reaching the earth's surface (Figure 3). In the longer wavelengths, there are series of absorption bands caused by water vapor, carbon dioxide, and ozone. The total amount of attenuation at any given location is determined by (1) the length of the atmospheric path through which the rays travel and (2) the composition of the atmosphere. The path length is expressed in terms of the air mass m, which is the ratio of the mass of atmosphere in the actual earth-sun path to the mass that would exist if the sun were directly overhead at sea level (m = 1.O). For all practical purposes, at sea level, m = 1.O/sin p. Beyond the earth's atmosphere, m=0. Before 1967, solar radiation data were based on an assumed solar constant of 1324 W/m2 and on a standard sea-level atmosphere containing the equivalent depth of 2.8 mm of ozone, 20 nnn of precipitable moisture, and 300 dust particles per cm3. Threlkeld and Jordan (1958) considered the wide variation of water vapor in the atmosphere above the United States at any given time, and particularly the seasonal variation, which fmds three times as much moisture in the atmosphere in midsummer as in December, January, and February. The basic atmosphere was assumed to be at sealevel barometric pressure, with 2.5 nnn of ozone, 200 dust particles per cm3, and an actual precipitable moisture content that varied throughout the year from 8 mm in midwinter to 28 nnn in mid- July. Figure 4 shows the variation of the direct normal irradiation with solar altitude, as estimated for clear atmospheres and for an atmosphere with variable moisture content. Stephenson (1967) showed that the intensity of the direct normal irradiation IDN at the earth's surface on a clear day can be estimated by the following equation:

zyxwvutsrq zyxwvutsrqpo z ~

cos 0 = cos p cos y sin C + sin p cos C

(8) For vertical surfaces, C = 90°, cos C = 0, and sin C = 1.O, so Equation (8) becomes cos 0 = cos p cosy For horizontal surfaces, C Equation (8) leads to

=

O", sin C

0,= 90"

~

(9) =

0, and cos C

p

=

1.0, so (10)

Example 2. Find 8 for a south-facing surface tilted upward 30" from the horizontal at 40" north latitude at 4:OO PM, AST, on August 21. Solution: From Equation (3), at 4:OO

PM

on August 21,

H = 4 x 15"=60" From Table 1, 6 = 12.1" From Equation (5), sin p

=

zyxwvutsrqpo

cos 40" cos 12.1" cos 60" + sin 40" sin 12.1"

p = 30.6"

From Equation (6),

sin 4 = cos 12.1" sin ~ O " / C O S30.6" 4 = 79.7"

The surface faces south, so 4 = y. From Equation (8),

cos 8 = cos 30.6" cos 79.7" sin 30" + sin 30.6" cos 30" 8 = 58.8"

where A , the apparent extraterrestrial irradiation at m = 0, and B, the atmospheric extinction coefficient, are functions of the date and take into account the seasonal variation of the earth-sun distance and the air's water vapor content. The values of the parameters A and B given in Table 1 were selected so that the resulting value of IDNwould be closely agree with the Threlkeld and Jordan (1958) values on average cloudless days. The values of IDN given in Tables 15 through 2 1 in Chapter 29 of the 1997 ASHRAE Handbook-Fundamentals were obtained by using

35.4

zyxwvutsrqp 201 1 ASHRAE Handbook-HVAC

Fig. 3

Applications (SI)

Spectral Solar Irradiation at Sea Level for Air Mass = 1.0

Fig. 5

Clearness Numbers for the United States

values should be adjusted by the clearness numbers applicable to each particular location.

Design Values of Total Solar Irradiation

zyxwvutsr zyxwvutsrqpon

Fig. 4

Variation with Solar Altitude and Time of Year for Direct Normal Irradiation

Equation (1 1) and data from Table 1. The values of solar altitude p and solar azimuth 4 may be obtained from Equations (5) and (6). Additional information may be found in Chapters 14 and 15 of the 20 09 ASHRAE Handboo k-Fundamentals . Because local values of atmospheric water content and elevation can vary markedly from the sea-level average, the concept of clearness number was introduced to express the ratio between the actual clear-day direct irradiation intensity at a specific location and the intensity calculated for the standard atmosphere for the same location and date. Figure 5 shows the Threlkeld-Jordan map of winter and summer clearness numbers for the continental United States. Irradiation

The total solar irradiation It0 of a terrestrial surface of any orientation and tilt with an incident angle 8 is the sum of the direct component IDN cos 8 plus the diffuse component I d 0 coming from the sky plus whatever amount of reflected shortwave radiation I, may reach the surface from the earth or from adjacent surfaces: It0

= IDN

cos 8 + Id0 +I,

(12)

The diffuse component is difficult to estimate because of its nondirectional nature and its wide variations. Figure 4 shows typical values of diffuse irradiation of horizontal and vertical surfaces. For clear days, Threlkeld (1963) derived a dimensionless parameter (designated as C in Table l), which depends on the dust and moisture content of the atmosphere and thus varies throughout the year:

where is the diffuse radiation falling on a horizontal surface under a cloudless sky.

Solar Energy Use

zyxwvutsr z 35.5

vertical south-facing surfaces experience their maximum irradiation during the winter. These curves show the combined effects of the varying length of days and changing solar altitudes. In general, flat-plate collectors are mounted at a fixed tilt angle C (above the horizontal) to give the optimum amount of irradiation for each purpose. Collectors intended for winter heating benefit from higher tilt angles than those used to operate cooling systems in summer. Solar water heaters, which should operate satisfactorily throughout the year, require an angle that is a compromise between the optimal values for summer and winter. Figure 6 shows the monthly variation of total day-long irradiation on the 21st day of each month at 40" north latitude for flat surfaces with various tilt angles. Tables in ASHRAE Standard 93 give the total solar irradiation for the 21st day of each month at latitudes 24 to 64" north on surfaces with the following orientations: normal to the sun's rays (direct normal data do not include diffuse irradiation); horizontal; south-facing, tilted at (LAT-1 0), LAT, (LAT+lO), (LAT+20), and 90" from the horizontal. The day-long total irradiation for fixed surfaces is highest for those that face south, but a deviation in azimuth of 15 to 20" causes only a small reduction.

zyxwv

Solar Energy for Flat-Plate Collectors

zyxwvutsrqpo

Fig. 6 Total Daily Irradiation for Horizontal, Tilted, and Vertical Surfaces at 40° North Latitude

The following equation may be used to estimate the amount of diffuse radiation Ido that reaches a tilted or vertical surface:

where

F,,

= =

1 +cos c 2 angle factor between the surface and the sky ~

(15)

The reflected radiation I, from the foreground is given by

The preceding data apply to clear days. The irradiation for average days may be estimated for any specific location by referring to publications of the U.S. Weather Service. The Climatic Atlas of the United States (U.S. GPO 2005) gives maps of monthly and annual values of percentage of possible sunshine, total hours of sunshine, mean solar radiation, mean sky cover, wind speed, and wind direction. Chapter 14 in the 2009 ASHRAE Handbook-Fundamentals also provides several sources for obtaining solar data. The total daily horizontal irradiation data reported by the U.S. Weather Bureau for approximately 100 stations before 1964 show that the percentage of total clear-day irradiation is approximately a linear function of the percentage of possible sunshine. The irradiation is not zero for days when the percentage of possible sunshine is reported as zero, because substantial amounts of energy reach the earth in the form of diffuse radiation. Instead, the following relationship exists for the percentage of possible sunshine: Day-long actual ItH

where pg

Clear day ItH

reflectance of the foreground ZtH =total horizontal irradiation =

Fsg

= =

1 + cos c 2 angle factor between surface and earth ~

The intensity of reflected radiation that reaches any surface depends on the nature of the reflecting surface and on the incident angle between the sun's direct beam and the reflecting surface. Many measurements made of the reflection (albedo) of the earth under varying conditions show that clean, fresh snow has the highest reflectance (0.87) of any natural surface. Threlkeld (1963) gives values of reflectance for commonly encountered surfaces at solar incident angles from 0 to 70". Bituminous paving generally reflects less than 10% of the total incident solar irradiation; bituminous and gravel roofs reflect from 12 to 15%; concrete, depending on its age, reflects from 21 to 33%. Bright green grass reflects 20% at 8 = 30" and 30% at 8 = 65". The maximum daily amount of solar irradiation that can be received at any given location is that which falls on a flat plate with its surface kept normal to the sun's rays so it receives both direct and diffuse radiation. For fixed flat-plate collectors, the total amount of clear-day irradiation depends on the orientation and slope. As shown by Figure 6 for 40" north latitude, the total irradiation of horizontal surfaces reaches its maximum in midsummer, whereas

100=a+b

(18)

where a and b are constants for any specified month at any given location. See also Duffie and Beckman (1992) and Jordan and Liu (1977).

Longwave Atmospheric Radiation In addition to the shortwave (0.3 to 2.0 pm) radiation it receives from the sun, the earth receives longwave radiation (4 to 100 pm, with maximum intensity near 10 pm) from the atmosphere. In turn, a surface on the earth emits longwave radiation q f i in accordance with the Stefan-Boltzmann law:

Table 3

Sky Emittance and Amount of Precipitable Moisture Versus Dew-Point Temperature

Dew Point, O C

-3 0 -2 5 -20 -15 -10 -5 0 5 10 15 20

Sky Emittance, e,, 0.68 0.70 0.72 0.74 0.76 0.78 0.80 0.82 0.84 0.86 0.88

Precipitable Water, mm

3.3 3.7 4.3 5.0 6.2 8.5 11.2 15.0 20.3 28.0 38.6

35.6

zyxwvutsrqp zyxwvutsrqpon 201 1 ASHRAE Handbook-HVAC

Applications (SI)

zyxwvutsrq

zyxwvutsrqpon (19)

where

e,

=

surface emittance

constant, 5.67 x absolute temperature of surface, K

CT = Stefan-Boltzmann

T,

=

zyxwvut

W/(m2.K4)

For most nonmetallic surfaces, the longwave hemispheric emittance is high, ranging from 0.84 for glass and dry sand to 0.95 for black built-up roofing. For highly polished metals and certain selective surfaces, e, may be as low as 0.05 to 0.20. Atmospheric radiation comes primarily from water vapor, carbon dioxide, and ozone (Bliss 1961); very little comes from oxygen and nitrogen, although they make up 99% of the air. Approximately 90% of the incoming atmospheric radiation comes from the lowest 90 m. Thus, air conditions at ground level largely determine the magnitude of the incoming radiation. Downward radiation from the atmosphere qRatmay be expressed as

The emittance of the atmosphere is a complex function of air temperature and moisture content. The dew point of the atmosphere near the ground determines the total amount of moisture in the atmosphere above the place where the dry-bulb and dew-point temperatures of the atmosphere are determined (Reitan 1963). Bliss (1961) found that the emittance of the atmosphere is related to the dew-point temperature, as shown by Table 3. The apparent sky temperature is defmed as the temperature at which the sky (as a blackbody) emits radiation at the rate actually emitted by the atmosphere at ground level temperature with its actual emittance eat.Then,

Fig. 7 Radiation Heat Loss to Sky from Horizontal Blackbody This analysis shows that radiation alone is not an effective means of dissipating heat under summer conditions of high dewpoint and ambient temperatures. In spring and fall, when both the dew-point and dry-bulb temperatures are relatively low, radiation becomes much more effective. On overcast nights, when cloud cover is low, the clouds act much like blackbodies at ground-level temperature, and virtually no heat can be lost by radiation. Exchange of longwave radiation between the sky and terrestrial surfaces occurs in the daytime as well as at night, but the much greater magnitude of the solar irradiation masks the longwave effects.

SOLAR ENERGY COLLECTION

Example 3. Consider a summer night condition when ground-level temperatures are 17.5"C dew point and 30°C dry bulb. From Table 3, e,, at 17.5"C dew point is 0.87, and the apparent sky temperature is

T,@ = 0.87°.25(30 + 273.15) = 292.8 K Thus, T,@ = 292.8 273.15 = 19.6"C, which is 10.4 K below the ground-level dry-bulb temperature. For a winter night in Arizona, when temperatures at ground level are 15°C db and -5°C dp, from Table 3, the emittance of the atmosphere is 0.78, and the apparent sky temperature is 270.8 K or -2.4"C.

Solar energy can be converted by (1) chemical, (2) electrical, and (3) thermal processes. Photosynthesis is a chemical process that produces food and converts CO, to 0,. Photovoltaic cells convert solar energy to electricity. The section on Photovoltaic Applications discusses some applications for these devices. The thermal conversion process, the primary subject of this chapter, provides thermal energy for space heating and cooling, domestic water heating, power generation, distillation, and process heating.

-

A simple relationship, which ignores vapor pressure of the atmosphere, may also be used to estimate the apparent sky temperature: 1.5

T,@ = 0.0552 Tat

(23)

where T is in kelvins. If the temperature of the radiating surface is assumed to equal the atmospheric temperature, the heat loss from a black surface (e, = 1.0) may be found from Figure 7. Example 4. For the conditions in the previous example for summer, 30°C db and 17.5"C dp, the rate of radiative heat loss is about 72 W/m2. For winter, 15°C db and -5°C dp, the heat loss is about 85 W/m2. Where a rough, unpainted roof is used as a heat dissipater, the rate of heat loss rises rapidly as the surface temperature goes up. For the summer example, a painted metallic roof, e, = 0.96, at 38°C (3 11 K) will have a heat loss rate of qR,

=

0.96 x 5.67 x 10-8[3114-292.84]

=

109 W/mL

Solar Heat Collection by Flat-Plate Collectors The solar irradiation calculation methods presented in the previous sections may be used to estimate how much energy is likely to be available at any specific location, date, and time of day for collection by either a concentrating device, which uses only the direct rays of the sun, or by a flat-plate collector, which can use both direct and diffuse irradiation. Temperatures needed for space heating and cooling do not exceed 90°C, even for absorption refrigeration, and they can be attained with carefully designed flat-plate collectors. Depending on the load and ambient temperatures, single-effect absorption systems can use energizing temperatures of 43 to 110°C. A flat-plate collector generally consists of the following components (see Figure 8):

Glazing. One or more sheets of glass or other radiation-transmitting material. Tubes, fins, or passages. To conduct or direct the heat transfer fluid from the inlet to the outlet. Absorber plates. Flat, corrugated, or grooved plates, to which the tubes, fms, or passages are attached. The plate may be integral with the tubes. Headers or manifolds. To admit and discharge the heat transfer fluid.

35.7

Solar Energy Use

zyxwvu zy

Table 4 Variation with Incident Angle of Transmittance for Single and Double Glazing and Absorptance for Flat-Black Paint

Fig. 8 Exploded Cross Section Through Double-Glazed Solar Water Heater Insulation. To minimize heat loss from the back and sides of the collector. Container or casing. To surround the other components and protect them from dust, moisture, etc. Flat-plate collectors have been built in a wide variety of designs from many different materials (Figure 9). They have been used to heat fluids such as water, water plus an antifreeze additive, or air. Their major purpose is to collect as much solar energy as possible at the lowest possible total cost. The collector should also have a long effective life, despite the adverse effects of the sun’s ultraviolet radiation; corrosion or clogging because of acidity, alkalinity, or hardness of the heat transfer fluid; freezing or air-binding in the case of water, or deposition of dust or moisture in the case of air; and breakage of the glazing because of thermal expansion, hail, vandalism, or other causes. These problems can be minimized by using tempered glass.

Transmittance

Incident Angle, Deg

Single Glazing

Double Glazing

Absorptance for Flat-Black Paint

0 10 20 30 40 50 60 70 80 90

0.87 0.87 0.87 0.87 0.86 0.84 0.79 0.68 0.42 0.00

0.77 0.77 0.77 0.76 0.75 0.73 0.67 0.53 0.25 0.00

0.96 0.96 0.96 0.95 0.94 0.92 0.88 0.82 0.67 0.00

glass have normal incidence transmittances of about 0.87 and 0.85, respectively. For direct radiation, the transmittance varies markedly with the angle of incidence, as shown in Table 4, which gives transmittances for single and double glazing using double-strength clear window glass. The 4% reflectance from each glassiair interface is the most important factor in reducing transmission, although a gain of about 3% in transmittance can be obtained by using water-white glass. Antireflective coatings and surface texture can also improve transmission significantly. The effect of dirt and dust on collector glazing may be quite small, and the cleansing effect of an occasional rainfall is usually adequate to maintain the transmittance within 2 to 4% of its maximum. The glazing should admit as much solar irradiation as possible and reduce upward loss of heat as much as possible. Although glass is virtually opaque to the longwave radiation emitted by collector plates, absorption of that radiation causes an increase in the glass temperature and a loss of heat to the surrounding atmosphere by radiation and convection. This type of heat loss can be reduced by using an infrared-reflective coating on the underside of the glass; however, such coatings are expensive and reduce the effective solar transmittance of the glass by as much as 10%. In addition to serving as a heat trap by admitting shortwave solar radiation and retaining longwave thermal radiation, the glazing also reduces heat loss by convection. The insulating effect of the glazing is enhanced by using several sheets of glass, or glass plus plastic. Loss from the back of the plate rarely exceeds 10% of the upward loss.

Glazing Materials Glass has been widely used to glaze flat-plate solar collectors because it can transmit as much as 90% of the incoming shortwave solar irradiation while transmitting very little of the longwave radiation emitted outward from the absorber plate. Glass with low iron content has a relatively high transmittance for solar radiation (approximately 0.85 to 0.90 at normal incidence), but its transmittance is essentially zero for the longwave thermal radiation (5.0 to 50 pm) emitted by sun-heated surfaces. Plastic films and sheets also have high shortwave transmittance, but because most usable varieties also have transmission bands in the middle of the thermal radiation spectrum, their longwave transmittances may be as high as 0.40. Plastics are also generally limited in the temperatures they can sustain without deteriorating or undergoing dimensional changes. Only a few kinds of plastics can withstand the sun’s ultraviolet radiation for long periods. However, they are not broken by hail and other stones and, in the form of thin films, they are completely flexible and have low mass. The glass generally used in solar collectors may be either singlestrength (2.2 to 2.5 nnn thick) or double-strength (2.92 to 3.38 nnn thick). Commercially available grades of window and greenhouse

Collector Plates The collector plate absorbs as much of the irradiation as possible through the glazing, while losing as little heat as possible up to the atmosphere and down through the back of the casing. The collector plates transfer retained heat to the transport fluid. The absorptance of the collector surface for shortwave solar radiation depends on the nature and color of the coating and on the incident angle, as shown in Table 4 for a typical flat-black paint. By suitable electrolytic or chemical treatments, selective surfaces can be produced with high values of solar radiation absorptance a and low values of longwave emittance e. Essentially, typical selective surfaces consist of a thin upper layer, which is highly absorbent to shortwave solar radiation but relatively transparent to longwave thermal radiation, deposited on a substrate that has a high reflectance and a low emittance for longwave radiation. Selective surfaces are particularly important when the collector surface temperature is much higher than the ambient air temperature. For fluid-heating collectors, passages must be integral with or firmly bonded to the absorber plate. A major problem is obtaining a good thermal bond between tubes and absorber plates without incurring excessive costs for labor or materials. Materials most fre-

zyxwvutsr

201 1 ASHRAE Handbook-HVAC quently used for collector plates are copper, aluminum, and steel. UV-resistant plastic extrusions are used for low-temperature application. If the entire collector area is in contact with the heat transfer fluid, the material's thermal conductance is not important. Whillier (1 964) concluded that steel tubes are as effective as copper if the bond conductance between tube and plate is good. Potential corrosion problems should be considered for any metals. Bond conductance can range from 5700 W/(m2.K) for a securely soldered or brazed tube, to 17 W/(m2.K) for a poorly clamped or badly soldered tube. Plates of copper, aluminum, or stainless steel with integral tubes are among the most effective types available. Figure 9 shows a few of the solar water and air heaters that have been used with varying degrees of success.

Concentrating Collectors Temperatures far above those attainable by flat-plate collectors can be reached if a large amount of solar radiation is concentrated on a relatively small collection area. Simple reflectors can markedly increase the amount of direct radiation reaching a collector, as shown in Figure 1OA. Because of the apparent movement of the sun across the sky, conventional concentrating collectors must follow the sun's daily motion. There are two methods by which the sun's motion can be readily tracked. The altazimuth method requires the tracking device to turn in both altitude and azimuth; when performed properly, this method enables the concentrator to follow the sun exactly. Paraboloidal solar furnaces (Figure 10B) generally use this system. The polar, or equatorial, mounting points the axis of rotation at the North Star, tilted upward at the angle of the local latitude. By rotating the collector 15" per hour, it follows the sun perfectly (on March 2 1 and September 21). If the collector surface or aperture must be kept normal to the solar rays, a second motion is needed to correct for the change in the solar declination. This motion is not essential for most solar collectors. The maximum variation in the angle of incidence for a collector on a polar mount is *23.5" on June 21 and December 21; the incident angle correction then is cos 23.5" = 0.917. Horizontal reflective parabolic troughs, oriented east and west (Figure lOC), require continuous adjustment to compensate for the changes in the sun's declination. There is inevitably some morning

Applications (SI)

and afternoon shading of the reflecting surface if the concentrator has opaque end panels. The necessity of moving the concentrator to accommodate the changing solar declination can be reduced by moving the absorber or by using a trough with two sections of a parabola facing each other, as shown in Figure 10D. Known as a compound parabolic concentrator (CPC), this design can accept incoming radiation over a relatively wide range of angles. By using multiple internal reflections, any radiation that is accepted finds its way to the absorber surface located at the bottom of the apparatus. By filling the collector shape with a highly transparent material having an index of refraction greater than 1.4, the acceptance angle can be increased. By shaping the surfaces of the m a y properly, total internal reflection occurs at the mediudair interfaces, which results in a high concentration efficiency. Known as a dielectric compound parabolic concentrator (DCPC), this device has been applied to the photovoltaic generation of electricity (Cole et al. 1977). The parabolic trough of Figure 10E can be simulated by many flat strips, each adjusted at the proper angle so that all reflect onto a common target. By supporting the strips on ribs with parabolic contours, a relatively efficient concentrator can be produced with less tooling than the complete reflective trough. Another concept applies this segmental idea to flat and cylindrical lenses. A modification is shown in Figure 1OF, in which a linear Fresnel lens, curved to shorten its focal distance, can concentrate a relatively large area of radiation onto an elongated receiver. Using the equatorial sun-following mounting, this type of concentrator has been used to attain temperatures well above those that can be reached with flat-plate collectors. One disadvantage of concentrating collectors is that, except at low concentration ratios, they can use only the direct component of solar radiation, because the diffuse component cannot be concentrated by most types. However, an advantage of concentrating collectors is that, in summer, when the sun rises and sets well to the north of the east-west line, the sun-follower, with its axis oriented north-south, can begin to accept radiation directly from the sun long before a fixed, south-facing flat plate can receive anything other than diffuse radiation from the portion of the sky that it faces. At 40" north latitude, for example, the cumulative direct radiation available to a sun-follower on a clear day is 361 MJ/m2, whereas the total radiation falling on the flat plate tilted upward at an angle equal

Fig. 9 Various Types of Solar Collectors

z

35.9

Solar Energy Use

z

Fig. 10 Types of Concentrating Collectors to the latitude is only 25.2 MJ/m2 each day. Thus, in relatively cloudless areas, the concentrating collector may capture more radiation per unit of aperture area than a flat-plate collector. To get extremely high inputs of radiant energy, many flat mirrors, or heliostats, using altazimuth mounts, can be used to reflect their incident direct solar radiation onto a common target. Using slightly concave mirror segments on the heliostats, large amounts ofthermal energy can be directed into the cavity of a steam generator to produce steam at high temperature and pressure.

=

areas of absorber surface and of aperture that admit or receive radiation, m2

zyxwv zyxwvutsrqpon zyxwvutsrqpo

Collector Performance

The performance of collectors may be analyzed by a procedure originated by Hottel and Woertz (1942) and extended by Whillier (ASHRAE 1977). The basic equation is

Equation (24) also may be adapted for use with concentrating collectors:

where

A , , A,

zDN

= =

Example 5. A flat-plate collector is operating in Denver, latitude = 40" north, on July 21 at noon solar time. The atmospheric temperature is 30°C, and the average temperature of the absorber plate is 60°C. The collector is single-glazed with flat-black paint on the absorber. The collector faces south, and the tilt angle is 30" from the horizontal. Find the rate of heat collection and collector efficiency. Neglect losses from the back and sides of the collector.

zyxwvutsrq zyxwvutsrqp

useful heat gained by collector per unit of aperture area, W/m2 total irradiation of collector, W/m2 = direct normal irradiation, W/m2 (raje =transmittance T of cover times absorptance a of plate at prevailing incident angle 8 U, =upward heat loss coefficient, W/(m2.K) tp = temperature of absorber plate, "C t, =temperature of atmosphere, "C tubs =temperature of absorber, "C k = fluid flow rate, kg/s cp = specific heat of fluid, kJ/(kg.K) tfe, tfi =temperatures of fluid leaving and entering collector, "C pT = reflectance of concentrator surface times fraction of reflected or refracted radiation that reaches absorber qu

Zte

The total and direct normal irradiation for clear days may be found in ASHRAE Standard 93. The transmittance for single and double glazing and the absorptance for flat-black paint may be found in Table 4 for incident angles from 0 to 90". These values, and the products of T and a, are also shown in Figure 11. The solar-optical properties of the glazing and absorber plate change little until 8 exceeds 30°, but, because all values reach zero when 8 = 90°, they drop off rapidly for values of 8 beyond 40". For nonselective absorber plates, U, varies with the temperature of the plate and the ambient air, as shown in Figure 12. For selective surfaces, which strongly reduce the emittance of the absorber plate, U, is much lower than the values shown in Figure 12. Manufacturers of such surfaces should be asked for values applicable to their products, or test results that give the necessary information should be consulted.

Solution: From Table 2, 6 = 20.6". From Equation (2),

pN = 90"

~

40" + 20.6" = 70.6"

From Equation (3j, H = 0; therefore from Equation (6), sin $ = 0 and thus, $ = 0". Because the collector faces south, v = O", and y = $. Thus y = 0". Then Equation (8) gives cos 8

= = =

8

=

cos 70.6" cos 0" sin 30" + sin 70.6" cos 30" (0.332)(1)(0.5) +(0.943)(0.866) 0.983 10.6"

35.10

z zyxwvu zyxw

201 1 ASHRAE Handbook-HVAC Applications (SI) From Table 1, A Equation (1 l),

=

1085 W/m2, B

0.207, and C

=

=

0.136. Using

ZDN= 1085e-0.207/SJI170.6"= 871 W/m2 Combining Equations (14) and (15) gives

Zde=0.136x871(1+cos30)/2=111 W/m2

Assuming Z, collector of

=

zyxw zyxw

0, Equation (12) gives a total solar irradiation on the

Zte

=

871 cos 10.6 + 111 = 967 W/m2

From Figure 11, for n = 1, T = 0.87 and a = 0.96. From Figure 12, for an absorber plate temperature of 60°C and an air temperature of 30°C, U, = 7.3 W/(m2.K). Then from Equation (24), qu = 967(0.87 x 0.96)

~

7.3(60

~

30) = 589 W/m2

Collector efficiency q is 589/967 = 0.60

The general expression for collector efficiency is

For incident angles below about 35", the product TCXis essentially constant and Equation (26) is linear with respect to the parameter (tp tu)/Ite,as long as U, remains constant. ASHRAE (1977) suggested that an additional term, the collector heat removal factor FR,be introduced to allow use of the fluid inlet temperature in Equations (24) and (26): -

Fig. 11 Variation of Absorptance and Transmittance with Incident Angle

qu = FR [Ite(Ta)e U L ( ~ ,tu)l -

-

(27)

where FR equals the ratio of the heat actually delivered by the collector to the heat that would be delivered if the absorber were at tfi. FR is found from the results of a test performed in accordance with ASHRAE Standard 93. The Solar Rating and Certification Corporation (SRCC) conducts this test in the United States and publishes the results, along with day-long performance outputs. Similar organizations around the world [e.g., the International Organization for Standardization (ISO), the European Committee for Standardization (CEN), Commonwealth Scientific and Industrial Research Organization (CISRO)] provide similar test results. For additional information on SRCC ratings, see Chapter 36 of the 2008 ASHRAE Handbook-HVAC Systems and Equipment. The results of such a test are plotted in Figure 13. When the parameter is zero, because there is no temperature difference between fluid entering the collector and the atmosphere, the value of the y-intercept equals FR(Tcx).The slope of the efficiency line equals the heat loss factor U, multiplied by FR. For the single-glazed, nonselective collector with the test results shown in Figure 13, the y-intercept is 0.82, and the x-intercept is 0.12 (m2.K)/W. This collector used high-transmittance single glazing, T = 0.91, and black paint with an absorptance of 0.97, so Equation (28) gives FR = 0.82/(0.91 x 0.97) = 0.93. Assuming that the relationship between q and the parameter is actuallylinear,asshown, thentheslopeis-0.8210.69 =-1.190.12= -6.78; thus U, = 6.7810.93 = 7.29 W/(m2.K). The tests on which Figure 13 is based were run indoors. Wind speed and fluid velocity can affect measured efficiency. Figure 13 also shows the efficiency of a double-glazed air heater with an u n f m e d absorber coated with flat-black paint. The y-intercept for the air heater B is considerably less than it is for water heater A because (1) transmittance of the double glazing used in B is lower than the transmittance of the single glazing used in A and

zy

Fig. 12 Variation of Upward Heat LOSS Coefficient UL with Collector Plate Temperature and Ambient Air Temperatures for Single-, Double-, and Triple-Glazed Collectors

35.11

Solar Energy Use

ASHRAE Standard 93 specifies that efficiency be reported in terms of the gross collector area A, rather than the aperture area A , . The reported efficiency is lower than that given by Equation (285, but the total energy collected is not changed by this simplification:

COMPONENTS This section describes the major components involved in the collection, storage, transportation, control, and distribution of solar heat for a domestic hot-water system. Collectors. Flat-plate collectors are most commonly used for water heating because of the year-round load requiring temperatures of 30 to 80°C. For discussions of other collectors and applications, see ASHRAE Standard 93, Chapter 36 of the 2008 ASHRAE Handbook-HVAC Systems and Equipment, and previous sections of this chapter. Collectors must withstand extreme weather (e.g., freezing, stagnation, high winds), as well as system pressures. Heat Transfer Fluids. Heat transfer fluids transport heat from the solar collectors to the domestic water. There are potential chemical and mechanical problems with this transfer, primarily in systems in which a heat exchanger interface exists with the potable water supply. Both the chemical compositions of the heat transfer fluids (pH, toxicity, and chemical durability) and their mechanical properties (specific heat and viscosity) must be considered. Except in unusual cases, or when potable water is being circulated, the energy transport fluid is nonpotable and could contaminate potable water. Even potable or nontoxic fluids in closed circuits are likely to become nonpotable because of contamination from metal piping, solderjoints, and packing, or by the inadvertent installation of a toxic fluid at a later date. Thermal Energy Storage. Heat collected by solar domestic and service water heaters is virtually always stored as a liquid in tanks. Storage tanks and bins should be well insulated. In domestic hotwater systems, heat is usually stored in one or two tanks. The hotwater outlet is at the top of the tank, and cold water enters the tank through a dip tube that extends down to within 100 to 150 mm of the tank bottom. The outlet on the tank to the collector loop should be approximately 100 mm above the tank bottom to prevent scale deposits from being drawn into the collectors. Water from the collector array returns to the middle to lower portion of the storage tank. This plumbing arrangement may take advantage of thermal stratification, depending on the delivery temperature from the collectors and the flow rate through the storage tank. Single-tank electric auxiliary systems often incorporate storage and auxiliary heating in the same vessel. Conventional electric water heaters commonly have two heating elements: one near the top and one near the bottom. If a dual-element tank is used in a solar energy system, the bottom element should be disconnected and the top left functional to take advantage of fluid stratification. Standard gas- and oil-fred water heaters should not be used in single-tank arrangements. In gas and oil water heaters, heat is added to the bottom of the tanks, which reduces both stratification and collection efficiency in single-tank systems. Dual-tank systems often use the solar domestic hot-water storage tank as a preheat tank. The second tank is normally a conventional domestic hot-water tank containing the auxiliary heat source. Multiple tanks are sometimes used in large institutions, where they operate similarly to dual-tank heaters. Although using two tanks may increase collector efficiency and the solar fraction, it increases tank heat losses. The water inlet is usually a dip tube that extends near the bottom of the tank. Estimates for sizing storage tanks usually range from 40 to 100 L per square metre of solar collector area. The estimate used most often is 75 L per square metre of collector area, which usually pro-

zyxwvutsrq zyxwvutsr zyxwvutsrqpon Fig. 13 Efficiency Versus (tfi-tat)/& for Single-Glazed Solar Water Heater and DoubleGlazed Solar Air Heater

(2) FR is lower for B than for A because of the lower heat transfer coefficient between air and the u n f m e d metal absorber. The x-intercept for air heater B is greater than it is for the water heater A because the upward loss coefficient U, is much lower for the double-glazed air heater than for the single-glazed water heater. The data for both A and B were taken at near-normal incidence with high values of Ite. For Example 5, using a single-glazed water heater, the value of the parameter would be close to (60 30)/ 967 = 0.031 (m2.K)/W, and the expected efficiency, 0.60, agrees closely with the test results. As ASHRAE Standard 93 shows, the incident angles encountered with south-facing tilted collectors vary widely throughout the year. Considering a surface located at 40" north latitude with a tilt angle C = 40°, the incident angle 8 depends on the time of day and the declination 6. On December 21,6 = 23.456'; at 4 h before and after solar noon, the incident angle is 62.7", and remains close to this value for the same solar time throughout the year. Total irradiation at these conditions varies from a low of 140 W/m2 on December 21 to approximately 440 W/m2 throughout most of the other months. When irradiation is below about 3 15 W/m2, losses from the collector may exceed the heat that can be absorbed. This situationvaries with the temperature difference between the collector inlet temperature and the ambient air, as suggested by Equation (27). When the incident angle rises above 30°, the product of the glazing's transmittance and the collector plate's absorptance begins to diminish; thus, heat absorbed also drops. Losses from the collector are generally higher as time moves farther from solar noon, and consequently efficiency also drops. Thus, daylong efficiency is lower than near-noon performance. During early afternoon, efficiency is slightly higher than at the comparable morning time, because the ambient air temperature is lower in the morning than in the afternoon. ASHRAE Standard 93 describes the incident angle modifier, which may be found by tests run when the incident angle is set at 30, 45, and 60". Simon (1976) showed that for many flat-plate collectors, the incident angle modifier is a linear function of the quantity (licos 8 1). For evacuated tubular collectors, the incident angle modifier may grow with rising values of 8. ~

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201 1 ASHRAE Handbook-HVAC Applications (SI)

35.12 vides enough heat for a sunless period of about a day. Storage volume should be analyzed and sized according to the project water requirements and draw schedule; however, solar applications typically require larger-than-normal tanks, usually the equivalent of the average daily load. Heat Exchangers. Indirect solar water heaters require one or more heat exchangers. The potential exists for contamination in the transfer of heat energy from solar collectors to potable hot water. Heat exchangers influence the effectiveness of energy collected to heat domestic water. They also separate and protect the potable water supply from contamination when nonpotable heat transfer fluids are used. For this reason, various codes regulate the need for and design of heat exchangers. Heat exchanger selection should consider the following: Heat exchange effectiveness Pressure drop, operating power, and flow rate Design pressure, configuration, size, materials, and location Cost and availability Reliable protection of potable water supply from contamination by heat transfer fluid Leak detection, inspection, and maintainability Material compatibility with other elements (e.g., metals and fluids) Thermal compatibility with design parameters such as operating temperature, and fluid thermal properties

-

Heat exchanger selection depends on characteristics of fluids that pass through the heat exchanger and properties of the exchanger itself. Fluid characteristics to consider are fluid type, specific heat, mass flow rate, and hot- and cold-fluid inlet and outlet temperatures. Physical properties of the heat exchanger to consider are the overall heat transfer coefficient of the heat exchanger and the heat transfer surface area. For most solar domestic hot-water designs, only the hot and cold inlet temperatures are known; the other temperatures must be calculated using the heat exchanger’s physical properties. Two quantities that are useful in determining a heat exchanger’s heat transfer and a collector’s performance characteristics when it is combined with a given heat exchanger are the (1) fluid capacitance rate, which is the product of the mass flow rate and specific heat of fluid passing through the heat exchanger, and (2) heat exchanger effectiveness, which relates the capacitance rate of the two fluids to the fluid inlet and outlet temperatures. Effectiveness is equal to the ratio of the actual heat transfer rate to the maximum heat transfer rate theoretically possible. Generally, a heat exchanger effectiveness of 0.4 or greater is desired. Expansion Tanks. An indirect solar water heater operating in a closed collector loop requires an expansion tank to prevent excessive pressure. Fluid in solar collectors under stagnation conditions can boil, causing excessive pressure to develop in the collector loop, and expansion tanks must be sized for this condition. Expansion tank sizing formulas for closed-loop hydronic systems, found in Chapter 12 of the 2008 ASHRAE Handbook-HVAC Systems and Equipment, may be used for solar heater expansion tank sizing, but the expression for volume change caused by temperature increase should be replaced with the total volume of fluid in the solar collectors and of any piping located above the collectors, if significant. This sizing method provides a passive means for eliminating fluid loss through overtemperature or stagnation, common problems in closed-loop solar systems. This results in a larger expansion tank than typically found in hydronic systems, but the increase in cost is small compared to the savings in fluid replacement and maintenance costs (Lister and Newel1 1989). Pumps. Pumps circulate heat transfer liquid through collectors and heat exchangers. In solar domestic hot-water heaters, the pump is usually a centrifugal circulator driven by a motor of less than 300 W. The flow rate for collectors generally ranges from 0.010 to

0.027 L/(s.m2). Pumps used in drainback systems must provide pressure to overcome friction and to lift the fluid to the collectors. Piping. Piping can be plastic, copper, galvanized steel, or stainless steel. The most widely used is nonlead, sweat-soldered L-type copper tubing. M-type copper is also acceptable if allowed by local building codes. If water/glycol is the heat transfer fluid, galvanized pipes or tanks must not be used because unfavorable chemical reactions will occur; copper piping is recommended instead. Also, if glycol solutions or silicone fluids are used, they may leak through joints where water would not. Piping should be compatible with the collector fluid passage material; for example, copper or plastic piping should be used with collectors having copper fluid passages. Piping that carries potable water can be plastic, copper, galvanized steel, or stainless steel. In indirect systems, corrosion inhibitors must be checked and adjusted no less than m u a l l y , preferably every three months. Inhibitors should also be checked if the system overheats during stagnation. If dissimilar metals are joined, dielectric or nonmetallic couplings should be used. The best protection is sacrificial anodes or getters in the fluid stream. Their location depends on the material to be protected, anode material, and electrical conductivity of the heat transfer fluid. Sacrificial anodes of magnesium, zinc, or aluminum are often used to reduce corrosion in storage tanks. Because many possibilities exist, each combination must be evaluated. A copper-aluminum or copper-galvanized steel joint is unacceptable because of severe galvanic corrosion. Aluminum, copper, and iron have a greater potential for corrosion. Elimination of air, pipe expansion, and piping slope must be considered to avoid possible failures. Collector pipes (particularly manifolds) should be designed to allow expansion from stagnation temperature to extreme cold weather temperature. Expansion can be controlled with offset elbows in piping, hoses, or expansion couplings. Expansion loops should be avoided unless they are installed horizontally, particularly in systems that must drain for freeze protection. The collector array piping should slope 5 mm per metre for drainage (DOE 1978a). Air can be eliminated by placing air vents at all piping high points and by air purging during filling. Flow control, isolation, and other valves in the collector piping must be chosen carefully so that these components do not restrict drainage significantly or back up water behind them. The collectors must drain completely. Valves and Gages. Valves in solar domestic hot-water systems must be located to ensure system efficiency, satisfactory performance, and safety of equipment and personnel. Drain valves must be ball-type; gate valves may be used if the stem is installed horizontally. Check valves or other valves used for freeze protection or for reverse thermosiphoning must be reliable to avoid significant damage. Auxiliary Heat Sources. On sunny days, a typical solar energy system should supply water at a predetermined temperature, and the solar storage tank should be large enough to hold sufficient water for a day or two. Because of the intermittent nature of solar radiation, an auxiliary heater must be installed to handle hot-water requirements. If a utility is the source of auxiliary energy, operation of the auxiliary heater can be timed to take advantage of off-peak utility rates. The auxiliary heater should be carefully integrated with the solar energy heater to obtain maximum solar energy use. For example, the auxiliary heater should not destroy any stratification that may exist in the solar-heated storage tank, which would reduce collector efficiency. Ductwork, particularly in systems with air-type collectors, must be sealed carefully to avoid leakage in duct seams, damper shafts, collectors, and heat exchangers. Ducts should be sized using conventional air duct design methods. Control. Controls regulate solar energy collection by controlling fluid circulation, activate system protection against freezing and overheating, and initiate auxiliary heating when it is required. The three major control components are sensors, controllers, and actuators.

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35.13

Solar Energy Use Sensors detect conditions or measure quantities, such as temperature. Controllers receive output from the sensors, select a course of action, and signal a component to adjust the condition. Actuators, such as pumps, valves, dampers, and fans, execute controller commands and regulate the system. Temperature sensors measure the temperature of the absorber plate near the collector outlet and near the bottom of the storage tank. The sensors send signals to a controller, such as a differential temperature thermostat, for interpretation. The differential thermostat compares signals from the sensors with adjustable set points for high and low temperature differentials. The controller performs different functions, depending on which set points are met. In liquid systems, when the temperature difference between the collector and storage reaches a high set point, usually 7 to 8 K, the pump starts, automatic valves are activated, and circulation begins. When the temperature difference reaches a low set point, usually 2 K, the pump is shut off and the valves are deenergized and returned to their normal positions. To restart the system, the differential temperature set point must again be met. If the system has either freeze or overheat protection, the controller opens or closes valves or dampers and starts or stops pumps or fans to protect the system when its sensors detect conditions indicating that either freezing or overheating is about to occur. Sensors must be selected to withstand high temperature, such as may occur during collector stagnation. Collector loop sensors should be located as close as possible to the outlet of the collectors, either in a pipe above the collector, on a pipe near the collector, or in the collector outlet passage. The storage temperature sensor should be near the bottom of the storage tank to detect the temperature of fluid before it is pumped to the collector or heat exchanger. Storage fluid is usually coldest at that location because of thermal stratification and the location of the makeup water supply. The sensor should be either securely attached to the tank and well insulated, or immersed inside the tank near the collector supply. The freeze protection sensor, if required, should be located so that it detects the coldest liquid temperature when the collector is shut down. Common locations are the back of the absorber plate at the bottom of the collector, the collector intake or return manifolds, or the center of the absorber plate. The center absorber plate location is recommended because reradiation to the night sky freezes the collector heat transfer fluid, even though the ambient temperature is above freezing. Some systems, such as the recirculation system, have two sensors for freeze protection; others, such as the draindown, use only one. Control of odoff temperature differentials affects system efficiency. If the differential is too high, the collector starts later than it should; if it is too low, the collector starts too soon. The turn-on differential for liquid systems usually ranges from 5.5 to 17 K) and is commonly lower in wanner climates and higher in cold climates. For air systems, the range is usually 14 to 25 K. The turn-off temperature differential is more difficult to estimate. Selection depends on a comparison between the value of the energy collected and the cost of collecting it. It varies with individual systems, but a value of 2 K is typical and generally the fixed default value in the control. Water temperature in the collector loop depends on ambient temperature, solar radiation, radiation from the collector to the night sky, and collector loop insulation. Freeze protection sensors should be set to detect 4". Sensors are important but often overlooked control components. They must be selected and installed properly because no control can produce accurate outputs from unreliable sensor inputs. Sensors are used in conjunction with a differential temperature controller and are usually supplied by the controller manufacturer. Sensors must survive the anticipated operating conditions without physical damage or loss of accuracy. Low-voltage sensor circuits must be located

away from high-voltage lines to avoid electromagnetic interference. Sensors attached to collectors should be able to withstand the stagnation temperature. Sensor calibration, which is often overlooked by installers and maintenance personnel, is critical to system performance; a routine calibration maintenance schedule is essential. Another control option is to use a photovoltaic (PV) panel that powers a pump. A properly sized and oriented PV panel converts sunlight into electricity to run a small circulating pump. No additional sensing is required because the PV panel and pump output increase with sunlight intensity and stop when no sunlight (collector energy) is available. Cromer (1984) showed that, with proper matching of pump and PV electrical characteristics, PV panel sizes as low as 1.35 W/m2 of thermal panel may be used successfully. Difficulty with late starting and running too long in the afternoon can be alleviated by tilting the PV panel slightly to the east during commissioning of the installed system.

WATER HEATING A solar water heater includes a solar collector that absorbs solar radiation and converts it to heat, which is then absorbed by a heat transfer fluid (water, a nonfreezing liquid, or air) that passes through the collector. The heat transfer fluid's heat is stored or used directly. Portions of the solar energy system are exposed to the weather, so they must be protected from freezing. The system must also be protected from overheating caused by high insolation levels during periods of low energy demand. In solar water heating, water is heated directly in the collector or indirectly by a heat transfer fluid that is heated in the collector, passes through a heat exchanger, and transfers its heat to the domestic or service water. The heat transfer fluid is transported by either natural or forced circulation. Natural circulation occurs by natural convection (thermosiphoning), whereas forced circulation uses pumps or fans. Except for thermosiphon systems, which need no control, solar domestic and service water heaters are controlled by differential thermostats. Five types of solar energy systems are used to heat domestic and service hot water: thermosiphon, direct circulation, indirect, integral collector storage, and site built. Recirculation and draindown are two methods used to protect direct solar water heaters from freezing.

Thermosiphon Systems Thermosiphon systems (Figure 14) heat potable water or a heat transfer fluid and rely on natural convection to transport it from the collector to storage. For direct systems, pressure-reducing valves are required when the city water pressure is greater than the working pressure of the collectors. In a thermosiphon system, the storage tank must be elevated above the collectors, which sometimes requires designing the upper level floor and ceiling joists to bear this additional load. Extremely hard or acidic water can cause scale deposits that clog or corrode the absorber fluid passages. Thermosiphon flow is induced whenever there is sufficient sunshine, so these systems do not need pumps.

Direct-Circulation Systems A direct-circulation system (Figure 15) pumps potable water from storage to the collectors when there is enough solar energy available to warm it. It then returns the heated water to the storage tank until it is needed. Collectors can be mounted either above or below the storage tank. Direct-circulation systems are only feasible in areas where freezing is infrequent. Freeze protection is provided either by recirculating warm water from the storage tank or by flushing the collectors with cold water. Direct water-heating systems should not be used in areas where the water is extremely hard or

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35.14

Applications (SI)

Fig. 16 Draindown System Fig. 14 Thermosiphon System

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Fig. 15 Direct Circulation System

acidic because scale deposits may clog or corrode the absorber fluid passages, rendering the system inoperable. Direct-circulation systems are exposed to city water line pressures and must withstand pressures as required by local codes. Pressure-reducing valves and pressure-relief valves are required when city water pressure is greater than the working pressure of the collectors. Direct-circulation systems often use a single storage tank for both solar energy storage and the auxiliary water heater, but twotank storage systems can be used. Draindown Systems. Draindown systems (Figure 16) are directcirculation water-heating systems in which potable water is pumped from storage to the collector array where it is heated. Circulation continues until usable solar heat is no longer available. When a freezing condition is anticipated or a power outage occurs, the system drains automatically by isolating the collector array and exterior piping from the city water pressure and using one or more valves for draining. Solar collectors and associated piping must be carefully sloped to drain the collector’s exterior piping.

Indirect Water-Heating Systems Indirect water-heating systems (Figure 17) circulate a freezeprotected heat transfer fluid through the closed collector loop to a heat exchanger, where its heat is transferred to the potable water. The most commonly used heat transfer fluids are wateriethylene glycol

and wateripropylene glycol solutions, although other heat transfer fluids such as silicone oils, hydrocarbons, and refrigerants can also be used (ASHRAE 1983). These fluids are nonpotable, sometimes toxic, and normally require double-wall heat exchangers. The double-wall heat exchanger can be located inside the storage tank, or an external heat exchanger can be used. The collector loop is closed and therefore requires an expansion tank and a pressure-relief valve. A one- or two-tank storage can be used. Additional overtemperature protection may be needed to prevent the collector fluid from decomposing or becoming corrosive. Designers should avoid automatic water makeup in systems using wateriantifreeze solutions because a significant leak may raise the freezing temperature of the solution above the ambient temperature, causing the collector array and exterior piping to freeze. Also, antifreeze systems with large collector arrays and long pipe runs may need a time-delayed bypass loop around the heat exchanger to avoid freezing the heat exchanger on start-up. Drainback Systems. Drainback systems are generally indirect water-heating systems that circulate treated or untreated water through the closed collector loop to a heat exchanger, where its heat is transferred to the potable water. Circulation continues until usable energy is no longer available. When the pump stops, the collector fluid drains by gravity to a storage or tank. In a pressurized system, the tank also serves as an expansion tank, so it must have a temperature- and pressure-relief valve to protect against excessive

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CHAPTER 36

ENERGY USE AND MANAGEMENT Energy Management ................................................................ Communications ...................................................................... Energy Accounting Systems ..................................................... Analyzing Energy Data ............................................................ Surveys and Audits ................................................................... Improving Discretionary Operations

36.1 36.2 36.3 36.3 36.6 36.9

Energy-Efficiency Measures .................................................. Implementing Energy-Efficiency Measures ........................... Monitoring Results ................................................................. Evaluating Success and Establishing New Goals .......................................................................... Building Emergency Energy Use Reduction

36.11 36.12 36.12 36.12 36.15

E

NERGY management in buildings is the control of energy use and cost while maintaining indoor environmental conditions to provide comfort and to fully meet functional needs. This chapter provides guidance on establishing an effective, ongoing energy management program, as well as information on planning and implementing energy management projects. The energy manager should understand how energy is used in the building, to manage it effectively. There are opportunities for savings by reducing the unit price of purchased energy, and by improving the efficiency and reducing the use of energy-consuming systems. Waterisewer costs and use may be included in the energy management activity. This could be called “utility management,” but “energy management” is used in this chapter.

ENERGY MANAGEMENT The specific processes by which building owners and operators control energy consumption and costs are as variable as their building types. Small buildings, such as residences and small commercial businesses, usually involve the efforts of one person. Energy management procedures should be as simple, specific, and direct as possible. General energy management advice, such as from utility energy surveys or state or provincial energy offices, can provide ideas, but these must be evaluated to determine whether they are applicable to the target building. Owners and operators of smaller buildings may only need advice on specific energy projects (e.g., boiler replacement, lighting retrofit). On the other hand, large or complex facilities, such as hospital or university campuses, industrial complexes, or large office buildings, usually require a team effort and process as represented in Figure 1. Figure 1 is adapted from the ENERGY STAR@Web site (www. energystar.gov). On the ENERGY STAR Web site, each box in the flowchart refers the reader to numerous useful tips. Energy management for existing buildings has these basic steps: 1. Appoint an energy manager to oversee the process and to ensure that someone is dedicated to the initiatives and accountable to the company. 2. Early communication to solicit feedback for other steps of the process. 3. Establish an energy accounting system that records energy and water consumption and associated costs. It should include comparisons with similar buildings, to benchmark and set performance goals. 4. Validate and analyze current and historical energy use data to help identify conservation energy-efficiency measures 5. Carry out energy surveys and walk-through audits to identify low-costho-cost operations, maintenance, and energy-efficiency measures. Having a qualified energy professional do this is recommended. The preparation of this chapter is assigned to TC 7.6, Building Energy Performance.

Fig. 1 An Energy Management Process 6. Using the survey results, change building operating procedures to eliminate energy waste. 7. Evaluate energy-efficiency measures for expected savings, estimated implementation costs, risks, and nonenergy benefits. Recommend a number of prioritized energy-efficiency projects for implementation. 8. Implement approved energy-efficiency measures (EEMs). Tender projects that must be outsourced. 9. Track results using the energy accounting system for overall performance, supplemented as needed by energy monitoring related to specific projects. 10. Compare results to past goals, revise as necessary, and develop new goals. Report to management and tenants. Return to step 7 and continue the process to maintain and continually improve building performance. Each of these energy management program components is discussed in detail in the following sections. ASHRAE Standard 100 gives details useful in energy management planning in existing buildings. Information on energy efficiency in new design can be found in all volumes of the ASHRAE Handbook and in ASHRAE Standards 90.1 and 90.2. The area most likely to be overlooked in new design is the ability to measure and monitor energy consumption and trends for each energy use category given in Chapter 41. Additional guidelines for this area can be found in Chapter 34 of the 2009 ASHRAE HandbookFundamentals.

36.1

zyxwvuts 201 1 ASHRAE Handbook-HVAC

36.2 Organizing for Energy Management

To be effective, energy management must be given the same emphasis as management of any other costiprofit center. Top management should

Establish the energy costiprofit center Assign management responsibility for the program Assign an energy manager and provide training Allocate resources Clearly communicate the energy management program to all departments and personnel Set clear program goals Encourage ownership of the program by all levels of the organization Set up an ongoing reporting and analysis procedure to monitor results Develop a feedback mechanism to allow timely revisions

Applications (SI)

Forecast and budget for short- and long-term energy requirements and costs Report regularly to top management and other stakeholders.

Public relations functions Make occupants aware of the benefits of efficient energy use Establish a mechanism to elicit and evaluate suggestions Recognize successful energy projects Establish an energy communications network Increase community awareness with press releases and appearances at civic group meetings

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It is common for a facility to allocate 3 to 10% of the a n n u l energy cost for administration of an energy management program. The budget should include funds for continuing education of the energy manager and staff.

Energy Managers The functions of an energy manager fall into four broad categories: technical, policy-related, planning and purchasing, and public relations. A list of specific tasks and a plan for their implementation must be clearly documented and communicated to building occupants. An energy manager in a large commercial complex may perform most of the following functions; one in a smaller facility may have only a few from each category to consider.

Technicalfunctions Conduct energy audits and identifying energy-efficiency measures Act as in-house technical consultant on new energy technologies, alternative fuel sources, and energy-efficient practices Evaluate energy efficiency of proposed new construction, building expansion, remodeling, and new equipment purchases Set performance standards for efficient operation and maintenance of equipment and facilities Review state-of-the-art energy management hardware Review building operation and maintenance procedures for optimal energy management Implement energy-efficiency measures (EEMs) Establish an energy accounting system Establish a baseline from which energy-saving improvements can be measured Measure and maintain effectiveness of EEMs Measure energy use in the field to verify design and operating conditions

Policy-related functions Fulfill energy policy established by top management Monitor federal and state (provincial) legislation and regulatory activities, and recommend policyiresponse Adhere to energy management building codes Represent the organization in energy associations Administer government-mandated reporting programs

Planning andpurchasing functions Take advantage of fuel-switching and load management opportunities Purchase equipment based on life-cycle cost Take advantage of energy-efficiency programs offered by utilities and agencies Negotiate or advise on major utility contracts Develop contingency plans for supply interruptions or shortages

General qualijkations

A technical background, preferably in engineering Experience in energy-efficient design of building systems and processes Practical, hands-on experience with systems and equipment Goal-oriented management style Ability to work with people at all levels Technical report-writing and verbal communication skills

Desirable educational and professional qualijkations Bachelor of science degree, preferably in mechanical, electrical, industrial, or chemical engineering Thorough knowledge of energy resource planning and conservation Ability to Analyze and compile technical and statistical information and reports Interpret plans and specifications for building facilities Knowledge of Utility rates, energy efficiency, and planning Automatic controls and systems instrumentation Energy-related metering equipment and practices Project management If it is not possible to add a full-time manager, an existing employee with a technical background should be considered and trained. Energy management should not be a collateral duty of an employee who is already fully occupied. Another option is to hire a professional energy management consultant. Energy services companies (ESCOs) provide energy services as part of a contract, with payments based on realized savings. Other companies charge a fee to perform a variety of energy management functions.

COMMUNICATIONS Energy management requires careful planning and help from all personnel that operate and use the facility. A communication plan should be regularly reviewed by both the energy manager and senior management. The initial communiquk should introduce the plan and express the support oftop management for high-level goals. Providing early information to tenants and staff is important, because it takes time to change behaviors. Once the communication plan is launched, the energy manager should be prepared to answer a variety of questions from different areas of the company. An effective communication strategy may include these tasks: Produce a regular newsletter Post energy-saving tips or reminders Hold annual seminars with maintenance and cleaning staff Meet with operations staff for training and feedback Report regularly to management and operations staff Message content should be tailored to the specific audience. The more successful the communication is, the more quickly the energy management activities will become second nature. Diligent reporting promotes accountability and persistence of performance.

Energy Use and Management ENERGY ACCOUNTING SYSTEMS

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An energy accounting system that tracks consumption and costs on a continuing basis is essential. It provides energy use data needed to confirm savings from energy-efficiency projects. The primary data source is utility bills, but other sources include

36.3

ANALYZING ENERGY DATA

Preparing for Cost and Efficiency Improvements

The energy manager establishes procedures for meter reading, monitoring, and tabulating facility energy use and profiles. The energy manager also periodically reviews utility rates, rate structures, and trends, and should subscribe to free utility mailing lists to track changes in their rate tariffs. The energy manager provides periodic reports to top management, summarizing the work accomplished, its cost-effectiveness, plans for future work, and projections of utility costs. Utility bill analysis software can be used to track avoided costs. If energy-efficiency measures are to be cost-effective, continued monitoring and periodic reauditing are necessary to ensure persistence. The procedures in ASHRAE Guideline 14 can be used for measurement and verification of energy savings.

Opportunities for savings come in reducing (1) the cost per unit of energy, and then (2) energy consumption. Historically, energy users had little choice in selecting energy suppliers, and regulated tariffs applied based on certain customer characteristics. In recent years there has been a move in North America and other parts of the world to deregulate energy markets. and there is more flexibility in supply and pricing. Electric rate structures vary widely in North America; Chapter 37 discusses these in detail. Electric utilities commonly meter both consumption and demand. Demand is the peak rate of consumption, typically averaged over a 15 or 30 min period. Electric ut es may also use a ratchet billing procedure for demand. Contact the local electric utility to fully understand the demand component. Some utilities use real-time pricing (RTP), in which the utility calculates the marginal cost of power per hour for the next day, determines the price, and sends this hourly price to customers. The customer can then determine the power consumption at different times of the day. A variation on RTP was introduced in some areas: demand exchange and active load management pays customers to shed loads during periods of high utility demand. Also called demand reduction or demand response, the utilities ask participating customers to reduce their consumption for a period of time on as little as a few hours’ notice. Caution is advised in designing or installing systems that take advantage of utility rate provisions, because the structure or provisions of utility rates cannot be guaranteed for the life of the system. Provisions that change include on-peak times, declining block rates, and demand ratchets. Chapter 56 has additional information on billing rates.

Energy Accounting

Analyzing Energy Use Data

Printouts from time-of-use meters Combustion efficiency, eddy current, and water quality tests Recordings of temperature and relative humidity Submetered energy use Event recordings Occupancy schedules and occupant activity levels Climate data Data from similar buildings in similar climates Infrared scans Production records Computer modeling

Energy Accounting Process

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Energy accounting means tracking utility bill data on a monthly basis to provide a current picture of building energy performance and to identify trends and instances of excess use. An Internet search for “energy accounting” will produce Web sites for the major commercial providers. In some cases software is sold for computer installation, or the accounting system is web-based and the user has a subscription. For many users, a simple spreadsheet is all that is needed. A comparison of the features of many available energy accounting software packages can be found at http:ll www.betterbricks.com/DetailPage.aspx?ID=518. Portfolio Manager, from the ENERGY STAR Web site, allows users to enter monthly energy usage, in kWh, therms, etc. The Portfolio Manager simultaneously calculates the facility’s EUI and develops a normalized ENERGY STAR score (http:llwww.energystax.govlbenchmark). Portfolio Manager facilitates comparison of multiple buildings and goal setting, is useful for numerous building types, and is normalized by building type for weather.

Utility Rates Because most energy management activities are dictated by economics, the energy manager must understand the utility rates that apply to each facility. Electric rates are more complex than gas or water rates and some rate structures make cost calculations difficult. In addition to general commercial or institutional electric rates, special rates may exist such as time of day, interruptible service, on peakioff peak, summerlwinter, and peak demand. Electric rate schedules vary widely inNorth America; Chapters 37 and 56 discuss these in detail. Energy managers should work with local utility companies to identify the most favorable rates for their buildings, and must understand how demand is computed as well as the distinction between marginal and average costs (see the section on Improving Discretionary Operations). The utility representative can help develop the most costeffective methods of metering and billing.

Any reliable utility data should be examined. Ut vide metered data with measurement intervals as short as 15 min. Data from shorter time intervals make anomalies more apparent. High consumption at certain periods may reveal opportunities for cost reduction (Haberl and Komor 1990a, 1990b). If monthly data are used, they should be analyzed over several years. A base year should be established as a reference point. Record the dates of meter readings so that energy use can be normalized for the number of days in a billing period. Any periods in which consumption was estimated rather than measured should be noted. If energy data are available for more than one building or department, each should be tabulated separately. Initial tabulations should include both energy and cost per unit area (in an industrial facility, this may be energy and cost per unit of goods produced). Document variables such as heating or cooling degree-days, percent occupancy, quantity of goods produced, building occupancy, hours of operation, or daily weather conditions (see Chapter 14, Climatic Design Information, in the 2009 ASHRAE Handbook-Fundarnentals). Because these variables may not be directly proportional to energy use, it is best to plot information separately or to superimpose one plot over another. Examples of ways to normalize energy consumption for temperature and other variations are provided in ASHRAE Guideline 14. Potential savings areas can be identified by separating base energy consumption from weather-dependent energy consumption. Base-load energy use is the amount of energy consumed independent of weather, such as for lighting, motors, domestic hot water, and miscellaneous office equipment. When a building has electric cooling and no electric heating, the base-load electric energy use is normally the energy consumed during the winter. The annual baseload energy use may also be estimated by taking the average monthly use during nonheating or noncooling months and multiplying by 12. For many buildings, subtracting the base-load energy use

201 1 ASHRAE Handbook-HVAC Applications (SI)

36.4

Table 1 Electricity Consumption for Atlanta Example Building Occupancy Factor

32.7%

Summer ELF 2002

82.5%

Year

Month

Billstart

BillEnd

2002 2002 2002 2002 2002 2002 2002 2002 2002 2002 2002 2002 2003 2003 2003 2003 2003 2003 2003 2003 2003 2003 2003 2003 2004 2004 2004 2004 2004 2004 2004 2004 2004 2004 2004 2004

Jan-02 Feb-02 Mar-02 Apr-02 May-02 Jun-02 Jul-02 Aug-02 Sep-02 Oct-02 Nov-02 Dec-02 Jan-03 Feb-03 Mar-03 Apr-03 May-03 Jun-03 Jul-03 Aug-03 Sep-03 Oct-03 Nov-03 Dec-03 Jan-04 Feb-04 Mar-04 Apr-04 May-04 Jun-04 Jul-04 Aug-04 Sep-04 Oct-04 Nov-04 Dec-04

1/2/2002 1/31/2002 2/28/2002 4/1/2002 4/29/2002 5/31/2002 6/28/2002 7/31/2002 8/30/2002 9/30/2002 10/29/2002 12/2/2002 1/2/2003 1/31/2003 3/3/2003 4/1/2003 4/30/2003 6/2/2003 6/28/2003 7/30/2003 8/29/2003 9/30/2003 10/30/2003 11/26/2003 12/30/2003 1/30/2004 2/28/2004 3/19/2004 3/3 1/2004 5/4/2004 6/2/2004 7/2/2004 8/3/2004 9/1/2004 10/1/2004 11/2/2004

1/31/2002 2/28/2002 4/1/2002 4/29/2002 5/31/2002 6/28/2002 7/31/2002 8/30/2002 9/30/2002 10/29/2002 12/2/2002 1/2/2003 1/31/2003 3/3/2003 4/1/2003 4/30/2003 6/2/2003 6/28/2003 7/30/2003 8/29/2003 9/30/2003 10/30/2003 11/26/2003 12/30/2003 1/30/2004 2/28/2004 3/19/2004 3/3 1/2004 5/4/2004 6/2/2004 7/2/2004 8/3/2004 9/1/2004 10/1/2004 11/2/2004 12/3/2004

2002 2003 2004

Summer ELF 2003

37.4%

Actual Billed Billing Billed Use, Demand, Demand, Period kWh kW kW 29 28 32 28 32 28 33 30 31 29 34 31 29 31 29 29 33 26 32 30 32 30 27 34 31 29 20 12 34 29 30 32 29 30 32 31

(kWh.y)/m*

Days

265.35 255.29 240.42

365 362 339

aMaximum or minimum value for year.

Building Area: 2852 m2

54,600 46,620 60,900 56,340 65,520 63,540 76,860 82,620 66,780 60,720 62,100 60,180 57,120 61,920 60,060 62,640 73,440 53,100 67,320 66,000 63,960 55,260 46,020 61,260 59,040 54,240 37,080 22,140 64,260 63,720 69,120 73,800 64,500 60,060 65,760 51.960

166 148 140b3C 166 159 180 158 192 195b 193 151 166 178 145 140 154 161 171 180b 170 149 122 140 141 145 159 122 133 148 148 169 170b 166b 152 128 132

166 166 166 166 166 180 171 192 195b 185 185 185 185 185 185 185 185 185 185b 185 171 171 171 171 171 171 171 171 171 171 169 170b 166b 161 161 161

Total kWh Peak kW Billed kW 756,780 728,100 685,680

195 180 170

bPeak demand for year.

from total m u a l energy use yields a good estimate of heating or cooling energy consumption. This approach is not valid when building operation differs from summer to winter, when cooling operates year-round, or when space heating is used during summer (e.g., for reheat). Base-load analysis can be improved by using hourly load data. Electric load factors (ELFs) and occupancy factors can also be used instead of hourly energy profiles (Haberl and Komor 1990a, 1990b). Although it can be difficult to relate heating and cooling energy directly to weather, several authors, including Fels (1986) and Spielvogel (1984), suggest that this is possible using a curve-fitting method to calculate the balance point of a building (discussed in Chapter 19 of the 2009 ASHRAE Handbook-Fundamentals). For this method, building use must be regular, and actual rather than estimated data must be used, along with accurate dates and weather data.

195 185 171

Summer ELF 2004

LF

Daily Use, kWh

47.3% 46.9% 56.6% 50.5% 53.7% 52.5% 61.4% 59.8% 46.0% 45.2% 50.4% 48.7% 46.1% 57.4% 61.6% 58.4% 57.6% 49.8% 48.7% 53.9% 55.9% 62.9% 50.7% 53.2% 54.7% 49.0% 63.3% 57.8% 53.2% 61.9% 56.8% 56.5% 55.8% 54.9% 66.9% 52.9%

1883 1665a 1903 2012 2048 2269 2329 2754a 2154 2094 1826 1941 1970 1997 2071 2160 2225a 2042 2104 2200 1999 1842 1704a 1802 1905 1870 1854 1845 1890 2197 2304 2306a 2224 2002 2055 1676a

54.7%

zy

Daily Monthly Percent Base Use, Base Use, Excessuse, kWh kWh kWh 1665 1665 1665 1665 1665 1665 1665 1665 1665 1665 1665 1665 1704 1704 1704 1704 1704 1704 1704 1704 1704 1704 1704 1704 1676 1676 1676 1676 1676 1676 1676 1676 1676 1676 1676 1676

48,285 46,620 53,280 46,620 53,280 46,620 54,945 49,950 51,615 48,285 56,610 51,615 49,429 52,838 49,429 49,429 56,247 44,316 54,542 51,133 54,542 51,133 46,020 57,951 51,960 48,608 33,523 20,114 56,988 48,608 50,284 53,636 48,608 50,284 53,636 51.960

11.6% 0.0% 12.5% 17.3% 18.7% 26.6% 28.5% 39.5% 22.7% 20.5% 8.8% 14.2% 13.5% 14.7% 17.7% 21.1% 23.4% 16.5% 19.0% 22.5% 14.7% 7.5% 0.0% 5.4% 12.0% 10.4% 9.6% 9.2% 11.3% 23.7% 27.3% 27.3% 24.6% 16.3% 18.4% 0.0%

Avg LF

Daily Base Use, kWh

Total Base Use, kWh

51.6% 51.5% 52.4%

1665 1704 1676

607,725 617,009 568,208

CMinimumdemand used in seasonal ELF calculation.

More detailed breakdown of energy use requires that some metered data be collected daily (winter versus summer days, weekdays versus weekends) and that some hourly information be collected to develop profiles for night (unoccupied), morning w m up, day (occupied), and shutdown. Submetering of energy end uses is recommended for optimal energy management. For more information, see Chapter 4 1. An example spreadsheet using three years of electricity bill data for a two-story office building in Atlanta, Georgia, is presented in Table 1. (See Chapter 18 of the 2009 ASHRAE Handbook-Fundamentals for floor plans and elevations of the building.)

zyxwvutsrqpo Electrical Use Profile

The electrical use profile (EUP) report, shown in Figure 2, divides electrical consumption into base and weather-dependent

36.5

Energy Use and Management

calculations for heating months to determine the electric cooling and heating loads, respectively.

z

Calculating Electrical Load and Occupancy Factors

Fig. 2

Electrical Use Profile for Atlanta Example Building

consumption. The average daily consumption for each month appears in the daily use column in Table 1, and is plotted in the EUP graph. The average daily consumption is calculated by dividing the consumption for a particular month by its billing days. The lowest value in the daily-use column is used to plot the facility’s base electrical consumption (shown as the base use line) in Figure 2. Where a facility uses electricity only for cooling or heating, or in an all-electric facility where there is no overlap between cooling and heating, the difference between these two lines represents the weather-dependent electrical consumption. Weather-dependent energy consumption (either electric or other fuels) may then be compared to the cooling degree-days (CDD) or heating degree-days (HDD) totals for the same time period (see Chapter 14 of the 2009 ASHRAE Handbook-Fundamentals). This comparison shows how the building performs from month to month or year to year. The HDDs stop and CDDs start at the balance point, defined as the outdoor temperature at which, for a specified interior temperature, the total heat loss is equal to the heat gain from the sun, occupants, lights, etc. Note that all-electric buildings may have periods of overlap between heating and cooling, causing the base load to be overestimated and the heating and cooling estimates to be conservative. Examine the average daily use line to see whether it follows the expected seasonal curve. For example, the shoulders ofthe curve for an electrically cooled, gas-heated hospital should closely follow the base electrical use line in the winter. As summer approaches, this curve should rise steadily to reflect the increased cooling load. Errors in meter readings, reading dates, or consumption variances appear as unusual peaks or valleys. Reexamine the data and correct errors as necessary. If an unusual profile remains after correcting any errors, an area of potential energy savings may exist. For example, if the average daily use line for the facility is running near summer levels during March, April, May, October, and November, simultaneous heating and cooling may be occurring. This situation is illustrated in Figure 2, and often occurs with dual-duct systems. Simultaneous heating and cooling is also indicated in the percent excess use column of Table 1. The values show the percent difference between the value appearing in the monthly base use column and the billed consumption for the month. In Figure 2, note how the excess consumption for spring and fall months runs close to the summer percentages. The monthly base use is the lowest value from the daily use column multiplied by the number of billing days for each month. For electrically cooled, gas-heated facilities, weather-dependent consumption is the difference between the totals of the monthly base use column and the billed use column. For an all-electric facility, subtract the total monthly consumption from total billed use for the cooling months, then do the same

Another method for detecting potential energy savings is to compare the facility’s electrical load factor to its occupancy factor. An ELF exceeding its occupancy factor indicates a higher-thanexpected electric use occurring outside normal occupancy (e.g., lights or fans are left on or air conditioning is not shut off as early in the day as possible in summer). Setback thermostats, direct digital control (DDC) strategies, time-of-day scheduling, and lighting controls can address this. The ELF is the ratio between the average daily use and the maximum possible use if peak demand operated for a 24 h period. The occupancy factor is the ratio between the hours a building actually is occupied and 24 hiday occupancy. To calculate the ELF, find the month with the lowest demand on the utility data analysis spreadsheet. This value represents the base monthly peak demand, and is usually found in the same or adjacent month as the month with the lowest consumption. From the EUP report, find the lowest value in the daily use column. For example, the lowest average daily use for the office building in Table 1 is 1704 kWh (in November 2003), and the lowest monthly demand from the spreadsheet is 122 kW (in October 2003). The ELF is calculated as follows:

zyx zyxwvutsrqpo ELF

=

Lowest average daily use Lowest monthly demand x 24

~

1704 122 x 24

~~

58%

~

The office is normally occupied from 7:30 AM to 6:30 PM, Monday to Friday. Therefore, the occupancy factor is calculated as

occupancyActual weekly occupied hours

~

factor

24 h x 7 days

-~ 55 33% 168 ~

Calculating Seasonal ELFs ELFs can also be calculated for cooling and heating seasons. Typical defaults are May to August as cooling months, and the rest .-the year as heating months, but these change based on climate. The steps for calculating a seasonal ELF are as follows: The daily base consumption is determined from the daily use column of the EUP report. Subtract the lowest value of the year from the highest value of the season. The base demand is determined by subtracting the lowest monthly demand for the year from the demand recorded for the month with the highest daily use. These calculations can be refined further if on- and off-peak data are available. For example, because the electrically cooled Atlanta example building operates year-round, the summer ELF must also be calculated. The daily base consumption (1089) is determined by subtracting the lowest value (1665) from the highest cooling-season value (2754) in the daily use column of the EUP report. From the spreadsheet, take the demand from September 2002 (the month with the peak cooling-season actual demand) and subtract the lowest monthly demand from the spreadsheet (195 140) to determine the cooling-season base demand (55). Thus, the summer ELF is ~

Summer ELF

=

1089 -= 82% (for 2002) 55 x 24

These calculations show that the cooling equipment is operating beyond building occupancy (82% versus 33%) Therefore, excessive equipment run times should be investigated. Note that comparing

201 1 ASHRAE Handbook-HVAC

36.6

Fig. 3

Comparison Between Actual and Billed Demand for Atlanta Example Building

the ELF to the occupancy factor is meaningless for buildings occupied 24 h a day, such as hospitals. Similar tables and charts may be created for natural gas, water, and other utilities.

Electric Demand Billing The Atlanta example building has a ratchet-type demand rate (see Chapter 56), and billed demand is determined as a percentage of actual demand in the summer months. The ratchet is illustrated in Figure 3, where billed demand is the greater of the measured demand or 95% of the highest measured demand within the past 12 months. The billed demand for January of year 3 was 171 kW (171 =0.95 x 180),or95%oftheactualdemandfromJulyofyear 2. In Table 1, the actual demand in the first six months of 2003 had no effect on the billed demand, and therefore no effect on the dollar amount of the bill; the same is true for the last three months of the year. Because of the demand ratchet, the billed demand in January 2004 (171 kW) was set in July 2003. This means that any conservation measures that reduce peak demand will not affect billed demand until the following summer (e.g., June to September 2004); however, consumption savings begin at the next billing cycle. The effect of demand ratchet rates is that any conservation measures implemented have a longer initial payback period simply because of the utility rate structure. The energy manager should investigate other rate structures, such as a time-of-use (TOU) or seasonal rates. Rate structures for smaller buildings may not include demand charges.

Benchmarking Energy Use Benchmarking (comparing a building’s normalized energy consumption to that of similar buildings) can be a useful first measure of energy efficiency. Relative energy use is commonly expressed in energy utilization index (EUI; energy use per unit area per year) and cost utilization index (CUI; energy cost per unit area per year). The Atlanta example building is 2852 m2 in size, so its 2004 EUI is 866 MJ/m2 and its CUI is $15.82/m2. Two sources of benchmarking data for U.S. buildings are ENERGY STAR (www.energystar.gov) and the U.S. Department of Energy’s Energy Information Administration (DOEIEIA). Data on U.S. buildings in all sectors are summarized in periodic reports by the DOEIEIA. Tables 2 to 4 present DOEiEIA CBECS data in a combined format. Table 2 lists EUI input data and EUI distributions for the buildings surveyed in 2003. Table 3 lists the 2003 Commercial Buildings Energy Consumption Survey (CBECS) electricity per unit of floor area, and Table 4 shows CUI distributions. More complete

Applications (SI)

zyx

and up-to-date information on the CBECS is available at www.eia.doe.gov/emeu/cbecs.When referring to these tables, keep in mind the facility’s operating or occupied hours of facility and current utility rates. Databases. Compiling a database of past energy use and cost is important. All reliable utility data should be examined. ASHRAE Standard 105 contains information that allows uniform, consistent expressions of energy consumption in new and existing buildings. The energy use database for a new building may consist solely of typical data for similar buildings, as in Table 2. This may be supplemented by energy simulation data developed during design. A new building should be commissioned to ensure proper operation of all systems, including any energy-efficiency features (see ASHRAE Guideline 1.1 and Chapter 43). All the data presented in these tables come from detailed reports of consumption patterns, and it is important to understand how they were derived. When using the data, verify correct use with the original EIA documents. Mazzucchi (1992) lists data elements useful for normalizing and comparing utility billing information. Metered energy consumption and cost data are also published by trade associations, such as the Building Owners and Managers Association International (BOMA), the National Restaurant Association (NRA), and the American Hotel and Lodging Association (AH&LA). In some cases, local energy consumption data may be available from local utility companies or state or provincial energy offices. Additional energy use information for homes and commercial buildings in Canada can be found at the Office of Energy Efficiency at http://www.oee.nrcan.gc .cdcorporate/statistics/neud/dpa/datape /publications.cfm. In Europe, benchmarking data are defmed on a national basis in the frame of the European Directive on the Energy Performance of Buildings (EPBD) (EC 2010). Balaras et al. (2007) provides an overview of relevant data for residential buildings, although detailed data for commercial buildings are rather limited (Gaglia et al. 2007).

zyxwvutsr SURVEYS AND AUDITS

This section provides guidance on conducting building surveys and describes the levels of intensity of investigation.

Energy Audits

The objective of an energy audit is to identify opportunities to reduce energy use andor cost. The results should provide the

36.7

Energy Use and Management Table 2 2003 Commercial Sector Floor Area and EUI Percentiles Calculated, Weighted

Building Use Administrative/professional office BanWother financial Clinic/other outpatient health College/university Convenience store Convenience store with gas station Distnbution/shipping center Dormitory/fraternity/soronty Elementary/middle school Entertainment/culture Fast food Fire statiodpolice station Government office Grocery store/food market High school HospitalUinpatient health Hotel Laboratory Library Medical office (diagnostic) Medical office (nondiagnostic) Mixed-use office Motel or inn Nonrefngerated warehouse Nursing home/assisted living Other Other classroom education Other food sales Other food service Other lodging Other office Other public assembly Other public order and safety Other retail Other service Post office/postal center Preschool/daycare Recreation Refrigerated warehouse Religious worship Repair shop Restaurant/cafetena Retail store Self-storage SocialUmeeting Vacant Vehicle dealership/showroom Vehicle service/repair shop Vehicle storage/maintenance

SUM or Mean for sector

Number of Buildings, Hundreds

Floor Area, lo9 m2

442 104 66 34 57 72 155 16 177 27 78 53 84 86 68 8 20 9 20 54 37 84 70 229 22 70 51 10 58 16 73 32 17 47 139 19 56 96 15 370 76 161 347 198 101 182 50 212 176

0.62 0.10 0.07 0.13 0.01 0.03 0.49 0.05 0.44 0.05 0.02 0.04 0.14 0.07 0.23 0.18 0.18 0.06 0.05 0.05 0.02 0.21 0.10 0.28 0.09 0.10 0.07 0.01 0.03 0.06 0.04 0.04 0.07 0.02 0.04 0.05 0.04 0.12 0.05 0.35 0.06 0.10 0.32 0.12 0.11 0.24 0.06 0.11 0.11

4645 .. ..

6.02

zyxwvutsrq zy Actual

Calculated, Weighted Energy Use Index (EUI) Values Site Energy, MJ/yr per gross square metre

Number of Buildings, N

10th

25th

50th

75th

90th

Mean

555 75 100 88 28 32 23 1 37 33 1 50 95 47 150 117 126 217 86 43 36 58 33 172 109 172 73 68 60 10 56 28 52 31 38 42 171 23 46 99 20 313 51 212 460 84 78 178 40 131 99

286 568 293 144 699 838 89 370 215 17 1799 70 321 1000 202 1103 405 999 357 143 262 204 243 23 424 56 44 321 404 318 156 101 449 334 285 73 191 137 66 95 71 529 145 22 80 14 250 103 9

420 688 414 684 1590 1375 169 663 355 300 2737 249 532 1407 444 1728 522 1681 682 25 1 407 390 373 63 78 1 295 232 375 724 546 416 307 592 659 506 588 360 245 134 178 128 1192 257 43 149 31 40 8 162 44

630 887 678 1098 2362 2149 333 754 553 470 4262 841 780 1892 662 1998 745 2759 935 453 532 724 688 194 1179 708 404 596 1274 722 578 43 1 95 1 936 88 1 65 1 597 403 1455 334 304 2107 46 1 72 420 117 839 381 214

947 1196 990 1815 3591 2836 550 1022 944 1369 8327 1146 1055 2441 1008 2844 1182 5152 1232 1018 678 1077 1041 466 1876 975 658 1938 3154 843 854 749 1636 1486 1671 77 1 1138 897 1939 648 550 471 1 945 98 72 1 313 1118 879 545

1407 1873 1787 2189 4233 4177 927 1566 1293 4264 9514 1402 1525 4457 1330 3619 1872 9433 2008 1402 1108 1614 2013 888 2095 1199 1098 3504 5590 1492 1494 1583 3 143 2092 3095 990 1234 1550 2622 90 1 730 6483 1734 155 949 78 1 2528 1393 1548

76 1 1084 860 1246 2792 2300 463 919 770 972 545 1 795 869 2174 765 2319 968 3691 1064 609 598 896 885 347 1268 759 519 1286 2470 776 708 660 1297 1222 1712 648 765 689 1300 468 379 3077 737 88 532 270 1127 592 553

545 1

100

267

572

1105

2116

99 1

Source: Calculated based on DOE/EIA preliminaly 2003 CBECS microdata.

information needed by an ownerloperator to decide which recommendations to implement. Energy audits may include the following:

1. Collect and analyze historical energy use Review more than one year of energy bills (preferably three years) Review billing rate class options with utility Review monthly patterns for irregularities

Percentiles

zy

Derive target goals for energy, demand, and cost indices for a building with similar characteristics and climate 2. Study the building and its operational characteristics Acquire a basic understanding of the mechanical and electrical systems Perform a walk-through survey to become familiar with its construction, equipment, operation, and maintenance

201 1 ASHRAE Handbook-HVAC Applications (SI)

36.8 Table 3

Electricity Index Percentiles from 2003 Commercial Survey Weighted Electricity Use Index Values, kWh/yr per gross square metre Percentiles

Building Use

10th

25th

50th

Administrative/professional office BanWother financial Clinic/other outpatient health College/university Convenience store Convenience store with gas station Distnbutiodshipping center Dormitory/fraternity/soronty Elementary/middle school Entertainment/culture Fast food Fire statiodpolice station Government office Grocery store/food market High school HospitalUinpatient health Hotel Laboratory Library Medical office (diagnostic) Medical office (nondiagnostic) Mixed-use office Motel or inn Nonrefngerated warehouse Nursing home/assisted living Other Other classroom education Other food sales Other food service Other lodging Other office Other public assembly Other public order and safety Other retail Other service Post office/postal center Preschool/daycare Recreation Refrigerated warehouse Religious worship Repair shop Restaurant/cafetena Retail store Self-storage SocialUmeeting Vacant Vehicle dealership/showroom Vehicle service/repair shop Vehicle storage/maintenance

38 67 53 44 216 259 19 23 37 5 30 1 12 43 28 1 38 164 72 123 68 24 26 37 53 4 68 17 14 99 95 31 33 12 59 52 44 23 36 17 20 11 20 105 26 7 11 3 27 21 3

72 156 101 113 466 406 32 35 61 11 516 41 87 346 48 235 125 274 93 44 48 59 81 11 88 32 30 99 166 39 48 28 154 72 81 35 59 31 41 20 28 164 42 13 19 5 77 36 13

119 239 164 162 702 5 17 49 55 100 80 881 71 116 456 80 259 153 422 167 82 80 119 116 32 160 62 53 116 292 151 101 36 180 241 144 77 95 55 379 38 65 309 87 22 32 19 148 61 36

161 317 222 259 847 85 1 80 71 151 182 1412 135 207 585 137 383 197 587 250 148 130 194 194 64 226 131 99 136 647 226 175 132 223 293 21 1 144 130 116 550 65 82 537 164 30 80 41 23 6 106 68

260 358 294 455 1157 1292 107 179 212 1319 1809 236 279 1083 208 494 295 1029 369 197 165 311 283 115 278 266 169 630 963 244 197 148 453 412 308 229 311 208 600 93 152 949 294 40 138 84 365 20 1 112

137 243 179 191 749 667 61 72 130 225 1028 105 154 557 104 309 177 474 186 103 93 154 147 58 171 102 71 237 434 130 116 81 204 213 175 106 124 94 307 49 73 408 134 24 66 35 168 89 56

17

19

89

184

181

169

qT IM nr Mrnn fnr wrtnr

Source: Calculated based on DOE/EIA preliminaly 2003 CBECS microdata.

Meet with ownerioperator and occupants to learn of special problems or needs Identify any required repairs to existing systems and equipment 3. Identify potential modifications to reduce energy use or cost Identify low-costino-cost changes to the facility or to operating and maintenance procedures Identify potential equipment retrofit opportunities Identify training required for operating staff

75th

90th

Mean

zy

zy zy

Perform a rough estimate of the breakdown of energy consumption for significant end-use categories 4. Perform an engineering and economic analysis of potential modifications For each practical measure, determine resultant savings Estimate effects on building operations and maintenance costs Prepare a financial evaluation of estimated total potential investment 5. Prepare a rank-ordered list

Next Page

36.9

Energy Use and Management Table 4

Electricity Index Percentiles from 2003 Commercial Survey Weighted Electricity Use Index Values, kWh/yr per gross square metre Percentiles

Building Use

10th

25th

50th

Administrative/professional office BanWother financial Clinic/other outpatient health College/university Convenience store Convenience store with gas station Distnbutiodshipping center Dormitory/fraternity/soronty Elementary/middle school Entertainment/culture Fast food Fire statiodpolice station Government office Grocery store/food market High school HospitalUinpatient health Hotel Laboratory Library Medical office (diagnostic) Medical office (nondiagnostic) Mixed-use office Motel or inn Nonrefngerated warehouse Nursing home/assisted living Other Other classroom education Other food sales Other food service Other lodging Other office Other public assembly Other public order and safety Other retail Other service Post office/postal center Preschool/daycare Recreation Refrigerated warehouse Religious worship Repair shop Restaurant/cafetena Retail store Self-storage SocialUmeeting Vacant Vehicle dealership/showroom Vehicle service/repair shop Vehicle storage/maintenance SUM or Mean for sector

38 67 53 44 216 259 19 23 37 5 30 1 12 43 28 1 38 164 72 123 68 24 26 37 53 4 68 17 14 99 95 31 33 12 59 52 44 23 36 17 20 11 20 105 26 7 11 3 27 21 3 17

72 156 101 113 466 406 32 35 61 11 516 41 87 346 48 235 125 274 93 44 48 59 81 11 88 32 30 99 166 39 48 28 154 72 81 35 59 31 41 20 28 164 42 13 19 5 77 36 13

119 239 164 162 702 5 17 49 55 100 80 881 71 116 456 80 259 153 422 167 82 80 119 116 32 160 62 53 116 292 151 101 36 180 241 144 77 95 55 379 38 65 309 87 22 32 19 148 61 36 89

_19_

Source: Calculated based on DOE/EIA preliminaly 2003 CBECS microdata.

List all possible energy savings modifications Select those that may be considered practical by the building owner Assume that modifications with highest operational priority andor best return on investment will be implemented first Provide preliminary implementation costs and savings estimates Assume that modifications with highest operational priority andor best return on investment will be implemented first

75th

161 317 222 259 847 85 1 80 71 151 182 1412 135 207 585 137 383 197 587 250 148 130 194 194 64 226 131 99 136 647 226 175 132 223 293 21 1 144 130 116 550 65 82 537 164 30 80 41 23 6 106 68 184

90th

260 358 294 455 1157 1292 107 179 212 1319 1809 236 279 1083 208 494 295 1029 369 197 165 311 283 115 278 266 169 630 963 244 197 148 453 412 308 229 311 208 600 93 152 949 294 40 138 84 365 20 1 112 381

Mean

137 243 179 191 749 667 61 72 130 225 1028 105 154 557 104 309 177 474 186 103 93 154 147 58 171 102 71 237 434 130 116 81 204 213 175 106 124 94 307 49 73 408 134 24 66 35 168 89 56 169

zy

zy

6. Report results Provide description of building, operating requirements, and major energy-using systems Clearly state savings from each modification and assumptions on which each is based Review list of practical modifications with the owner Prioritize modifications in recommended order of implementation Recommend measurement and verification methods

CHAPTER 37

OWNING AND OPERATING COSTS

zy zyx

Owning Costs ................................................................................................................................ 37.1 Operating Costs............................................................................................................................. 37.4 Maintenance Costs ........................................................................................................................ 37.7 Refrigerant Phaseouts 37.8 Other Issues ................................................................................................................................... 37.8 Economic Analysis Techniques 37.9 Symbols ........................................................................................................................................ 37.12

0

W I N G and operating cost information for the HVAC system should be part of the investment plan of a facility. This information can be used for preparing m u a l budgets, managing assets, and selecting design options. Table 1 shows a representative form that summarizes these costs. A properly engineered system must also be economical, but this is difficult to assess because of the complexities surrounding effective money management and the inherent difficulty of predicting future operating and maintenance expenses. Complex tax structures and the time value of money can affect the final engineering decision. This does not imply use of either the cheapest or the most expensive system; instead, it demands intelligent analysis of financial objectives and the owner’s requirements. Certain tangible and intangible costs or benefits must also be considered when assessing owning and operating costs. Local codes may require highly skilled or certified operators for specific types of equipment. This could be a significant cost over the life of the system. Similarly, intangible items such as aesthetics, acoustics, comfort, safety, security, flexibility, and environmental impact may vary by location and be important to a particular building or facility.

Table 1

Owning and Operating Cost Data and Summary

OWNING COSTS I.

Initial Cost of System

11. Periodic Costs A. B. C. D. E.

Income taxes Property taxes Insurance Rent Other periodic costs Total Periodic Costs

111. Replacement Cost IV. Salvage Value Total Owning Costs OPERATING COSTS V. Annual Utility, Fuel, Water, etc., Costs Utilities

1. Electricity

OWNING COSTS

2. Natural gas

The following elements must be established to calculate m u a l owning costs: (1) initial cost, (2) analysis or study period, (3) interest or discount rate, and (4) other periodic costs such as insurance, property taxes, refurbishment, or disposal fees. Once established, these elements are coupled with operating costs to develop an economic analysis, whichmay be a simple payback evaluation or an indepth analysis such as outlined in the section on Economic Analysis Techniques.

3. Watedsewer

4. Purchased steam

5. Purchased hot/chilled water Fuels

1. Propane 2. Fuel oil 3. Diesel

Initial Cost Major decisions affecting annual owning and operating costs for the life of the building must generally be made before completing contract drawings and specifications. To achieve the best performance and economics, alternative methods of solving the engineering problems peculiar to each project should be compared in the early stages of design. Oversimplified estimates can lead to substantial errors in evaluating the system. The evaluation should lead to a thorough understanding of installation costs and accessory requirements for the system(s) under consideration. Detailed lists of materials, controls, space and structural requirements, services, installation labor, and so forth can be prepared to increase accuracy in preliminary cost estimates. A reasonable estimate of capital cost of components may be derived from cost records of recent installations of comparable design or from quotations submitted by manufacturers and contractors, or by

4. Coal On-site generation of electricity Other utility, fuel, water, etc., costs

Total VI. Annual Maintenance Allowances/Costs A. B. C. D.

In-house labor Contracted maintenance service In-house materials Other maintenance allowances/costs (e.g., water treatment)

Total VII. Annual Administration Costs Total Annual Operating Costs

The preparation of this chapter is assigned to TC 7.8, Owning and Operating Costs.

TOTAL ANNUAL OWNING AND OPERATING COSTS

37.1

zyxwvutsrqpo 201 1 ASHRAE Handbook-HVAC

37.2 Table 2

Initial Cost Checklist

Enerev and Fuel Service Costs

Fuel service, storage, handling, piping, and distribution costs Electrical service entrance and distribution equipment costs Total energy plant Heat-Producing Equipment Boilers and furnaces Steam-water converters Heat pumps or resistance heaters Makeup air heaters Heat-producing equipment auxiliaries Refrigeration Equipment Compressors, chillers, or absorption units Cooling towers, condensers, well water supplies Refrigeration equipment auxiliaries Heat Distribution Equipment Pumps, reducing valves, piping, piping insulation, etc. Terminal units or devices Cooling Distribution Equipment Pumps, piping, piping insulation, condensate drains, etc. Terminal units, mixing boxes, diffusers, grilles, etc. Air Treatment and Distribution Equipment Air heaters, humidifiers, dehumidifiers, filters, etc. Fans, ducts, duct insulation, dampers, etc. Exhaust and return systems Heat recovery systems System and Controls Automation Terminal or zone controls System program control Alarms and indicator system Energy management system Building Construction and Alteration Mechanical and electric space Chimneys and flues Building insulation Solar radiation controls Acoustical and vibration treatment Distribution shafts, machinery foundations, fumng

consulting commercially available cost-estimating guides and software. Table 2 shows a representative checklist for initial costs.

Analysis Period The time frame over which an economic analysis is performed greatly affects the results. The analysis period is usually determined by specific objectives, such as length of planned ownership or loan repayment period. However, as the length of time in the analysis period increases, there is a diminishing effect on net present-value calculations. The chosen analysis period is often unrelated to the equipment depreciation period or service life, although these factors may be important in the analysis.

Service Life For many years, this chapter included estimates of service lives for various HVAC system components, based on a survey conducted in 1976 underASHRAEresearchproject RP-186 (Akalin 1978). These estimates have been useful to a generation of practitioners, but changes in technology, materials, manufacturing techniques, and maintenance practices now call into question the continued validity of the original estimates. Consequently, ASHRAE research project TRP-1237 developed an Internet-based data collection tool and database on HVAC equipment service life and maintenance costs, to allow equipment owning and operating cost data to be continually

Table 3

Applications (SI)

Median Service Life

Equipment Type

DX air distribution equipment Chillers, centrifugal Cooling towers, metal Boilers, hot-water, steel gas-fired Controls, pneumatic electronic Potable hot-water heaters, electric

Median Service Life, Years

Total No. of Units

No. of units Replaced

>24 >25 >22 >22 >18 >7 >21

1907 234 170 117 101 68 304

284 34 24 24 25 6 36

updated and current. The database was seeded with information gathered from a sample of 163 commercial office buildings located in major metropolitan areas across the United States. Abramson et al. (2005) provide details on the distribution of building size, age, and other characteristics. Table 3 presents estimates of median service life for various HVAC components in this sample. Median service life in Table 3 is based on analysis of survival curves, which take into account the units still in service and the units replaced at each age (Hiller 2000). Conditional and total survival rates are calculated for each age, and the percent survival over time is plotted. Units still in service are included up to the point where the age is equal to their current age at the time of the study. After that point, these units are censored (removed from the population). Median service life in this table indicates the highest age at which the survival rate remains at or above 50% while the sample size is 30 or more. There is no hard-and-fast rule about the number of units needed in a sample before it is considered statistically large enough to be representative, but usually the number should be larger than 25 to 30 (Lovvorn and Hiller 2002). This rule-of-thumb is used because each unit removal represents greater than a 3% change in survival rate as the sample size drops below 30, and that percentage increases rapidly as the sample size gets even smaller. The database initially developed and seeded under research project TRP-1237 (Abramson et al. 2005) is now available online, providing engineers with equipment service life and annual maintenance costs for a variety of building types and HVAC systems. The database can be accessed at www.ashrae.orgldatabase. As of the end of 2009 this database contained more than 300 building types, with service life data on more than 38 000 pieces of equipment. The database allows users to access up-to-date information to determine a range of statistical values for equipment owning and operating costs. Users are encouraged to contribute their own service life and maintenance cost data, further expanding the utility of this tool. Over time, this input will provide sufficient service life and maintenance cost data to allow comparative analysis of many different HVAC systems types in a broad variety of applications. Data can be entered by logging into the database andregistering, which is free. With this, ASHRAE is providing the necessary methods and information to assist in using life-cycle analysis techniques to help select the most appropriate HVAC system for a specific application. This system of collecting data also greatly reduces the time between data collection and when users can access the information. Figure 1 presents the survival curve for centrifugal chillers, based on data in Abramson et al. (2005). The point at which survival rate drops to 50% based on all data in the survey is 3 1 years. However, because the sample size drops below the statistically relevant number of 30 units at 25 years, the median service life of centrifugal chillers can only be stated with confidence as >25 years. Table 4 compares the estimates of median service life in Abramson et al. (2005) with those developed with those in Akalin (1978). Most differences are on the order of one to five years. Estimated service life of new equipment or components of systems not listed in Table 3 or 4 may be obtained from manufacturers,

37.3

Owning and Operating Costs Table 4

Comparison of Service Life Estimates

zyxwvutsrqpon Median Service Life, Years

Equipment Item

Air Conditioners Window unit Residential single or split package Commercial through-the-wall Water-cooled package Heat pumps Residential air-to-air Commercial air-to-air Commercial water-to-air Roof-top air conditioners Single-zone Multizone Boilers, Hot-Water (Steam) Steel water-tube Steel fire-tube Cast iron Electric Burners Furnaces Gas- or oil-fired Unit heaters Gas or electric Hot-water or steam Radiant heaters Electric Hot-water or steam

Median Service Life, Years

Abramson Akalin et al. (2005) (1978) Equipment Item N/A* N/A* N/A* >24

N/A* N/A* >24 N/A* N/A*

>22 N/A* N/A* N/A* N/A* N/A* N/A* N/A* N/A*

Abramson Akalin et al. (2005) (1978) Equipment Item

Air Terminals Diffusers, grilles, and registers Induction and fan-coil units VAV and double-duct boxes Air washers Ductwork 15b Dampers 15 Fans 19 Centrifugal Axial 15 Propeller 15 Ventilating roof-mounted coils 24 (30) DX, water, or steam 25 (25) Electric 35 (30) Heat Exchangers 15 Shell-and-tube 2 1 Reciprocating compressors Packaged Chillers 18 Reciprocating Centrifugal 13 Absorption 20 Cooling Towers Galvanized metal 10 Wood 25 Ceramic

10 15 15 15

Median Service Life, Years

N/A* N/A* N/A* N/A* N/A* N/A* N/A* N/A* N/A* N/A* N/A*

27 20 20 17 30 20

N/A* N/A*

20 15

N/A* N/A*

24 20

N/A* >25 N/A*

20 23 23

>22 N/A* N/A*

20 20 34

25 20 15 20

Condensers Air-cooled Evaporative Insulation Molded Blanket Pumps Base-mounted Pipe-mounted Sump and well Condensate Reciprocating engines Steam turbines Electric motors Motor starters Electric transformers Controls Pneumatic Electric Electronic Valve actuators Hydraulic Pneumatic Self-contained

Abramson Akalin et al. (2005) (1978) N/A N/A*

20 20

N/A* N/A*

20 24

N/A* N/A* N/A* N/A* N/A* N/A* N/A* N/A* N/A*

20 10 10 15 20 30 18 17 30

N/A* N/A* N/A*

20 16 15

N/A* N/A*

15 20 10

*N/A: Not enough data yet in Abramson et al. (2005). Note that data from Akalin (1978) for these categories may be outdated and not statistically relevant. Use these data with caution until enough updated data are accumulated in Abramson et a1

Service lives shown in the tables are based on the age of the equipment when it was replaced, regardless of the reason it was replaced. Locations in potentially corrosive environments and unique maintenance variables affect service life. Examples include the following:

Fig. 1 Survival Curve for Centrifugal Chillers [Based on data in Abramson et al. (2005)l

associations, consortia, or governmental agencies. Because of the proprietary nature of information from some of these sources, the variety of criteria used in compiling the data, and the diverse objectives in disseminating them, extreme care is necessary in comparing service life from different sources. Designs, materials, and components of equipment listed in Tables 3 and 4 have changed over time and may have altered the estimated service lives of those equipment categories. Therefore, establishing equivalent comparisons of service life is important. As noted, service life is a function of the time when equipment is replaced. Replacement may be for any reason, including, but not limited to, failure, general obsolescence, reduced reliability, excessive maintenance cost, and changed system requirements (e.g., building characteristics, energy prices, environmental considerations).

Coastal and marine environments, especially in tropical locations, are characterized by abundant sodium chloride (salt) that is carried by sea spray, mist, or fog. Many owners require equipment specifications stating that HVAC equipment located along coastal waters will have corrosion-resistant materials or coatings. Design criteria for systems installed under these conditions should be carefully considered. Industrial applications provide many challenges to the HVAC designer. It is very important to know if emissions from the industrial plant contain products of combustion from coal, fuel oils, or releases of sulfur oxides (SO,, SO,) and nitrogen oxides (NO,) into the atmosphere. These gases typically accumulate and return to the ground in the form of acid rain or dew. Not only is it important to know the products being emitted from the industrial plant being designed, but also the adjacent upwind or downwind facilities. HVAC system design for a plant located downwind from a paper mill requires extraordinary corrosion protection or recognition of a reduced service life of the HVAC equipment. Urban areas generally have high levels of automotive emissions as well as abundant combustion by-products. Both of these contain elevated sulfur oxide and nitrogen oxide concentrations. Maintenance factors also affect life expectancy. The HVAC designer should temper the service life expectancy of equipment with a maintenance factor. To achieve the estimated service life values in Table 3, HVAC equipmentmust be maintainedproperly,

37.4 including good filter-changing practices and good maintenance procedures. For example, chilled-water coils with more than four rows and close fin spacing are virtually impossible to clean even using extraordinary methods; they are often replaced with multiple coils in series, with a maximum of four rows and lighter fin spacing.

Depreciation Depreciation periods are usually set by federal, state, or local tax laws, which change periodically. Consult applicable tax laws for more information on depreciation.

Interest or Discount Rate Most major economic analyses consider the opportunity cost of borrowing money, inflation, and the time value of money. Opportunity cost of money reflects the earnings that investing (or lending) the money can produce. Inflation (price escalation) decreases the purchasing or investing power (value) of future money because it can buy less in the future. Time value of money reflects the fact that money received today is more useful than the same amount received a year from now, even with zero inflation, because the money is available earlier for reinvestment. The cost or value of money must also be considered. When borrowing money, a percentage fee or interest rate must normally be paid. However, the interest rate may not necessarily be the correct cost ofmoney to use in an economic analysis. Another factor, called the discount rate, is more commonly used to reflect the true cost of money [see Fuller and Petersen (1 996) for detailed discussions]. Discount rates used for analyses vary depending on individual investment, profit, and other opportunities. Interest rates, in contrast, tend to be more centrally fixed by lending institutions. To minimize the confusion caused by the vague definition and variable nature of discount rates, the U.S. government has specified particular discount rates to be used in economic analyses relating to federal expenditures. These discount rates are updated annually (Rushing et al. 201 0) but may not be appropriate for private-sector economic analyses.

Periodic Costs Regularly or periodically recurring costs include insurance, property taxes, income taxes, rent, refurbishment expenses, disposal fees (e.g., refrigerantrecycling costs), occasional major repair costs, and decommissioning expenses. Insurance. Insurance reimburses a property owner for a financial loss so that equipment can be repaired or replaced. Insurance often indemnifies the owner from liability, as well. Financial recovery may include replacing income, rents, or profits lost because of property damage. Some of the principal factors that influence the total m u a l insurance premium are building size, construction materials, amount and size of mechanical equipment, geographic location, and policy deductibles. Some regulations set minimum required insurance coverage and premiums that may be charged for various forms of insurable property. Property Taxes. Property taxes differ widely and may be collected by one or more agencies, such as state, county, or local governments or special assessment districts. Furthermore, property taxes may apply to both real (land, buildings) and personal (everything else) property. Property taxes are most often calculated as a percentage of assessed value, but are also determined in other ways, such as fixed fees, license fees, registration fees, etc. Moreover, definitions of assessed value vary widely in different geographic areas. Tax experts should be consulted for applicable practices in a given area. Income Taxes. Taxes are generally imposed in proportion to net income, after allowance for expenses, depreciation, and numerous other factors. Special tax treatment is often granted to encourage

201 1 ASHRAE Handbook-HVAC

Applications (SI)

certain investments. Income tax professionals can provide up-todate information on income tax treatments. Other Periodic Costs. Examples of other costs include changes in regulations that require unscheduled equipment refurbishment to eliminate use of hazardous substances, and disposal costs for such substances. Replacement Costs and Salvage Value. Replacement costs and salvage value should be evaluated when calculating owning cost. Replacement cost is the cost to remove existing equipment and install new equipment. Salvage value is the value of equipment or its components for recycling or other uses. Equipment’s salvage value may be negative when removal, disposal, or decommissioning costs are considered.

OPERATING COSTS

z

zy

Operating costs are those incurred by the actual operation of the system. They include costs of fuel and electricity, wages, supplies, water, material, and maintenance parts and services. Energy is a large part of total operating costs. Chapter 19 of the 2009 ASHRAE Handbook-Fundamentals outlines how fuel and electrical requirements are estimated. Because most energy management activities are dictated by economics, the facility manager must understand the utility rates that apply to each facility. Electric rates are usually more complex than gas or water rates. In addition to general commercial or institutional electric rates, special rates may exist such as time of day, interruptible service, on-peakioff-peak, summeriwinter, and peak demand. Electric rate schedules vary widely in North America. The facility manager should work with local utility companies to identify the most favorable rates and to understand how to qualify for them. The local utility representative can help the facility manager develop the most cost-effective methods of metering and billing. The facility manager must understand the utility rates, including the distinction between marginal and average costs and, in the case of demand-based electric rates, how demand is computed. Note that, in general, total energy consumption cannot be multiplied by a per-unit energy cost to arrive at a correct m u a l utility cost, because rate schedules (especially for electricity) often have a sliding scale of prices that vary with consumption, time of day, and other factors. Future energy costs used in discounted payback analyses must be carefully evaluated. Energy costs have historically escalated at a different rate than the overall inflation rate as measured by the consumer price index. To assist in life-cycle cost analysis, fuel price escalation rate forecasts by end-use sector and fuel type are updated annually by the National Institute of Standards and Technology and published in the Annual Supplement to NIST Handbook 135 (Rushing et al. 2010). There are no published projection rates for water prices for use in life-cycle cost analyses. Water escalation rates should be obtained from the local water utility when possible. Building designers should use energy price projections from their local utility in place of regional forecasts whenever possible, especially when evaluating alternative fuel types. Deregulation in some areas may allow increased access to nontraditional energy providers and pricing structures; in other areas, traditional utility infrastructures and practices may prevail. The amount and profile of the energy used by the facility will also determine energy cost. Unbundling energy services (having separate contracts for energy and for its transportation to point of use) may dictate separate agreements for each service component or may be packaged by a single provider. Contract length and price stability are factors in assessing nontraditional versus traditional energy suppliers when estimating operating costs. The degree of energy supply and system reliability and price stability considered necessary by the ownerioccupants of a building may require considerable deliberation. The sensitivity of a building’s functionality to energyrelated variables should dictate the degree of attention allocated in evaluating these factors.

zyxwvutsrq 37.5

Owning and Operating Costs Electrical Energy

Table 5

The total cost of electricity is determined by a rate schedule and is usually a combination of several components: consumption (megajoules), demand (kilowatts) fuel adjustment charges, special allowances or other adjustments, and applicable taxes. Of these, consumption and demand are the major cost components and the ones the owner or facility manager may be able to affect. Electricity Consumption Charges. Most electric rates have step-rate schedules for consumption, and the cost of the last unit consumed may be substantially different from that of the first. The last unit is usually cheaper than the first because the fixed costs to the utility may already have been recovered from earlier consumption costs. Because of this, the energy analysis cannot use average costs to accurately predict savings from implementation of energy conservation measures. Average costs will overstate the savings possible between alternative equipment or systems; instead, marginal (or incremental) costs must be used. To reflect time-varying operating costs or to encourage peak shifting, electric utilities may charge different rates for consumption according to the time of use and season, with higher costs occurring during the peak period of use. Fuel Adjustment Charge. Because of substantial variations in fuel prices, electric utilities may apply a fuel adjustment charge to recover costs. This adjustment may not be reflected in the rate schedule. The fuel adjustment is usually a charge per unit of consumption and may be positive or negative, depending on how much of the actual fuel cost is recovered in the energy consumption rate. The charge may vary monthly or seasonally. Allowances or Adjustments. Special discounts or rates may be available for customers who can receive power at higher voltages or for those who own transformers or similar equipment. Special rates or riders may be available for specific interruptible loads such as domestic water heaters. Certain facility electrical systems may produce a low power factor [i.e., ratio of real (active) kilowatt power to apparent (reactive) kVA power], which means that the utility must supply more current on an intermittent basis, thus increasing their costs. These costs may be passed on as an adjustment to the utility bill if the power factor is below a level established by the utility. When calculating power bills, utilities should be asked to provide detailed cost estimates for various consumption levels. The final calculation should include any applicable special rates, allowances, taxes, and fuel adjustment charges. Demand Charges. Electric rates may also have demand charges based on the customer’s peak kilowatt demand. Whereas consumption charges typically cover the utility’s operating costs, demand charges typically cover the owning costs. Demand charges may be formulated in a variety of ways:

Electricity Data Consumption and Demand for ASHRAE Headquarters, 2003 to 2004

Actual Billing Billing Consumption, Demand, Demand, Total Days GJ kW kW Cost,US$

Jan. 2003 Feb. 2003 Mar. 2003 Apr. 2003 May.2003 Jun. 2003 Jul. 2003 Aug.2003 Sep. 2003 Oct. 2003 Nov. 2003 Dec. 2003 Total 2003 Jan. 2004 Feb. 2004 Mar. 2004 Apr. 2004 May.2004 Jun. 2004 Jul. 2004 Aug.2004 Sep. 2004 Oct. 2004 Nov. 2004 Dec. 2004 Total 2004

29 31 29 29 33 26 32 30 32 30 27 34 362 31 29 20 12 34 29 30 32 29 30 32 31 339

205.6 222.9 216.2 225.5 264.4 191.2 242.4 237.6 230.3 198.9 165.7 220.5 2621.2 212.5 195.3 133.5 79.7 231.3 229.4 248.8 265.7 232.2 216.2 236.7 187.1 2468.4

178 145 140 154 161 171 180 170 149 122 140 141

185 185 185 185 185 185 185 185 171 171 171 171

145 159 122 133 148 148 169 170 166 152 128 132

171 171 171 171 171 171 169 170 166 161 161 161

4,118 4,25 1 4,199 4,271 4,569 4,007 4,400 4,364 4,127 3,865 3,613 4,028 49,812 3,967 3,837 2,584 1,547 4,110 4,321 4,458 4,605 4,281 3,866 4,018 3,646 45,240

The portion of the total bill attributed to demand may vary greatly, from 0% to as high as 70%. Real-time or time-ofday rates. Cost of electricity at time ofuse. An increasing number of utilities offer these rates. End users who can shift operations or install electric load-shifting equipment, such as thermal storage, can take advantage of such rates. Because these rates usually reflect a utility’s overall load profile and possibly the availability of specific generating resources, contact with the supplying utility is essential to determine whether these rates are a reasonable option for a specific application.

zyxwvutsr

Straight charge. Cost per kilowatt per month, charged for the peak demand of the month. Excess charge. Cost per kilowatt above a base demand (e.g., 50 kW), which may be established each month. Maximum demand (ratchet). Cost per kilowatt for maximum annual demand, which may be reset only once a year. This established demand may either benefit or penalize the owner. Combination demand. Cost per hour of operation of demand. In addition to a basic demand charge, utilities may include further demand charges as demand-related consumption charges. The actual demand represents the peak energy use averaged over a specific period, usually 15, 30, or 60 min. Accordingly, high electrical loads of only a few minutes’ duration may never be recorded at the full instantaneous value. Alternatively, peak demand is recorded as the average of several consecutive short periods (i.e., 5 min out of each hour). The particular method of demand metering and billing is important when load shedding or shifting devices are considered.

Understanding Electric Rates. To illustrate a typical commercial electric rate with a ratchet, electricity consumption and demand data for an example building are presented in Table 5. The example building in Table 5 is on a ratcheted rate, and bill demand is determined as a percentage of actual demand in the summer. How the ratchet operates is illustrated in Figure 2. Table 5 shows that the actual demand in the first six months of 2004 had no effect on the billing demand, and therefore no effect on the dollar amount of the bill. The same is true for the last three months of the year. Because of the ratchet, the billing demand in the f r s t half of 2004 was set the previous summer. Likewise, billing demand for the last half of 2004 and first half of 2005 was set by the peak actual demand of 180 kW in July 2003. This tells the facility manager to pay attention to demand in the summer months (June to September) and that demand is not a factor in the winter (October to May) months for this particular rate. (Note that Atlanta’s climate is hot and humid; in other climates, winter electric demand is an important determinant of costs.) Consumption must be monitored all year long. Understanding the electric rates is key when evaluating the economics of energy conservation projects. Some projects save electrical demand but not consumption; others save mostly consumption but have little effect on demand. Electric rates must be correctly

201 1 ASHRAE Handbook-HVAC

37.6

Applications (SI)

Other Fossil Fuels Propane, fuel oil, and diesel are examples of other fossil fuels in widespread use. Calculating the cost of these fuels is usually much simpler than calculating typical utility rates. The cost of the fuel itself is usually a simple charge per unit volume or per unit mass. The customer is free to negotiate for the best price. However, trucking or delivery fees must also be included in fmal calculations. Some customers may have their own transport trucks, but most seek the best delivered price. If storage tanks are not customer-owned, rental fees must be considered. Periodic replacement of diesel-type fuels may be necessary because of storage or shelf-life limitations and must also be considered. The final fuel cost calculation should include any of these costs that are applicable, as well as appropriate taxes. It is usually difficult, however, to relate usage of stored fossil fuels (e.g., fuel oil) with their operating costs. This is because propane or fuel oil is bought in bulk and stored until needed, and normally not metered or measured as it is consumed, whereas natural gas and power are metered and billed for as they are used.

Fig. 2

zyxwvutsr

Bill Demand and Actual Demand for Atlanta Example Building, 2004

applied for economic analyses to be accurate. Chapter 56 contains a thorough discussion of various electric rates.

Natural Gas Rates. Conventional natural gas rates are usually a combination of two main components: (1) utility rate or base charges for gas consumption and (2) purchased gas adjustment (PGA) charges. Although gas is usually metered by volume, it is often sold by energy content. The utility rate is the amount the local distribution company charges per unit of energy to deliver the gas to a particular location. This rate may be graduated in steps; the first 10 GJ of gas consumed may not be the same price as the last 10 GJ. The PGA is an adjustment for the cost of the gas per unit of energy to the local utility. It is similar to the electric fuel adjustment charge. The total cost per unit of energy is then the sum of the appropriate utility rate and the PGA, plus taxes and other adjustments. Interruptible Gas Rates and Contract/Transport Gas. Large industrial plants usually have the ability to burn alternative fuels and can qualify for special interruptible gas rates. During peak periods of severe cold weather, these customers’ supply may be curtailed by the gas utility, and they may have to switch to propane, fuel oil, or some other back-up fuel. The utility rate and PGA are usually considerably cheaper for these interruptible customers than they are for firm-rate (noninterruptible) customers. Deregulation of the natural gas industry allows end users to negotiate for gas supplies on the open market. The customer actually contracts with a gas producer or broker and pays for the gas at the source. Transport fees must be negotiated with the pipeline companies carrying the gas to the customer’s local gas utility. This can be a very complicated administrative process and is usually economically feasible only for large gas users. Some local utilities have special rates for delivering contract gas volumes through their system; others simply charge a standard utility fee (PGA is not applied because the customer has already negotiated with the supplier for the cost of the fuel itself). When calculating natural gas bills, be sure to determine which utility rate and PGA and/or contract gas price is appropriate for the particular interruptible or firm-rate customer. As with electric bills, the final calculation should include any taxes, prompt payment discounts, or other applicable adjustments.

Energy Source Choices

In planning for a new facility, the designer may undertake energy master planning. One component of energy master planning is choice of fuels. Typical necessary decisions include, for example, whether the building should be heated by electricity or natural gas, how service hot water should be produced, whether a hybrid heating plant (i.e., a combination of both electric and gas boilers) should be considered, and whether emergency generators should be fueled by diesel or natural gas. Decision makers should consider histories or forecasts of price volatility when selecting energy sources. In addition to national trending, local energy price trends from energy suppliers can be informative. These evaluations are particularly important where relative operating costs parity exists between various fuel options, or where selecting more efficient equipment may help mitigate utility price concerns. Many sources ofhistoric and projected energy costs are available for reference. In addition to federal projections, utility and energy supplier annual reports and accompanying financial data may provide insight into future energy costs. Indicators such as constrained or declining energy supply or production may be key factors in projecting future energy pricing trends. Pricing patterns that suggest unusual levels of energy price volatility should be carefully analyzed and tested at extreme predicted price levels to assess potential effects on system operating costs. Under conditions of rapidly evolving energy prices or new pricing options, imminent technological improvements, or pending environmental standards and mandates, the adaptability of design options must be carefully evaluated. Where appropriate, contingency planning for accommodating foreseeable alterations to building systems may be prudent. Using diverse energy sources or suppliers in lieu of single sourcing may reduce cost of shifting energy use in the event that single-source pricing becomes volatile, and may even provide negotiating leverage for facility owners.

Water and Sewer Costs Water and sewer costs have risen in many parts of the country, and should not be overlooked in economic analyses. Fortunately, these rates are usually very simple and straightforward: commonly, a charge per unit volume for water and a different charge per unit volume for sewer. Because water consumption is metered and sewage is not, most rates use the water consumption quantity to compute the sewer charge. If an owner uses water that is not returned to sewer, there may be an opportunity to receive a credit or refund. Owners frequently use irrigation meters for watering grounds when the water authority has a special irrigation rate with no sewer charge. Another opportunity that is sometimes overlooked is to sep-

37.7

Owning and Operating Costs arately meter makeup water for cooling towers. This can be done with an irrigation meter if the costs of setting the meter can be justified; alternatively, it may be done by installing an in-line water meter for the cooling tower, in which case the owner reports the usage annually and applies for a credit or refund. Because of rising costs of water and sewer, water recycling and reclamation is becoming more cost effective. For example, it may now be cost effective in some circumstances to capture cooling coil condensate and pump it to a cooling tower for makeup water.

MAINTENANCE COSTS The quality of maintenance and maintenance supervision can be a major factor in overall life-cycle cost of a mechanical system. The maintenance cost of mechanical systems varies widely depending upon configuration, equipment locations, accessibility, system complexity, service duty, geography, and system reliability requirements. Maintenance costs can be difficult to predict, because each system or facility is unique. Dohrmann and Alereza (1986) obtained maintenance costs and HVAC system information from 342 buildings located in 35 states in the United States. In 1983 U.S. dollars, data collected showed a mean HVAC system maintenance cost of $3.40/m2 per year, with a median cost of $2.60/m2 per year. Building age has a statistically significant but minor effect on HVAC maintenance costs. Analysis also indicated that building size is not statistically significant in explaining cost variation. The type of maintenance program or service agency that building management chooses can also have a significant effect on total HVAC maintenance costs. Although extensive or thorough routine and preventive maintenance programs cost more to administer, they usually extend equipment life; improve reliability; and reduce system downtime, energy costs, and overall life-cycle costs. Some maintenance cost data are available, both in the public domain and from proprietary sources used by various commercial service providers. These sources may include equipment manufacturers, independent service providers, insurers, government agencies (e.g., the U.S. General Services Administration), and industry-related organizations [e.g., the Building Owners and Managers Association (BOMA)] and service industry publications. More traditional, widely used products and components are likely to have statistically reliable records. However, design changes or modifications necessitated by industry changes, such as alternative refrigerants, may make historical data less relevant. Newer HVAC products, components, system configurations, control systems and protocols, and upgraded or revised system applications present an additional challenge. Care is required when using data not drawn from broad experience or field reports. In many cases, maintenance information is proprietary or was sponsored by a particular entity or group. Particular care should be taken when using such data. It is the user’s responsibility to obtain these data and to determine their appropriateness and suitability for the application being considered. ASHRAE research project TRP-1237 (Abramson et al. 2005) developed a standardized Internet-based data collection tool and database on HVAC equipment service life and maintenance costs. The database was seeded with data on 163 buildings from around the country. Maintenance cost data were gathered for total HVAC system maintenance costs from 100 facilities. In 2004 dollars, the mean HVAC maintenance cost from these data was $5.06/m2, and the median cost was $4.74/m2. Table 6 compares these figures with estimates reported by Dohrmann and Alereza (1983), both in terms of contemporary dollars, and in 2004 dollars, and shows that the cost per square metre varies widely between studies.

Table 6

Comparison of Maintenance Costs Between Studies Cost per m2, as

Survey Dohrmann and Alereza (1983) Abramson et al. (2005)

Cost per m2, 2004 Dollars

Reported Consumer Mean Median PriceIndex

Mean

Median

$3.44

$2.58

99.6

$6.57

$4.95

$5.06

$4.74

188.9

$5.06

$4.74

Estimating Maintenance Costs Total HVAC maintenance cost for new and existing buildings with various types of equipment may be estimated several ways, using several resources. Equipment maintenance requirements can be obtained from the equipment manufacturers for large or custom pieces of equipment. Estimating in-house labor requirements can be difficult; BOMA (2003) provides guidance on this topic. Many independent mechanical service companies provide preventative maintenance contracts. These firms typically have proprietary estimating programs developed through their experience, and often provide generalized maintenance costs to engineers and owners upon request, without obligation. When evaluating various HVAC systems during design or retrofit, the absolute magnitude of maintenance costs may not be as important as the relative costs. Whichever estimating method or resource is selected, it should be used consistently throughout any evaluation. Mixing information from different resources in an evaluation may provide erroneous results. Applying simple costs per unit of building floor area for maintenance is highly discouraged. Maintenance costs can be generalized by system types. When projecting maintenance costs for different HVAC systems, the major system components need to be identified with a required level of maintenance. The potential long-term costs of environmental issues on maintenance costs should also be considered.

Factors Affecting Maintenance Costs Maintenance costs are primarily a measure of labor activity. System design, layout, and configuration can significantly affect the amount of time and effort required for maintenance and, therefore, the maintenance cost. Factors to consider when evaluating maintenance costs include the following:

Quantity and type of equipment. Each piece of equipment requires a core amount of maintenance and time, regardless of its size or capacity. A greater number of similar pieces of equipment are generally more expensive to maintain than larger but fewer units. For example, one manufacturer suggests the annual maintenance for centrifugal chillers is 24 h for a nominal 3500 kW chiller and 16 h for a nominal 1800 kW chiller. Therefore, the total maintenance labor for a 3500 kW chiller plant with two 1800 kW chillers would be 32 h, or 113 more than a single 3500 kW chiller. Equipment location and access. The ability to maintain equipment in a repeatable and cost-effective manner is significantly affected by the equipment’s location and accessibility. Equipment that is difficult to access increases the amount of time required to maintain it, and therefore increases maintenance cost. Equipment maintenance requiring erection of ladders and scaffolding or hydraulic lifts increases maintenance costs while likely reducing the quantity and quality of maintenance performed. Equipment location may also dictate an unusual working condition that could require more service personnel than normal. For example, maintenance performed in a confined space (per OSHA definitions) requires an additional person to be present, for safety reasons. System run time. The number of hours of operation for a HVAC system affects maintenance costs. Many maintenance tasks are

z

201 1 ASHRAE Handbook-HVAC

37.8 dictated by equipment run time. The greater the run time, the more often these tasks need to be performed. Critical systems. High-reliability systems require more maintenance to ensure uninterrupted system operation. Critical system maintenance is also usually performed with stringent shutdown and failsafe procedures that tend to increase the amount of time required to service equipment. An office building system can be turned off for a short time with little effect on occupants, allowing maintenance ahnost any time. Shutdown of a hospital operating room or pharmaceutical manufacturing HVAC system, on the other hand, must be coordinated closely with the operation of the facility to eliminate risk to patients or product. Maintenance on critical systems may sometimes incur labor premiums because of unusual shutdown requirements. System complexity. More complex systems tend to involve more equipment and sophisticated controls. Highly sophisticated systems may require highly skilled service personnel, who tend to be more costly. Service environment. HVAC systems subjected to harsh operating conditions (e.g., coastal and marine environments) or environments like industrial operations may require more frequent andor additional maintenance. Local conditions. The physical location of the facility may require additional maintenance. Equipment in dusty or dirty areas or exposed to seasonal conditions (e.g., high pollen, leaves) may require more frequent or more difficult cleaning of equipment and filters. Additional maintenance tasks may be needed. Geographical location. Maintenance costs for remote locations must consider the cost of getting to and from the locations. Labor costs for the number of anticipated trips and their duration for either in-house or outsourced service personnel to travel to and from the site must be added to the maintenance cost to properly estimate the total maintenance cost. Equipment age. The effect of age on equipment repair costs varies significantly by type of HVAC equipment. Technologies in equipment design and application have changed significantly, affecting maintenance costs. Available infrastructure. Maintenance costs are affected by the availability of an infrastructure that can maintain equipment, components, and systems. Available infrastructure varies on a national, regional, and local basis and is an important consideration in the HVAC system selection process.

REFRIGERANT PHASEOUTS Production phaseout of many commonly used refrigerants has required building owners to decide between, replacing existing equipment or retrofitting for alternative refrigerants. Several factors must be considered, including

Initial Cost. New equipment may have a significantly higher installed cost than retrofitting existing equipment. For example, retrofitting an existing centrifugal chiller to operate on R-123 may cost 50% of the cost for anew chiller, making the installation cost ofanew chiller seem aprudent alternative. Conversely, the cost of rigging a new unit may significantly raise the installed cost, improving the first-cost advantage of refrigerant conversion. Operating Costs. The overall efficiency of new equipment is often substantially better than that of existing equipment, depending on age, usage, and level of maintenance performed over the life of the existing unit. In addition, conversion to alternative refrigerants may reduce capacity andor efficiency of the existing equipment. Maintenance Costs. The maintenance cost for new equipment is generally lower than that for existing equipment. However, the level of retrofit required to attain compatibility between existing equipment and new refrigerant often includes replacement or remanufacture of major unit components, which can bring the

Applications (SI)

maintenance and repair costs in line with those expected of new equipment. Equipment Useful Life. The effect of a retrofit on equipment useful life is determined by the extent of modification required. Complete remanufacture of a unit should extend the remaining useful life to a level comparable to that of new equipment. Replacing existing equipment or converting to alternative refrigerants can improve overall system efficiency. Reduced capacity requirements and introduction of new technologies such as vaxiablespeed drives and microprocessor-based controllers can substantially reduce annual operating costs and significantly improve a project’s economic benefit. Information should be gathered to complete Table 1 for each alternative. The techniques described in the section on Economic Analysis Techniques may then be applied to compare the relative values of each option.

z

zyxwv

Other Sources

The DOE’S Federal Energy Management Program (FEMP) Web site (www.eere.energy.gov/femp/procurement) has up-to-date information on energy-efficient federal procurement. Products that qualify for the EPMDOE ENERGY STAR label are listed, as are efficiency recommendations, cost effectiveness examples, and purchasing guidance. FEMP also provides Web-based cost-calculator tools that simplify the energy cost comparison between products with different efficiencies. The General Services Administration (GSA) has a basic ordering agreement (BOA) that offers a streamlined procurement method for some HVAC products based on lowest life-cycle cost. For chillers purchased through commercial sources, the BOA can still be used as a guide in preparing specifications.

OTHER ISSUES Financing Alternatives Alternative financing is commonly used in third-party funding of projects, particularly retrofit projects, and is variously called privatization, third-party financing, energy services outsourcing, performance contracting, energy savings performance contracting (ESPC), or innovative fmancing. In these programs, an outside party performs an energy study to identify or quantify attractive energysaving retrofit projects and then (to varying degrees) designs, builds, and finances the retrofit program on behalf of the owner or host facility. These contracts range in complexity from simple projects such as lighting upgrades to more detailed projects involving all aspects of energy consumption and facility operation. Alternative financing can be used to accomplish any or all of the following objectives: Upgrade capital equipment Provide for maintenance of existing facilities Speed project implementation Conserve or defer capital outlay Save energy Save money The benefits of alternative financing are not free. In general terms, these financing agreements transfer the risk of attaining future savings from the owner to the contractor, for which the contractor is paid. In addition, these innovative owning and operating cost reduction approaches have important tax consequences that should be investigated on a case-by-case basis. There are many variations of the basic arrangements and nearly as many terms to define them. Common nomenclature includes guaranteed savings (performance-based), shared savings, paid from savings, guaranteed savings loans, capital leases, municipal leases, and operating leases. For more information, refer to the U.S.

37.9

Owning and Operating Costs Department of Energy’s Web site and to the DOE (2007). A few examples of alternative financing techniques follow. Leasing. Among the most common methods of alternative financing is the lease arrangement. In a true lease or lease-purchase arrangement, outside financing provides capital for construction of a facility. The institution then leases the facility at a fixed monthly charge and assumes responsibility for fuel and personnel costs associated with its operation. Leasing is also commonly available for individual pieces of equipment or retrofit systems and often includes all design and installation costs. Equipment suppliers or independent third parties retain ownership of new equipment and lease it to the user. Outsourcing. For a cogeneration, steam, or chilled-water plant, either a lease or an energy output contract can be used. An energy output contract enables a private company to provide all the capital and operating costs, such as personnel and fuel, while the host facility purchases energy from the operating company at a variable monthly charge. Energy Savings. Retrofit projects that lower energy usage create an income stream that can be used to amortize the investment. In paid-from-savings programs, utility payments remain constant over a period of years while the contractor is paid out of savings until the project is amortized. In shared savings programs, the institution receives a percentage of savings over a longer period of years until the project becomes its property. In a guaranteed savings program, the owner retains all the savings and is guaranteed that a certain level of savings will be attained. A portion of the savings is used to amortize the project. In any type of energy savings project, building operation and use can strongly affect the amount of savings actually realized. Low-Interest Financing. In this arrangement, the supplier offers equipment with special financing arrangements at belowmarket interest rates. Cost Sharing. Several variations of cost-sharing programs exist. In some instances, two or more groups jointly purchase and share new equipment or facilities, thereby increasing use of the equipment and improving the economic benefits for both parties. In other cases, equipment suppliers or independent third parties (such as utilities) who receive an indirect benefit may share part of the equipment or project cost to establish a market foothold for the product.

District Energy Service District energy service is increasingly available to building owners; district heating and cooling eliminates most on-site heating and cooling equipment. A third party produces treated water or steam and pipes it from a central plant directly to the building. The building owner then pays a metered rate for the energy that is used. A cost comparison of district energy service versus on-site generation requires careful examination of numerous, often sitespecific, factors extending beyond demand and energy charges for fuel. District heating and cooling eliminates or minimizes most costs associated with installation, maintenance, administration, repair, and operation of on-site heating and cooling equipment. Specifically, costs associated with providing water, water treatment, specialized maintenance services, insurance, staff time, space to house on-site equipment, and structural additions needed to support equipment should be considered. Costs associated with auxiliary equipment, which represent 20 to 30% of the total plant m u a l operating costs, should also be included. Any analysis that fails to include all the associated costs does not give a clear picture of the building owner’s heating and cooling alternatives. In addition to the tangible costs, there are a number of other factors that should be considered, such as convenience, risk, environmental issues, flexibility, and back-up.

On-Site Electrical Power Generation On-site electrical power generation covers a broad range of applications, from emergency back-up to power for a single piece of equipment to an on-site power plant supplying 100% of the facility’s electrical power needs. Various system types and fuel sources are available, but the economic principles described in this chapter apply equally to all ofthem. Other chapters (e.g., Chapters 7 and 36 of the 2008 ASHRAE Handbook-HVAC Systems and Equipment) may be helpful in describing system details. An economic study of on-site electrical power generation should include consideration of all owning, operating, and maintenance costs. Typically, on-site generation is capital intensive (i.e., high frst cost) and therefore requires a high use rate to produce savings adequate to support the investment. High use rates mean high run time, which requires planned maintenance and careful operation. Owning costs include any related systems required to adapt the building to on-site power generation. Additional equipment is required if the building will also use purchased power from autility. Costs associated with shared equipment should also be considered. For example, if the power source for the generator is a steam turbine, and a hot-water boiler would otherwise be used to meet the HVAC demand, the boiler would need to be a larger, high-pressure steam boiler with a heat exchanger to meet the hot-water needs. Operation and maintenance costs for the boiler also are increased because of the increased operating hours. Costs of an initial investment and ongoing inventory of spare parts must also be considered. Most equipment manufacturers provide a recommended spare parts list as well as recommended maintenance schedules, typically daily, weekly, and monthly routine maintenance and periodic major overhauls. Major overhaul frequency depends on equipment use and requires taking the equipment off-line. The cost of either lost building use or the provision of electricity from an alternative source during the shutdown should be considered.

z

zyxwvu

ECONOMIC ANALYSIS TECHNIQUES Analysis of overall owning and operating costs and comparisons of alternatives require an understanding of the cost of lost opportunities, inflation, and the time value of money. This process of economic analysis of alternatives falls into two general categories: simple payback analysis and detailed economic analyses (life-cycle cost analyses). A simple payback analysis reveals options that have short versus long paybacks. Often, however, alternatives are similar and have similar paybacks. For a more accurate comparison, a more comprehensive economic analysis is warranted. Many times it is appropriate to have both a simple payback analysis and a detailed economic analysis. The simple payback analysis shows which options should not be considered further, and the detailed economic analysis determines which of the viable options are the strongest. The strongest options can be accepted or further analyzed if they include competing alternatives.

Simple Payback In the simple payback technique, a projection of the revenue stream, cost savings, and other factors is estimated and compared to the initial capital outlay. This simple technique ignores the cost of borrowing money (interest) and lost opportunity costs. It also ignores inflation and the time value of money. Example 1. Equipment item 1 costs $10 000 and will save $2000 per year in operating costs; equipment item 2 costs $12 000 and saves $3000 per year. Which item has the best simple payback? Item 1

$10 000($2000/yr) = 5-year simple payback

201 1 ASHRAE Handbook-HVAC

37.10 Item 2

$12 000/($3000/yr) = 4-year simple payback

Applications (SI)

CRF = PMT/P

(6)

z

Because analysis of equipment for the duration of its realistic life can produce a very different result, the simple payback technique should be used with caution.

More Sophisticated Economic Analysis Methods Economic analysis should consider details of both positive and negative costs over the analysis period, such as varying inflation rates, capital and interest costs, salvage costs, replacement costs, interest deductions, depreciation allowances, taxes, tax credits, mortgage payments, and all other costs associated with a particular system. See the section on Symbols for definitions of variables. Present-Value (Present Worth) Analysis. All sophisticated economic analysis methods use the basic principles of present value analysis to account for the time value of money. Therefore, a good understanding of these principles is important. The total present value (present worth) for any analysis is determined by summing the present worths of all individual items under consideration, both future single-payment items and series of equal future payments. The scenario with the highest present value is the preferred alternative. Single-Payment Present- Value Analysis. The cost or value of money is a function of the available interest rate and inflation rate. The future value F of a present sum of money P over n periods with compound interest rate i per period is F = P ( 1 +i)"

or

Example 4. Determine the present value of an annual operating cost of $1000 per year over 10 years, assuming 10% per year interest rate. PWF(i,n),,,

=

P

[( 1 + 0.1)"-

1]/[0.1(1 + O.l)'O] = 6.14

$1000(6.14)

$6140

zyxwvutsr zyxwvuts (1)

Conversely, the present value or present worth P of a future sum of money F is given by

P = F/(1 + i)"

The CRF is often used to describe periodic uniform mortgage or loan payments. Note that when payment periods other than annual are to be studied, the interest rate must be expressed per appropriate period. For example, if monthly payments or return on investment are being analyzed, then interest must be expressed per month, not per year, and n must be expressed in months.

CRF(i,n)

= =

PMT

= =

(3)

where the single-payment present-worth factor PWF(i,n),gl is defmed as

=

Example 5. Determine the uniform monthly mortgage payments for a loan of $100 000 to be repaid over 30 years at 10% per year interest. Because the payment period is monthly, the payback duration is 30(12) = 360 monthly periods, and the interest rate per period is 0.1/12 = 0.00833 per month.

(4

P = F x PWF(i,n),gl

=

=

0.008 33(1 + 0.008 33)360/[(1 + 0.008 33)360- 11 0.008 773 P(CRF) $100 OOO(0.008 773) $877.30 per month

Improved Payback Analysis. This somewhat more sophisticated payback approach is similar to the simple payback method, except that the cost of money (interest rate, discount rate, etc.) is considered. Solving Equation (7) for n yields the following: h[CRF/(CRF - i ) ]

zyxwvutsr

PWF(i,n),gl

=

l/(l

+ i)"

Example 2. Calculate the value in 10 years at 10% per year interest of a system presently valued at $10 000

F = P ( l + i)"

=

$10 000 (1 + 0.1)'O

=

n=

(4)

$25,937.42

Example 3. Using the present-worth factor for 10% per year interest and an analysis period of 10 years, calculate the present value of a future sum of money valued at $10 000. (Stated another way, determine what sum of money must be invested today at 10% per year interest to yield $10 000 10 years from now.)

(8)

Given known investment amounts and earnings, CRFs can be calculated for the alternative investments. Subsequently, the number of periods until payback has been achieved can be calculated using Equation (8).

Example 6. Compare the years to payback of the same items described in Example 2 if the value of money is 10% per year. Item 1

P = F x PWF(i,n),,, P = $10 000 x 1/(1 + 0.1)'O = $3855.43

h(1 +i)

cost savings CRF n

=

cost savings CRF n

=

= = =

$10000 $2000/year $2000/$10 000 = 0.2 ln[0.2/(0.2 O.l)]/ln(l + 0.1) = 7.3 years -

Item 2

Series of Equal Payments. The present-worth factor for a series of future equal payments (e.g., operating costs) is given by

= = =

$12000 $3000/year $3000/$12 000 = 0.25 ln[0.25/(0.25 -O.l)]/ln(l + 0.1) = 5.4 years

(5)

If years to payback is the sole criteria for comparison, Item 2 is preferable because the investment is repaid in a shorter period of time.

The present value P of those future equal payments (PMT) is then the product of the present-worth factor and the payment [i.e., P = PWF(i,n),, x PMT]. The number of future equal payments to repay a present value of money is determined by the capital recovery factor (CRF), which is the reciprocal of the present-worth factor for a series of equal payments:

Accounting for Inflation. Different economic goods may inflate at different rates. Inflation reflects the rise in the real cost of a commodity over time and is separate from the time value of money. Inflation must often be accounted for in an economic evaluation. One way to account for inflation is to substitute effective interest rates that account for inflation into the equations given in this chapter.

37.11

Owning and Operating Costs The effective interest rate i', sometimes called the real rate, accounts for inflation rate j and interest rate i or discount rate id; it can be expressed as follows (Kreider and Kreith 1982):

A more practical SIR base-case equation for buildings is as follows: SIR,:,,

=

z

E+W+OM&R I , + Repl - Res

zyxwvutsrqpo i'= E - 1 l + j

=

(9)

i-j l + j

Different effective interest rates can be applied to individual components of cost. Projections for future fuel and energy prices are available in the Annual Supplement to NISTHandbook 135 (Rushing et al. 2010).

where SIR,:,,

=

E

=

W OM&R

=

ratio of operational savings to investment-related additional costs computed for alternative A to base case BC (E,, E,), savings in energy costs attributable to alternative relative to base case (W,, W,), savings in water costs attributable to alternative difference in OM&R costs; OM&R,, OM&R, additional initial investment cost required for alternative relative to base case; (I, I,,) difference in capital replacement costs; (Repl, Repl,,) difference in residual value; (Res, Res,,)

zyxwvutsrq

Example 7. Determine the present worth P of an annual operating cost of $1000 over 10 years, given a discount rate of 10% per year and an inflation rate of 5% per year.

=

I,,

=

Repl Res

=

~

~

~

~

i' PWF(i',n),,,

P

=

=

=

(0.1 - 0.05)/( 1 + 0.05) (1 + 0.0476)'O

-

1

=

0.0476(1 + 0.0476)'O $1000(7.813) = $7813

=

0.0476

7.813

The following are three common methods of present-value analysis that include life-cycle cost factors (life of equipment, analysis period, discount rate, energy escalation rates, maintenance cost, etc., as shown in Table 1). These comparison techniques rely on the same assumptions and economic analysis theories but display the results in different forms. They also use the same definition of each term. All can be displayed as a single calculation or as a cash flow table using a series of calculations for each year of the analysis period. Savings-to-Investment Ratio. Most large military-sponsored work and many other U.S. government entities require a savings-toinvestment-ratio (SIR) method. Simply put, SIR is the ratio of an option's savings to its costs. This ratio defines the relative economic strength of each option. The higher the ratio, the better the economic strength. If the ratio is less than 1, the measure does not pay for itself within the analysis period. The escalated savings on an annual and a special (nonannual) basis is calculated and discounted. Costs are shown on an annual and special basis for each year over the life of the system or option. Savings and investments are both discounted separately on an annual basis, and then the discounted total cumulative savings is divided by the discounted total cumulative investments (costs). The analysis period is usually the life ofthe system or equipment being considered. The SIR is the sum of a series of operation-related savings from a project alternative divided by the sum of its additional investmentrelated costs. Typically, this is over a period of years (5, 10, or 20 years, or the typical expected life span). The general equation for the SIR simply rearranges these two terms as a ratio:

where SIR,,,

ratio of PV savings to additional PV investment costs of (mutually exclusive) alternative A to base case BC s, = savings in year t in operational costs attributable to alternative I, = investment-related costs in year t attributable to alternative t = year of occurrence (where 0 is base date) d = discount rate N = length of study =

=

~

~

where all amounts are in present values. Example 8: SIR Computation. For this example, the numerator and denominator are defined as follows: Numerator: PV of operational savings attributable to the alternative = $91 030 Denominator: PV of additional investment costs required for the alternative = $7 239 Thus. SIR,:,,

=

$91030 $7 239

=

12.6

A ratio of 12.6 means that the energy-conserving design generates an average return of $12.6 for every $1 invested, over and above the minimum required rate of return imposed by the discount rate. The project alternative in this example is clearly cost effective. A ratio of 1.0 indicates that the cost ofthe investment equals its savings; a ratio of less than 1.0 indicates an uneconomic alternative that would cost more than it would save.

Summary of SIR Method An investment is cost effective if its SIR is greater than 1.O; this is equivalent to having net savings greater than zero. The SIR is a relative measure; it must be calculated with respect to a designated base case. When computing the SIR of an alternative relative to its base case, the same study period and the same discount rate must be used. The SIR is useful for evaluating a single project alternative against a base case or for ranking independent project alternatives; it is not useful for evaluating multiple mutually exclusive alternative. Internal Rate of Return. The internal rate of return (IRR) method calculates a return on investment over the defined analysis period. The annual savings and costs are not discounted, and a cash flow is established for each year of the analysis period, to be used with an initial cost (or value of the loan). Annual recurring and special (nonannual) savings and costs can be used. The cash flow is then discounted until a calculated discount rate is found that yields a net present value of zero. This method assumes savings are reinvested at the same calculated rate of return; therefore, the calculated rates of return can be overstated compared to the actual rates of return. Another version of this is the modified or adjusted internal rate of return (MIRR or AIRR). In this version, reinvested savings are assumed to have a given rate of return on investment, and the fmanced moneys a given interest rate. The cash flow is then discounted until a calculated discount rate is found that yields a net present value of zero. This method gives a more realistic indication of expected return on investment, but the difference between alternatives can be small.

201 1 ASHRAE Handbook-HVAC

37.12

Applications (SI)

Table 7 Two Alternative LCC Examples Alternative 1: Purchase Chilled Water from Utility Year

1

0 First costs Chilled-water costs Replacement costs Maintenance costs Net annual cash flow Present value of cash flow

65250 60417

2

66881 57340

3

68553 54420

4

70267 51648

5

72024 49018

6

73824 46522

7

75670 44153

8

77501 41904

9

79501 39770

10

zy

81488 37745

Year

11 Financing annual payments Chilled-water costs Replacement costs Maintenance costs

~

12 ~

$83526

13 ~

$85614

14 ~

$87754

$89948 ~

~

Net annual cash flow Present value of cash flow

~

83526 35823

15 ~

16 ~

$92 197 ~

17 ~

$94501 ~

18 ~

$96864 ~

19 ~

20 ~

$99286 $101768 $104312 ~

~

~

~

85614 33998

87754 32267

89948 30624

92197 29064

94501 27584

96864 26179

99286 24846

101768 23581

104312 22380

20-year life-cycle cost $769 823 Alternative 2: Install Chiller and Tower Year

1

0 First costs Energy costs Replacement costs Maintenance costs Net annual cash flow Present value of cash flow

$220000

3

4 ~

~

$18 750 ~

220000 220000

2

15200 33950 31435

~

$19 688 ~

15656 35344 30301

5 ~

6 ~

7 ~

8 ~

9 ~

10 ~

~

$20 672 ~

16126 36798 29211

$21 705 ~

$22 791 ~

16609 38315 28163

17108 39898 27154

$23 930 ~

17621 41551 26184

$25 127 ~

18150 43276 25251

$26 383 ~

18694 45077 24354

$27 702 ~

19255 46957 23490

$29 087 90 000 19833 138920 64347

Year

11 Financing annual payments Energy costs Replacement costs Maintenance costs Net annual cash flow Present value of cash flow 20-vear life-cvcle cost

~

$30 542 ~

20428 50969 21860

12 ~

$32 069 ~

21040 53109 21090

13 ~

$33 672 ~

21672 55344 20350

14 ~

15 ~

$35 356 ~

$37 124 ~

22322 57678 19637

22991 60115 18951

16 ~

$38 980 ~

23681 62661 18290

17 ~

$40 929 ~

24392 65320 17654

18 ~

$42 975 ~

25123 68099 17042

19 ~

$45 124 ~

25877 71001 16452

20 ~

$47 380 ~

26653 74034 15884

$717 100

The most straightforward method of calculating the AIRR requires that the SIR for a project (relative to its base case) be calculated frst. Then the AIRR can be computed easily using the following equation:

of the analysis period. The options are compared to determine which has the lowest total cost over the anticipated project life.

zyxwvutsrqpon AIRR = (1 + r)(SIR)l/N- 1

(12)

where r is the reinvestment rate and N is the number of years in the study period. Using the SIR of 12.6 from Equation (10) and a reinvestment rate of 3% [the minimum acceptable rate of return (MARR)], the AIRR is found as follows:

AIRR,:., = (1 + 0.03)(12.6)1/20 1 = 0.1691 -

Because an AIRR of 16.9% for the alternative is greater than the MARR, which in this example is the FEMP discount rate of 3%, the project alternative is considered to be cost effective in this application.

Life-Cycle Costs. This method of analysis compares the cumulative total of implementation, operating, and maintenance costs. The total costs are discounted over the life of the system or over the loan repayment period. The costs and investments are both discounted and displayed as a total combined life-cycle cost at the end

Example 9. A municipality is evaluating two different methods of providing chilled water for cooling a government office building: purchasing chilled water from a central chilled-water utility service in the area, or installing a conventional chiller plant. Because the municipality is not a tax-paying entity, the evaluation does not need to consider taxes, allowing for either a current or constant dollar analysis. The first-year price of the chilled-water utility service contract is $65 250 per year, and is expected to increase at a rate of 2.5% per year. The chiller and cooling tower would cost $220 000, with an expected life of 20 years. A major overhaul ($90 000) of the chiller is expected to occur in year ten. Annual costs for preventative maintenance ($1400), labor ($10 000), water ($2000) and chemical treatments ($1800) are all expected to keep pace with inflation, which is estimated to average 3% annually over the study period. The annual electric cost ($18 750) is expected to increase at a rate of 5% per year. The municipality uses a discount rate of 8% to evaluate financial decisions. Which option has the lowest life-cycle cost? Solution. Table 7 compares the two alternatives. For the values provided, alternative 1 has a 20-year life cycle cost of $769 283 and alternative 2 has a 20-year life cycle cost of $717 100. If LCC is the only basis for the decision, alternative 2 is preferable because it has the lower life-cycle cost.

zy zyxwvutsrq zyxwvutsrqponm 37.13

Owning and Operating Costs

Table 8

Name

Single compound-amount (SCA) equation

Commonly Used Discount Formulas

Algebraic Forma,b

Name

F

Uniform compound-amount (UCA) equation

=

P . [ ( l +d),]

Uniform present-value (UPV) equation

Single present-value (SPV) equation

d

Uniform sinking-fund (USF) equation

A = '.[(l+d),-l]

equation A = '.[(l+d)'-l] where A = end-of-period payment (or receipt) in a uniform series of payments (or receipts) over n periods at d interest or discount rate =

Modifieduniformpresent-value

(UPV*) equation

d ( 1 + d),

=

A . l+e [d-J

.

[

1+e

[l+d)3

d ( 1 + d),

Uniform capital recovery (UCR)

A,

Algebraic F ~ r m ~ , ~

A, d e

=

Ao(l+e)t,wheret=l,...,n interest or discount rate price escalation rate per period

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initial value of a periodic payment (receipt) evaluated at beginning of study period

Source: NIST Handbook 135 (Fuller and Petersen 1996). aNote that the USF, UCR, UCA, and UPV equations yield undefined answers when d = 0. The correct algebraic forms for this special case would be as follows: USF formula, A = FAV; UCR formula, A = PAV;UCA formula, F = A n . The UPV* equation also yields an undefined answer when e = d. In this case, P = Ao.n.

Computer Analysis Many computer programs are available that incorporate economic analysis methods. These range from simple macros developed for popular spreadsheet applications to more comprehensive, menudriven computer programs. Commonly used examples of the latter include Building Life-Cycle Cost (BLCC) and PC-ECONPACK. BLCC was developed by the National Institute of Standards and Technology (NIST) for the U.S. Department of Energy (DOE). The program follows criteria established by the Federal Energy Management Program (FEMP) and the Office of Management and Budget (OMB). It is intended for evaluation of energy conservation investments in nonmilitary government buildings; however, it is also appropriate for similar evaluations of commercial facilities. PC-ECONPACK, developed by the U.S. Army Corps of Engineers for use by the DOD, uses economic criteria established by the OMB. The program performs standardized life-cycle cost calculations such as net present value, equivalent uniform annual cost, SIR, and discounted payback period. Macros developed for common spreadsheet programs generally contain preprogrammed functions for various life-cycle cost calculations. Although typically not as sophisticated as the menudriven programs, the macros are easy to install and learn.

Reference Equations Table 8 lists commonly used discount formulas as addressed by NIST. Refer to NIST Handbook 135 (Fuller and Petersen 1996) for detailed discussions.

SYMBOLS AIRR =modified or adjusted internal rate of return (MIRR or AIRR) c =cooling system adjustment factor C =total annual building HVAC maintenance cost Ce =annual operating cost for energy Cs,assess =assessed system value C,mt =initial system cost CS,SUlV = system salvage value at end of study period CY =uniform annualized mechanical system owning, operating, and maintenance costs CRF =capital recovery factor CRF(i,n) =capital recovery factor for interest rate i and analysis period n CRF(i',n) = capital recovery factory for interest rate i' for items other than fuel and analysis period n

= =

bThe terms by which known values are multiplied are formulas for the factors found in discount factor tables. Using acronyms to represent the factor formulas, the discounting equations can also be written as F = P x SCA, P = F x SPV, A = F x USF, A = P x UCR, F = UCA, P = A x UPV, and P = A o x UPV*.

CRF(i",n) =capital recovery factor for fuel interest rate i" and analysis period n CRF(i,,n) =capital recovery factor for loan or mortgage rate i, and analysis period n d =distribution system adjustment factor D, =depreciation during period k DbsL = depreciation during period k from straight-line depreciation method DbsD = depreciation during period k from sum-of-digits depreciation method F = future value of sum of money h =heating system adjustment factor i = compound interest rate per period id = discount rate per period i, = market mortgage rate i ' =effective interest rate for all but fuel i " =effective interest rate for fuel Z = insurance cost per period ITC = investment tax credit j = inflation rate per period je = fuel inflation rate per period k = end of period(s) during which replacement(s), repair(s), depreciation, or interest are calculated M = maintenance cost per period n = number of periods under analysis P = present value of a sum of money P, = outstanding principle on loan at end of period k PMT = future equal payments PWF = present worth factor PWF(id,k) = present worth factor for discount rate id at end of period k PWF(i',k) = present worth factor for effective interest rate i' at end of period k PWF(i,n)sgl= single payment present worth factor PWF(i,n),= present worth factor for a series of future equal payments R, = net replacement, repair, or disposal costs at end of period k SIR = savings-to-investment ratio T,,, = net income tax rate Tprop = property tax rate Tsulv = tax rate applicable to salvage value of system

REFERENCES Abramson, B., D. Herman, and L. Wong. 2005. Interactive Web-based owning and operating cost database (TRP-1237). ASHRAE Research Project, Final Report.

37.14

z zyxwvutsr 201 1 ASHRAE Handbook-HVAC Applications (SI)

Akalin, M.T. 1978. Equipment life and maintenance cost survey (RP-186). ASHRAE Transactions 84(2):94- 106. BOMA. 2003. Preventive maintenance and building operation ef$ciency. Building Owners and Managers Association, Washington, D.C. DOE. 2007. The international performances measurement and verification protocol (IPMVP). Publication No. DOE/EE-0 157. U.S. Department of Energy. http://www.ipmvp.org/. Dohrmann, D.R. and T. Alereza. 1986. Analysis of survey data on HVAC maintenance costs (RP-382). ASHRAE Transactions 92(2A):550-565. Fuller, S.K. and S.R. Petersen. 1996. Life-cycle costing manual for the federal energy management program, 1995 edition. NIST Handbook 135. National Institute of Standards and Technology, Gaithersburg, MD. http://fire.nist.gov/bfrlpubs/build96/art121 .html. Hiller, C.C. 2000. Determining equipment service life. ASHRAE Journal 42(8):48-54. Kreider, J. and F. Kreith. 1982. Solar heating and cooling: Active andpassive design. McGraw-Hill, New York. Lovvorn, N.C. and C.C. Hiller. 2002. Heat pump life revisited. ASHRAE Transactions 108(2): 107-112. NIST. Building life-cycle cost computer program (BLCC 5.2-04). Available from the U.S. Department of Energy Efficiency and Renewable Energy Federal Energy Management Program, Washington, D.C. http://www. eere.energy.gov/femp/information/download~blcc.cfm#blcc5. OMB. 1992. Guidelines and discount rates for benefit-cost analysis of federal programs. Circular A-94. Office of Management and Budget, Washington, D.C. Available at http://www.whitehouse.gov/OMB/circulars/ a094/a094.html.) Rushing, A.S., Kneifel, J.D., and B.C. Lippiatt. 2010. Energy price indices and discount factors for life-cycle cost analysis-20 10. Annual Supplement to NISTHandbook 135 and NBSSpecial Publication 709. NISTIR 85-3273-25. National Institute of Standards and Technology, Gaithersburg, MD. http://wwwl .eere.energy.gov/femp/pdfs/ashb 1O.pdf

BIBLIOGRAPHY

ASHRAE. 1999. HVAC maintenance costs (RP-929). ASHRAE Research Project, Final Report. ASTM. 2004. Standard terminology ofbuilding economics. Standard E83304. American Society for Testing and Materials, International, West Conshohocken, PA. Easton Consultants. 1986. Survey of residential heat pump service life and maintenance Issues. AGA S-77 126. American Gas Association, Arlington, VA. Haberl, J. 1993. Economic calculations for ASHRAE Handbook. ESL-TR93/04-07. Energy Systems Laboratory, Texas A&M University, College Station. http://repository.tamu.edu/bitstream/handle/l969.1/2 113/ESL-

zyxwvut zyxwv TR-93-04-07.pdf?sequence=l.

Kurtz, M. 1984. Handbook of engineering economics: Guidefor engineers, technicians, scientists, and managers. McGraw-Hill, New York. Lovvorn, N.C. and C.C. Hiller. 1985. A study of heat pump service life. ASHRAE Transactions 9 1(2B):573 -588. Quirin, D.G. 1967. The capital expenditure decision. Richard D. Win, Inc., Homewood, IL. U.S. Department of Commerce, Bureau of Economic Analysis. (Monthly) Suwey of current business. U.S. Department of Commerce Bureau of Economic Analysis, Washington, D.C. http://www.bea.gov/scb/index. htm. USA-CERL. 1998. Life cycle cost in design computer program (WinLCCID 98). Available from Building Systems Laboratory, University of Illinois, Urbana-Champaign. U.S. Department of Labor. 2005. Annualpercent changesfrom 1913 topresent. Bureau of Labor Statistics. Available from http://www.bls.gov/cpi. USACE. PC-ECONPACK computer program (ECONPACK 4.0.2). U.S. Army Corps of Engineers, Huntsville, AL. http://www.hnd.usace.army. mil/paxspt/econ/download.aspx.

zy zyxwvut CHAPTER 38

TESTING, ADJUSTING, AND BALANCING Hydronic Balancing Methods

Air VolumetricMeasurement Methods Balancing Proceduresf o r Air Distribution .............................. Variable-Volume Systems Principles and Proceduresfor Balancing Hydronic Systems ................................................................. Water-SideBalancing ...............................................................

38.3

38.6 38.8

S

YSTEMS that control the environment in a building change with time and use, and must be rebalanced accordingly. The designer must consider initial and supplementary testing and balancing requirements for commissioning. Complete and accurate operating and maintenance instructions that include intent of design and how to test, adjust, and balance the building systems are essential. Building operating personnel must be well-trained, or qualified operating service organizations must be employed to ensure optimum comfort, proper process operations, and economical operation. This chapter does not suggest which groups or individuals should perform a complete testing, adjusting, and balancing procedure. However, the procedure must produce repeatable results that meet the design intent and the owner’s requirements. Overall, one source must be responsible for testing, adjusting, and balancing all systems. As part of this responsibility, the testing organization should check all equipment under field conditions to ensure compliance. Testing and balancing should be repeated as systems are renovated and changed. Testing boilers and other pressure vessels for compliance with safety codes is not the primary function of the testing and balancing firm; rather, it is to verify and adjust operating conditions in relation to design conditions for flow, temperature, pressure drop, noise, and vibration. ASHRAE Standard 111 details procedures not covered in this chapter.

TERMINOLOGY Testing, adjusting, and balancing (TAB) is the process of checking and adjusting all environmental systems in a building to produce the design objectives. This process includes (1) balancing air and water distribution systems, (2) adjusting the total system to provide design quantities, (3) electrical measurement, (4) establishing quantitative performance of all equipment, (5) verifying automatic control system operation and sequences of operation, and (6) sound and vibration measurement. These procedures are accomplished by checking installations for conformity to design, measuring and establishing the fluid quantities of the system as required to meet design specifications, and recording and reporting the results. The following definitions are used in this chapter. Refer to ASHRAE Terminology ofHVAC&R (1991) for additional definitions.

Test. Determine quantitative performance of equipment. Adjust. Regulate the specified fluid flow rate and air patterns at terminal equipment (e.g., reduce fan speed, adjust a damper). Balance. Proportion flows in the distribution system (submains, branches, and terminals) according to specified design quantities. Balanced System. A system designed to deliver heat transfer required for occupant comfort or process load at design conditions. A minimum heat transfer of 97% should be provided to the space or The preparation of this chapter is assigned to TC 7.7, Testing and Balancing.

Steam Distribution Cooling Towers ...................................................................... Temperature Control Verijkation Field Surveyfor Energy Audit ................................................ Reports ................................................................................... Testingfor Sound and Vibration.............................................

38.15 38.17 38.18 38.18

load served at design flow. The flow required for minimum heat transfer establishes the system’s flow tolerance. The fluid distribution system should be designed to allow flow to maintain the required tolerance and verify its performance. Procedure. An approach to and execution of a sequence of work operations to yield repeatable results. Report forms. Test data sheets arranged in logical order for submission and review. They should also form the permanent record to be used as the basis for any future TAB work. Terminal. A point where the controlled medium (fluid or energy) enters or leaves the distribution system. In air systems, these may be variable- or constant-volume boxes, registers, grilles, diffusers, louvers, and hoods. In water systems, these may be heat transfer coils, fan-coil units, convectors, or fnmed-tube radiation or radiant panels.

GENERAL CRITERIA Effective and efficient TAB requires a systematic, thoroughly planned procedure implemented by experienced and qualified staff. All activities, including organization, calibration of instruments, and execution of the work, should be scheduled. Air-side work must be coordinated with water-side and control work. Preparation includes planning and scheduling all procedures, collecting necessary data (including all change orders), reviewing data, studying the system to be worked on, preparing forms, and making preliminary field inspections. Air leakage in a conduit (duct) system can significantly reduce performance, so conduits (ducts) must be designed, constructed, and installed to minimize and control leakage. During construction, all duct systems should be sealed and tested for air leakage. Water, steam, and pneumatic piping should be tested for leakage, which can harm people and equipment.

Design Considerations TAB begins as design functions, with most of the devices required for adjustments being integral parts of the design and installation. To ensure that proper balance can be achieved, the engineer should show and specify a sufficient number of dampers, valves, flow measuring locations, and flow-balancing devices; these must be properly located in required straight lengths of pipe or duct for accurate measurement. Testing depends on system characteristics and layout. Interaction between individual terminals varies with pressures, flow requirements, and control devices. The design engineer should specify balancing tolerances. Minimum flow tolerances are *lo% for individual terminals and branches in noncritical applications and *5% for main air ducts. For critical water systems where differential pressures must be maintained, tolerances of *5% are suggested. For critical air systems, recommendations are the following:

38.1

201 1 ASHRAE Handbook-HVAC

38.2 Positive zones: Supply air Exhaust and return air Negative zones: Supply air Exhaust and return air

0 to +lo% 0 to -10% 0 to -10% 0 to +lo%

Balancing Devices. Balancing devices should be used to provide maximum flow-limiting ability without causing excessive noise. Flow reduction should be uniform over the entire duct or pipe. Single-blade dampers or butterfly balancing valves are not good balancing valves because of the uneven flow pattern at high pressure drops. Pressure drop across equipment is not an accurate flow measurement but can be used to determine whether the manufacturer design pressure is within specified limits. Liberal use of pressure taps at critical points is recommended.

AIR VOLUMETRIC MEASUREMENT METHODS General The pitot-tube traverse is the generally accepted method of measuring airflow in ducts; ways to measure airflow at individual terminals are described by manufacturers. The primary objective is to establish repeatable measurement procedures that correlate with the pitot-tube traverse. Laboratory tests, data, and techniques prescribed by equipment and air terminal manufacturers must be reviewed and checked for accuracy, applicability, and repeatability of results. Conversion factors that correlate field data with laboratory results must be developed to predict the equipment's actual field performance.

Air Devices All flow-measuring instruments should be field verified by comparing to pitot-tube traverses to establish correction andor density factors. Generally, correction factors given by air diffuser manufacturers should be checked for accuracy by field measurement and by comparing actual flow measured by pitot-tube traverse to actual measured velocity. Air diffuser manufacturers usually base their volumetric test measurements on a deflecting vane anemometer. The velocity is multiplied by an empirical effective area to obtain the air diffuser's delivery. Accurate results are obtained by measuring at the vena contracta with the probe of the deflecting vane anemometer. Methods advocated for measuring airflow of troffer-type terminals are similar to those for air diffusers. A capture hood is frequently used to measure device airflows, primarily of diffusers and slots. Loss coefficients should be established for hood measurements with varying flow and deflection settings. If the air does not fill the measurement grid, the readings will require a correction factor. Rotating vane anemometers are commonly used to measure airflow from sidewall grilles. Effective areas (correction factors) should be established with the face dampers fully open and deflection set uniformly on all grilles. Correction factors are required when measuring airflow in open ducts [i.e., damper openings and fume hoods (Sauer and Howell 1990)].

Duct Flow

Applications (SI)

by a reliable method (e.g., pitot-tube traverse of system's main) that considers possible system effects. For some fans, the flow rate is not proportional to the power needed to drive them. In some cases, as with forward-curved-blade fans, the same power is required for two or more flow rates. The backward-curved-blade centrifugal fan is the only type with a flow rate that varies directly with power input. If an installation has an inadequate straight length of ductwork or no ductwork to allow a pitot-tube traverse, the procedure from Sauer and Howell (1 990) can be followed: a vane anemometer reads air velocities at multiple points across the face of a coil to determine a loss coefficient.

z

Mixture Plenums Approach conditions are often so unfavorable that the air quantities comprising a mixture (e.g., outdoor and return air) cannot be determined accurately by volumetric measurements. In such cases, the mixture's temperature indicates the balance (proportions) between the component airstreams. Temperatures must be measured carefully to account for stratification, and the difference between outdoor and return temperatures must be greater than 10 K. The temperature of the mixture can be calculated as follows:

where (7, = (7, = (7, = tm = to = t, =

total measured air quantity, % outdoor air quantity, % return air quantity, % temperature of outdoor and return mixture, "C outdoor temperature, "C return temperature, "C

Pressure Measurement Air pressures measured include barometric, static, velocity, total, and differential. For field evaluation of air-handling performance, pressure should be measured per ASHRAE Standard 111 and analyzed together with manufacturers' fan curves and system effect as predicted by AMCA Standard 210. When measured in the field, pressure readings, air quantity, and power input often do not correlate with manufacturers' certified performance curves unless proper correction is made. Pressure drops through equipment such as coils, dampers, or filters should not be used to measure airflow. Pressure is an acceptable means of establishing flow volumes only where it is required by, and performed in accordance with, the manufacturer certifying the equipment.

Stratification Normal design minimizes conditions causing air turbulence, to produce the least friction, resistance, and consequent pressure loss. Under some conditions, however, air turbulence is desirable and necessary. For example, two airstreams of different temperatures can stratify in smooth, uninterrupted flow conditions. In this situation, design should promote mixing. Return and outdoor airstreams at the inlet side of the air-handling unit tend to stratify where enlargement of the inlet plenum or casing size decreases air velocity. Without a deliberate effort to mix the two airstreams (e.g., in cold climates, placing the outdoor air entry at the top of the plenum and return air at the bottom of the plenum to allow natural mixing), stratification can be carried throughout the system (e.g., filter, coils, eliminators, fans, ducts). Stratification can freeze coils and rupture tubes, and can affect temperature control in plenums, spaces, or both. Stratification can also be reduced by adding vanes to break up and mix the airstreams. No solution to stratification problems is guaranteed; each condition must be evaluated by field measurements and experimentation.

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The preferred method of measuring duct volumetric flow is the pitot-tube traverse average. The maximum straight run should be obtained before and after the traverse station. To obtain the best duct velocity profile, measuring points should be located as shown in Chapter 36 of the 2009 ASHRAE Handbook-Fundamentals and ASHRAE Standard 111. When using factory-fabricated volumemeasuring stations, the measurements should be checked against a pitot-tube traverse. Power input to a fan's driver should be used as only a guide to indicate its delivery; it may also be used to verify performance determined

38.3

Testing, Adjusting, and Balancing BALANCING PROCEDURES FOR AIR DISTRIBUTION No one established procedure is applicable to all systems. The bibliography lists sources of additional information.

Instruments for Testing and Balancing The minimum instruments necessary for air balance are Manometer calibrated in 1 Pa divisions Combination inclinedivertical manometer (0 to 2.5 kPa) Pitot tubes in various lengths, as required Tachometer (direct-contact, self-timing) or strobe light Clamp-on ammeter withvoltage scales [root-mean-square (RMS) type1 Rotating vane anemometer Deflecting vane anemometer Thermal anemometer Capture hood Digital thermometers (0.05 K increments as a minimum) and glass stem thermometers (0.05 K graduations minimum) Sound level meter with octave band filter set, calibrator, and microphone Vibration analyzer capable of measuring displacement velocity and acceleration Water flowmeters (0 to 12 kPa and 0 to 100 kPa ranges) Compound gage Test gages (700 kPa and 2000 kPa) Sling psychrometer Etched-stem thermometer 10 to 50°C in 0.05 K increments) Hygrometers Relative humidity and dew-point instruments Instruments must be calibrated periodically to verify their accuracy and repeatability before use in the field.

Preliminary Procedure for Air Balancing 1. Before balancing, all pressure tests (duct leakage) of duct and piping systems must be complete and acceptable. 2. Obtain as-built design drawings and specifications, and become thoroughly acquainted with the design intent. 3. Obtain copies of approved shop drawings of all air-handling equipment, outlets (supply, return, and exhaust), and temperature control diagrams, including performance curves. Compare design requirements with shop drawing capacities. 4. Compare design to installed equipment and field installation. 5 . Walk the system from air-handling equipment to terminal units to determine variations of installation from design. 6. Check dampers (both volume and fre) for correct and locked position and temperature control for completeness of installation before starting fans. 7. Prepare report test sheets for both fans and outlets. Obtain manufacturer’s outlet factors and recommended test procedure. A summation of required outlet volumes allows cross-checking with required fan volumes. 8. Determine the best locations in the main and branch ductwork for the most accurate duct traverses. 9. Place all outlet dampers in full open position. 10. Prepare schematic diagrams of system as-built ductwork and piping layouts to facilitate reporting. 11. Check filters for cleanliness and proper installation (no air bypass). If specifications require, establish procedure to simulate dirty filters. 12. For variable-volume systems, develop a plan to simulate diversity (if required).

Motor amperage and voltage to guard against overload Fanrotation Operability of static pressure limit switch Automatic dampers for proper position Air and water controls operating to deliver required temperatures Air leaks in the casing and around the coils and filter frames must be stopped. Note points where piping enters the casing to ensure that escutcheons are right. Do not rely on pipe insulation to seal these openings (insulation may shrlnk). In prefabricated units, check that all panel-fastening holes are filled. 2. Traverse the main supply ductwork whenever possible. All main branches should also be traversed where duct arrangement allows. Traverse points and method of traverse should be selected as follows: Traverse each main or branch after the longest possible straight run for the duct involved. For test hole spacing, refer to Chapter 36 of the 2009 ASHRAE Handbook-Fundamentals. Traverse using a pitot tube and manometer where velocities are over 3 d s ) . Below this velocity, use either a micromanometer and pitot tube or an electronic multimeter and a pitot tube. Note temperature and barometric pressure and correct for standard air quantity if needed. After establishing the total air being delivered, adjust fan speed to obtain design airflow, if necessary. Check power and speed to c o n f m motor power andior critical fan speed are not exceeded. Proportionally adjust branch dampers until each has the proper air volume. With all dampers and registers in the system proportioned and with supply and return fans operating at or near design airflow, set the minimum outdoor and return air ratio. If duct traverse locations are not available, this can be done by measuring the mixture temperature in the return air, outdoor air louver, and filter section. The mixture temperature may be approximated from Equation (1). The greater the temperature difference between outdoor and return air, the easier it is to get accurate damper settings. Take the temperature at many points in a uniform traverse to be sure there is no stratification. After the minimum outdoor air damper has been set for the proper percentage of outdoor air, run another traverse of mixture temperatures and install baffling if variation from the average is more than 5%. Remember that stratified mixed-air temperatures vary greatly with outdoor temperature in cold weather, whereas return air temperature has only a minor effect. 3. Balance terminal outlets in each control zone in proportion to each other, as follows: Once the preliminary fan quantity is set, proportion the terminal outlet balance from the outlets into the branches to the fan. Concentrate on proportioning the flow rather than the absolute quantity. As fan settings and branch dampers change, the outlet terminal quantities remain proportional. Branch dampers should be used for major adjusting and terminal dampers for trim or minor adjustment only. It may be necessary to install additional sub-branch dampers to decrease the use of terminal dampers that create objectionable noise. Normally, several passes through the entire system are necessary to obtain proper outlet values. The total tested outlet air quantity compared to duct traverse air quantities may indicate duct leakage. With total design air established in the branches and at the outlets, (1) take new fan motor amperage readings, (2) fmd static pressure across the fan, (3) read and record static pressure across each component (intake, filters, coils, mixing dampers), and (4) take a fmal duct traverse.

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Equipment and System Check 1. All fans (supply, return, and exhaust) must be operating before checking the following items:

zyxwvutsrq 201 1 ASHRAE Handbook-HVAC

Multizone Systems

Balancing should be accomplished as follows:

1. When adjusting multizone constant-volume systems, establish the ratio of the design volume through the cooling coil to total fan volume to achieve the desired diversity factor. Keep the proportion of cold to total air constant during the balance. However, check each zone on full cooling. If the design calls for full flow through the cooling coil, the entire system should be set to full flow through the cooling side while making tests. Perform the same procedure for the hot-air side. 2. Check leaving air temperature at each zone to verify that hot and cold damper inlet leakage is not greater than the established maximum allowable leakage. 3. Check apparatus and main trunks, as outlined in the section on Equipment and System Check. 4. Proportionately balance diffusers or grilles. 5 . Change control settings to full heating, and ensure that controls function properly. Verify airflow at each diffuser. Check for stratification. 6. If the engineer included a diversity factor in selecting the main apparatus, it will not be possible to get full flow to all zones simultaneously, as outlined in item 3 under Equipment and System Check. Zones equaling the diversity should be set to heating.

Applications (SI)

are simulated by using the same configuration of thermostat settings each time the system is tested (i.e., the same terminal boxes are fixed in the minimum and maximum positions for the test). Each terminal box requires a balancing damper upstream of its inlet. In a pressure-dependent system with pneumatic controls, setting minimum airflows to the space (other than at no flow) is not suggested unless the terminal box has a normally closed damper and the manufacturer of the damper actuator provides adjustable mechanical stops. Pressure-independent systems incorporate air terminal boxes with a thermostat signal used as a master control to open or close the damper actuator, and a velocity controller used as a sub-master control to maintain the maximum and minimum amounts of air to be supplied to the space. Air volume to the space varies to maintain the space temperature; air temperature supplied to the terminal remains constant. Take care to verify the operating range of the damper actuator as it responds to the velocity controller to prevent dead bands or overlap of control in response to other system components (e.g., double-duct VAV, fan-powered boxes, retrofit systems). Care should also be taken to verify the action of the thermostat with regard to the damper position, as the velocity controller can change the control signal ratio or reverse the control signal. The pressure-independent system requires verifying that the velocity controller is operating properly; it can be adversely affected by inlet duct configurations if a multipoint sensor is not used (Griggs et al. 1990). The primary difference between the two systems is that the pressure-dependent system supplies a different amount of air to the space as pressure upstream of the terminal box changes. If the thermostats are not calibrated properly to meet the space load, zones may overcool or overheat. When zones overcool and receive greater amounts of supply air than required, they decrease the amount of air that can be supplied to overheated zones. The pressure-independent system is not affected by improper thermostat calibration in the same way as a pressure-dependent system, because minimum and maximum airflow limits may be set for each zone.

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Dual-Duct Systems Balancing should be accomplished as follows: 1. When adjusting dual-duct constant-volume systems, establish the ratio of the design volume through the cooling coil to total fan volume to achieve the desired diversity factor. Keep the proportion of cold to total air constant during the balance. If the design calls for full flow through the cooling coil, the entire system should be set to full flow through the cooling side while making tests. Perform the same procedure for the hot-air side. 2. Check leaving air temperature at the nearest terminal to verify that hot and cold damper inlet leakage is not greater than the established maximum allowable leakage. 3. Check apparatus and main trunks, as outlined in the section on Equipment and System Check. 4. Determine whether static pressure at the end of the system (the longest duct run) is at or above the minimum required for mixing box operation. Proceed to extreme end of the system and check the static pressure with an inclined manometer. Pressure should exceed the minimum static pressure recommended by the mixing box manufacturer. 5 . Proportionately balance diffusers or grilles on the low-pressure side of the box, as described for low-pressure systems in the previous section. 6. Change control settings to full heating, and ensure that the controls and dual-duct boxes function properly. Spot-check airflow at several diffusers. Check for stratification. 7. If the engineer has included a diversity factor in selecting the main apparatus, it will not be possible to get full flow from all boxes simultaneously, as outlined in item 3 under Equipment and System Check. Mixing boxes closest to the fan should be set to full heating to force the air to the end of the system.

VARIABLE-VOLUME SYSTEMS Many types of variable-air-volume (VAV) systems have been developed to conserve energy. They can be categorized as pressuredependent or pressure-independent. Pressure-dependent systems incorporate air terminal boxes with a thermostat signal controlling a damper actuator. Air volume to the space varies to maintain space temperature; air temperature supplied to terminal boxes remains constant. The balance of this system constantly varies with loading changes; therefore, any balancing procedure will not produce repeatable data unless changes in system load

Static Control Static control saves energy and prevents overpressurizing the duct system. The following procedures and equipment are some of the means used to control static pressure. Fan Control. Consult ASHRAE Standard 90.1. Discharge Damper. Losses and noise should be considered. Vortex Damper. Losses from inlet air conditions are a problem, and the vortex damper does not completely close. The minimum expected airflow should be evaluated. Variable Inlet Cones. System loss can be a problem because the cone does not typically close completely. The minimum expected airflow should be evaluated. Varying Fan Speed Mechanically. Slippage, loss of belts, cost of belt replacement, and the initial cost of components are concerns. Variable Pitch-in-Motion Fans. Maintenance and preventing the fan from running in the stall condition must be evaluated. Varying Fan Speed Electrically. Varying voltage or frequency to the fan motor is usually the most efficient method. Some motor drives may cause electrical noise and affect other devices. In controlling VAV fan systems, location of the static pressure sensors is critical and should be field-verified to give the most representative point of operation. After the terminal boxes have been proportioned, static pressure control can be verified by observing static pressure changes at the fan discharge and the static pressure sensor as load is simulated from maximum to minimum airflow (i.e., set all terminal boxes to balanced airflow conditions and determine whether any changes in static pressure occur by placing one terminal box at a time to minimum airflow, until all terminals are placed at the minimal airflow setting). The maximum to minimum air volume changes should be within the fan curve performance (speed or total pressure).

zyxwvut zyxwvutsrqp 38.5

Testing, Adjusting, and Balancing Diversity

Diversity may be used on a VAV system, assuming that total airflow is lower by design and that all terminal boxes never fully open at the same time. Duct leakage should be avoided. All ductwork upstream of the terminal box should be considered mediumpressure, whether in a low- or medium-pressure system. A procedure to test the total air on the system should be established by setting terminal boxes to the zero or minimum position nearest the fan. During peak load conditions, care should be taken to verify that adequate pressure is available upstream of all terminal boxes to achieve design airflow to the spaces.

Outdoor Air Requirements Maintaining a space under a slight positive or neutral pressure to atmosphere is difficult with all variable-volume systems. In most systems, the exhaust requirement for the space is constant; thus, outdoor air used to equal the exhaust air and meet minimum outdoor air requirements for building codes must also remain constant. Because of the location of the outdoor air intake and pressure changes, this does not usually happen. Outdoor air should enter the fan at a point of constant pressure (i.e., supply fan volume can be controlled by proportional static pressure control, which can control the return air fan volume). Makeup air fans can also be used for outdoor air control.

Return Air Fans If return air fans are required in series with a supply fan, control and sizing of the fans is most important. Serious over- and underpressurization can occur, especially during economizer cycles.

Types of VAV Systems Single-Duct VAV. This system uses a pressure-dependent or -independent terminal and usually has reheat at a minimal setting on the terminal unit, or a separate heating system. Consult ASHRAE Standard 90.1 when considering this system. Bypass. This system uses a pressure-dependent damper, which, on demand for heating, closes the damper to the space and opens to the return air plenum. Bypass sometimes uses a constant bypass airflow or a reduced amount of airflow bypassed to the return plenum in relation to the amount supplied to the space. No economic value can be obtained by varying fan speed with this system. A control problem can exist if any return air sensing is done to control a w m up or cool-down cycle. Consult ASHRAE Standard 90.1 when considering this system. VAV Using Single-Duct VAV and Fan-Powered, PressureDependent Terminals. This system has a primary source of air from the fan to the terminal and a secondary powered fan source that pulls air from the return air plenum before the additional heat source. In some fan-powered boxes, backdraft dampers allow duct leakage when the system calls for the damper to be fully closed. Typical applications include geographic areas where the ratio of heating hours to cooling hours is low. Double-Duct VAV This type of terminal uses two single-duct variable terminals. It is controlled by velocity controllers that operate in sequence so that both hot and cold ducts can be opened or closed. Some controls have a downstream flow sensor in the terminal unit. The total-airflow sensor is in the inlet and controlled by the thermostat. As this inlet damper closes, the downstream controller opens the other damper to maintain set airflow. Low pressure in the decks controlled by the thermostat may cause unwanted mixing of air, which results in excess energy use or discomfort in the space.

Balancing the VAV System The general procedure for balancing a VAV system is 1. Determine the required maximum air volume to be delivered by the supply and return air fans. Load diversity usually means that the volume will be somewhat less than the outlet total.

2. Obtain fan curves on these units, and request information on surge characteristics from the fan manufacturer. 3. If inlet vortex damper control is used, obtain the fan manufacturer’s data on deaeration of the fan when used with the damper. If speed control is used, find the maximum and minimum speed that can be used on the project. 4. Obtain from the manufacturer the minimum and maximum operating pressures for terminal or variable-volume boxes to be used on the project. 5 . Construct a theoretical system curve, including an approximate surge area. The system curve starts at the boxes’ minimum inlet static pressure, plus system loss at minimum flow, and terminates at the design maximum flow. The operating range using an inlet vane damper is between the surge line intersection with the system curve and the maximum design flow. When variable-speed control is used, the operating range is between (1) the minimum speed that can produce the necessary minimum box static pressure at minimum flow still in the fan’s stable range and (2) the maximum speed necessary to obtain maximum design flow. 6. Position the terminal boxes to the proportion of maximum fan air volume to total installed terminal maximum volume. 7. Proportion outlets, and verify design volume with the VAV box on maximum flow. Verify minimum flow setting. 8. Set the fan to operate at approximate design speed. 9. Verify flow at all terminal boxes. Identify which boxes are not in control and the inlet static pressures, if any. If all terminal boxes are in control, reduce the fan flow until the remote terminals are just in control and within the tolerances of filter loading. 10. Run a total air traverse with a pitot tube. 1. Run steps (8) through (10) with the return or exhaust fan set at design flow as measured by a pitot-tube traverse and with the system set on minimum outdoor air. 2. Set terminals to minimum, and adjust the inlet vane or speed controller until minimum static pressure and airflow are obtained. 3. Temperature control personnel, balancing personnel, and the design engineer should agree on final placement of the sensor for the static pressure controller. This sensor must be placed in a representative location in the supply duct to sense average maximum and minimum static pressures in the system. 4. Check return air fan speed or its inlet vane damper, which tracks or adjusts to the supply fan airflow, to ensure proper outdoor air volume. 5 . Operate the system on 100% outdoor air (weather permitting), and check supply and return fans for proper power and static pressure.

zyxwvuts Induction Systems Most induction systems use high-velocity air distribution. Balancing should be accomplished as follows: 1. For apparatus and main t r d capacities, perform general VAV balancing procedures. 2. Determine primary airflow at each terminal unit by reading the unit plenum pressure with a manometer and locating the point on the charts (or curves) of air quantity versus static pressure supplied by the unit manufacturer. 3. Normally, about three complete passes around the entire system are required for proper adjustment. Make a final pass without adjustments to record the end result. 4. To provide the quietest possible operation, adjust the fan to run at the slowest speed that provides sufficient nozzle pressure to all units with minimum throttling of all unit and riser dampers.

z zyxwvutsrqponml zyx

38.6

5. After balancing each induction system with minimum outdoor air, reposition to allow maximum outdoor air and check power and static pressure readings.

Report Information

To be of value to the consulting engineer and owner’s maintenance department, the air-handling report should consist of at least the following items:

1. Design Air quantity to be delivered Fan static pressure Motor power installed or required Percent of outdoor air under minimum conditions Fan speed Input power required to obtain this air quantity at design static pressure 2. Installation Equipment manufacturer (indicate model and serial numbers) Size of unit installed Arrangement of air-handling unit Nameplate power and voltage, phase, cycles, and full-load amperes of installed motor 3. Field tests Fan speed Power readings (voltage, amperes of all phases at motor terminals) Total pressure differential across unit components Fan suction and fan discharge static pressure (equals fan total pressure) Plot of actual readings on manufacturer’s fan performance curve to show the installed fan operating point Measured airflow rate It is important to establish initial static pressures accurately for the air treatment equipment and duct system so that the variation in air quantity caused by filter loading can be calculated. It enables the designer to ensure that the total air quantity never is less than the minimum requirements. Because the design air quantity for peak loading of the filters has already been calculated, it also serves as a check of dirt loading in coils. 4. Terminal Outlets Outlet by room designation and position Manufacture and type Size (using manufacturer’s designation to ensure proper factor) Manufacturer’s outlet factor [where no factors are available, or field tests indicate listed factors are incorrect, a factor must be determined in the field by traverse of a duct leading to a single outlet); this also applies to capture hood readouts (see ASHRAE Standard 11l)] Adjustment pattern for every air terminal 5. Additional Information @“applicable) Air-handling units - Belt number and size - Drive and driven sheave size - Belt position on adjusted drive sheaves (bottom, middle, and top) - Motor speed under full load - Motor heater size - Filter type and static pressure at initial use and full load; time to replace - Variations of velocity at various points across face of coil - Existence of vortex or discharge dampers, or both Distribution system - Unusual duct arrangements - Branch duct static readings in double-duct and induction system

201 1 ASHRAE Handbook-HVAC

Applications (SI)

- Ceiling pressure readings where plenum ceiling distribution is used; tightness of ceiling - With wind conditions outside less than 2.2 m i s , relationship of building to outdoor pressure under both minimum and maximum outdoor air - Induction unit manufacturer and size (including required air quantity and plenum pressures for each unit) and test plenum pressure and resulting primary air delivery from manufacturer’s listed curves All equipment nameplates visible and easily readable

Many independent f m s have developed detailed procedures suitable to their own operations and the area in which they function. These procedures are often available for information and evaluation on request.

PRINCIPLES AND PROCEDURES FOR BALANCING HYDRONIC SYSTEMS Heat Transfer at Reduced Flow Rate The typical heating-only hydronic terminal (90°C, 11 K At) gradually reduces heat output as flow is reduced (). Decreasing water flow to 20% of design reduces heat transfer to 65% of that at full design flow. The control valve must reduce water flow to 10% to reduce heat output to 50%. This relative insensitivity to changing flow rates is because the governing coefficient for heat transfer is the air-side coefficient; a change in internal or water-side coefficient with flow rate does not materially affect the overall heat transfer coefficient. This means (1) heat transfer for water-to-air terminals is established by the mean air-to-water temperature difference, (2) heat transfer is measurably changed, and (3) a change in mean water temperature requires a greater change in water flow rate. Tests of hydronic coil performance show that when flow is throttled to the coil, the water-side differential temperature of the coil increases with respect to design selection. This applies to both constant-volume and variable-volume air-handling units. In constantly circulated coils that control temperature by changing coil entering water temperature, decreasing source flow to the circuit decreases the water-side differential temperature.

Fig. 1 Effects of Flow Variation on Heat Transfer from a Hydronic Terminal

38.7

Testing, Adjusting, and Balancing

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Fig. 2 Percent of Design Flow Versus Design A t to Maintain 90% Terminal Heat Transfer for Various Supply Water Temperatures

A secondary concern applies to heating terminals. Unlike chilled water, hot water can be supplied at a wide range of temperatures. Inadequate terminal heating capacity caused by insufficient flow can sometimes be overcome by raising supply water temperature. Design below the 120°C limit (ASME low-pressure boiler code) must be considered. Figure 2 shows the flow variation when 90% terminal capacity is acceptable. Note that heating tolerance decreases with temperature and flow rates and that chilled-water terminals are much less tolerant of flow variation than hot-water terminals. Dual-temperature heatingicooling hydronic systems are sometimes frst started during the heating season. Adequate heating ability in the terminals may suggest that the system is balanced. Figure 2 shows that 40% of design flow through the terminal provides 90% of design heating with 60°C supply water and a 5 K temperature drop. Increased supply water temperature establishes the same heat transfer at terminal flow rates of less than 40% design. Sometimes, dual-temperature water systems have decreased flow during the cooling season because of chiller pressure drop; this could cause a flow reduction of 25%. For example, during the cooling season, a terminal that heated satisfactorily would only receive 30% of the design flow rate. Although the example of reduced flow rate at At = 10 K only affects heat transfer by lo%, this reduced heat transfer rate may have the following negative effects:

Fig. 3

Typical Heating Coil Heat Transfer Versus Water Flow Table 1 Load Flow Variation

Other Load, Order of %

Design Flow at 90% Load

Sensible

Total

Latent

65 15 90

90 95 98

84 90 95

58 65 90

%O

Load Type Sensible Total Latent

Note: Dual-temperature systems are designed to chilled flow requirements and often operate on a 5 K temperature drop at full-load heating.

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Object of the system is to deliver (or remove) heat where required. When flow is reduced from design rate, the system must supply heating or cooling for a longer period to maintain room temperature. As load reaches design conditions, the reduced flow rate is unable to maintain room design conditions. Control valves with average range ability (30:l) and reasonable authority (p = 0.5) may act as odoff controllers instead of throttling flows to the terminal. The resultant change in riser friction loss may cause overflow or underflow in other system terminals. Attempting to throttle may cause wear on the valve plug or seat because of higher velocities at the vena contracta of the valve. In extreme situations, cavitations may occur. Terminals with lower water temperature drops have meater tolerance for unbalanced conditions. However, larger water flows are necessary, requiring larger pipes, pumps, and pumping cost. System balance becomes more important in terminals with a large temperature difference. Less water flow is required, which reduces the size ofpipes, valves, andpumps, as well as pumping costs. A more linear emission curve gives better system control. If flow varies by more than 5% at design flow conditions, heat transfer can fall off rapidly, ultimately causing poorer control of the wet-bulb temperature and potentially decreasing system air quality.

Heat Transfer at Excessive Flow

Increasing the flow rate above design in an effort to increase heat transfer requires careful consideration. Figure 3 shows that increasing the flow to 200% of design only increases heat transfer by 6% but increases resistance or pressure drop four times and power by the cube of the original power (pump laws) for a lower design At. In coils with larger water-side design At, heat transfer can increase.

Generalized Chilled Water TerminalHeat Transfer Versus Flow Heat transfer for a typical chilled-water coil in an air duct versus water flow rate is shown in Figure 4. The curves are based on ARI rating points: 7.2"C inlet water at a 5.6 K rise with entering air at 26.7"C db and 19.4"C wb. The basic curve applies to catalog ratings for lower dry-bulb temperatures providing a consistent entering-air moisture content (e.g., 24°C db, 18°C wb). Changes in inlet water temperature, temperature rise, air velocity, and dry- and wet-bulb temperatures cause terminal performance to deviate from the curves. Figure 4 is only a general representation and does not apply to all chilled-water terminals. Comparing Figure 4 with Figure 1 indicates the similarity of nonlinear heat transfer and flow for both the heating and cooling terminals. Table 1 shows that if the coil is selected for the load and flow is reduced to 90% of load, three flow variations can satisfy the reduced load at various sensible and latent combinations. Note that the reduction in flow will not maintain a chilled-water design differential when coil velocity drops below 0.5 d s . This affects chiller loading and unloading.

Flow Tolerance and Balance Procedure The design procedure rests on a design flow rate and an allowable flow tolerance. The designer must defme both the terminal's

201 1 ASHRAE Handbook-HVAC

38.8

Applications (SI)

Dynamic balancing valves or flow-limiting valves (for prebalanced systems only); field adjustment of these devices is not normally required or possible (see Chapter 46) Pumps with factory-certified pump curves Components used as flowmeters (terminal coils, chillers, heat exchangers, or control valves if using manufacturer’s factorycertified flow versus pressure drop curves)

Record Keeping Balancing requires accurate record keeping while making field measurements. Dated and signed field test reports help the designer or customer in work approval, and the owner has a valuable reference when documenting future changes.

Sizing Balancing Valves

Fig. 4

Chilled Water Terminal Heat Transfer Versus Flow

A balancing valve is placed in the system to adjust water flow to a terminal, branch, zone, riser, or main. It should be located on the leaving side of the hydronic branch. General branch layout is from takeoff to entering service valve, then to the coil, control valve, and balancingiservice valve. Pressure is thereby left on the coil, helping keep dissolved air in solution and preventing false balance problems resulting from air bind. A common valve sizing method is to select for line size; however, balancing valves should be selected to pass design flows when near or at their fully open position with 3 kPa minimum pressure drop. Larger Ap is recommended for accurate pressure readings. Many balancing valves and measuring meters give an accuracy of *5% of range down to a pressure drop of 3 kPa with the balancing valve wide open. Too large a balancing valve pressure drop affects the performance and flow characteristic of the control valve. Too small a pressure drop affects its flow measurement accuracy as it is closed to balance the system. Equation (2) may be used to determine the flow coefficient A, for a balancing valve or to size a control valve. The flow coefficient A, is defined as the number of cubic metres per second that flows through a wide-open valve with a pressure drop of 1 Pa.This is shown as

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flow rates and feasible flow tolerance, remembering that the cost of balancing rises with tightened flow tolerance. Any overflow increases pumping cost, and any flow decrease reduces the maximum heating or cooling at design conditions.

WATER-SIDE BALANCING Water-side balancing adjustments should be made with a thorough understanding of piping friction loss calculations and measured system pressure losses. It is good practice to show expected losses of pipes, fittings, and terminals and expected pressures in operation on schematic system drawings. The water side should tested by direct flow measurement. This method is accurate because it deals with system flow as a function of differential pressures, and avoids compounding errors introduced by temperature difference procedures. Measuring flow at each terminal enables proportional balancing and, ultimately, matching pump head and flow to actual system requirements by trimming the pump impeller or reducing pump motor power. Often, reducing pump operating cost pays for the cost of water-side balancing.

where Q p Ap

Flowmeters (ultrasonic stations, turbines, venturi, orifice plate, multiported pitot tubes, and flow indicators) Manometers, ultrasonic digital meters, and differential pressure gages (analog or digital) Portable digital meter to measure flow and pressure drop Portable pyrometers to measure temperature differentials when test wells are not provided Test pressure taps, pressure gages, thermometers, and wells. Balancing valve with a factory-rated flow coefficient A,, a flow versus handle position and pressure drop table, or a slide rule flow calculator

= =

design flow for terminal or valve, m3/s density of fluid, k4m3 pressure drop across valve, Pa

The inch-pound equivalent of A, is C,, measured in gallons per minute; C, can be converted by the following factor: A,=24x1C6C,

(3)

HYDRONIC BALANCING METHODS

Equipment Proper equipment selection and preplanning are needed to successfully balance hydronic systems. Circumstances sometimes dictate that flow, temperature, and pressure be measured. The designer should specify the water flow balancing devices for installation during construction and testing during hydronic system balancing. The devices may consist of all or some of the following:

=

Various techniques are used to balance hydronic systems. Balance by temperature difference and water balance by proportional method are the most common. Preparation. Minimally, preparation before balancing should include collecting the following: 1. 2. 3. 4. 5. 6. 7. 8.

Pump submittal data; pump curves, motor data, etc. Starter sizes and overload protection information Control valve A, ratings and temperature control diagrams Chiller, boiler, and heat exchanger information; flow and head loss Terminal unit information; flow and head loss data Pressure relief and reducing valve setting Flowmeter calibration curves Other pertinent data

System Preparation for Static System 1. Examine piping system: Identify main pipes, risers, branches and terminals on as-built drawings. Check that flows for all

38.9

Testing, Adjusting, and Balancing

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balancing devices are indicated on drawings before beginning work. Check that design flows for each riser equal the sum of the design flows through the terminals. 2. Examine reducing valve 3. Examine pressure relief valves 4. Examine expansion tank 5 . For pumps, c o n f m Location and size Vented volute Alignment Grouting Motor and lubrication Nameplate data Pump rotational direction 6. For strainers, confirm Location and size Mesh size and cleanliness 7. Confirm location and size of terminal units 8. Control valves: C o n f m location and size C o n f m port locations and flow direction Set all valves open to coil C o n f m actuator has required force to close valve under loaded conditions 9. Ensure calibration of all measuring instruments, and that all calibration data are known for balancing devices 10. Remove all air from piping; all high points should have air vents

Pump Start-up 1. Start pump and c o n f m rotational direction; if rotation is incorrect, have corrected. 2. Read differential head and apply to pump curve to observe flow approximates design. 3. Slowly close pump (if pump is under 20 kW) throttle valve to shutoff. Read pump differential head from gages. If shutoff head corresponds with published curve, the previously prepared velocity head correction curve can be used as a pump flow calibration curve. A significant difference between observed and published shutoff head can be caused by an unvented volute, a partially plugged impeller, or by an impeller size different from that specified.

Confirmation of System Venting 1. 2. 3. 4.

Confirm tank location and size. Shut off pump; record shutoff gauge pressure at tank junction. Start pump and record operating pressure at tank junction. Compare operating to shutoff pressures at tank junction. If there is no pressure change, the system is air-free. 5. Eliminate free air. No air separation: Shut off pump and revent. Retest and revent until tank junction pressure is stable. Air separation: Operate system until free air has been separated out, indicated by stable tank junction pressure.

For multiple-pump systems only,

5. Check for variable flow in source circuits when control valves are operated. 6. Confirm Pump suction pressure remains above cavitations range for all operating conditions. Pump flow rates remain constant. Source working pressures are unaffected.

For parallel-pump systems, follow steps (1) to (4), then shut off pumps alternately and

5. Record head differential and flow rate through operating pump, and operating pump motor voltage and current. 6. C o n f m that operational point is satisfactory (no overload, cavitation potential, etc.).

Balance by Temperature Difference This common balancing procedure is based on measuring the water temperature difference between supply and return at the terminal. The designer selects the cooling andor heating terminal for a calculated design load at full-load conditions. At less than full load, which is true for most operating hours, the temperature drop is proportionately less. Figure 5 demonstrates this relationship for a heating system at a design At of 10 K for outdoor design of -20°C and room design of 20°C. For every outdoor temperature other than design, the balancing technician should construct a similar chart and read off the At for balancing. For example, at 50% load, or -1°C outdoor air, the At required is 5 K, or 50% of the design drop. This method is a rough approximation and should not be used where great accuracy is required. It is not accurate enough for cooling systems.

Water Balance by Proportional Method Preset Method. A thorough understanding of the pressure drops in the system riser piping, branches, coils, control valves, and balancing valves is needed. Generally, several pipe and valve sizes are available for designing systems with high or low pressure drops. A flow-limiting or trim device will be required. Knowing system pressure losses in design allows the designer to select a balancing device to absorb excess system pressures in the branch, and to shift pressure drop (which might be absorbed by a balancing device nearly close to achieve balance) to the pipes, coils, and valves so the balancing device merely trims these components’ performance at

Balancing For single-, multiple-, and parallel pump systems, after pump start-up and confmation of system venting, Adjust pump throttle until pump head differential corresponds to design. Record pump motor voltage and amperage, and pump strainer head, at design flow. Balance equipment room piping circuit so that pumped flow remains constant over alternative flow paths. Record chiller and boiler circuits (for multiple-pump systems, requires a flowmeter installed between header piping).

Fig. 5 Water Temperature Versus Outdoor Temperature Showing Approximate Temperature Difference

201 1 ASHRAE Handbook-HVAC

38.10 design flow. It may also indicate where high-head-loss circuits can exist for either relocation in the piping network, or hydraulic isolation through hybrid piping techniques. The installed balancing device should never be closed more than 40 to 50%; below this point flow reading accuracy falls to k20 to 30%. Knowing a starting point for setting the valve (preset) allows the designer to iterate system piping design. This may not always be practical in large systems, but minimizing head and flow saves energy over the life of the facility and allows for proper temperature control. In this method, 1. Analyze the piping network for the largest hydraulic loss based on design flow and pipe friction loss. The pump should be selected to provide the total of all terminal flows, and the head required to move water through the hydraulically greatest circuit. Balance devices in this circuit should be sized only for the loss required for flow measurement accuracy. Trimming is not required. 2. Analyze differences in pressure drop in the pumping circuit for each terminal without using a balancing device. The difference between each circuit and the pump head (which represents the drop in the farthest circuit) is the required drop for the balancing device. 3. Select a balancing device that will achieve this drop with minimum valve throttling. If greater than two pipe sizes smaller, shift design drop into control valve or coil (or both), equalizing pressure drop across the devices. 4. Monitor system elevations and pressure drops to ensure air management, minimizing pocket collections and false pressure references that could lead to phantom balancing problems. 5. Use proportional balancing methods as outlined for field testing and adjustment.

Proportional Balancing Proportional water-side balancing may use design data, but relies most on as-built conditions and measurements and adapts well to design diversity factors. This method works well with multiple-riser systems. When several terminals are connected to the same circuit, any variation of differential pressure at the circuit inlet affects flows in all other units in the same proportion. Circuits are proportionally balanced to each other by a flow quotient: Flow quotient =

Actual flow rate Design flow rate

(4)

To balance a branch system proportionally,

Applications (SI)

The reference circuit has the lowest quotient and the greatest pressure loss. Adjust all other balancing valves in that branch until they have the same quotient as the reference circuit (at least one valve in the branch should be fully open). When a second valve is adjusted, the flow quotient in the reference valve also changes; continued adjustment is required to make their flow quotients equal. Once they are equal, they will remain equal or in proportional balance to each other while other valves in the branch are adjusted or until there is a change in pressure or flow. When all balancing valves are adjusted to their branches’ respective flow quotients, total system water flow is adjusted to the design by setting the balancing valve at the pump discharge to a flow quotient of 1. Pressure drop across the balancing valve at pump discharge is produced by the pump that is not required to provide design flow. This excess pressure can be removed by trimming the pump impeller or reducing pump speed. The pump discharge balancing valve must then be reopened fully to provide the design flow. As in variable-speed pumping, diversity and flow changes are well accommodated by a system that has been proportionately balanced. Because the balancing valves have been balanced to each other at a particular flow (design), any changes in flow are proportionately distributed. Balancing the water side in a system that uses diversity must be done at full flow. Because components are selected based on heat transfer at full flow, they must be balanced to this point. To accomplish full-flow proportional balance, shut off part of the system while balancing the remaining sections. When a section has been balanced, shut it off and open the section that was open originally to complete full balance of the system. When balancing, care should be taken if the building is occupied or if load is nearly full. Variable-Speed Pumping. To achieve hydronic balance, full flow through the system is required during balancing, after which the system can be placed on automatic control and the pump speed allowed to change. After the full-flow condition is balanced and the system differential pressure set point is established, to control the variable-speed pumps, observe the flow on the circuit with the greatest resistance as the other circuits are closed one at a time. The flow in the observed circuit should remain equal to, or more than, the previously set flow. Water flow may become laminar at less than 0.6 d s , which may alter the heat transfer characteristics of the system.

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1. Fully open the balancing and control valves in that circuit. 2. Adjust the main balancing valve for total pump flow of 100 to 110% of design flow. 3. Calculate each riser valve’s quotient based on actual measurements. Record these values on the test form, and note the circuit with the lowest flow quotient. Note: When all balancing devices are open, flow will be higher in some circuits than others. In some, flow may be so low that it cannot be accurately measured. The situation is complicated because an initial pressure drop in series with the pump is necessary to limit total flow to 100 to 110% of design; this decreases the available differential pressure for the distribution system. After all other risers are balanced, restart analysis of risers with unmeasurable flow at step (2). 4. Identify the riser with the highest flow ratio. Begin balancing with this riser, then continue to the next highest flow ratio, and so on. When selecting the branch with the highest flow ratio, Measure flow in all branches of the selected riser. In branches with flow higher than 150% of design, close the balancing valves to reduce flow to about 110% of design. Readjust total pump flow using the main valve. Start balancing in branches with a flow ratio greater than or equal to 1. Start with the branch with the highest flow ratio.

Other Balancing Techniques

Flow Balancing by Rated Differential Procedure. This procedure depends on deriving a performance curve for the test coil, comparing water temperature difference At, to entering water temperature t,, minus entering air temperature teu.One point of the desired curve can be determined from manufacturer’s ratings, which are published as (t,, t,J. A second point is established by observing that the heat transfer from air to water is zero when (t,, teu)is zero (consequently, At, = 0). With these two points, an approximate performance curve can be drawn (Figure 6). Then, for any other (t,, teu),this curve is used to determine the appropriate At,. The basic curve applies to catalog ratings for lower dry-bulb temperatures, providing a consistent entering air moisture content (e.g., 24°C db, 18°C wb). Changes in inlet water temperature, temperature rise, air velocity, and dry- and wet-bulb temperatures cause terminal performance to deviate from the curves. The curve may also be used for cooling coils for sensible transfer (dry coil). Flow Balancing by Total Heat Transfer. This procedure determines water flow by running an energy balance around the coil. From field measurements of airflow, wet- and dry-bulb temperatures up- and downstream of the coil, and the difference At, between entering and leaving water temperatures, water flow can be determined by the following equations: ~

~

~

Next Page

38.11

Testing, Adjusting, and Balancing

1. Develop a flow diagram if one is not included in the design drawings. Illustrate all balance instrumentation, and include any additional instrument requirements. 2. Compare pumps, primary heat exchangers, and specified terminal units, and determine whether a design diversity factor can be achieved. 3. Examine the control diagram and determine the control adjustments needed to obtain design flow conditions.

Balance Procedure-Primary and Secondary Circuits

Fig. 6

where

Coil Performance Curve

1. Inspect the system completely to ensure that (1) it has been flushed out, it is clean, and all air is removed; (2) all manual valves are open or in operating position; (3) all automatic valves are in their proper positions and operative; and (4) the expansion tank is properly charged. 2. Place controls in position for design flow. 3. Examine flow diagram and piping for obvious short circuits; check flow and adjust the balance valve. 4. Take pump suction, discharge, and differential pressure readings at both full and no flow. For larger pumps, a no-flow condition may not be safe. In any event, valves should be closed slowly. 5 . Read pump motor amperage and voltage, and determine approximate power. 6. Establish a pump curve, and determine approximate flow rate. 7. If a total flow station exists, determine the flow and compare with pump curve flow. 8. If possible, set total flow about 10% high using the total flow station frst and the pump differential pressure second; then maintain pumped flow at a constant value as balance proceeds by adjusting the pump throttle valve. 9. Any branch main flow stations should be tested and set, starting by setting the shortest runs low as balancing proceeds to the longer branch runs. 10. With primary and secondary pumping circuits, a reasonable balance must be obtained in the primary loop before the secondary loop can be considered. The secondary pumps must be running and terminal units must be open to flow when the primary loop is being balanced, unless the secondary loop is decoupled.

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Q, = water flow rate, L/s q = load, W qcoohng= cooling load, W qheUhng = heating load, W Q, = airflow rate, L/s h = enthalpy, kJ/kg t = temperature, "C

Example 1. Find the water flow for a cooling system with the following characteristics: Test data tmb = entering wet-bulb temperature = 20.3"C tlwb = leaving wet-bulb temperature = 11.9"C Q, = airflow rate = 10 000 L/s tlw = leaving water temperature = 15.0"C tm = entering water temperature = 8.6"C From psychrometric chart hi = 76.52 kJ/kg h, = 52.01 kJ/kg Solution: From Equations (5) and (6). 1.20 x 10 OOO(76.52 - 52.01 j 4180(15.0-8.6)

=

11.0 L/s

The desired water flow is achieved by successive manual adjustments and recalculations. Note that these temperatures can be greatly influenced by the heat of compression, stratification, bypassing, and duct leakage.

General Balance Procedures All the variations of balancing hydronic systems cannot be listed; however, the general method should balance the system and minimize operating cost. Excess pump pressure (operating power) can be eliminated by trimming the pump impeller. Allowing excess pressure to be absorbed by throttle valves adds a lifelong operatingcost penalty to the operation. The following is a general procedure based on setting the balance valves on the site:

FLUID FLOW MEASUREMENT

Flow Measurement Based on Manufacturer's Data

Any component (terminal, control valve, or chiller) that has an accurate, factory-certified flowipressure drop relationship can be used as a flow-indicating device. The flow and pressure drop may be used to establish an equivalent flow coefficient as shown in Equation (3). According to the Bernoulli equation, pressure drop varies as the square of the velocity or flow rate, assuming density is constant:

For example, a chiller has a certified pressure drop of 80 kPa at 10 Lis. The calculated flow with a field-measured pressure drop of 90 kPa is

Flow calculated in this manner is only an estimate. The accuracy of components used as flow indicators depends on the accuracy of (1) cataloged information concerning flowipressure drop relationships and (2) pressure differential readings. As a rule, the component should be factory-certified flow tested if it is to be used as a flow indicator.

CHAPTER 39

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OPERATION AND MAINTENANCE MANAGEMENT Operation and Maintenance as Part of Building Life-Cycle Costs .............................................. Elements ofSuccessfu1 Programs ................................................................................................. Benefits of Detecting and Diagnosing Equipment Faults Documentation .............................................................................................................................. Staffing Managing Changes In Buildings ...................................................................................................

C

APITAL investments provide most of the built environment humankind enjoys today. To derive the greatest return on the capital investment, and to ensure future generations will continue to enjoy these benefits, the built environment must be sustainable. Significant components ofthe sustainable facility are the ways in which the structure and its systems are operated and preserved for the long term. This chapter presents several strategies, methods, procedures, and techniques for building operation and maintenance management programs that minimize asset failure and preserve system function to deliver its intended purpose. Evolving building system complexity and increasing operating costs demand that equipment and systems providing thermal comfort and beneficial indoor air quality be properly maintained to achieve energy efficiency and building owner reliability requirements. These factors clearly imply that a highly organized, systematic approach for properly and effectively functioning building assets is necessary to achieve a successful maintenance program. Maintenance management is the formal effort required to plan, design, and implement a maintenance program tailored to the specific needs of the facility. Traditionally, considerable focus has been devoted to minimizing first costs (i.e., capital investment) of construction. However, choices made regarding operation and maintenance (O&M) can have a greater impact on costs of ownership over the entire life of a facility.

39.1 39.2 39.6 39.7 39.8 39.9

and design and construction, operations and maintenance, and employee salaries and benefits. From Figures 2 and 3, it is clear that operation and maintenance costs contribute a considerable amount to the total cost of ownership over the life cycle of any facility. Figure 4 (BOMA 2008) further defmes operations and maintenance costs for a typical office building and shows that operations and maintenance costs most directly related to HVAC&R (i.e., maintenance and repair and utilities) make up over 50% of the operations costs for a building. Given the life-cycle cost of a facility, the operations and maintenance staff should be involved with the predesign, design, and construction

OPERATION AND MAINTENANCE AS PART OF BUILDING LIFE-CYCLE COSTS Operation and maintenance are major contributors to the total costs of ownership over the life of the facility. It is useful to compare maintenance costs to the total costs of facility ownership. In general, the major categories of the life-cycle cost of facility ownership include design and construction; operations and maintenance; acquisition, renewal, and disposal; and employee salaries and benefits. Life-cycle costs of a facility are distributed as shown in Figures 1,2, and 3. Figure 1 represents the major categories of facility life-cycle costs as pillars supporting a building. Within each category, examples of the typical elements that make up the foundation of the category are shown. Figure 2 (Christian and Pandeya 1997) illustrates the relative financial resources required to sustain each phase of facility ownership when the major categories are defmed as design and construction; operations and maintenance; and acquisition, renewal, and disposal. Over a nominal 30-year term, O&M comprises the largest segment of facility ownership cost: between 60 and 85% of the life-cycle cost. Figure 3 (NIBS 1998) categorizes life-cycle costs The preparation of this chapter is assigned to TC 7.3, Operation and Maintenance Management. Significant content on fault detection and diagnostics was provided by TC 7.5, Smart Building Systems.

39.1

Fig. 1 Three Pillars of Typical Life-Cycle Cost with Cost Elements

Fig*

Life-Cycle Cost for Operating, and Maintaining Nonresidential Buildings (Adapted from Christian and Pandeya 1997)

201 1 ASHRAE Handbook-HVAC

39.2

Applications (SI)

in-house or contracted) is key to keeping systems running in optimal fashion. Successful facility ownership requires investing appropriately in acquisition, design, and construction practices that consider future O&M expenses. Low frst cost of capital projects or replacement of obsolete equipment must be weighed against the long-term effects of potentially more frequent andor more time-consuming maintenance and repair, resulting in higher operating costs. In addition, maintenance management should consider an optimum mix of techniques to minimize maintenance costs and mitigate risk of equipment and system failure. Critical components of a fac es maintenance program plan include an inventory of assets to be maintained, program performance objectives, defmed condition indicators, inspection and work tasks created to achieve the performance objectives, documentation, and a process to review changes in asset condition and task effectiveness.

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Fig. 3 Life-Cycle Cost Elements: Business Costs for Nonresidential Buildings, Including Salaries and Benefits to Occupants (Adapted from NIBS 1998)

Creating and Implementing an Effective O&M Program

An effective operation and maintenance program is created from the preceding elements. In addition to the inventory of maintained assets, a maintenance plan should be developed to describe the goals, objectives, and implementation procedures of the maintenance program. The maintenance plan is written for the size, scope, age, and complexity of the specific systems and equipment serving the facility. The plan describes all required tasks, their frequency, salient condition indicators and the parties responsible for performing the work, documentation, and program monitoring tasks. The following is a list of important terms to understand when developing a maintenance program:

Fig. 4

Operations and Maintenance Cost Elements for Typical Office Building (Adapted from BOMA 2008)

phases of the facility. During each phase, life-cycle costs, occupant comfort, energy efficiency, and maintenance strategies should be considered in all decision-making. For example, any first-cost compromises made during the construction phase must consider the long-term impacts on both life-cycle cost and ability to satisfy occupant thermal comfort while maintaining indoor air quality with efficient energy use.

ELEMENTS OF SUCCESSFUL PROGRAMS A successful O&M management program combines a maintenance program that preserves the condition and performance of building assets along with prudent operation strategies that meet building ownerioccupant requirements for thermal comfort, indoor air quality, and energy efficiency. The success of maintenance management depends on dedicated, trained, and accountable personnel; clearly defmed goals and objectives; measurable benefits; management support; and constant examination and reexamination of process results and goal achievement. The challenge is to meet these requirements with fixed or declining budgets and increasing costs. A successful maintenance program depends on the quality of planning and execution. Successful maintenance management planning includes proper cost analysis and developing operations practices that are energy efficient and minimize equipment downtime and disruption to building occupants and/or processes. With increasing equipment and system complexity, appropriate technical expertise (whether

Maintenance management is the planning, implementation, and review of maintenance activities. Specific levels of maintenance rigor should be established, ideally determined by cost-effectiveness, health, and safety concerns. Cost-effectiveness is the balance among system effectiveness, including maintenance levels, equipment and system availability, reliability, maintainability, performance, and life-cycle costs. Performance objectives can be addressed in many ways. Desired outcomes can be measured in terms of equipment and system deliverables such as thermal comfort, energy efficiency, and indoor air quality. Other measures include up-time, mean time between failure, mean time to repair, and normalized cost data. The plan should include the source of the objectives. Condition indicators rely on descriptions of unacceptable equipment and system conditions, which can be based on physical condition andor performance output. In general, condition indicators are measurements and observations of conditions known to lead to equipment and system failure or performance degradation. Presence of these indicators is a signal that remedial actions should be expedited to avoid failures or larger repair costs later on. Inspection and maintenance tasks are developed to minimize the risk of equipment and system failure to achieve operating performance goals for the facility. Inspection tasks are devoted to asset condition assessment. When abnormal conditions are found, the cause must be investigated and remedied. Maintenance tasks in general comprise a series of activities such as cleaning, adjustment, service, or replacement as conditions warrant. Arguably, unacceptable conditions require more significant repair work. Task frequency for inspection and maintenance of new equipment and systems is initially established based on the manufacturer’s recommendations. Based on the rate of asset condition or performance degradation, the task frequency can be adjusted to provide cost-effective assurance that the asset is in acceptable condition. The monitoring and review elements of a maintenance program are important for keeping maintenance costs in control. For maintenance programs established for equipment and systems in service past the

39.3

Operation and Maintenance Management waxranty period, task frequencies based on O&M staff experience or advice from a maintenance engineer may be used. Documentation is a critical element of any maintenance program and includes identifying the asset’s capacity, its location, the list of inspection and maintenance tasks and their frequencies, results of inspections and maintenance, and verification that inspection and maintenance tasks have been carried out. Archived results of prior conditions and maintenance are key factors in determining whether task frequencies can be adjusted.

Setting Clearly Defined Maintenance Goals Maintenance management goals are closely related and interdependent with facility operating goals and objectives. The maintenance program must account for building operating strategy and procedures, and for the criticality of the equipment and system in question. In general, the maintenance program is established to mitigate asset degradation and failure while enabling these assets to deliver the required indoor environment. Goals must account for expected funding and human capital resources, age of equipment and systems, and capital projects planned for the near term. The facility’s operating strategy dictates when equipment and systems can be shut down for inspection and maintenance. In some systems for which continuous operation is a critical requirement, outages must be scheduled in advance or workarounds must be developed. In extreme cases, there may need to be redundant capacity to allow off-line maintenance without interrupting operation of the equipment or system. In general, maintenance goals are focused on equipment reliability or uptime. Either task intervals or procedures are developed to eliminate or minimize asset downtime. Clearly defmed, measurable goals provide targets against which to measure progress and serve to align the facility maintenance and maintenance management staff with the facility operating strategy, required resources and acceptable levels of risk. It is helpful to understand the interrelationship between several terms that are related to asset performance when establishing program goals. Common descriptors of desired outcomes include the following:

improve the effectiveness and efficiency of maintenance so that up time may be optimized. Maintainability is an important design consideration and contributes to availability.

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For some industries, maintainability is quantitative, corresponding to the probability of performing a maintenance action or repair in a specified period of time using prescribed procedures in a specified environment. For others, maintainability is simply the ease with which maintenance actions can be performed.

Operability is the efficient conversion of labor, raw materials, and energy into product, in which the value of the ratio of output to input is optimal. Maintainability and reliability contribute to availability. High levels of availability minimize the input required for a given output, thereby contributing to high levels of operability. Reliability is the probability that a system or facility will perform its intended function for a specified period of time when used under specific conditions and environment. Issues affecting reliability include operating practices, equipment and system design, installation, and maintenance practices. Reliability contributes to availability. Sustainability is “providing for the needs of the present without detracting from the ability to fulfill the needs of the future” (ASHRAE 20 10). Sustainable maintenance management includes identifying and reducing a building’s detrimental environmental impacts during its operating life. Sustainability in buildings cannot be achieved simply through sustainable design practices, but also requires sustainable operation and maintenance.

-

There are multide llersllectives of the interrelationshill among maintainability, reliability, and availability. Maintainability and reliability are often grouped together, because they deal with essentially the same design concepts from different perspectives. Reliability analyses often serve as input to maintainability analyses. Here, maintainability and reliability are considered independent concepts, both of which contribute to availability. Increased availability and operability can significantly improve profitability. Figure 5 shows these relationships: reliability and maintainability combine to yield availability, which then combines with operability to yield deliverability. Improvements in any area (all else being equal) ultimately lead to improved results or profitability, because these concepts are interrelated. For example, good reliability and availability may minimize or eliminate the need for installed spare capacity, reducing the facility’s footprint and resource consumption. Good operability increases efficiency and reduces energy use. The facility operating strategy should embody the preceding concepts, which can be described in measurable outcomes that support achieving the goals of the maintenance program. A maintenance program’s effectiveness can be measured by its impact on profitability. Cost-effective improvements to any of the concepts shown in Figure 5 will contribute to profitability and the maintenance program’s effectiveness. In addition, goals may be established to indicate how efficiently the maintenance program is implemented. Good maintenance management monitors progress toward achieving goals over time. The trends are more important than the incremental values.

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Availability is the amount of time that machinery or equipment is operable when needed. Often referred to as uptime, availability improvements lead to increased production for manufacturing and industrial companies. Availability is often confused with reliability, which is a component of availability. Capability is a system’s ability to satisfactorily provide required service. It is the probability of meeting functional requirements when operating under a designated set of conditions. An example of capability is the ability of a heating system to meet the heating load at the winter design temperature. Capability must be verified when the system is first commissioned and whenever functional requirements change. Deliverability is the total amount of production delivered to users per unit of time. High deliverability is clearly supported by levels of the other concepts. Dependability is the measure of a system’s condition. Assuming the system was operative at the beginning of its service life, dependability is the probability of its operating at any other given time until the end of its life. For systems that cannot be repaired during use, dependability is the probability that there will not be a failure during use. For systems that can be repaired, dependability is governed by how easily and quickly repairs can be made. Durability is the average expected service life of a system or facility. Table 3 of Chapter 37 lists median years of equipment service life. Individual manufacturers quantify durability as design life, which is the average number of hours of operation before failure, extrapolated from accelerated life tests and from stressing critical components to economic destruction. Maintainability is the ease, accuracy, safety, and economy of performing maintenance. The purpose of maintainability is to

Fig. 5

General Interrelationship of Concepts

39.4 Comparing recent with historical data on condition and performance provides valuable input for an effective maintenance program.

Choosing the Best Combination of O&M Strategies Operation is the processes and methods used when the building is working correctly, in contrast to maintenance, which is the processes and methods necessary to repair and replace equipment. Operation of a building includes a set of procedures and standards to keep systems and equipment operating as designed. Daily or weekly wakthroughs of mechanical rooms, roofs with mechanical equipment, and other locations with mechanical equipment should be performed to help identify equipment conditions that adversely affect equipment operation. A building automation system (BAS) is an important tool to measure, benchmark, and analyze energy consumption and other operational data over the building’s life. To use a BAS to track whole-building, system, and equipment performance, it is important to make sure the BAS has been properly commissioned, has an appropriate number of alarms set, and has properly set-up trends logs to collect necessary data. For more information about benchmarking and analyzing energy use, see Chapter 36. There are three basic maintenance strategies. In run-to-failure maintenance, minimal or no resources are invested in maintenance until equipment or systems break down (i.e., fail). Preventive maintenance is scheduled, either by run time or by the calendar. Condition-based and predictive maintenance uses predictions of future equipment condition to optimize maintenance actions. Within each group, the skills and management tools required can vary from simple to complex. Maintenance programs may incorporate features of all three approaches into a single program. Many arguments can be made about the cost-effectiveness of each ofthese programs. Operation and maintenance costs represent a significant portion of a facility’s total life-cycle cost (see Figure 2). Therefore, the costeffectiveness of maintenance management is paramount. Run-to-Failure and Repair. Failure is the inability of a system or equipment to perform its intended function at an acceptable level. Run-to-failure is applied when the cost of maintenance or repair may exceed the cost of replacement or losses in the event of failure. Only minimum maintenance, such as cleaning or filter change, is performed. The equipment may or may not be monitored for proper operation, depending on the consequences of failure. This is a highly reactive approach to dealing with abnormal conditions. For example, a window air conditioner may be run although it is vibrating and making noise, then be replaced rather than repaired (a failuretriggered response in which operation is fully restored without embellishment). Preventive Maintenance. Preventivemaintenance classifies available resources to ensure proper operation of a system or equipment under the maintenance program. Durability, reliability, efficiency, and safety are the principal objectives. Preventive maintenance is scheduled, based on run time or by the calendar. Condition-Based and Predictive Maintenance. Many repairs are a direct result of maintenance-induced faults occurring during scheduled maintenance. Condition-based maintenance uses measurements of the performance of equipment and systems to guide maintenance activities. As performance degradation or operational faults are identified through measurements, they are addressed through corrective actions or deferred for correction until future condition measurements indicate sufficient degradation to warrant maintenance action. In essence, condition-based maintenance uses condition and performance indices to optimize maintenance intervals. Maintenance is then only performed on the basis of the actual conditions monitored and the interpretation of them. By basing maintenance actions on measurements of conditions, both excessive and too-infrequent maintenance can be avoided, thereby optimizing plant reliability and maximizing maintenance personnel productiv-

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Applications (SI)

ity. There can, however, be added costs involved in supplementary training and instrumentation that must be evaluated for cost effectiveness relative to the benefits of other maintenance strategies. Measurements can be performed continuously or periodically (e.g., weekly, monthly). Continuous monitoring provides continual information, enabling identification of catastrophic failures (e.g., failure of a motor or compressor) as they occur. Faults and performance degradation are detected by comparing the monitored indicator of performance with expected values, based on benchmarks (e.g., manufacturer specifications, historical performance, values from models). In some cases, alarms based on measured values of conditions exceeding known threshold values (e.g., maximum acceptable temperature, tabulated values of acceptable vibration) are used to notify operations and maintenance staff that action may be warranted to correct conditions. For complex systems, it may be necessary to monitor several conditions (e.g., temperatures, vibration, and load) to assess the overall system condition. Trending over a period of time, either using measurements of conditions at intervals over time or continuous measurements can be used to track gradual deterioration and remedial work can be performed when deterioration reaches a critical level or planned in advance based on the rate of deterioration (which is a predictive approach). In the case of air filters in a variable-air-volume (VAV) system in which the supply fan draws air through the filter and is controlled to a fixed static pressure, the criterion for replacing the filter is a function of the maximum differential pressure the fully loaded filter can withstand without bursting and the energy consumption of the fan as the filter loading increases. It may be more economical to change the filter before the bursting pressure is reached if the rate of loading is slow. Continuous monitoring with a building automation system rather than changing filters on a fixed time schedule makes it possible to detect rapidly accelerated dust loading (e.g., by nearby construction work), so that the system alerts building staff before filters are overloaded and could potentially burst. In a constant-volume system (again, assuming the main fan draws air through the filter), the filter change criterion is a function of the maximum differential pressure the filter can withstand without bursting and the drop in flow rate that can be tolerated by the system. As the filter becomes dirty, energy consumption increases and filter efficiency decreases. A fixed time interval for filter bank changingicleaning may not be optimum. Changing the filter based on a monitored condition optimizes filter life and minimizes labor costs. Routine operating plant inspection conducted by the technician during regularly scheduled plant tours can be an effective conditionmonitoring practice. A technician’s knowledge, experience, and familiarity with the plant can be valuable tools in plant diagnostics. Plant familiarity, however, is valuable only when based on a solid knowledge of the underlying physical principles, and it is lost with frequent technician staff changes.Many physical parameters or conditions can be measured objectively using both special equipment and conventional building automation system sensors. One such condition is vibration on rolling element bearings. Vibration data are captured by computers. Special software is used to analyze the data to determine whether shaft alignment is correct, whether there are excessively unbalanced forces in the rotating mass, the state of bearing lubrication, andor faults with the fixed or moving bearing surfaces or rolling elements. Not only can this technique be used to diagnose faults and determine repair requirements at an early stage, but it can also be used after completing a repair to ensure that the underlying cause of fault has been removed. Other techniques include (1) using thermal infrared images of electrical connections to determine whether mechanical joints are tight, (2) analyzing oil and grease for contamination (e.g., water in fuel oil on diesel engines), (3) analyzing electrical current to diagnose motor winding faults, (4) measuring differential pressure

z

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Operation and Maintenance Management

across filter banks and heat exchangers to determine optimum changeicleaning frequency, and ( 5 ) measuring temperature differences for correct control valve response, chiller operation, and air handling. In some cases, multiple parameters are required. For example, to determine the degree of contamination of an air filter bank on a VAV system, it is necessary to measure the differential pressure across the filter and interpret it in terms of the actual flow rate through the filter. This can be done either by forcing the fan on to high speed and then measuring the differential pressure, or by combining a flow rate signal with a differential pressure signal. With predictive maintenance, indicators of performance degradation are extrapolated into the future to predict when an unacceptable degree of degradation will be reached and repair or maintenance should be performed. The extrapolation is based on a statistically valid approach that accounts for uncertainty in the future projections. The resulting projections of the time to failure (or unacceptable performance) can be used to plan maintenance in advance. Predictions can be based on nearly any indicator of performance degradation (e.g., pressure drop across a filter) that changes gradually over time. Several techniques are frequently associated with predictive maintenance, including nondestructive testing, chemical analysis, vibration and noise monitoring, and routine visual inspection and logging. Automated Fault Detection and Diagnosis (AFDD). Whereas the previously described techniques and methods generally require human expertise to interpret quantitative information (e.g., a timeseries plot of the values of a measured variable, such as electric power use) to reach conclusions about the condition of equipment or a system, AFDD interprets values and trends in measured parameters to automatically reach conclusions about the presence of faults or degree of performance degradation. This enables performance monitoring to be performed continuously for a large inventory of equipment, which is not possible manually. AFDD uses a set of software-based systematic procedures that automatically compare measured and expected system performance and determine the causes of discrepancies (i.e., symptoms or indicators of faults, caused by the faults themselves). Fault detection is the process of determining whether the monitored system deviates from normal operation, and fault diagnosis is the process of isolating the detected fault(s) from other possible faults. This procedure is based on a thorough knowledge of the physical principles underlying the operation of HVAC systems, equipment, and components. Measurements provide data on actual performance at the time they are taken, and models that capture normal operational behavior are generally used to provide values of the same variables if the system were operating properly. Models used include engineering frstprinciples-based models, purely empirical models based on past performance, gray-box models that combine some engineering modeling with empirical data, and various statistical approaches. These methods differ primarily by the modeling technique used, methods for detecting differences between measured and expected performance, and methods used to distinguish among diagnostic outcomes. These methods are then coded in software to automate execution on measured data as they become available. The ability to detect unacceptable conditions in HVAC&R systems has existed for some time and has been used primarily in safety devices intended to protect expensive equipment from catastrophic failure and for single point a l m s tied to occupant comfort. These techniques were generally based on a parameter exceeding a predefmed threshold (e.g., a maximum acceptable pressure above which a relief valve opens or equipment shuts down). They have also been used for alarms in building automation systems to alert operators to an unacceptable condition (e.g., a chilled-water temperature that is too high). These a l m s are usually provided for binary devices that, when activated, indicate an abnormal condition or discrepancy. More recent motivating factors for development and use of AFDD include increasing energy efficiency, improving indoor air

39.5

quality, and reducing unscheduled equipment downtime (Braun 1999). At the same time, AFDD capab es have been expanded well beyond single-point a l m s , providing the ability to detect and diagnose faults based on many different variables. AFDD has the potential to be a significant element of a maintenance program by enabling prolonged equipment life for everything from chillers and other large equipment to individual actuators. The benefits of AFDD capabilities have been validated in part by surveys and site measurements that have documented a wide variety of operating faults in common HVAC equipment. Numerous studies of maintenance records and independent field studies of faults show that the prevalence of faults in HVAC equipment is substantial (Breuker and Braun 1998; Breuker et al. 2000; Comstock 2002; House et al. 2001a, 2003; Jacobs et al. 2003; Katipamula et al. 1999; Proctor 2004; Rossi 2004; Seem et al. 1999). These faults included packaged air conditioners and heat pumps with economizers not operating properly; low (and high) refrigerant charges; condenser and filter fouling; faulty sensors; electrical problems; chillers with faulty controls, condensers, compressors, lubrication, piping, and evaporators; and air-handling units with too little or too much outdoor-air ventilation, poor economizer control, stuck outdoor-air dampers and other problems. Types ofAFDD Tools. Portable service tools exist to evaluate the performance of packaged and unitary vapor-compression equipment systems and perform corrective measures to address problems. Self-contained, microprocessor-based portable hardware is used during a service visit for data acquisition and analysis. The sensors for making measurements and evaluating system performance may be installed temporarily or permanently. Data are usually collected for a relatively small period of time (minutes) while the equipment is operating at steady-state conditions. Application of these tools generally involves using connected sensors to collect values of several performance parameters (e.g., superheat or subcooling) that have corresponding performance expectations based on system characteristics (e.g., expansion device) and operating conditions. The measured and expected performance are compared using rules defined in the analysis software to detect and diagnose system faults. Data and messages are displayed in real time to guide system service or repair. Several different methods are used for analysis and detection among these tools. Local controllers with embedded AFDD include fault detection and diagnostic algorithms as part of the software code. Integrated diagnostic and control logic gives the AFDD code access to data at the controller’s short sampling interval; these higher-frequency data may enable detection of problems (e.g., unstable control loops) that might be difficult to detect using data collected at typical trending intervals. Embedded AFDD tools can also reduce network traffic, if applicable, by executing algorithms locally and propagating only key parameters or results to a display or central control-system computer. Embedding algorithms in the controllers can also facilitate integration of the output from the AFDD tool with the alarming capabilities of the equipment control system. Computational and memory limits, however, may place practical restrictions on the complexity of the algorithms that are embedded in local controllers. Central workstation AFDD tools use dedicated software to detect and diagnose HVAC system faults using data from a building automation system (where applicable) and, in some cases, from other dedicated stand-alone sensors. This software usually resides on a computer that is part of a building automation system, or has access to stored data from a BAS. The BAS may serve one or several buildings. Data acquisition and analysis may be near-real time or periodic (e.g., hourly or daily), depending on the software features. Because the algorithms are implemented on a computer that has significant computational resources, analytical methods and historical data can be used in ways that are not possible with hand-held devices and local controllers. A key strength of workstation AFDD

201 1 ASHRAE Handbook-HVAC

39.6 software is its ability to detect system-level faults arising from interactions among components. Workstation AFDD software may require extensive effort for configuration. In particular, mapping points from the building automation system to the AFDD tool can be a significant programming task, depending on the number of measurement and control points used by the AFDD tool. Web-based AFDD software may obtain data from a BAS, independent data acquisition system, or controller-embedded AFDD software. In this case, the Internet is used to remotely acquire and display results. In some cases, wireless data acquisition systems are used to communicate between equipment and a remote network operations center, where data are managed and a Web-based user interface is hosted. Using the Internet or long-distance wireless communication for data acquisition allows gathering data from many buildings, virtually on a coincident basis, and supports enterprisewide reporting. AFDD processing and analysis may be done locally at the building or remotely. Updating software remotely is another advantage of Web-based AFDD. Web-based systems are emerging for detecting and diagnosing faults in individual equipment and whole-building energy consumption (Brambley et al. 2005). A significant challenge for Web-based AFDD is Internet security, which may require additional hardware and software administration, even if the access is periodic and not continuous. Characteristics of AFDD Systems. Inherent characteristics of AFDD systems can be adjusted to suit a variety of applications and users. Sensitivity is the lowest fault severity level required to trigger the correct detection and diagnosis of a fault. This characteristic is vital for monitoring safety-critical systems where early identification of small malfunctions could prevent loss of life, costly loss of product, and/or catastrophic damage to equipment. In this case, the fault severity threshold should be established at a low level. For nonsafety-critical applications (which covers most HVAC equipment), the sensitivity threshold can be higher so that faults have significant performance or cost impacts before operators are alerted. False alarm rate is the rate at which an AFDD system reports faults when they do not actually exist (i.e., when operation is normal). A high false alarm rate could result in significant economic loss from unnecessary service inspections or stoppage of equipment operation. The challenge is to establish a balance between adequate AFDD system sensitivity and minimizing false alarms. One technique used for critical systems, installing redundant sensors, has been found to mitigate excessive false alarms while maintaining desired fault sensitivity. Installation of redundant sensors, however, increases equipment costs and has been resisted for most HVAC equipment. Anecdotal evidence based on traditional building automation syses suggests that a method to disable or adjust AFDD system sensitivity is required for HVAC systems so operations and maintenance staff may cope with excessive false a l m s . Without this capability, AFDD tools may be removed from service for the nuisance they create. Sensitivity and false alarm rate are useful for quantifying the performance on an AFDD tool; however, AFDD tools have numerous other characteristics that impact these performance criteria and also affect the cost of implementing a particular method. House et al. (200 1b) identified the following additional characteristics that should be considered when selecting an AFDD tool:

Applications (SI)

users should seek a balance between these considerations that is appropriate for the intended application. AFDD in Practice. The primary objective of an AFDD system is early detection of faults and diagnosis of their causes, enabling correction of the faults before additional damage to the system, loss of service, or measurable energy waste occurs. This is accomplished by continuously monitoring the operations of a system, using AFDD procedures to detect and diagnose abnormal fault conditions, evaluating the significance of the detected faults, and deciding how to respond. Figure 6 shows an example of an operation and maintenance process using AFDD comprising four distinct functional processes. The frst two steps in this process are fault detection and, if a fault is detected, fault diagnosis. After diagnosis, the software can analyze the various consequences of the faults detected. System operators can then evaluate the results from the automated fault impact analysis to arrive at an integrated assessment of overall fault significance (based on operational requirements for safety, availability, cost, energy use, comfort, health, environmental impacts, or effects on other performance indicators). Once fault evaluation is completed, system operators determine how to respond (e.g., by taking a corrective action or possibly even no action). Together, these four steps can alert operations and maintenance staff to problems, help identify the root causes of problems so that they can be properly corrected, and help prioritize maintenance activities to ensure that the most important problems are attended to frst. This forms the basis for condition-based maintenance.

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Number of sensors and control signals used Amount of design data used Training data required User-selected parameters Generally, increases in any of these factors lead to increased complexity, time, and cost associated with using the AFDD method or tool, but often with increased quality of the results. Therefore,

BENEFITS OF DETECTING AND DIAGNOSING EQUIPMENT FAULTS Most O&M studies conducted from 1995 to 2007 demonstrated that maintenance performed on HVAC systems to preserve intended equipment performance and condition also accrued beneficial energy and operating cost savings. However, the magnitude of the benefit may not offset the effort to achieve the savings. A study of rooftop air-handling units by the Electric Power Research Institute (Krill 1997) concluded that the cost of annual maintenance would likely exceed utility savings but could result in improved occupant comfort. A preponderance of other studies, however, shows that savings on operating exceed the cost of AFDD and servicing of equipment, particularly when account is taken for optimizing service task scheduling, reducing unnecessary on-site inspections, and decreasing the peaks and valleys of seasonal work (Li and Braun 2007a, 2007b, 2007c; Rossi 2004). Indications to date for specific applications are that use of AFDD can contribute to avoiding operating and maintenance costs. Building owners and operators must carefully evaluate the cost and benefits of implementing and administering AFDD technology in their specific situation.

Effective Maintenance Effective maintenance provides the required reliability and availability at the lowest cost by identifying and implementing actions that reduce the probability of failure to an acceptable level. Effective maintenance management provides reliability and availability at the lowest cost. This strategy involves identifying and implementing actions that cost-effectively reduce the probability of failure. In general, investments are made to promote longevity of mission-critical assets to help the organization succeed over the long term. The intent of effective maintenance management is to minimize operation and maintenance costs through proactive efforts in all three segments. Maintenance management is effective when integrating proactive maintenance effectiveness and efficiency into the total cost of facility ownership. If adequate measures for cost-effective maintainability are not integrated into the design and construction phases of a project, reliability andor uptime are likely to be adversely

39.7

Operation and Maintenance Management

Fig. 6

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Generic Application of AFDD to Operation and Maintenance of Engineered Systems [Adapted from Katipamula and Brambley (2005)l

affected and total life-cycle costs increase significantly. Appropriate levels of maintainability seldom occur by chance. They require upfront planning, setting objectives, disciplined design implementation, and feedback from prior projects. It is vital to identify critical maintainability and production reliability issues and integrate them into facility project designs to achieve long-term facility owning and operating benefits. Dirty evaporator and condenser coils and filters require additional energy to operate, because inefficient heat transfer creates higher compressor discharge pressures, so more energy is required for a given load. The system must also operate longer to satisfy space conditions. Although these items are variable and difficult to quantify, proper maintenance improves system operation and equipment life, regardless of system size.

Additional Maintenance Strategies Corrective maintenance classifies resources (expended or reserved) for predicting and correcting conditions of impending failure. Corrective action is strictly remedial and always performed before failure occurs. An identical procedure performed in response to failure is classified as a repair. Corrective action may be taken during a shutdown caused by failure, if the action is optional and unrelated. Planned maintenance classifies resources invested in selected functions at specified intervals. All functions and resources in this classification must be planned, budgeted, and scheduled. Planned maintenance includes preventive and corrective maintenance. Unplanned maintenance classifies resources expended or reserved to handle interruptions in the operation or function of systems or equipment covered by the maintenance program. This classification is defmed by a repair response.

DOCUMENTATION

Information on the facilities, collateral equipment, and intended operation procedures is essential for planning facilities maintenance actions, efficiently performing facilities maintenance, documenting maintenance histories, following up on maintenance performance, energy reporting, and management reporting. For these reasons, documentation is a critical element in a successful maintenance program. Operation and maintenance documentation should be prepared as outlined in ASHRAE Guideline 4. For new construction, operation and maintenance documentation requirements should be established as part of the project requirements. Deliverables should support the expected maintenance strategy, skills of the maintenance and operations staff, and anticipated resources to be committed to performing operations and maintenance. For maintenance programs being developed for existing facilities, the requirements are the same; however, the operations and maintenance staff may be more involved with sourcing and compiling the documents.

Operation and Maintenance Documents Information should be compiled into a manual as soon as it becomes available. This information can be used to support design and construction activities, systems commissioning, training of operation and maintenance staff, start-up, and troubleshooting. In addition to the operation and maintenance manual being available to the construction team, an appropriate number of manuals should be set aside for the building owner’s staff after construction turnover. It is critical that all information required operating the systems and maintaining the equipment must be compiled prior to

39.8 project turnover to the owner’s staff and be available to the entire facilities department. A complete operation and maintenance documentation package consists of the following documents: The operation and maintenance document directory provides easy access to the various sections within the document. The operation and maintenance manual will serve the facility potentially for decades. During this time staff turnover will occur many times. A directory that is well organized and clearly identified will facilitate quick reference by technicians and operators new on the job. Emergency information. In addition to being directly distributed to emergency response personnel, including emergency information in the operation and maintenance documents would enable this critical information to be kept in a single place and be immediately available during emergencies. Emergency information should include emergency and staff andor agency notification procedures. The operating manual should contain the following information: I. General information A. Building function B. Basis of design C. Building description D. Operating standards and logs 11. Technical information A. System description B. Operating routines and procedures C. Seasonal start-up and shutdown D. Special procedures E. Basic troubleshooting The maintenance manual should contain the following information: I. Equipment data sheets (specific to installed equipment) A. Operating and nameplate data B. Warranty information 11. Maintenance program and procedure information A. Manufacturer’s installation, operation, and maintenance instructions B. Spare parts information C. Corrective, preventive, and predictive maintenance actions, as applicable D. Schedule of actions, including frequency E. Action descriptions F. History Test reports provide a record of observed performance during start-up and commissioning. The records should be compiled throughout the service life of the facility. Copies of construction documents (“as builts”). These documents should be available to the entire facilities department. Initial system maintenance procedures should be detailed in the maintenance manual (with individual equipment maintenance frequency detailed in manufacturers’ literature) that was furnished during the initial installation or developed after installation. The maintenance program should be tailored to each specific facility and system type.

Documentation Methods There are two basic methods for collecting and archiving operation and maintenance documents: (1) a bound written document that is executed and updated by hand, and (2) an electronic, computerbased database management system. The chosen method should be congruent with facility and maintenance program complexity and scope and with the skill level of maintenance staff. The object is to

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Applications (SI)

be able to enter, archive, update, and evaluate information on building systems and assets efficiently and effectively. A computerized maintenance management system (CMMS) is a software . program to plan, schedule, and track maintenance activities; store maintenance histories and inventory information; communicate building operation and maintenance information; and generate reports to quantify maintenance productivity. A CMMS is used by facility managers, maintenance technicians, third-party maintenance service providers, and asset managers to track the status, asset condition, and cost of day-to-day maintenance activities. The number and type of modules in the CMMS is specified by the facility management team, depending on the facility’s needs and the management team’s goals. Typical CMMS modules include work order generator and tracking, work order requests, inventory control, preventive maintenance, equipment histories, maintenance contracts, and key performance indicator (KPI) reporting. Although a CMMS is not required to manage maintenance activities, they are becoming more commonly used (Sapp 2008). When implementing a CMMS in a new or existing facility, or upgrading an existing CMMS, the needs of the CMMS and the planning process must be carefully determined. Although using a CMMS has the potential to increase the facility management team’s efficiency and serve as a historical maintenance archive, more than 50% of implementations fail (Berger 2009). Selecting the right software does not guarantee that using a CMMS will improve maintenance productivity: when selecting or upgrading a CMMS, business process changes are as important, if not more important. When implementing or upgrading a CMMS, the following is recommended (Berger 2009): Determine the maintenance process and software requirements, considering the needs of all stakeholders (maintenance, operations, engineering, IT, materials management, purchasing, and fmance). Allow 3 to 6 months to design new processes and develop a set of system requirements, using a participatory approach to include all stakeholders.

STAFFING Skills, Responsibilities, and Training To be effective and efficient, operation and maintenance management staff must have both technical and managerial skills. Technical skills include the ability to understand how mechanical systems operate and how maintenance of mechanical equipment is performed, as well as analytical problem-solving expertise of the physical plant engineer. Physical plant engineers require a variety of skills to effectively operate HVAC systems, implement a maintenance program, and manage operating and maintenance staff and meet requirements of the investment plan. Good physical plant engineering solutions are developed while the investment plan is being formulated, and continue throughout the life of the facility. Managerial skills include overseeing the facility in life cycle terms and on a day-to-day basis. Facility management at this level requires the development of maintenance strategies; determination of program goals and objectives; and administration of contracts with tenants, service providers, and labor unions. Even when specialized contract maintenance companies provide service, the facility manager requires these skills. An effective facility manager should be able to manage and train staff, and plan and control a facility’s operation and maintenance with the cooperation of senior management and all departments. The facility manager’s responsibilities include administering the O&M budget and protecting the life-cycle objectives. There are nine core competency areas of facility management (IFMA 2009), seven of which apply to operations and maintenance:

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Operation and Maintenance Management

Operations and maintenance: Oversee acquisition; installation; operation; maintenance; and disposition of building systems, furniture and equipment, grounds, and exterior elements Human and environmental factors: Develop and implement practices that promote and protect health, safety, security, quality of work life, the environment, and organizational effectiveness Planning and project management: Develop facility plans; plan and manage each phase of the project, including construction and relocations Leadership and management: Plan, organize, administer, and manage the facility’s functions; manage personnel assigned to each function Quality assessment and innovation: Manage the process of assessing the quality of services and facility effectiveness; manage benchmarking process and audits Communication: Communicate effectively Technology: Plan, direct, and manage facility management business and operational technologies, and support the organization’s technological infrastructure Training should be an important part a facility management department. The pace of technology used in buildings continues to increase, making training for all facilities even more important. Training can be done in-house or by a contracted third party who provides training as a business. When developing an in-house training program or evaluating training by a third-party, make sure these key components are addressed:

Personnel: Who will attend the training; create a list of maintenance managers, supervisors, and trades workers Course content: Course requirements, type of training, and media required Schedule: When the training will take place and how it will be coordinated with day-to-day assignments Master training plan: A written document to record personnel, course content, and time schedule requirements (Westerkamp 1997)

In-House Versus Contracted Staff In most situations, an on-site maintenance staff changes filters, belts and motors and lubricates bearings. However, tasks such as cleaning condenser and evaporator coils; assessing refrigeration and building automation systems; and assessing and repairing heating components, such as gas and oil burners and electronic elements; may require a specialized technician. Additionally, tasks that may have previously been done by the on-site maintenance staff may now require certification and special equipment: for example, the U.S. Environmental Protection Agency (EPA) certifies technicians and recovery units for refrigerant handling. In most small fac maintenance contractors provide services requiring specialized technicians. In larger facilities, maintenance may be contracted out for complex equipment when staff does not have adequate technical expertise. Whenever the operator cannot service and repair the systems or components installed, the owner should ensure that qualified contractors and technicians perform the work. The frequency of maintenance depends in part on system run time and type of operation in the facility. ASHRAE Standard 180 provides maintenance frequencies for air distribution systems, chillers, boilers, condensing units, building automation systems, cooling towers, dehumidification and humidification, engines, microturbines, fan coils, pumps, rooftop units, and other HVAC systems. Commissioning and training on how to commission and retrocommission mechanical systems are increasingly important with these types of systems to ensure optimum comfort, efficient system operation, and minimal operation and maintenance costs. Without detailed commissioning documentation, operation staff cannot effectively consider factors such as energy budgets when addressing building occupants’ comfort complaints.

Criticality and Complexity

The criticality and complexity of a system or piece of equipment must be considered when developing the maintenance strategy. Building complexity and criticality ranges from residential, commercial, institutional, and industrial, to mission-critical facilities, such as cleanrooms and operating rooms. The operations and maintenance strategy selected must balance system and equipment up-time, customer needs, energy efficiency, cost, and the use of proactive and reactive maintenance approaches. Criticality and complexity of systems and equipment also vary in a facility. In many facilities, larger, more complex systems and equipment (e.g., chillers and boilers) are more critical than smaller equipment, such as toilet exhaust fans and vestibule cabinet unit heaters.

Customer Service Customer service here means responding to requests and complaints of the building occupants. In nonmanufacturing facilities, the level of customer service provided, or the perceived level of service provided, is a key component of a successful maintenance organization. All people in the maintenance organization, from technicians to management, should work together to deliver highquality customer service to building occupants.

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MANAGING CHANGES IN BUILDINGS Renovation and Retrofit Projects

Design for Ease of Operation and Maintenance. Operation, maintenance, and maintainability of all HVAC&R systems should be considered during building design. Any successful operation and maintenance program must include proper documentation of design intent and criteria. ASHRAE Guideline 4 provides a methodology to properly document HVAC systems. Newly installed systems should be commissioned according to the methods and procedures in ASHRAE Guideline 1.1 to ensure that they are functioning as designed. It is then the responsibility of management and operational staff to maintain design functionality throughout the life of the building. For new construction or renovation, the building owner should work with the designer to clearly defme facility requirements. In addition to meeting the owner’s project requirements, the designer must provide a safe and efficient facility with adequate space to inspect and repair components. The designer must reach agreement with the owner on the criticality of each system to establish issues such as access, redundancy, and component isolation requirements. Commissioning Throughout Turnover to Operation and Maintenance. Existing systems may need to be reconfigured and recommissioned to accommodate changes. See Chapter 43 for additional information on commissioning. Retrocommissioning or Ongoing Commissioning. Retrocommissioning (or ongoing commissioning; see Chapter 43) applies to buildings that have been in operation for some time, regardless of whether they were initially commissioned. This process needs to be applied any time major building retrofits or usage changes are contemplated by the ownerimanager. It is also advisable to consider this process if there has been a significant changeover in operational personnel, to ensure proper facility operation as originally intended.

zyxwvutsrq Conversion to New Technology

Building systems and equipment are based on the technology available to planners and designers at the time of preparation, construction, and installation. Maintenance, repairs, and operating schemes should be adhered to throughout the required service life of the facility or system. During the service life, new technology (e.g., high-efficiency equipment, smart technology systems, sustainability advances) may become available to increase overall efficiency and affect maintenance, repair, and replacement programs. Conversion from existing to new technology must be assessed in life-cycle

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39.10 terms. Existing technology must be assessed for the degree of loss from a shorter return on investment. The new technology must be assessed for (1) all initial, operation, and maintenance costs; (2) the correlation between service life and the facility’s remaining service life; and (3) the cost of conversion, including revenue losses from associated downtime. As facilities and systems are upgraded to new technologies, facility operations and maintenance personnel must be trained to ensure that new equipment operates efficiently and effectively throughout its service life to maintain the anticipated benefits of technology improvements.

Document and Communicate As a facility is planned, designed, constructed, and occupied, the documentation and information about the facility increases. Facility owners are increasingly aware of the need to document and communicate from the early stages of planning through the facility’s life to ensure minimal information is lost. During planning and design, documentation must include detailed plans and specifications identifying all aspects of the equipment, including physical size, location, system interactions, operating set points (e.g., temperature, humidity, airflow, energy usage, relative pressure), flow diagrams, instrumentation, and control sequences. The equipment supplier must provide equipment meeting the specifications, and should also recommend alternatives that offer lower life-cycle costs for the owner and designer to evaluate. The installing contractor must turn over the newly installed system to the owner in an organized and comprehensive manner, including complete documentation with O&M manuals and commissioning reports (e.g., air balance, fume hood certification). The design and commissioning team should ensure that a comprehensive systems manual as outlined in ASHRAE Guideline 0 is provided to the owner, along with training on equipment and systems. The design team and the contractor should also ensure that complete and correct as-built or conformance drawings are provided showing the actual built facility, including all changes required during the construction process.

Applications (SI)

Brambley, M.R., S. Katipamula, and P. O’Neill. 2005. Facility energy management via a commercial web service. Ch. 18 in Information technology for energy managers, vol. 11: Web based energy information and control systems case studies and applications, pp. 229-240, B.L. Capehart and L.C. Capehart, eds. FairmontKRC, Lilburn, GA. Braun, J.E. 1999. Automated fault detection and diagnostics for the HVAC&R industry. HVAC&R Research 5(2):8 5- 86. Breuker, M.S. and J.E. Braun. 1998. Common faults and their impact for rooftop air conditioners. HVAC&R Research 4(3):303-3 18. Breuker, M.S., T. Rossi, and J. Braun. 2000. Smart maintenance for rooftop units. ASHRAE Journal 42(11):41-47. Christian, J. and A. Pandeya. 1997. Cost predictions of facilities. Journal oj Management in Engineering 13(1):52-61. Comstock, M.C., J.E. Braun, and E.A. Groll. 2002. A survey of common faults for chillers. ASHRAE Transactions 108(1):819-825. House, J.M., H. Vaezi-Nejad, and J.M. Whitcomb. 2001a. An expert rule set for fault detection in air-handling units. ASHRAE Transactions 107(1): 858-871. House, J.M., J.E. Braun, T.M. Rossi, and G.E. Kelly. 2001b. Section D: Evaluation of FDD tools. In Final report: Demonstrating automated fault detection and diagnosis methods in real buildings, A. Dexter and J. Pakanen, eds. International Energy Agency on Energy Conservation in Buildings and Community Systems, Annex 34. VTT Technical Research Centre of Finland, Espoo, Finland. House, J.M., K.D. Lee, and L.K. Norford. 2003. Controls and diagnostics for air distribution systems. ASME Journal of Solar Energy Engineering 125(3):310-317. IFMA. 2009. Facility management competency areas. http://www.ifma.org/ learning/fm_credentials/competencies.cfm. Jacobs, P., V. Smith, C. Higgins, and M. Brost. 2003. Small commercial rooftops: Field problems, solutions and the role of manufacturers. Proceedings of the 2003 National Conference on Building Commissioning, Portland Energy Conservation, Portland, OR. Katipamula, S. and M.R. Brambley. 2005. Methods for fault detection, diagnostics and prognostics for building systems-a review, part I. HVAC&R Research 11(1):3-25. Katipamula, S., R.G. Pratt, D.P. Chassin, Z.T. Taylor, K. Gown, and M.R. Brambley. 1999. Automated fault detection and diagnosis for outdoor-air ventilation systems and economizers: Methodology and results from field testing. ASHRAE Transactions 105(1):555-567. Krill, W. 1997. The impact of maintenance on package unitary equipment. Final Report, TR-107273 383 1, Electric Power Research Institute, Palo Alto, CA. Li, H. and J.E. Braun. 2007a. An overall performance index for characterizing the economic impact of faults in direct expansion cooling equipment. International Journal of Refiigeration 30(2):299-3 10 Li, H. and J.E. Braun. 2007b. An economic evaluation of the benefits associated with application of automated fault detection and diagnosis in rooftop air conditioners. ASHRAE Transactions 113(2):200-210. Li, H. and J.E. Braun. 2007c. A methodology for diagnosing multiple-simultaneous faults in vapor compression air conditioners. HVACdR Research 13(2):369-395. NIBS. 1998. Excellence in facility management: Five federal case studies. Publication 5600-1. Facility Maintenance and Operations Committee, National Institute of Building Sciences, Washington, D.C. Proctor, J. 2004. Residential and small commercial air conditioning-Rated efficiency isn’t automatic. ASHRAE Public Session, Winter Meeting, Anaheim, CA. Rossi, T.M. 2004. Unitary air conditioning field performance. Proceedings of the Tenth International Refiigeration and Air Conditioning Conference at Purdue, pp. R146.1-R146.9. Sapp, D. 2008. Computerized maintenance management systems (CMMS). www.wbdg.org/omlcmms.php. Seem, J.E., J.M. House and R.H. Monroe. 1999. On-line monitoring and fault detection of control system performance. ASHRAE Journal 41(7):21-26. Westerkamp, T. 1997. Maintenance manager’s standard manual. Prentice Hall, Paramus, NJ.

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Technological advances now allow much of this information to be provided electronically. Software and hardware systems are available to create building information models (BIM) during facility planning and construction that can become a resource for the owner throughout the facility’s service life. Building information may be llnked into the CMMS, building automation, and other smart building systems to allow building owners, operating engineers, technicians, and other facility personnel immediate access to the information required to maintain, operate, and service the building systems. During the building’s life cycle, as modifications and changes are made to the facility, this information must be continuously updated to ensure accurate records continue to be maintained.

REFERENCES ASHRAE. 2005. The commissioning process. Guideline 0-2005. ASHRAE. 2007. HVAC&R technical requirements for the commissioning process. Guideline 1.1-2007. ASHRAE. 2008. Preparation of operating and maintenance documentation for building systems. Guideline 4-2008 ASHRAE. 2008. Standard practice for inspection and maintenance of commercial building HVAC systems. ANSI/ASHRAE/ACCA Standard 1802008. ASHRAE. 20 10. ASHRAE greenguide: The design, construction, and operation of sustainable buildings, 3rd ed. Berger, D. 2009.2009 CMMS/EAMreview: Power up a winner-How tojnd the right asset management system for your plant. www.plantservices. com/articles/2009/066.html. BOMA. 2008. Experience exchange report JEER). Building Owners and Managers Association International, Washington D.C.

zyxwvutsrqpon zy BIBLIOGRAPHY

Blanchard, B.S., D. Verma, and E.L. Peterson. 1995. Maintainability: A key to effective serviceability and maintenance management. John Wiley & Sons, New York.

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Campbell, J.D. 1995. Uptime,strategiesfor excellence in maintenance management. Productivity Press, Portland, OR. Criswell, J.W. 1989. Planned maintenancefor productivity and energy conservation, 3rd ed. Prentice Hall, Englewood Cliffs, NJ. Fuchs, S.J. 1992. Complete building equipment maintenance desk book. Prentice Hall, Englewood Cliffs, NJ. Katipamula, S., and M.R. Brambley. 2004. Methods for fault detection, diagnostics and prognostics for building systems-A review, part 11. International Journal of HVAC&R Research (now HVAC&R Research) 11(2):169-187. Mobely, R.K. 1989. An introduction to predictive maintenance. Van Nostrand Reinhold, New York. Moubray, J. 1997. Reliability-centered maintenance, 2nd ed. Industrial Press, New York.

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NCMS. 1999. Reliability and maintainability guideline for manufacturing machinery and equipment, 2nd ed. National Center for Manufacturing Sciences, Ann Arbor, MI. National Academy of Sciences. 1998. Stewardship of federal facilities: A proactive strategy for managing the nation 's public assets. National Academy, Washington, D.C. Petrocelly, K.L. 1988. Physical plant operations handbook. Prentice Hall, Englewood Cliffs, NJ. Smith, A.M. 1993. Reliability-centered maintenance. McGraw-Hill, New York. Stum, K. 2000. Compilation and evaluation of information sources for HVAC&R system operations and maintenance procedures. Report, ASHRAE Research Project RP-1025.

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CHAPTER 40

COMPUTER APPLICATIONS Computer System Components and Technologies ................... 40.1 Networking Components 40.5 Internet and Applications. ........................................................ 40.7

HVAC Software Applications ................................................... Monitoring and Control Wireless Communication........................................................

C

OMPUTERS are used in a wide variety of applications in the HVAC industry. Rapid technological advances and the decreasing cost of computing power, memory, and secondary storage have changed many aspects of the HVAC industry. New HVAC design tools allow optimal solutions to be found in engineering applications. Building operations benefit from low-cost networking to achieve multivendor control system interoperability. Consulting engineers can search manufacturers’ equipment and specifications interactively over the Internet. Designers can collaborate from remote locations. More powerful applications that are also easier to use are now affordable by a wider segment of the industry; many HVAC calculations, such as heating and cooling loads, can be performed easily and automatically. Business applications and infrastructure have also positively affected the HVAC industry. Open communications standards and internetworking allow fast, efficient communications throughout company and industry circles. HVAC design, manufacture, installation, and maintenance functions benefit as businesses build computing infrastructure through corporate information services (IS) or information technology (IT). Many advances in the business community have been adopted by the HVAC industry as de fact0 standards.

Virtually all brand-name personal computers now have more than enough speed for basic business applications such as word processing and spreadsheets. Personal computers differ in their ability to handle multimedia graphics and sound, which are useful in advanced software applications. An information system comprised of computer networks depends on the ability of computers to communicate with each other in a standard architecture. Technological advances have resulted in computer systems becoming obsolete in less than five years. Therefore, it is important to plan for compatibility with future business computer requirements. Software and hardware must match the needs of the user, and be consistent with the business system architecture. System architecture standards from organizations such as the Institute of Electrical and Electronics Engineers (IEEE), the American National Standards Institute (ANSI), and the International Organization for Standardization (ISO) have resulted in welldefined standards such as Ethernet, TCPIIP, and HTTP, further described in the section on Networking Components. The combination of popular standards has resulted in network and Internet accessibility from local computers.

COMPUTER SYSTEM COMPONENTS AND TECHNOLOGIES

Hardware is the physical equipment (electronic parts, cables, printed circuit boards, etc.) that provides the foundation for the software to run. Hardware processing power has increased dramatically, such that the average business system provides much more capacity than the average user needs. Specialized tasks, however, often require specialized hardware. Mainframes are large, expensive computer systems that serve the majority of large-scale business and technical needs. Mainframe computers best serve large nationwide databases, weather prediction, and scientific modeling applications. They support many users simultaneously, and are usually accessed over a network from a personal computer (PC). More powerful mainframes are called supercomputers. Personal computers (PCs) are desktop computers tailored to individual user needs, and provide much more convenient access to computing resources than the traditional mainframe. PCs are used in a wide variety of information-gathering, communication, organization, computation, and scheduling roles. PC servers allow access to files and data on a network. PC servers are a special class of computers that support large amounts of memory, fast connection speed to the network, large disk storage for access of many files, and applications designed to be usable from other computer systems. Because system reliability is critical, there are additional features such as better construction, component redundancy, and removable hard drives. Workstations are application-specific computers serving specialized needs such as computer-aided design (CAD) and manufacturing (CAM), product design and simulation, mapping geographic information system (GIs), or specialized graphics design. Workstations have greater processing power and graphical display capabilities than personal computers, and may also have other improvements found in PC servers.

40.9 40.17 40.19

COMPUTER HARDWARE

Because of rapid advances in computer technology, computers offer tremendous power at very low cost. However, the total cost of ownership of a personal computer is not limited to the cost of the computer hardware. Software, network connectivity, support, and maintenance expenses quickly surpass the initial cost of hardware. Selecting a computer platform includes a wide variety of issues, such as Analysis of application needs Corporate computer support architecture and standards Vendor support, including guaranteed response time Central processing unit (CPU) power, random-access memory (RAM), and secondary or hard disk storage capacity System compatibility and interoperability between vendors Ease of use and required training Data backup strategy: how will the data on the computer be restored in the event of a system failure? Security issues: what data will be accessible, and how will data be protected from unauthorized access? Network communications capability and compatibility Technical support live andor online, including driver update support Costibenefits comparison Information system infrastructureiinteroperabilityrequirements Technology reliability and obsolescence Total cost of ownership The preparation of this chapter is assigned to TC 1.5, Computer Applications.

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Clusters are several computers organized to work together. Clusters of PCs can approach the computing power of a mainframe at a fraction of the cost, if efficient application software is available. Clusters of workstations can provide more computing power than even the largest mainframe. Clusters of mainframes can be extremely powerful tools. Minicomputers are medium-sized business computer systems that serve medium to large application needs. Minicomputers have been used to economically scale applications that have grown too large for PC servers. Many small business e-commerce applications have moved to the minicomputer platform. A Web server is a PC server, minicomputer, or mainframe that stores and distributes Web-based information; it is typically used to distribute documents and other information across the Internet. Laptop computers are smaller, battery-powered personal computers optimized for light weight and portability. Compared to a similarly priced personal computer, laptops are generally slower and have fewer features, though they generally include most basic features found in a desktop computer. A smaller, lighter laptop computer is called a notebook or netbook. Palmtop computers serve a specialized niche, allowing access to some of the same information available from a laptop, but in a much smaller package. Palmtops may have no keys, or very small keys that are much smaller than the standard keyboard. Personal digital assistants (PDAs) support limited functionality of laptop computers in a notecard-sized format. A typical interface method is a stylus with a graphical touch-sensitive screen; standard functions include a calendar, address book, e-mail, and a calculator. Options include synchronizing hardware to upload address lists or e-mail to a PC, and a modem or wireless card for portable Internet access. Some models combine the functionality of a PDA with a cell phone and a digital camera. Smartphones are mobile phones that offer advanced computing ability and connectivity. Smartphones run complete operating system software, providing a platform for application developers, and are able to run many different types of software applications, including those specific to HVAC engineering. The advantages of smartphone applications over desktop applications are that they are simple to use and can easily be deployed in the field for quick calculations. Calculators and organizers are available usually for fixed arithmetic functions and, on the high end, programmable applications. This hardware format is typically inexpensive and portable, but software is typically proprietary. Laptops, palmtops, and PDAs have challenged the advantages of calculators and organizers.

Applications (SI)

Utility Software

Utility programs perform a wide variety of organizing and datahandling operations such as copying files, printing files, file management, network analysis, disk size utilities, CPU speed tests, improving security, and other related operations. Most form one or two specific functions. Compression Software. These utilities compress and archive data files in a standard format, such as ZIP. Compression allow files and file systems to be compressed, making the transfer of information and files much more efficient without any loss of content or data. These utilities are valuable when file size is important, such as transmitting files over a limited-bandwidth communication system, and for archival purposes. A typical compression ratio for text files is 3: 1. E-mail attachments are often compressed. Antivirus Software. An important software package for most computer systems is antivirus software (see the section on E-mail, Viruses, and Hoaxes). Antivirus software detects, quarantines, repairs, and eliminates files that contain viruses. A computer virus may take various forms and is commonly attached invisibly to a word-processed or e-mailed document. Antivirus software is imperative when a computer is accessing Internet-based information. Antivirus software must be updated frequently to be able to catch new viruses. Updates are often available for free after purchasing antivirus software, Antispyware Software. Spyware is a type of program that sends information from your computer to another computer, usually with malicious intent. It may send passwords, credit card numbers, or any other information that is typed into your computer. Antispyware software will detect spyware and remove it. Firewall Software. A firewall is a utility that controls and limits all network communications going from or to your computer. With a firewall, only programs with permission are allowed to communicate over the network. This should stop spyware and other similar malicious programs. Also, a firewall limits the communications it accepts over the network, which acts against other types of attacks. A large organization should have a firewall separating their entire network from the Internet, but it is still important to have a firewall on each PC. Back-up Software. The ability to recover from amassive failure such as a successful virus attack, accidental deletion of files, flood, f r e , hardware (especially hard disk) failure, and other inevitable disasters is extremely important. Typically, information service (IS) computers use a rotating digital tape back-up strategy that performs massive back-ups of network resources. Individual computers may not be included in these back-ups, so regularly scheduled back-ups must be performed. A relatively inexpensive way to back up small amounts of data is to store data files and documents in a compact disk recordable (CD-R) format, which allows roughly up to 700 MB of storage at low cost. Digital versatile disks (DVDs) promise roughly 10 times the storage capacity of CD-R. Tape back-up provides an extremely low cost per megabyte stored and is useful if quick access and retrieval of individual back-up files is not an issue. Back-ups should be stored in a secure location away from the computer system. There are two basic types of back-ups: complete, in which all files are backed up, or incremental, in which only files changed since the last back-up are stored. A typical strategy is to perform a complete back-up once a week or month, and an incremental back-up every day.

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COMPUTER SOFTWARE Software is computer instructions or data that can be stored electronically in storage hardware, such as random access memory (RAM), or secondary storage such as hard disk drives, DVDs, or CDs. Software is often divided into two categories:

Systems software includes the operating system and utilities associated with the operating system, such as file copying. Applications software includes the programs used to do the user’s work, such as word processors, spreadsheets, or databases. HVACspecific programs belong to the applications software category.

Operating Systems The operating system (0s)is the basic control program that allows execution and control of application software. Operating systems (system software) also provide a common environment for applications to use shared resources such as memory, secondary storage (e.g., hard disk storage), processing time, network access, the keyboard, graphic display environments, desktops, file services, and printer services. Application software must be selected first; that decision will typically limit the hardware computer platform and 0s.

Application Software Most useful application software falls into one of these categories:

Word Processing. Word processing applications are used for tasks that range from creating simple printable documents to providing products for advanced enterprise-level electronic distribution and publishing systems. Features may include automatic text layout, spellchecking, printing, index and table of contents generation,

Computer Applications simple graphics, and the ability to save files in a variety of formats such as rich text format (RTF), hypertext markup language (HTML), plain text, or American Standard Code for Information Interchange (ASCII). Most word processors allow the user to view the output before printing. Specification Writing. A useful extension to word processors is application software to create specifications for the consulting engineer. Features include ensuring selectable sections for creating desired features, and consistent naming of materials, specifications, and processes or sequences. Specification software can save time by allowing the reuse of sections from a master specification, along with previously developed specification details, sometimes with small changes. Specification tools are most useful in situations that do not require completely new specifications from project to project. Desktop Publishing. This is a specialized class of word processors with high-end, professional text and graphics layout features. Desktop publishing systems have been extended to incorporate professional-quality graphical images, many different styles of text and fonts, and special effects such as color fading, shadowing, and artistic effects. Using inexpensive, high-quality printers, the quality of output from desktop publishing software can be remarkable. In general, the limiting factor in the use of desktop publishing software is the time and training investment to use it efficiently. Web Publishing. Word processors are best suited for printing documents on paper; Web publishing tools are designed to format information and transfer the documents to Web sites. In many regards, Web publishing software is similar to word processing software, allowing text, graphics, and tables to be formatted for display. Unique extensions from Web software include the ability to manage llnks, or connections within a related collection of documents. Web publishing software saves information in HTML, a standard format used by Web browsers. Web browsers can display information in many different screen resolutions and sizes, which makes a standard layout of documents especially difficult. Other features of Web publishing software include tools to enforce consistency of Web page format and style, lower resolution of pictures and graphics to reduce loading time, and preview what the fmal Web page will look like to the end user. Standardized Web Document Formats. Created as a result of special formatting requirements for printing and display on Web pages, this software converts word processing documents to a standard format. This standard format requires the use of a Web browser software extension called a “plug-in,” typically offered at no charge as a viewing tool. The viewing tool allows users to see and print the document in exactly the same format. The disadvantage of standardized formats is the inability to modify the information. Spreadsheets. Spreadsheet applications allow the user to create tables for adding and subtracting columns of numbers in one complete view. Spreadsheets contain thousands of cells into which the user may enter labels, numbers, formulas, or even programs (“macros”) to execute such functions as subroutines for a specific calculation, database sorting and searching, conversions, and other calculations. Automatic recalculations allow displayed information to be evaluated quickly. Spreadsheets are useful for importing and formatting data into a graphical display, trend analysis, andor statistical computations. Users can input different variable values into a mathematical representation of the process or system, and evaluate the results immediately or save them as separate files of graphs for later analysis. Databases. Database applications are designed to store, organize, and sort information in a specialized format optimized for speed and utility. Simple PC database applications are typically designed for single users, whereas database management systems (DBMSs) are designed for larger applications involving multipleuser access. DBMSs support security hierarchies, record and file locking, and mission-critical network-accessible applications such

40.3 as financial and banking applications. The standard language for accessing the database information is structured query language (SQL). Presentations. Software optimized for group presentations displays information on digital projection systems. Presentation software is able to present simple text and graphics in an attractive screen format package for seminars, demonstrations, and training. Additionally, most presentation software allows the creation of notes for the speaker to consult during the presentation, and slide handouts. Popular extensions to presentation software include sound effects and multimedia effects such as video and audio clips. Libraries of vendor and third-party graphics are available at extra charge or from the Internet. Accounting. Accounting software for accounts receivable, accounts payable, payroll, and taxes is available for many hardware platforms. Many accounting software packages contain extra modules and applications that allow extensions for unique accounting requirements. Financial reports for projects can be easily generated from standard report packages. Large accounting systems can be integrated with databases and automatic tax-reporting functions. Individual accounts and corrections can be monitored and updated automatically. Large accounting systems also allow integration and reporting from individual employees via Web browser applications. Project Scheduling. Meeting project requirements and efficiently coordinating project resources are difficult tasks; project scheduling software helps solve these problems. Most project scheduling software can take resources (such as individual workers), length of task, percent allocation of resources, and task interdependencies, and present the information as a critical path method (CPM) chart or as a program evaluation and review technique (PERT) chart to evaluate the schedule. Many applications can perform resource leveling, resulting in an efficient allocation of resources to complete the project. As project scheduling software is updated to include real data, the predicted completion date and the total amount of resources used (e.g., hours worked on individual tasks, material requirements) can be used as predictive record for future projects. Management. Management software can review past and current data on inventory, accounting, purchasing, and project control, and predict future performance. As more data are accumulated, statistical analysis can predict performance with a specified level of confidence. Much of the data required for these techniques may require access to standard industry data in industry-wide databases, fmancial forecasts, code standards, and demographic and other resources. In many cases, this information can be obtained on the Internet for a nominal fee. Web Meetings. Similar to teleconferences, Web meetings coordinate demonstrations and meetings over the Internet. Participants use a common Web site to view and update a slide show presentation, with optional voice commentary handled either through traditional teleconferencing or through streaming audio or video feeds. Some types allow participants to view the desktop of the moderator’s computer, allowing them to share a live view of any application the moderator chooses. Graphics and Imaging. Graphics software packages readily produce images, x-y charts, graphs, pie charts, and custom graphics. Libraries of graphics and images exist for use in word processing, presentation, desktop publishing, and Web page applications. Many graphics programs can produce output in numerous popular computer graphics formats such as Joint Photographic Experts Group (JPG), graphics interchange format (GIF), tagged information file format (TIFF), bitmap (BMP), and other standards. Specialty programs allow graphics files to be converted between graphics formats. Multimedia tools allow video and sound to be combined with traditional text and graphics.

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40.4 Images require large amounts of data to be represented accurately. Graphics are usually stored in either bitmap or vector format. The bitmap format is commonly used for picture and photooriented graphics, whereas vector formats are commonly used in CAD/CAM and architectural drawings. Although the output of bitmap images is simple on devices such as graphic printers, rescaling these images does not always produce satisfactory output. Conversions between formats give varying results. Bitmap images are frequently converted to JPG (typically for photographic images) and GIF (typically for simple drawings) file formats. Web Browsers. Most Internet-enabled computers have Web browsers that support text and graphical Web page displays. The underlying language of the World Wide Web is HTML, and navigation is by clicking on links to access different computer systems and pages on the Web. Browsers are a preferred interface for accessing vastly different computer systems. Full-feature browsers also support Java@applets (small programs) and a host of extension applications that are available at nominal or no charge. These include streaming sound, streaming multimedia, and graphics formats other than GIF and JPG, which are natively supported by browsers. Some other available features include access to e-mail, file transfer protocol (FTP; for transferring files to and from servers over the Internet), chat rooms, newsgroups and forums, Tehet access to computers, and access to secure e-commerce sites that use encryption routines to protect sensitive data such as credit card information, bank account balances, and stock transfer information. Communications Applications. Communication over the Internet has become widespread, for both business and personal use. Voice over Internet protocol (VOIP) services allow users to place phone calls over a data network, such as the Internet or a local intranet. Calls can be placed to another user on the network, or to users on the traditional telephone (land-line) network. Text messaging sends short messages (less than 160 characters), usually from a digital cell phone. Instant messaging (IM) allows interactive text-based messaging, usually from a PC to another user on a PC. It is also possible to send messages between text messaging and IM systems.

such as client-server applications. If, after careful evaluation, prepackaged software will not suffice, the choice must be made between in-house and outside development. Custom software can be (1) contracted out to a specialized firm, (2) developed solely by internal staff, or (3) developed by internal staff with consultation help by an outside firm. Contracting to an outside firm involves hiring a specialized outside party to define, estimate, schedule, and create the software. Funds should be budgeted for the outside organization to support modifications or enhancements not specifically covered in the contract. Contracting outside is suitable for an organization that does not have the resources or expertise to accomplish the project. Disadvantages of this approach include the expense and lack of control over the program. Licensing and ownership issues must be defined in the contract. Developing the program internally is viable only if the skills and resources are available. Internal projects are easier to control because the people involved are co-located. Consultation help from an outside firm involves a skilled outside party assisting internal staff, who may have insufficient skill in the area on their own. Outside firms can provide expertise to get a project going quickly. Long-term support and maintenance of the software are done in-house. Specifications are key to the success of a software project. Calculations, human interface, reports, user documents, and testing procedures should be carefully detailed and agreed on by all parties before development begins. Software testing should be specified at the beginning of the project to avoid the common problem of low quality because of hasty and inadequate testing. Design testing should address the human interface, a wide range of input values including improper input, the various functions, and output to screen, disk, or other media. Field tests should include conditions experienced by the final users of the software. With any development approach, good, understandable documentation is required. If for any reason the software cannot be adequately supported, the program will have to be replaced at substantial cost.

SOFTWARE AVAILABILITY

SOFTWARE LANGUAGES

Freeware is copyrighted software that is free. The user can run the software, but must obey the copyright restrictions. Public domain software is available to the public for little or no charge. Public domain software, which is not copyrighted, is often confused with freeware, which is copyrighted. Public domain software can be used without the restrictions associated with copyrighted software. Shareware is software available for users to try before buying it; after the trial period, users are expected to register or stop using the application. There is usually a nominal registration fee. Software can be purchased from manufacturers, distributors, representatives, discount stores, and computer specialty stores. Software price, support, return policies, and distribution vary from vendor to vendor. During installation, most software displays a detailed software license granting use rather than ownership of the software program. This license gives specific restrictions on how the software is to be used. Most high-volume software does not offer direct support, but many software companies offer pay-per-incident and other fee arrangements if desired. Many applications have discussion groups or message boards on the Internet, where solutions to problems may be found. Most off-the-shelf, shrinkwrapped software is nonreturnable once opened.

Application software is written in a variety of computer languages. Most commercial software today is written in C++ or C to allow fast speed and efficient use of resources. Visual Basic@is an extremely popular and easy-to-use graphical programming language for Windows@that has proprietary extensions of the original BASIC language. High-performance software modeling tools such as finite element analysis (FEA) and graphics modeling use languages such as FORTRAN and C. Several modern languages, such as Java@ and Smalltalk, use object-oriented programming. Java is a favored programming language for applications that run over computer networks such as the Internet. C++ mixes both traditional procedural C language programming and object-oriented extension concepts. The major disadvantage of Java and c + + is the high level of programming skill required to create programs. Java is a powerful programming language and environment with extensions to support Internet, security, and multiplatform implementation. Java applets are small, secure, self-contained programs that need a host environment, such as a Web browser, to run. Many new applications use standard Web browsers with applets to create useful displays and interfaces. JavaBeans are modular components that provide users with standard modular and graphical interfaces of components. Enterprise JavaBeans (EJB) are server-based programs that allow interoperability and language - - standardization to be scalable and interchangeable between server vendors. Relational system databases use structured query language (SQL). Object databases are still relatively new, but fully support

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CUSTOM PROGRAMMING Using an existing software package is usually preferable to designing a custom application, which is much more expensive and potentially riskier, especially for large, mission-critical software

Computer Applications

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the object-oriented paradigm of object references, instead of the traditional relational model.

INPUT/OUTPUT (UO) DEVICES Basic computer peripherals (e.g., monitor, keyboard, mouse, etc.) allow interaction with the computer and are sufficient for many applications. More advanced IiO capability is available through digital cameras, scanners, bar code readers, stylus pads, voice recognition devices, and fax machines. Common devices include the following.

Printer types include laser and ink-jet. Laser printers offer a lower cost per sheet, double-sided printing, faster throughput, and large storage capacity. Ink-jet printers offer color printing and lower initial cost but have a higher operating cost. CD and DVD drives can be used to read data from a CD or DVD. CD and DVD burners can be used to write data to anew CD or DVD, or to copy an existing one. A CD typically holds 700 MB of data, whereas a DVD holds 4.7 GB. There are two types of writeable CDs: CD-R, and CD-RW. Once data is written to a CD-R, it cannot be changed. Data written to a CD-RW can be modified or deleted, like data on a floppy disk. DVD+R and DVD-R are similar to CDR, and DVD+RW and DVD-RW are similar to CD-RW. There is also a double-layer (DL) DVD that holds 8.5 GB. Newer types of disks can hold up to 50 GB. External storage can be used to store files on a location other than the local computer. USB flash drives are a simple way to save files or to move files between computers. They are typically very small (40 to 70 mm), but offer less capacity than other methods (usually between 128 MB and 64 GB). External hard drives offer a wide range of capacity (typically 2 to 1000 GB), but are often larger and less convenient to move between computers. External hard drives are often used to supplement the storage located on a PC’s internal hard drive, or to store a back-up of data on an internal hard drive. Digital cameras are useful for photographs and digital storage of images. These digitized images can be transmitted electronically and viewed or incorporated into Web or traditional documents. Most digital cameras can store dozens or hundreds of pictures, depending on the amount of memory they have. Some can also store up to several minutes of video. PC video cameras (Web cams) allow a live image such as live conferencing to be viewed and recorded. A cell phone with a digital camera may allow users to transmit (e-mail) pictures or video from any location where there is cell phone service. Scanners digitize printed photographs and images, and have a characteristic image quality expressed in dots per inch (dpi). The image files can be large and should preferably be stored using a compression format such as JPG. Special scanner software can also read text from a scanned document through a process called optical character recognition (OCR). The scanned text can then be viewed or edited in a word processor. Bar code readers speed database input by converting a manual scan of a bar code to the alphanumeric input in a database field. Stylus pads combine the navigational functionality of a mouse with the ability to enter handwritten notes and sketches and run automated scripts based on movements on the pad. Voice recognition software automatically converts speech to typed text. These programs take some tuning to learn the accent, diction, and idioms of the user. Many voice recognition software packages also enable automated scripts or macros to run on verbal commands. Fax software emulates a printer driver. It allows the user to print a document to a target fax machine through a modem. It also allows the user to receive faxes as electronic documents. Other features include integration with electronic contact databases, templates for transmittal pages, and automated tracking of faxes sent and received.

40.5

Convergence

Many devices serve more than one purpose. A common example is devices that combine the functions of a scanner, printer, fax machine, and copier. Many new cell phones also have cameras and MP3 players, and can also function like a USB flash drive or a modem. This trend toward multifunctionality is expected to continue.

NETWORKING COMPONENTS Computers use resources that are commonly arranged into networks comprised of hardware and software components. Hardware network components include hubs, switches, routers, bridges, and repeaters. Software network components usually take one of two forms: (1) dynamic lit& libraries (DLLs) to control network hardware, or (2) applications to communicate between computers according to adopted networking standards (e.g., IEEE 802.3 Ethernet). Numerous computer network configurations exist for intra-, inter-, and extra-office data communication. Some common examples include local area networks (LANs), wide-area networks (WANs), metropolitan area networks (MANS), intranets, extranets, and the Internet. Figure 1 is a diagram of large business system architecture with Internet connections. The system has a large number of personal computers connected via Ethernet to a central wiring closet device called a hub. This hub simplifies the wiring infrastructure by allowing centralized wiring termination for modular utility connections to individual computers. The firewall, a computer security barrier, protects against unauthorized access from the outside Internet to individual nodes inside the firewall. Users may connect to the Internet either through a corporate router or indirectly from home through an Internet service provider (ISP), which may charge a fee for the service. Higher-bandwidth connections typically cost more as speed increases.

LAN PROTOCOLS The Ethernet protocol is the most widely used and accepted local area network (LAN) standard, and is used extensively in industry. Because of its pervasive acceptance in industry, HVAC building automation protocols such as BACnet@and LonWorks@allow their protocols to use Ethernet in their physical layer. Ethernet is a multiaccess, packet-switching network where each node can request access to the network on an equal basis with any other node. Ethernet uses the collision sense, multiple accessicollision detect (CSMAI CD) technique: if two nodes transmit at the same time, a collision occurs; both nodes then wait a random period of time and try again. This allows efficient allocation of bandwidth based on need. An Ethernet LAN can use different media, such as the following: 10Base5, also known as Thick Net, which uses the large coaxial cable RG-11 1OBase2, also known as Thin Net, which uses the smaller coaxial cable RG-58 Fiber-optic cable 1OBase-T (Twisted Pair), the most popular type, which has a wiring limitation length of 30 m and is typically used in centralized wiring systems. These cables typically use a RJ-45 connector. Faster versions of Ethernet include 1OOBase-T or Fast Ethernet, 1000Base-T or Gigabit Ethernet, and 10GBase-T or 10-Gigabit Ethernet,whichsupportdataratesof lOOMbps, lOOOMbps(1 Gbps), and 10 Gbps respectively. 1000Base-T and 10GBase-T have variants that use fiber or twisted pair connections. 802.1 1, also known as Wi-Fi, is a wireless LAN standard created and maintained by the IEEE LANiMAN Standards Committee (IEEE 802). The base current version is IEE Standard 802.1 1-2007, andtheolderprotocolsare802,1la,802.11b,and801.11g;thelatest

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40.6

Fig. 1 Example of Business System Architecture

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protocol is 802.1 In. Instead of a cable, the computer and hub communicate using low-power radio waves. 802.16, also known as WiMAX, is a wireless protocol that can be used over a much longer distance than Wi-Fi. It may be configured to act as an element of a LAN, a WAN, or a MAN.

requests, and maintenance from a remote computer at the job site to determine repair history on a piece of equipment. Issues such as reliability, battery replacement alerts, maintenance, and reliability because of electromagnetic noise and interference should be considered when using wireless communications.

TRANSMISSION CONTROL PROTOCOL/ INTERNET PROTOCOL

TELEPHONY STANDARDS

Transmission control protocoliInternet protocol (TCPIIP, RFCll22) is a set of protocols that allow computers to communicate with each other. TCPIIP is the language of the Internet, and is also used in local networks, intranets, and extranets. As communication protocols such as TCPIIP have gained acceptance, availability of components based on these protocols has increased and driven networking costs down. A complementary protocol, UDPIIP (RFC768), is often used by HVAC controllers, as well as by many streaming audio, video, and VOIP sites.

WIRELESS SERVICE One of several immediately applicable new technologies is wireless connections for computers and equipment (e.g., to the Internet or to a LAN). Wireless communications to remote sensors can provide a low-cost solution where the cost ofrunning conventional wiring is prohibitive or inappropriate. Wireless monitoring components include a wireless transmitter and a Web site. The transmitter is mounted on or near the equipment being monitored. The Web site determines what alerts are sent to whom, and the method of delivery (e.g., e-mail, pager, telephone). Alert messages specify the condition that triggered the alert and the location, make, model, and serial number of the equipment. Also, field service technicians can inspect service procedures, service

Regular analog phone service offers limited bandwidth and can support analog phone modems up to 56 kilobits per second (kbps). Digital phone standards include digital subscriber line (DSL), which can support bandwidth from 640 kbps to 3 Mbps but is limited to a 3050 m wire length from the telephone switching office. Cable modems provide high-speed access from traditional cable TV service companies. Cable networks generally have download speeds roughly between 500 kbps and 6 Mbps, but are often limited to about 768 kbps upload speed. Fiber-optic Internet connections are available in some areas, offering download bandwidth up to 50 Mbps and upload bandwidth up to 20 Mbps. As with DSL and cable modems, fiber-optic users may not have the maximum bandwidth available at all times. Note that, for most Internet users, even the slowest bandwidth available from a DSL, cable, or fiber-optic connection is sufficient. Higher bandwidth is most useful for users who frequently download music, video, or other large files. In addition to the wired connection types, wireless connection standards with a range and bandwidth suitable to compete with DSL, cable, and fiber connections are being developed. T1 and T3 are high-speed digital communication lines used by main communications tru&s between servers, or for access to the Internet from an Internet service provider or company connection line. T1 connection speed is a maximum of 1.5 Mbps; T3 maximum speed is 44.736 Mbps. Asynchronous transfer mode (ATM) digital

40.7

Computer Applications service provides high-speed communication at a typical maximum data rate of 155 Mbps.

FIREWALLS Firewalls (computer security barriers), frequently used to prevent outside individuals from accessing internal, proprietary networked resources, can be designed to block certain messages from coming into or leaving the network. Firewalls may be implemented in a high-speed router, or as a separate device connected to a router. They can efficiently block all communication to or from a specific IP address. All messages that enter and leave the intranet pass through the firewall, which examines each message and halts progress of illegal communications. Firewalls are an essential part of corporate computer security systems, and are also commonly implemented as software on a PC.

INTERNET AND APPLICATIONS The Internet originated in 1969 as an experimental project of the Advanced Research Project Agency (ARPA), and was called ARPANET. From its inception, the network was designed to be a decentralized, self-maintaining series of redundant llnks between computers and computer networks, capable of rapidly transmitting communications without direct human involvement or control, and with the automatic ability to reroute communications if one or more individual llnks were damaged or otherwise unavailable. Among other goals, this redundancy of linked computers was designed to allow vital research and communications to continue even if portions of the network were damaged by a war or other catastrophic event. Messages between computers on the Internet do not necessarily travel entirely along the same path. The Internet uses packetswitching communication protocols that allow individual messages to be subdivided into smaller packets. These are then sent independently to the destination and automatically reassembled by the receiving computer. Although all packets of a given message often travel along the same path to the destination, if computers along the route become overloaded, packets can be rerouted to less loaded computers. No single entity (academic, corporate, governmental, or nonprofit) administers the Internet. It exists and functions because hundreds ofthousands of separate operators of computers and computer networks independently decided to use common data transfer protocols to exchange communications and information with other computers. No centralized storage location, control point, or communications channel exists for the Internet, and no single entity can control all of the information conveyed on the Internet.

INTERNET COMMUNICATION METHODS The most common methods of communications on the Internet (as well as within the major on-line services) can be grouped into the following categories and are described in the following sections: One-to-one messaging (e.g., e-mail or text messaging) One-to-many messaging (e.g., mailing list servers) Distributed message databases (e.g., USENET news groups) Real-time communication (e.g., Internet Relay Chat, IM, VOIP) Real-time remote computer use (e.g., Telnet) Remote information retrieval (e.g., ftp, gopher, the World Wide Web) Most of these methods of communication can be used to transmit text, data, computer programs, sound, visual images (i.e., pictures), and moving video images.

Servers Network servers are fast becoming an important part of building automation and computer services systems. A Web page runs on a

generic Web server. Files available for central storage and shared resources among users of a network are referred to as a file server. FTP servers allow users outside a company to store and manage large files such as drawing and construction documents. Mail servers are central storage servers that provide e-mail services to users. Database servers provide core database functionality, and can be added to application servers to access specific application services.

E-mail Electronic mail (e-mail) is an extremely useful communications tool for use with local area networks, wide area networks, and the Internet. Using e-mail software, a message can be sent to individuals or to groups. Unlike postal mail, simple e-mail generally is not “sealed” or secure, and can be accessed or viewed on intermediate computers between the sender and recipient unless the message is encrypted. Modern e-mail software can attach graphics, executable programs, and other types of files. These features should be used with caution because of the large network resources required to support the file transfer. Computer Viruses, Worms, and Trojan Horses. Computer viruses are programs that replicate themselves and typically do damage to the host system; they are frequently received through e-mail attachments. A worm is a self-contained program that spreads working copies of itself to other computer systems, typically through network connections. A Trojan horse is a program that performs undocumented activities not desired by the program user. Antivirus software is vital to maintaining system security. Some PC operating systems are more vulnerable to viruses and worms than others. Some e-mail programs automatically execute script files attached to e-mail; this leaves the user open to viruses and other types of attack. As a precaution, e-mail programs that automatically execute script files should not be used, or, if no other program is available, automatic script execution should be turned off. Only attachments from reputable or trusted sources should be opened, and then only after scanning the attachment with antivirus software. Hoaxes. A common problem associated with e-mail is the hoax or chain letter. A hoax is commonly spread as a w d n g about serious consequences of a new virus, offers of free money or prizes, or dubious information about a person, product, or organization. A common request from the hoax is to send it to everyone you know, in effect overloading the system with useless information. Although hoaxes and chain letters do not damage the host computer, they tax network resources, spread misinformation, and distract users from real work. Users should not pass hoaxes along, but should simply delete the message. Legitimate warnings about viruses come from IT staff or antivirus vendors. Individual hoaxes can be investigated through Web sites devoted to hoaxes and virus myths (e.g., Lawrence Livermore National Laboratory 2002).

Mailing Lists The Internet also contains automatic mailing list services (e.g., LISTSERV) that allow communication about particular subjects of interest to a group of people. Users can subscribe to a mailing list on a particular topic of interest to them. The subscriber can submit messages on the topic to the mailing list server that are forwarded, either automatically or through a human moderator overseeing the list, to the e-mail accounts of all list subscribers. A recipient can reply to the message and have the reply also distributed to everyone on the mailing list. Most mailing lists automatically forward all incoming messages to all mailing list subscribers (i.e., they are moderated).

Distributed Message Databases Distributedmessage databases, such as USENET newsgroups, are similar to mailing lists but differ in how communications are transmitted. User-sponsored newsgroups are among the most popular and

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40.8 widespread applications of Internet services, and cover all imaginable topics of interest. Like mailing lists, newsgroups are open discussions and exchanges on particular topics. Users can view the entire database of messages at any time. Some newsgroups are moderated, but most are open. One common variation of a user-generated message database is called a wiki.

Real-Time Communication Internet users can also engage in an immediate dialogue, in real time, with other people on the Internet, ranging from one-to-one communications to Internet Relay Chat (IRC), which allows two or more to type messages to each other that almost immediately appear on the receivers’ computer screens. IRC is analogous to a telephone party line, using a computer and keyboard rather than a telephone. With IRC, however, at any one time there are thousands of different party lines available, with collectively tens of thousands of users discussing a huge range of subjects. Moreover, a user can create a new party line to discuss a different topic at any time. Some IRC conversations are moderated or have channel operators. Commercial online services often have their own chat systems to allow their members to converse.

Real-Time Remote Computer Use Another method to access and control remote computers in real time is using Telnet, the main Internet protocol for connecting remote computers. For example, using Telnet, a researcher can use the computing power of a supercomputer located at a different university, or a student can connect to a remote library to access the library’s online catalog program.

Remote Information Retrieval The most well-known use of the Internet is searching for and retrieving information located on remote computers. The three primary methods to locate and retrieve information on the Internet are ftp, Gopher, and HTTP (the World Wide Web). A simple method, file transfer protocol (ftp) allows the user to transfer files between the local computer and a remote computer. The program and format named Gopher guides a search through the resources available on a remote computer. World Wide Web. The World Wide Web (WWW) serves as the platform for a global, online store of knowledge, containing information from diverse sources and accessible to Internet users around the world. Though information on the Web is contained in individual computers, the fact that each of these computers is connected to the Internet allows all of the information to become part of a single body of knowledge. It is currently the most advanced information system developed on the Internet, and encompasses most information in previous networked information systems such as ftp, Gopher, wide-area information server (WAIS) protocol (used to search indexed databases on remote servers), and USENET. Basic Operation. The WWW is a series of documents stored in different computers all over the Internet. An essential element of the Web is that each document has an address (like a telephone number). Most organizations now have home pages on the Web, which guide users through llnks to information about or relevant to that organization. Llnks may also take the user from the original Web site to another Web site on another computer connected to the Internet. These links from one computer to another, from one document to another across the Internet, are what unify the Web into a single body of knowledge, and what makes the Web unique. Publishing. The WWW allows people and organizations to communicate easily and quickly. Publishing information on the Web requires only a computer connected to the Internet and running WWW server software. The computer can be anything from an inexpensive personal computer to several state-of-the-art computers

Applications (SI)

filling a small building. Many Web publishers choose instead to lease disk storage space from a company with the necessary facilities, eliminating the need to own any equipment. Information to be published on the Web must be formatted according to Web standards, which ensure that all users who want to view the material will be able to do so. Web page design can significantly affect user satisfaction. Pages with content limited to one screen tend be easier to use than long pages that require scrolling. Large graphics files or special software requirements for viewing may discourage low-bandwidth-connection users (e.g., Internet access over regular analog phone lines) because of long waits. Maintaining and updating content is important: regular changes encourage repeatusers. Web pages that give current information available nowhere else create value for users and encourage new and repeat visitors. However, care must be taken to obtain written permission for use of copyrighted material. Web sites can be open to all Internet users, or closed (an intranet), accessible only to those with advance authorization. Many publishers choose to keep their sites open to give their information the widest potential audience. Searching the Web. Systems known as search engines allow users to search by category or by key words for particular information. The engine then searches the Web and presents a list linked to sites that contain the search term(s). Users can then follow individual llnks, browsing through the information on each site, until the desired material is found. There are also Web-based directories maintained by humans that can often give more precise results for a search in a particular area. Search engines results can be narrowed by adding more key words: for example, a search for the word “HVAC” may end up with a list several hundred pages long, but a search for “HVAC VAV” could narrow the focus. Common Standards. The Web llnks disparate information on Internet-llnked computers by using a common information storage format called hypertext markup language (HTML) and a common language for the exchange of Web documents, hypertext transfer protocol (HTTP). HTML documents can contain text, images, sound, animation, moving video, and links to other resources. Although the information itself may be in many different formats and stored on computers that are not otherwise compatible, these Web standards provide a basic set of standards that allow communication and exchange of information. Many specialized programs exist to create and edit HTML files. Like HTML, extensible markup language (XML), is a subset of the standard generalized markup language (SGML) protocol. XML applies the same document presentation principles of HTML to data interchange beyond simply displaying the data. XML separates data content from its presentation. This allows for different visual renditions of the same message, for displays on different devices. Supervisory Groups. No single authority controls the entire Internet, but it is guided by the Internet Society (ISOC). ISOC is a voluntary membership organization intended to promote global information exchange through the Internet. The Internet Architecture Board (IAB) defines Internet communication standards. The IAB also keeps track of information that must remain unique. For example, each computer on the Internet has a unique 32-bit address. The IAB does not actually assign the addresses, but it makes the rules about how to assign them.

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zyxwvutsr Collaborative Design The Internet is revolutionizing how project teams collaborate. Interactions such as sharing or jointly developing drawings, documents, or software can now take place efficiently with collaborators around the world. Collaborative design raises many coordination issues. Methods of sharing data, such as distributed databases, revision and developmental accounting, and security concerns associated with the transmission of design information must be carefully considered.

Computer Applications SECURITY ISSUES

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Computer security requires sound planning and continuous maintenance and monitoring. Mail servers can scan for viruses before users open e-mail, and individual virus software loaded on individual machines serves as a second layer of protection (see also the section on Computer Viruses, Worms, and Trojan Horses). Always save attached files to a safe directory and scan with antivirus software before using. Typically, IS and IT staff have a dedicated support person and strategy to maintain security. A critical area for computer security is user names and passwords. Many systems require frequent changes of passwords with minimum length, number, case, and other requirements. Passwords should never be released to anyone.

HVAC SOFTWARE APPLICATIONS Over the past decade, the use of computer software designing mechanical systems has increased. The advantages of softwareassisted design over traditional manual methods include the following: Computers can better preserve design assumptions and document the design intent through consolidating and organizing resources (e.g., central databases, Web sites with design documents) It is often faster and easier to modify assumptions used in a calculation and recalculate the results using a computer The computational speed of computers allows designers to tackle more difficult design problems and to use more accurate (but computationally intensive) methods Computers assist designers in analyzing design alternatives. In the future, interoperable software design and application of expert systems could reduce the burden of design. Interoperable applications automatically pass design assumptions and calculation results between applications, reducing both the burden of user input and the opportunity for user error. Expert and rule-based systems could automate design standards to the point where simple system selection or distribution system sizing can be automated. There is a wide variety of software used in the HVAC industry. This section covers applications that assist mechanical engineers in design, analysis, and specification of mechanical systems, including HVAC design software HVAC simulation software CADigraphics software Miscellaneous utilities and applets Much of this software is also used by HVAC equipment manufacturers to design their products, and by controls contractors to develop control systems. In addition, sources for these applications and the fundamentals of interoperable computer applications for the HVAC&R industry are discussed. The distinction between HVAC design and simulation is subtle. The convention used here is that design software is used for static analysis: evaluating equipment and distribution systems under a specific design condition. In contrast, HVAC simulation is used for dynamic system analysis over a range of time or operating conditions. Many applications provide both functions through a single interface.

HVAC DESIGN CALCULATIONS HVAC design software includes programs for the following tasks: HVAC heating and cooling load calculations Duct system sizing and analysis Pipe system sizing and analysis

40.9

Acoustical analysis Equipment selection

Although computers are now widely used in the design process, most programs perform analysis, not design, of a specified system. That is, the engineer proposes a design and the program calculates the consequences of that design. When the engineer can define alternatives, a program may aid design by analyzing the performance of the alternatives and then selecting the best according to predetermined criteria. Thus, a program to calculate the cooling load of a building requires specifications for the building and its systems; it then simulates that building’s performance under certain conditions of weather, occupancy, and scheduling. Although most piping and duct design tools can size pipe or ductwork based on predetermined criteria, most engineers still decide duct dimensions, air quantities, duct routing, and so forth and use software to analyze the performance of that design. Some interoperable software can pass values from one design phase to be used as inputs in the next. For example, a load program may be used to determine the design air quantities at the zone and space level. Through interoperability, this information can be preserved in the building model and used as an input for the duct sizing program. Interoperable software is further described in the section on Interoperable Computer Applications for the HVAC&R Industry. Because computer programs perform repetitive calculations rapidly, the designer can explore a wide range of alternatives and use selection criteria based on annual energy costs or life-cycle costs.

Heat and Cooling Load Design Calculating design thermal loads in a building is a necessary step in selecting HVAC equipment for virtually any building project. To ensure that heating equipment can maintain satisfactory building temperature under all conditions, peak heating loads are usually calculated for steady-state conditions without solar or internal heat gains. This relatively simple calculation can be performed by hand or with a computer. Peak cooling loads are more transient than heating loads. Radiative heat transfer within a space and thermal storage cause thermal loads to lag behind instantaneous heat gains and losses. This lag can be important with cooling loads, because the peak is both reduced in magnitude and delayed in time compared to the heat gains that cause it. A further complication is that loads peak in different zones at different times (e.g., the solar load in a west-facing zone will peak in the afternoon, and an east-facing zone will usually peak in the morning). To properly account for thermal lag and the noncoincidence of zone loads, a computer program is generally required to calculate cooling loads for a multiple-zone system. These programs simulate loads for each hour of the day for every day of the year (or a representative subset of the days of the year), and report peak loads at both the zone and system level, recording the date and time of their occurrence. Because the same input data are used for heating and cooling loads, these programs report peak heating loads, as well. Various calculation methods are used to account for the transience of cooling loads; the most common methods are described in detail in Chapters 17 and 18 of the 2009 ASHRAE HandbookFundamentals. The most accurate but computationally intensive method, the heat-balance (HB) method, is a fundamental calculation of heat transfer from all sources with the construction elements of the building (walls, floor, windows, skylights, furniture, ceiling, slab, and roof). Only the computational speed of present-day personal computers allows these calculations to be performed for large multizone buildings in a reasonable amount of time (ranging from several minutes to an hour or more). Several simplified methods or approximations of thermal lag are available to speed computation time, including the radiant time-series (RTS), transfer function (TFM), total equivalent temperature differential with time

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40.10

Applications (SI)

averaging (TETDITA) and cooling load temperature differential with cooling load factors (CLTDICLF) methods. These approximations are less accurate than the heat balance method, but can be sufficient if they are appropriately applied. Both the TETDITA and the TFM methods require a history of thermal gains and loads. Because histories are not initially known, they are assumed zero and the building under analysis is taken through a number of daily weather and occupancy cycles to establish a proper 24 h load profile. Thus, procedures required for the TFM and TETDITA methods involve so many individual calculations that noncomputerized calculations are highly impractical. The CLTDICLF method, on the other hand, is meant to be a manual calculation method and can be implemented by a spreadsheet program. The CLTD and CLF tables presented in the 2001 ASHRAE Handbook-Fundamentals are, in fact, based on application of the TFM to certain geometries and building constructions. An automatedversion of TFM is preferred to CLTDICLF because it is more accurate. The automated TETDITA method, however, can provide a good approximation with significantly less computation than the TFM. Characteristics of a Loads Program. In general, a loads program requires user input for most or all of the following:

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Full building description, including the construction and other heat transfer characteristics of the walls, roof, windows, and other building elements; size; orientation; geometry of the rooms, zones, and building; and possibly also shading geometries Sensible and latent internal loads from lights and equipment, and their corresponding operating schedules Sensible and latent internal loads from people Indoor and outdoor design conditions Geographic data such as latitude and elevation Ventilation requirements and amount of infiltration Number of zones per system and number of systems With this input, loads programs calculate both the heating and cooling loads and perform a psychrometric analysis. Output typically includes peak room and zone loads, supply air quantities, and total system (coil) loads. Selecting a Loads Program. Beyond general characteristics, such as hardware and software requirements, type of interface (icon-based, menu-driven versus command-driven), availability of manuals and support, and cost, some program-specific characteristics should be considered when selecting a loads program. The following are among items to be considered: Ease of use and compatibility with the existing operating system Type of building to be analyzed residential versus commercial (residential-only loads programs tend to be simpler to use than more general-purpose programs meant for commercial and industrial use, but residential-only programs generally have limited abilities) Method of calculation for the cooling load (note that some programs support more than one method of calculation) Program limits on such items as number of systems, zones, rooms, and surfaces per room Sophistication of modeling techniques (e.g., capability of handling exterior or interior shading devices, tilted walls, daylighting, skylights, etc.) Units of input and output Program complexity (in general, the more sophisticated and flexible programs require more input and are somewhat more difficult to use than simpler programs) Capability of handling the system types under investigation Certification of the program for energy code compliance Ability to share data with other programs, such as CAD and energy analysis

Fig. 2

Example of Duct System Node Designation

Duct Design Chapter 21 of the 2009 ASHRAE Handbook-Fundamentals describes several methods for duct design. Major considerations in duct design include the physical space required by the duct, cost of the ductwork and fittings, energy required to move air through the duct, acoustics, minimum velocities to maintain contaminants in suspension (fume exhaust), flexibility for future growth, zoning, and constructability. Duct software can help with the layout and analysis of new and/or existing distribution systems. Duct design is more an art than a science, which complicates automation of design. Duct design programs and calculation methods are limited in their ability to (1) calculate actual operating pressures because of the impact of fan and duct system effects, and (2) take into consideration many unmeasurable factors in the process of laying out and sizing ducts (e.g., provision for space limitations, local duct construction preferences and practices, local labor and material costs, acoustics, and accommodating future remodeling). Selecting and Using a Program. Duct design involves routing or laying out ductwork, selecting fittings, and sizing ducts. Computer programs can rapidly analyze design alternatives and determine critical paths in long and complicated distribution systems. Furthermore, programs and printouts can preserve the assumptions used in the design: any duct calculation requires accurate estimates of pressure losses in duct sections and the definition of the interrelations of velocity heads, static pressures, total pressures, and fitting losses. The general computer procedure is to designate nodes (the beginning and end of duct sections) by number. Details about each node (e.g., divided flow fitting and terminal) and each section of duct between nodes (maximum velocity, flow rate, length, fitting codes, size limitation, insulation, and acoustic liner) are used as input data (Figure 2). Characteristics of a duct design program include the following:

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Calculations for supply, return, and exhaust Sizing by constant friction, velocity reduction, static regain, and constant velocity methods Analysis of existing ducts Inclusion of fitting codes for a variety of common fittings

40.11

Computer Applications Identification of the duct run with the highest pressure loss, and tabulation of all individual losses in each run Printout of all input data for verification Provision for error messages Calculation and printout of airflow for each duct section Printout of velocity, fitting pressure loss, duct pressure loss, and total static pressure change for each duct section Graphics showing schematic or line diagrams indicating duct size, shape, flow rate, and air temperature Calculation of system heat gaidloss and correction of temperatures and flow rates, including possible system resizing Specification of maximum velocities, size constraints, and insulation thicknesses Consideration of insulated or acoustically lined duct Bill of materials for sheet metal, insulation, and acoustic liner Acoustic calculations for each section File-sharing with other programs, such as spreadsheets and CAD Because many duct design programs are available, the following factors should be considered & program selection: Maximum number of branches that can be calculated Maximum number of terminals that can be calculated Types of fittings that can be selected Number of different types of fittings that can be accommodated in each branch Ability of the program to balance pressure losses in branches Ability to handle two- and three-dimensional layouts Ability to size a double-duct system Ability to handle draw-through and blow-through systems Ability to prepare cost estimates Ability to calculate fan motor power Provision for determining acoustical requirements at each terminal Ability to update the fitting library Optimization Techniques for Duct Sizing. For an optimized duct design, fan pressureand duct cross sections are selected by minimizing the life-cycle cost, which is an objective function that includes initial and energy costs. Many constraints, including constant pressure balancing, acoustic restrictions, and size limitations, must be satisfied. Duct optimization is a mathematical problem with a nonlinear objective function and many nonlinear constraints. The solution must be taken from a set of standard diameters and standard equipment. Numerical methods for duct optimization exist, such as the T method (Tsal et al. 1988), coordinate descent (Tsal and Chechik 1968), Lagrange multipliers (Kovarik 1971; Stoecker et al. 1971), dynamic programming (Tsal and Chechik 1968), and reduced gradient (Arkin and Shitzer 1979).

Piping Design Many computer programs are available to size or calculate the flexibility of piping systems. Sizing programs normally size piping and estimate pump requirements based on velocity and pressure drop limits. Some consider heat gain or loss from piping sections. Several programs produce a bill of materials or cost estimates for the piping system. Piping flexibility programs perform stress and deflection analysis. Many piping design programs can account for thermal effects in pipe sizing, as well as deflections, stresses, and moments. Numerous programs are available to analyze refrigerant piping layouts. These programs aid in design of properly sized pipes or in troubleshooting existing systems. Some programs are generic, using the physical properties of refrigerants along with system practices to give pipe sizes that may be used. Other programs “mix and match” evaporators and condensers from a particular manufacturer and recommend pipe sizes. See Chapters 2 and 3 of the 2010

Fig. 3

Examples of Nodes for Piping System

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ASHRAE Handbook-Refrigeration for specifics on refrigerant pipe sizing. The general technique for computerizing piping design problems is similar to that for duct design. A typical piping problem in its nodal representation is shown in Figure 3. Useful piping programs do the following:

Provide sufficient design information Perform calculations for both open and closed systems Calculate flow, pipe size, and pressure drop in each section Handle three-dimensional piping systems Cover a wide selection of common valves and fittings, including specialized types (e.g., solenoid and pressure-regulating valves) Consider different piping materials such as steel, copper, and plastic by including generalized friction factor routines Accommodate liquids, gases, and steam by providing property information for a multiplicity of fluids Calculate pump capacity and head required for liquids Calculate available terminal pressure for nonreturn pipes Calculate required expansion tank size Estimate heat gain or loss for each portion of the system Prepare a cost estimate, including costs of pipe and insulation materials and associated labor Print out a bill of materials Calculate balance valve requirements Perform a pipe flexibility analysis Perform a pipe stress analysis Print out a graphic display of the system Allow customization of specific design parameters and conditions, such as maximum and minimum velocities, maximum pressure drops, condensing temperature, superheat temperature, and subcooling temperature Allow piping evaluation for off-design conditions Provide llnks to other programs, such as equipment simulation programs Limiting factors to consider in piping program selection include the following: Maximum number of terminals the program can accommodate Maximum number of circuits the program can handle Maximum number of nodes each circuit can have Maximum number of nodes the program can handle Compressibility effects for gases and steam Provision for two-phase fluids

Acoustic Calculation Chapter 48 summarizes sound generation and attenuation in HVAC systems. Applying these data and methodology often re-

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40.12 quires a large amount of computation. All sound-generation mechanisms and transmission paths are potential candidates for analysis. Adding to the computational work load is the need to extend the analysis over, at a minimum, octave bands 1 through 8 (63 Hz through 8 kHz). A computer can save a great amount of time and difficulty in the analysis of any noise situation, but the HVAC system designer should be wary of using unfamiliar software. Caution and critical acceptance of analytical results are necessary at all frequencies, but particularly at low frequencies. Not all manufacturers of equipment and sound control devices provide data below 125 Hz; in such cases, the HVAC designer conducting the analysis and the programmer developing the software must make experiencebased assumptions for these critical low-frequency ranges. The designerianalyst should be well satisfied if predictions are within 5 dB of field-measured results. In the low-frequency “rumble” regions, results within 10 dB are often as accurate as can be expected, particularly in areas of fan discharge. Conservative analysis and application of results is necessary, especially acoustically critical spaces. Several easy-to-use acoustics programs are currently available, but they are often less detailed than custom programs developed by acoustic consultants for their own use. Acoustics programs are designed for comparative sound studies and allow the design of comparatively quiet systems. Acoustic analysis should address the following key areas of the HVAC system: Sound generation by HVAC equipment Sound attenuation and regeneration in duct elements Wall and floor sound attenuation Ceiling sound attenuation Sound breakout or break-in in ducts or casings Room absorption effect (relation of sound power criteria to sound pressure experienced) Algorithm-based programs are preferred because they cover more situations (see Chapter 48); however, algorithms require assumptions. Basic algorithms, along with sound data from the acoustics laboratories of equipment manufacturers, are incorporated to various degrees in acoustics programs. The HVAC equipment sound levels in acoustics programs should come from the manufacturer and be based on measured data, because there is a wide variation in the sound generated by similar pieces of equipment. Some generic equipment sound generation data, which may be used as a last resort in the absence of specific measured data, are found in Chapter 48. Whenever possible, equipment sound power data by octave band (including 32 Hz and 63 Hz) should be obtained for the path under study. A good sound prediction program relates all performance data. Many more specialized acoustics programs are also available. Various manufacturers provide equipment selection programs that not only select optimum equipment for a specific application, but also provide associated sound power data by octave bands. Data from these programs should be incorporated in the general acoustic analysis. For example, duct design programs may contain sound predictions for discharge airborne sound based on the discharge sound power of fans, noise generatiodattenuation of duct fittings, attenuation and end reflections of VAV terminals, attenuation of ceiling tile, and room effect. VAV terminal selection programs generally contain subprograms that estimate the space NC level near the VAV unit in the occupied space. However, projected space NC levels alone may not be acceptable substitutes for octave-band data. The designer/ analyst should be aware of assumptions, such as room effect, made by the manufacturer in presenting acoustical data. Predictive acoustic software allows the designer to examine HVAC-generated sound in a realistic, affordable time frame. HVAC-oriented acoustic consultants generally assist designers by providing cost-effective sound control ideas for sound-critical applications. A well-executed analysis of the various components

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Applications (SI)

and sound paths enables the designer to assess the relative importance of each and to direct corrective measures, where necessary, to the most critical areas. However, computer-generated results should supplement the designer’s skills, not replace them.

Equipment Selection and Simulation Equipment-related computer applications include programs for equipment selection, equipment optimization, and equipment simulation. Equipment selection programs are basically computerized catalogs. The program locates an existing equipment model that satisfies the entered criteria. The output is a model number, performance data, and sometimes alternative selections. Equipment optimization programs display all possible equipment alternatives and let the user establish ranges of performance data or first cost to narrow the selection. The user continues to narrow performance ranges until the best selection is found. The performance data used to optimize selections vary by product family. Equipment simulation programs calculate the full- and partload performance of specific equipment over time, generally one year. The calculated performance is matched against an equipment load profile to determine energy requirements. Utility rate structures and related economic data are then used to project equipment operating cost, life-cycle cost, and comparative payback. Before accepting output from an equipment simulation program, the user must understand the assumptions made, especially concerning load profile and weather. Some advantages of equipment programs include the following: High speed and accuracy of the selection procedure Pertinent data presented in an orderly fashion More consistent selections than with manual procedures More extensive selection capability Multiple or alternative solutions Small changes in specifications or operating parameters easily and quickly evaluated Data-sharing with other programs, such as spreadsheets and CAD Simulation programs have the advantages of (1) projecting partload performance quickly and accurately, (2) establishing minimum part-load performance, and (3) projecting operating costs and offering payback-associated higher-performance product options. There are programs for nearly every type of HVAC equipment, and industry standards apply to the selection of many types. The more common programs and their optimization parameters include the following: Air distribution units Air-handling units, rooftop units Boilers Cooling towers Chillers

Coils Fan-coils Fans Heat recovery equipment Pumps Air terminal units (variable- and constant-volume flow)

Pressure drop, first cost, sound, throw Power, first cost, sound, filtration, footprint, heating and cooling capacity First cost, efficiency, stack losses First cost, design capacity, power, flow rate, air temperatures Power input, condenser head, evaporator head, capacity, first cost, compressor size, evaporator size, condenser size Capacity, f r s t cost, fluid pressure drop, air pressure drop, rows, fin spacing Capacity, f r s t cost, sound, power Volume flow, power, sound, first cost, minimum volume flow Capacity, frst cost, air pressure drop, water pressure drop (if used), effectiveness Capacity, head, impeller size, f r s t cost, power Volume flow rate, air pressure drop, sound, first cost

CHAPTER 41

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BUILDING ENERGY MONITORING

Reasons for Energy Monitoring .................................................................................................... Small Projects ............................................................................................................................... Protocols for Performance Monitoring ........................................................................................ Common Monitoring Issues Steps for Project Design and Implementation ..............................................................................

B

UILDING energy monitoring was conducted on a large scale in the 1980s and 199Os, and the need to capture lessons learned and document project requirements that often were not addressed adequately in these large projects led to the development of this chapter. The intent of such projects is to provide realistic, empirical information from field data to enhance understanding of actual building energy performance and help quantify changes in performance over time. Although different building energy monitoring projects can have different objectives and scopes, all have several issues in common that allow methodologies and procedures (monitoring protocols) to be standardized. This chapter provides guidelines for developing building monitoring projects that provide the necessary measured data at acceptable cost. The intended audience comprises building owners, building energy monitoring practitioners, and data end users such as energy and energy service suppliers, energy end users, building system designers, public and private research organizations, utility program managers and evaluators, equipment manufacturers, and officials who regulate residential and commercial building energy systems. A new section has been added on small projects to show how the methodology can be simplified. Monitoring projects can be uninstrumented (i.e., no additional instrumentation beyond the utility meter) or instrumented (i.e., billing data supplemented by additional sources, such as an installed instrumentation package, portable data loggers, or building automation system). Uninstrumented approaches are generally simpler and less costly, but they can be subject to more uncertainty in interpretation, especially when changes made to the building represent a small fraction of total energy use. It is important to determine (1) the accuracy needed to meet objectives, (2) the type of monitoring needed to provide this accuracy, and (3) whether the desired accuracy justifies the cost of an instrumented approach. Instrumented field monitoring projects generally involve a data acquisition system (DAS), which typically comprise various sensors and data-recording devices (e.g., data loggers) or a suitably equipped building automation system. Projects may involve a single building or hundreds of buildings and may be carried out over periods ranging from weeks to years. Most monitoring projects involve the following activities: Project planning Site installation and calibration of data acquisition equipment (if required) Ongoing data collection and verification Data analysis and reporting

41.1 41.3 4 1.3 41.6 41.7

demand and load factors, excess capacity, controller actuation, and building and component lifetimes. Current monitoring practices vary considerably. For example, a utility load research project may tend to characterize the average performance of buildings with relatively few data points per building, whereas a test of new technology performance may involve monitoring hundreds of parameters in a single facility. Monitoring projects range from broad research studies to very specific, contractually required savings verification carried out by performance contractors. However, all practitioners should use accepted standards of monitoring practices to communicate results. Key elements in this process are (1) classifying the types of project monitoring and (2) developing consensus on the purposes, approaches, and problems associated with each type (Haberl et al. 1990; Misuriello 1987). For example, energy savings from energy service performance contracts can be specified on either a wholebuilding or component basis. Monitoring requirements for each approach vary widely and must be carefully matched to the specific project. Procedures in ASHRAE Guideline 14-2002 and the IPMVP (2007) can be used to determine monitoring requirements.

REASONS FOR ENERGY MONITORING Monitoring projects can be broadly categorized by their goals, objectives, experimental approach, level of monitoring detail, and uses (Table 1). Other factors, such as resources available, data validation and analysis procedures, duration and frequency of data collection, and instrumentation, are common to most, if not all, projects.

Energy End Use Energy end-use projects typically focus on individual energy systems in a particular market sector or building type. Monitoring usually requires separate meters or data collection channels for each end use, and analysts must account for all factors that may affect energy use. Examples of this approach include detailed utility load research efforts, evaluation of utility incentive programs, and enduse calibration of computer simulations. Depending on the project objectives, the frequency of data collection may range from onetime measurements of full-load operation to continuous time-series measurements.

Specific Technology Assessment

These activities often require support by several professional disciplines (e.g., engineering, data analysis, management) and construction trades (e.g., electricians, controls technicians, pipe fitters). Useful building energy performance data cover whole buildings, lighting, HVAC equipment, water heating, meter readings, utility The preparation of this chapter is assigned to TC 7.6, Building Energy Performance.

Specific technology assessment projects monitor field performance of particular equipment or technologies that affect building energy use, such as envelope retrofit measures, major end-use system loads or savings from retrofits (e.g., lighting), or retrofits to or performance of mechanical equipment. The typical goal of retrofit performance monitoring projects is to estimate savings resulting from the retrofit despite potentially significant variation in indoorioutdoor conditions, building characteristics, and occupant behavior unrelated to the retrofit. The frequency and complexity of data collection depend on project objectives and site-specific conditions. Projects in this category assess variations in

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41.2 Table 1

Characteristics of Major Monitoring Project Types

Project Type

Goals and Objectives

General Approach

Level of Detail

Energy end use

Determine characteristics of specific energy end uses in building.

Often uses large, statistically designed sample. Monitor energy demand or use profile of each end use of interest.

Detailed data on end uses metered. Collect building and operating data that affect end use.

Specific technology Measure field performance of assessment building system technology or retrofit measure in individual buildings. Energy savings measurement and verification

Building operation and diagnostics

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Characterize individual building or technology, occupant behavior, and operation. Account and correct for variations. Estimate the impact of retrofit, Preretrofit consumption is used commissioning, or other build- to create baseline model. Posting alteration to serve as basis retrofit consumption is meafor payments or benefits calcu- sured; the difference between lation. the two is savings. Solve problems. Measure phys- Typically uses one-time andor ical or operating parameters that short-term measurement with affect energy use or that are special methods, such as infraneeded to model building or red imaging, flue gas analysis, system performance. blower door, or coheating.

performance between different buildings or for the same building before and after the retrofit. Field tests of end-use equipment are often characterized by detailed monitoring of all critical performance parameters and operational modes. In evaluating equipment performance or energy efficiency improvements, it is preferable to measure in situ performance. Although manufacturers’ data and laboratory performance measurements can provide excellent data for sizing and selecting equipment, installed performance can vary significantly from that at design conditions. The project scope may include reliability, maintenance, design, energy efficiency, sizing, and environmental effects (Phelan et al. 1997a, 1997b).

Savings Measurement and Verification (M&V) Accountability is increasingly necessary in energy performance retrofits, whether they are performed as part of energy savings performance contracting (ESPC) or performed directly by the owner. In either case, savings measurement and verification (M&V) is an important part of the project. Because the actual energy savings cannot be measured directly, the appropriate role of energy monitoring methodology is to Ensure that appropriate data are available, including preretrofit data if retrofits are installed Accurately define baseline conditions and assumptions Confirm that proper equipment and systems were installed and have the potential to generate the predicted energy savings Take postretrofit measurements Estimate the energy savings achieved Proper assessment of an energy retrofit involves comparing before and after energy use, and adjusting for all nonretrofit changes that affected energy use. Weather and occupancy are examples of factors that often change. To assess the effectiveness of the retrofit alone, the influence of these other complicating factors must be removed as best possible. Relationships must be found between energy use and these factors to remove the influence of the factors from the energy savings measurement. These relationships are usually determined through data analysis, not textbook equations. Because data analysis can be conducted in an infinite number of ways, there can be no absolute certainty about the relationship chosen. The need for certainty must be carefully balanced with measurement and analysis costs, recognizing that absolute certainty is not achievable. Among the numerous sources of uncertainty are instrumentation or

Uses

Applications (SI)

Load forecasting by end use. Identify and confirm energy conservation or demand-side management opportunities. Simulation calculations. Rate design. Uses detailed audit, subTechnology evaluation. Retrofit metering, indoor temperature, performance. Validate models and on-site weather, and occupant predictions. surveys. May use weekly, hourly, or short-term data. Varies substantially, includFocused on specific campus, building verification of potential to ing, component, or system. provide savings, retrofit isola- Amount and frequency of data vartion, or whole-building or cal- ies widely between projects. ibrated simulation. Focused on specific building Energy audit. Identify and solve component or system. operation and maintenance, indoor Amount and frequency of data air quality, or system problems. vary widely between projects. Provide input for models. Building commissioning.

measurement error, normalization or model error, sampling error, and errors of assumptions. Each source can be minimized to varying degrees by using more sophisticated measurement equipment, analysis methods, sample sizes, and assumptions. However, more certain savings determinations generally follow the law of diminishing returns, where further increases in certainty come at progressively greater expense. Total certainty is seldom achievable, and even less frequently cost-effective (ASHRAE Guideline 14). Other resources are also available. One of the widest known is the International Performance Measurement and Verijkation Protocol (IPMVP 2007). The IPMVP is more general than ASHRAE Guideline 14 but provides important background for understanding the larger context of M&V efforts.

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Building Diagnostics Diagnostic projects measure physical and operating parameters that determine the energy use of buildings and systems. Usually, the project goal is to determine the cause of problems, model or improve energy performance of a building or system(s), or isolate effects of components. Diagnostic tests frequently involve one-time measurements or short-term monitoring. To give insight, the frequency of measurement must be several times faster than the rate of change of the effect being monitored. Some diagnostic tests require intermittent, ongoing data collection. The most basic energy diagnostic for buildings is determining rate of energy use or power for a specific period, from essentially a single point in time to a few weeks. The scope of measurement may include the whole building or only one component. The purpose can range from measurement system parameter estimation to verification of nameplate information. Daily or weekly profiles may also be of interest. A large number of diagnostic measurement procedures are used for energy measurements in residential buildings, particularly single-family. Typical measurements for single-family residences include (1) flue gas and other analysis procedures to determine steady-state furnace combustion efficiency and the efficiency of other end uses, such as air conditioners, refrigerators, and water heaters; (2) fan pressurization tests to measure and locate building envelope air leakage (ASTM Standard E779) and tests to measure airtightness of air distribution systems (Modera 1989; Robison and Lambert 1989); and (3) infrared thermography to locate thermal defects in the building envelope and other methods to determine overall building envelope parameters (Subbarao 1988).

41.3

Building Energy Monitoring Table 2

Comparison of Small Projects to Overall Methodology

Project Characteristic Small Project Approach Project problem areas

Overall Methodology Coverage

Project goals and resources are iteratively evaluated in short time. Project goals, project costs and resources, data products, data Only one to possibly a few people involved. Small group allows management, data quality control, commitment, accuracy more informal procedures and high interaction as needed. requirements, advice. Data products loosely defined. Data collection starts. Initial and ongoing analysis indicates any data management or quality control issues. Data products refined over time as needed, based on analysis. Accuracy evaluated on the fly as data are collected. Commitment is simply needing to finish the work. Advice still sought where needed.

Building and occupant characteristics

Typically, only one to few buildings included; work is reasonably local. Characteristic data collected on site, at convenience of project person(s), depending on project location. Return trips likely already needed for simplified data collection approach; supporting data can be collected on return trips.

Fairly extensive data structure (e.g., a characteristic database) and definition of levels of detail may be needed to handle possibly many buildings and improve ability to report results. With many buildings, only one trip per building may be acceptable.

Project design

Project personnel usually know what they want to measure and report, and may not want to be confused by complex approach in this chapter. Knowledge of experimental approaches may also be understood minimally but still applied successfully, without specific declaration, to small project.

Three higher-level general approaches: (1) fewer buildings or systems with more detailed measurements, (2) many buildings or systems with less detailed measurements, or (3) many buildings or systems with more detailed measurements. Six major experimental design approaches: odoff, before/after, tedreference, simulated occupancy, nonexperimental reference, engineering field test.

Reporting

Reporting is informal to somewhat formal (more like straightforward engineering project than research project). Reported results are often minimal but provide key information sought.

Research project report is likely required, possibly hundreds of pages long, with multiple appendices. Extensive databases likely generated and must be quality checked and corrected for use by others. Data user access procedures may have to be developed. Databases must be maintained over years in many cases and must be well documented. Extensive research results may have been generated and should be reported. For example, Fracastoro and Lyberg (1983) discussion of guiding principles for residential proiects is 300 pages long.

Energy systems in multifamily buildings can be much more complex than those in single-family homes, but the types of diagnostics are similar: combustion equipment diagnostics, air leakage measurements, and infrared thermography to identify thermal defects or moisture problems (DeCicco et al. 1995). Some techniques are designed to determine the operating efficiency of steam and hotwater boilers and to measure air leakage between apartments. Diagnostic techniques have been designed to measure the overall airtightness of office building envelopes and the thermal performance of walls (Armstrong et al. 2001; Persily et al. 1988; Sellers et al. 2004). Practicing engineers also use a host of monitoring techniques to aid in diagnostics and analysis of equipment energy performance. Portable data loggers are often used to collect time-synchronized distributed data, allowing multiple data sets (e.g., chiller performance and ambient conditions) to be collected and quickly analyzed. Similar short-term monitoring procedures are used to provide more detailed and complete commercial building system commissioning. Short-term, in situ tests have also been developed for pumps, fans, and chillers (Phelan et al. 1997a, 1997b). Diagnostics are also well suited to support development and implementation of building energy management programs (see Chapter 36). Long-term diagnostic measurements have even supported energy improvements (Liu et al. 1994). Diagnostic measurement projects can generally be designed using procedures adapted to specific project requirements (see the section on Steps for Project Design and Implementation). Equipment for diagnostic measurement may be installed temporarily or permanently to aid energy management efforts. Designers should consider providing permanent or portable check metering of major electrical loads in new building designs. Building automation systems also can be used to collect the data required for diagnostics. The same concept can be extended to fuel and thermal energy use.

SMALL PROJECTS Most energy metering projects are done on a small scale and will have the project steps described in this chapter simplified and compacted. This section describes briefly how to use the information in this chapter for a small project. Small projects will still be potentially impacted by the issues described here, but if only a small group of people are doing all the work, they can choose what to address and how to address the project requirements. Table 2 compares small-project approaches and the material in this chapter.

How to Use This Chapter for Small Projects Skim through the chapter and make a few notes on items that may apply for the project in question. Generate a brief project plan to make sure major issues that may cause problems are not overlooked. Generate a brief checklist from the item notes for fmal check-off during or at the end of project. Clarify what building or site characteristics data may be needed, and be sure to collect those data. Analyze data from the start, to make sure there are no quality or data issues. Consider whether any data should be made available to others at the end of the project, and if so, develop a data format for exchange. Skim through the chapter again when the report is being prepared to gather ideas about what to include in the report.

PROTOCOLS FOR PERFORMANCE MONITORING Examples of procedures (protocols) for evaluating energy savings for projects involving retrofit of existing building energy systems are

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41.4

201 1 ASHRAE Handbook-HVAC

presented here. These protocols should also be useful to those interested in more general building energy monitoring. Building monitoring has been significantly simplified and made more professional in recent years by the development of fairly standardized monitoring protocols. Although there may be no way to defme a protocol to encompass all types of monitoring applications, repeatable and understandable methods of measuring and verifying retrofit savings are needed. However, following a protocol does not replace adequate project planning and careful assessment of project objectives and constraints.

Residential Retrofit Monitoring Protocols for residential building retrofit performance can answer specific questions associated with actual measured performance. For example, Ternes (1986) developed a single-family retrofit monitoring protocol, a data specification guideline that identifies important parameters to be measured. Both one-time and timesequential data parameters are covered, and parameters are defmed carefully to ensure consistency and comparability between experiments. Discrepancies between predicted and actual performance, as measured by the energy bill, are common. This protocol improves on billing data methods in two ways: (1) internal temperature is monitored, which eliminates a major unknown variable in data interpretation; and (2) data are taken more frequently than monthly, which potentially shortens monitoring duration. Utility bill analysis generally requires a full season of pre- and post-retrofit data. The single-family retrofit protocol may require only a single season. Ternes (1986) identified both a minimum set of data, which must be collected in all field studies that use the protocol, and optional extensions to the minimum data set that can be used to study additional issues. See Table 3 for details. Szydlowski and Diamond (1989) developed a similar method for multifamily buildings. The single-family retrofit monitoring protocol recommends a beforeiafter experimental design, and the minimum data set allows performance to be measured on a normalized basis with weekly time-series data. (Some researchers recommend daily.) The protocol also allows hourly recording intervals for time-integrated parameters, an extension of the basic data requirements in the minimum data set. The minimum data set may also be extended through optional data parameter sets for users seeking more information. Data parameters in this protocol have been grouped into four data sets: basic, occupant behavior, microclimate, and distribution system (Table 3). The minimum data set consists of a weekly option of the basic data parameter set. Time-sequential measurements are monitored continuously during the field study. These are all timeintegrated parameters (i.e., appropriate average values of a parameter over the recording period, rather than instantaneous values). This protocol also addresses instrumentation installation, accuracy, and measurement frequency and expected ranges for all time-sequential parameters (Table 4). The minimum data set (weekly option of the basic data) must always be collected. At the user’s discretion, hourly data may be collected, which allows two optional parameters to be monitored. Parameters from the optional data sets may be chosen, or other data not described in the protocol added, to arrive at the final data set. This protocol standardizes experimental design and data collection specifications, enabling independent researchers to compare project results more readily. Moreover, including both minimum and optional data sets and two recording intervals accommodates projects of varying financial resources.

Commercial Retrofit Monitoring

Table 3

Applications (SI)

Data Parameters for Residential Retrofit Monitoring

z

Recording Period Minimum Optional

Basic Parameters House description Space-conditioning system description Entrance interview information Exit interview information Pre- and post-retrofit infiltration rates Metered space-conditioning system performance Retrofit installation quality verification Heating and cooling equipment energy consumption Weather station climatic information Indoor temperature House gas or oil consumption House electricity consumption Wood heating use Domestic hot water energy consumption Optional Parameters Occupant behavior Additional indoor temperatures Heating thermostat set point Cooling thermostat set point Indoor humidity Microclimate Outdoor temperature Solar radiation Outdoor humidity Wind speed Wind direction Shading Shielding Distribution system Evaluation of ductwork infiltration

Once Once Once Once Once Once Once Weekly Hourly Weekly Hourly Weekly Hourly Weekly Hourly Weekly Hourly Hourly Weekly Hourly ~

Weekly ~

~

Hourly Hourly Hourly

Weekly

~

Weekly Hourly Weekly Hourly Weekly Hourly Weekly Hourly Weekly Hourly Once Once Once

Source: Ternes (1986).

energy and demand savings from energy conservation measures in residential, commercial, or industrial buildings. These measurements can serve as the basis for commercial transactions between energy services providers and customers who rely on measured energy savings as the basis for financing payments. Three approaches are discussed whole building, retrofit isolation, and calibrated simulation. The guideline includes an extensive resource on physical measurement, uncertainty, and regression techniques. Example M&V plans are also provided. The International Performance Measurement and Verijkation Protocol (IPMVP 2007) provides guidance to buyers, sellers, and fmanciers of energy projects on quantifying energy savings performance of energy retrofits. The Federal Energy Management Program has produced guidelines specific to federal projects, which include many procedures usable for calculating retrofit savings in nonfederal buildings (FEMP 2008). On a more detailed level, ASHRAE Research Project RP-827 resulted in separate guidelines for in situ testing of chillers, fans, and pumps to evaluate installed energy efficiency (Phelan et al. 1997a, 1997b). The guidelines specify the physical characteristics to be measured; number, range, and accuracy of data points required; methods of artificial loading; and calculation equations with a rigorous uncertainty analysis. In addition to these specialized protocols for particular monitoring applications, a number of specific laboratory and field measurement standards exist (see Chapter 57), and many monitoring source books are in circulation. Finally, MacDonald et al. (1989) developed a protocol for field monitoring studies of energy improvements (retrofits) for commercial buildings. Similar to the residential protocol, it addresses data

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Several related guidelines have been created for the particular application of retrofit savings (M&V). ASHRAE Guideline 14 provides methods for effectively and reliably measuring the energy and demand savings due to building energy projects. The guideline defmes a minimum acceptable level of performance in measuring

41.5

Building Energy Monitoring

zy zyxwvutsrqpon Table 4

Time-Sequential Parameters for Residential Retrofit Monitoring

Scan Rateb

Data Parameter

Accuracya

Basic Parameters Heatindcooling equipment energy consumption Indoor temperature House gas or oil consumption House electricity consumption Wood heating use Domestic hot water Optional Data Parameter Sets Occupant behavior Additional indoor temperatures Heating thermostat set point Cooling thermostat set point Indoor humidity Microclimate Outdoor temperature Solar radiation Outdoor humidity Wind speed Wind direction Source: Temes (1986).

3% 0.5 K 3% 3% 0.5 K 3%

Range

10 to 35°C

10 to 450°C

Total consumption Average temperature Total consumption Total consumption Average surface temperature or total use time Total consumption

15s lh 15s 15s 15s

0.5 K 0.5 K 0.5 K 5% rh

10 to 35°C 10 to 35°C 10 to 35°C 10 to 95% rh

Average temperature Average set point Average set point Average humidity

lh

0.5 K 30 W/m2 5% rh 0.2 d s 5"

4 0 to 50°C 0 to 1100 W/m2 10 to 95% rh 0 to 10 m/s 0 to 360"

Average temperature Total horizontal radiation Average humidity Average speed Average direction

lh 1 min lh 1 min 1 min

aAll accuracies are stated values.

Table 5

Option 1 Option 2

Stored Value per Recording Period

15s 1 min 15s 15s 1 min 15s

1 min 1 min 1 min

lh 1 min 1 min 1 min 1 min 1 min

bApplicable scan rates ifnonintegrating instrumentation is used.

Performance Data Requirements of Commercial Retrofit Protocol Projects with Submetering

Utility billing data (for each fuel) Submetered data (for all recording intervals)

Before Retrofit 12 month minimum

After Retrofit 3 month minimum (12 months if weather normalization required) All data for each major end All data for each major end use, up to use, up to 12 months 12 months

Temperature data (daily maximum and minimum must be provided for any periods without integrated averages)

Type Maximum and minimum +rIntegrated averages

Recording Interval Daily +rSame as for submetered data but not longer than daily

Period Length Same as billing data length +rLength of submetering

Projects Without Submetering Utility billing data (for each fuel) Temperature data

Before Retrofit 12 month minimum Type

After Retrofit 12 month minimum Recording Interval

Period Length

Maximum and minimum +rIntegrated averages

Daily

Same as billing data length

requirements for monitoring studies. Commercial buildings are more complex, with a diverse array of potential efficiency improvements. Consequently, the approach to specifying measurement procedures, describing buildings, and determining the range of analysis must differ. The strategy used for this protocol is to specify data requirements, analysis, performance data with optional extensions, and a building core data set that describes the field performance of efficiency improvements. This protocol requires a description of the approach used for analyzing building energy performance. The necessary performance data, including identification of a minimum data set, are outlined in Table 5.

Commercial New Construction Monitoring New building construction offers the potential for monitoring building subsystem energy consumption at a reasonable cost. Information obtained by monitoring operating hours or direct energy consumption can benefit building owners and managers by Verifying design intent Alerting them to inefficient or improper operation of equipment

Providing data that can be useful in determining benefits of alternative operating strategies or replacement equipment Evaluating costs of operation for extending occupancy hours for special conditions or event Demonstrating effects of poor maintenance or identifying when maintenance procedures are not followed Diagnosing and fixing comfort and other space condition problems Diagnosing power quality problems Submetering tenants Verifyingiimproving savings of a performance contract Maintaining persistence of energy savings To provide data necessary to improve building systems operation, monitoring should be considered for boilers, chillers, cooling towers, heat pumps, air-handling unit fans, large fan-coil units, major exhaust fans, major pumps, comfort cooling compressors, lighting panels, electric heaters, receptacle panels, substations, motor control centers, major feeders, service water heaters, process loads, and computer rooms. Guidance on energy monitoring to determine energy savings for new construction design modifications is available in IPMVP (2006).

201 1 ASHRAE Handbook-HVAC

41.6 Construction documents may include provisions for various meters to monitor equipment and system operation. Some equipment can be specified to have factory-installed hour meters that record actual operating hours of the equipment. Hour meters can also be easily field-installed on any electrical motor. More sophisticated power-monitoring systems, with electrical switchgear, substations, switchboards, and motor control centers, can be specified. These systems can monitor energy demand, energy consumption, power factor, neutral current, etc., and can be linked to a computer. These same systems can be installed on circuits to existing or retrofit fans, chillers, lighting panels, etc. Some equipment commonly used for improving system efficiency, such as variablefrequency drives, can be provided with capability to monitor kilowatt output, kilowatt-hours consumed, and other variables. Using direct digital control (DDC) or building automation systems for monitoring is particularly appropriate in new construction. These systems can monitor, calculate, and record system status, water use, energy use at the main meter or of particular end-use systems, demand, and hours of operation, as well as start and stop building systems, control lighting, and print alarms when systems do not operate within specified limits. Initial specification of the new control system should include specific requirements for sensors, calculations, and trend logging and reporting functions. Special issues related to sensors and monitoring approaches can be found in Piette et al. (2000).

COMMON MONITORING ISSUES Field monitoring projects require effective management of various professional skills. Project staff must understand the building systems being examined, quality control of data, data management, data acquisition, and sensor technology. In addition to data collection, processing, and analysis, the logistics of field monitoring projects require coordinating equipment procurement, delivery, and installation. Key issues include the accuracy and reliability of collected data. Projects have been compromised by inaccurate or missing data, which could have been avoided by periodic sensor calibration and ongoing data verification.

P1anning Many common problems in monitoring projects can be avoided by effective and comprehensive planning. Project Goals. Project goals and data requirements should be established before hardware is selected. Unfortunately, projects are often driven by hardware selection rather than by project objectives, either because monitoring hardware must be ordered several months before data collection begins or because project initiation procedures are lacking. As aresult, the hardware may be inappropriate for the particular monitoring task, or critical data points may be overlooked. Project Costs and Resources. After goal setting, the feasibility of the anticipated project should be reviewed in light of available resources. Projects to which significant resources can be devoted usually involve different approaches from those with more limited resources. This issue should be addressed early on and reviewed throughout the course of the project. Although it is difficult at this early stage to assess with certainty the cost of an anticipated project, rough estimates can be quite helpful. Data Products. It is important to establish the type and format of the fmal results calculated from data before selecting data points. Failure to plan these data products frst may lead to failure to answer critical questions. Data Management. Failure to anticipate the typically large amounts of data collected can lead to major difficulties. The computer and personnel resources needed to verify, retrieve, analyze,

Applications (SI)

and archive data can be estimated based on experience with previous projects. Data Quality Control. It is also important to check and validate the quality and reasonableness of data before use. Failure to use some type of quality control typically results in data errors and invalid results. Commitment. Many projects require long-term commitment of personnel and resources. Project success depends on long-term, daily attention to detail and on staff continuity. Accuracy Requirements. The required accuracy of data products and accuracy of the final data and experimental design needed to meet these requirements should be determined early on. After the required accuracy is specified, the sample size (number of buildings, control buildings, or pieces of equipment) must be chosen, and the required measurement precision (including error propagation into final data products) must be determined. Because tradeoffs must usually be made between cost and accuracy, this process is often iterative. It is further complicated by a large number of independent variables (e.g., occupants, operating modes) and the stochastic nature of many variables (e.g., weather). Advice. Expert advice should be sought from others who have experience with the type of monitoring envisioned.

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Implementation and Data Management The following steps can facilitate smooth project implementation and data management:

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Calibrate sensors before installation. Spot-check calibration on site. During long-term monitoring projects, recalibrate sensors periodically. Appropriate procedures and standards should be used in all calibration procedures [see ASHRAE Guideline 14 and IPMVP (2007)l. Track sensor performance regularly. Quick detection of sensor failure or calibration problems is essential. Ideally, this should be an automated or a daily task. The value of data is high because they may be difficult or impossible to reconstruct. Generate and review data on a timely, periodic basis. Problems that often occur in developing fmal data products include missing data from failed sensors, data points not installed because of planning oversights, and anomalous data for which there are no explanatory records. If data products are specified as part of general project planning and produced periodically, production problems can be identified and resolved as they occur. Automating the process of checking data reliability and accuracy can be invaluable in keeping the project on track and in preventing sensor failure and data loss.

Data Analysis and Reporting For most projects, the collected data must be analyzed and put into reports. Because the objective of the project is to translate these data into information and ultimately into knowledge and action, the importance of this step cannot be overemphasized. Clear, convenient, and informative formats should be devised in the planning stages and adhered to throughout the project. Close attention must be paid to resource allocation to ensure that adequate resources are dedicated to verification, management, and analysis of data and to ongoing maintenance of monitoring equipment. As a quality control procedure and to make data analysis more manageable, these activities should be ongoing. Data analysis should be carefully defined before the project begins.

STEPS FOR PROJECT DESIGN AND IMPLEMENTATION This section describes methodology for designing effective field monitoring projects that meet desired goals with available project resources. The task components and relationships among the nine activities constituting this methodology are identified in Figure 1.

41.7

Building Energy Monitoring

needed for different project objectives. Scheduling requirements must also be considered, and any project constraints defmed and considered. Tradeoffs on budget and objectives require that priorities be established. Even if a project is not research-oriented, it is attempting to obtain information, which can be stated in the form of questions. Research questions can have varying scopes and levels of detail, addressing entire systems or specific components. Some examples of research questions follow: Measurement and verification: Have contractors fulfilled their responsibilities of installing equipment and improving systems to achieve the agreed-upon energy savings? Classes of buildings: To an accuracy of 20%, how much energy has been saved by using a building constructiodperformance standard mandated in the jurisdiction? Particular buildings: Has a lapse in building maintenance caused energy performance to degrade? Particular components: What is the average reduction in demand charges during summer peak periods because of the installation of an ice storage system in this building?

Fig. 1 Methodology for Designing Field Monitoring Projects

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The activities fall into four categories: project management, project development, resolution and feedback, and production quality and data transfer. Field monitoring projects vary in terms of resources, goals and objectives, data product requirements, and other variables, affecting how methodology should be applied. Nonetheless, the methodology provides a proper framework for advance planning, which helps minimize or prevent implementation problems. An iterative approach to planning activities is best. The scope, accuracy, and techniques can be adjusted based on cost estimates and resource assessments. The initial design should be performed simply and quickly to estimate cost and evaluate resources. If costs are out of line with resources, such as when desired levels of instrumentation exceed the resources available for the project, adjustments are needed. Planning should identify and resolve any tradeoffs necessary to execute the project within a given budget. Examples include reducing the scope of the project versus relaxing instrumentation specifications or accuracy requirements. These decisions often depend on what questions the project must answer and which questions can be eliminated, simplified, or narrowed. One frequent oversight in project planning is failing to reserve sufficient time and resources for later analysis and reporting of data. Unanticipated additional costs associated with data collection and problem resolution should not jeopardize these resources. Documenting the results of project planning should cover all nine parts of the process. This report can be a useful part of an overall project plan that may document other important project information, such as resources to be used, schedule, etc.

Part One: Identify Project Objectives, Resources, and Constraints Start with a clear understanding of the decision to be made or action to be taken as a result of the project. The goals and objectives statement determines the overall direction and scope of the data collection and analysis effort. The statement should also list questions to be answered by empirical data, noting the error or uncertainty associated with the desired result. Realistic assessment of error is needed because requiring too small an uncertainty leads to an overly complex and expensive project. It is important in monitoring projects that a data acquisition plan be developed and followed with a clear idea of the research questions to be answered. Resource requirements for equipment, personnel, and other items must feed into budget estimates to determine expected funding

Research questions vary widely in technical complexity, generally taking one of the following three forms:

How does the buildingicomponent perform? Why does the buildingicomponent perform as it does? Which buildingicomponent should be targeted to achieve optimal cost-effectiveness?

The frst form of question can sometimes be answered generically for a class of typical buildings without detailed monitoring and analysis, although detailed planning and thorough analysis are still required. The second and third forms usually require detailed monitoring and analysis and, thus, detailed planning. In general, more detailed and precise goal statements are better. They ensure that the project is constrained in scope and developed to meet specific accuracy and reliability requirements. Usually, projects attempt to answer more than one research question, and often consider both primary and secondary questions. All data collected should have a purpose of helping to answer a project question; the more specific the questions, the easier identifying required data becomes.

Part Two: Specify Building and Occupant Characteristics Measured energy data will not be meaningful later to people who were not involved in the project unless the characteristics of the building being monitored and its use have been documented. To meet this need, a data structure (e.g., a characteristic database) can be developed to describe the buildings. Building characteristics can be collected at many levels of detail, depending on the type of monitoring project and the parameters that affect results. For projects that determine whole-building performance, it is important to provide at least enough detail to document the following: General building type, use, configuration, and envelope (particularly energy-related aspects) Building occupant information (number, occupancy schedule, activities) Internal loads HVAC system descriptive information characterizing key parameters affecting HVAC system performance Type and quantity of other energy-using systems Any building changes that occur during the monitoring project Entrance interview information focusing on energy-related behavior of building occupants before monitoring

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201 1 ASHRAE Handbook-HVAC

41.8 Exit interview information documenting physical or lifestyle changes at the test site that may affect data analysis The minimum level of detail is known as summary characteristics data. Simulation-level characteristics (detailed information collected for hourly simulation model input) may be desirable for some buildings. Regardless of the level of detail, the data should provide a context for analysts, who may not be familiar with the project, to understand the building and its energy use.

Part Three: Specify Data Products and Project Output The objective of a monitoring project is typically not to produce data, but to answer a question. However, the data must be of high quality and must be presented to key decision makers and analysts in a convenient, informative format. The specific data products (format and content of data needed to meet project goals and objectives) must be identified and evaluated for feasibility and usefulness in answering project questions identified in Part One. Final data products must be clearly specified, together with the minimum acceptable data requirements for the project. It is important to clearly defme an analysis path showing what will be calculated and what data are necessary to achieve desired results. Clear communication is critical to ensure that project requirements are satisfied and factors contributing to monitoring costs are understood. Evaluation results can be presented in many forms, often as interim and fmal reports (possibly by heating andor cooling season), technical notes, or technical papers. These documents must convey specific results of the field monitoring clearly and concisely. They should also contain estimates of the accuracy of the results. The composition of data presentations and analysis summaries should be determined early to ensure that all critical parameters are identified (Hough et al. 1987). For instance, mock-ups of data tables, charts, and graphs can be used to identify requirements. Previously reported results can be used to provide examples of useful output. Data products should also be prioritized to accommodate possible cost tradeoffs or revisions resulting from other steps in the process such as error analysis (see Part Seven). Although requirements for the minimum acceptable data results can often be specified during planning, data analysis typically reveals further requirements. Thus, budget plans should include allowances and optional data product specifications to handle additional or unique project output requirements uncovered during data analysis. Longer-term goals and future information needs should be anticipated and explained to project personnel. For example, a project may have short- and long-term data needs (e.g., demonstrating reductions in peak electrical demand versus demonstrating costeffectiveness or reliability to a target audience). Initial results on demand reduction may not be the ultimate goal, but rather a step toward later presentations on cost reductions achieved. Thus, it is prudent to consider long-term and potential future data needs so that additional supporting information, such as photographs or testimonials, may be identified and obtained.

Part Four: Specify Monitoring Design Approach A general monitoring design must be developed that defines three interacting factors: the number of buildings in the study, the monitoring approach (or experimental design), and the level of detail in the data being measured. A less detailed or precise approach can be considered if the number of buildings is increased, and vice versa. If the goal is related to a specific product, the monitoring design must isolate the effects of that product. Haberl et al. (1990) discuss monitoring designs. For example, for retrofit M&V, protocols have been written allowing a range of different monitoring methods, from retrofit verification to retrofit isolation (ASHRAE Guideline 14; FEMP 2008; IPMVP 2007). Some monitoring approaches are more suited than others to larger numbers of buildings.

Applications (SI)

Specifying the monitoring design approach is particularly important because total building performance is a complex function of several variables, changes in which are difficult to monitor and to translate into performance. Unless care is taken with measurement organization and accuracy, uncertainties, errors (noise), and other variations, such as weather, can make it difficult to detect performance changes of less than 20% (Fracastoro and Lyberg 1983). In some cases, judgment may be required in selecting the number of buildings involved in the project. If an owner seeks information about a particular building, the choice is simple: the number of buildings in the experiment is fixed at one. However, for other monitoring applications, such as drawing conclusions about effects in a sample population of buildings, some choice is involved. Generally, error in the derived conclusions decreases as the square root of the number of buildings increases (Box 1978). A specific project may be directed at Fewer buildings or systems with more detailed measurements Many buildings or systems with less detailed measurements Many buildings or systems with more detailed measurements For projects of the frst type, accuracy requirements are usually resolved initially by determining expected variations of measured quantities (dependent variables) about their average values in response to expected variations of independent variables. For buildings, a typical concern is the response of heating and cooling loads to changes in temperature or other weather variables. The response of building lighting energy use to daylighting is another example of the relationship between dependent and independent variables. Fluctuations in response are caused by (1) outside influences not quantified by measured energy use data and (2) limitations and uncertainties associated with measurement equipment and procedures. Thus, accuracy must often be determined using statistical methods to describe mean tendencies of dependent variables. For projects of the second and third types, the increased number of buildings improves confidence in the mean tendencies of the dependent response(s) of interest. Larger sample sizes are also needed for experimental designs with control groups, which are used to adjust for some outside influences. For more information, see Box (1978), Fracastoro and Lyberg (1983), and Hirst and Reed (1991). Projects can also use more complex, multilevel measurement and modeling approaches to handle an array of technologies or help improve confidence in results (Hughes and Shonder 1998). Most monitoring procedures use one or more of the following general experimental approaches:

Before/After. Building, system, or component energy consumption is monitored before and after a new component or retrofit improvement is installed. Changes in factors not related to the retrofit, such as the weather and building operation during the two periods, must be accounted for, often requiring a model-based analysis (Fels 1986; Hirst et al. 1983; Kissock et al. 1992; Robison and Lambert 1989; Sharp and MacDonald 1990). This experimental design is the primary concern of most current building energy monitoring documents (ASHRAE Guideline 14; FEMP 2008; IPMVP 2002). TedReference. The building energy consumption data of two “identical” buildings, one with the product or retrofit being investigated, are compared. Because buildings cannot be absolutely identical (e.g., different air leakage distributions, insulation effectiveness, temperature settings, and solar exposure), measurements should be taken before installation as well, to allow calibration. Once the product or retrofit is installed, any deviation from the calibration relationship can be attributed to the product or retrofit (Fracastoro and Lyberg 1983; Levins and Karnitz 1986). On/Off. If the retrofit or product can be activated or deactivated at will, energy consumption can be measured in a number of repeated odoff cycles. On-period consumption is then compared to off-period consumption (Cohen et al. 1987; Woller 1989).

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CHAPTER 42

SUPERVISORY CONTROL STRATEGIES AND OPTIMIZATION OPTIMIZATION METHODS Static Optimization ................................................................... 42.4 Dynamic Optimization ............................................................. 42.7 Applications of Static Optimization ......................................... 42.9 Applications of Dynamic Optimization .................................. 42.1 5 SUPERVISORY CONTROL STRATEGIESAND TOOLS ..... 42.21 Cooling Tower Fan Control................................................... 42.21

C

OMPUTERIZED energy management and control systems provide an excellent means of reducing utility costs associated with maintaining environmental conditions in commercial buildings. These systems can incorporate advanced control strategies that respond to changing weather, building conditions, and utility rates to minimize operating costs. HVAC systems are typically controlled using a two-level control structure. Lower-level local-loop control of a single set point is provided by an actuator. For example, the supply air temperature from a cooling coil is controlled by adjusting the opening of a valve that provides chilled water to the coil. The upper control level, supervisory control, specifies set points and other time-dependent modes of operation. The performance of large, commercial HVAC systems can be improved through better local-loop and supervisory control. Proper tuning of local-loop controllers can enhance comfort, reduce energy use, and increase component life. Set points and operating modes for cooling plant equipment can be adjusted by the supervisor to maximize overall operating efficiency. Dynamic control strategies for ice or chilled-water storage systems can significantly reduce onpeak electrical energy and demand costs to minimize total utility costs. Similarly, thermal storage inherent in a building’s structure can be dynamically controlled to minimize utility costs. In general, strategies that take advantage of thermal storage work best when forecasts of future energy requirements are available. This chapter focuses on the opportunities and control strategies associated with using computerized control for centralized cooling and heating systems. The chapter is divided into three major sections: (1) background information on the effects of and opportunities for adjusting control variables, terminology, and descriptions of the systems and control variables considered in this chapter; (2) basic optimization methods used throughout in the application sections of the chapter (intended for researchers and developers of advanced control strategies); and (3) applications of both static and dynamic optimization methods (e.g., cooling plants with and without storage) as well as supervisory control strategies that can be implemented in computerized control systems, intended for practitioners.

TERMINOLOGY ~

~~

Air distribution system: includes terminal units [variable-air(vAv) boxes, etc.13 air-handing units ducts, and controls. In each AHU, ventilation air is mixed with return air from the zones and fed to the coolingiheating coil. The preparation of this chapter is assigned to TC 7.5, Smart Building Systems.

Chilled-Water Reset with Fixed-Speed Pumping Chilled-Water Reset with Variable-Speed Sequencing and Loading Multiple Chillers Strategies for Boilers .............................................................. 42.34 Strategies for Air-Handling Units .......................................... 42.35 Strategies for Building Zone Temperature Set Points ............ 42.36 Control ofDiscrete Cool Thermal Storage ............................ 42.38 Forecasting Diurnal Demand ProjZes ................................... 42.40 Predictive Control Strategies ................................................. 42.42

Air-side economizer control: used to select between minimum and maximum ventilation air, depending on the condition of the outdoor air relative to the conditions of the return air. Under certain outdoor air conditions, AHU dampers may be modulated to provide a mixed air condition that can satisfy the cooling load without the need for mechanical cooling. Building thermal mass storage: storing energy in the form of sensible heat in building materials, interior equipment, and furnishings. CAV systems: air-handling systems that have fixed-speed fans and provide no feedback control of airflow to the zones. Zone temperature is controlled to a set point using a feedback controller that regulates the amount of local reheat applied to the air entering each zone. Charging: storing cooling capacity by removing heat from a cool storage device; or storing heating capacity by adding heat to a heat storage device. Chilled-hot-waterkteam loop: consists of pumps, pipes, valves, and controls. Two different types of pumping systems are considered in this chapter: primary and primarylsecondaxy. With a primary pumping system, a single piping loop is used and water that flows through the chiller or boiler also flows through the cooling or heating coils. When steam is used, a steam piping loop sends steam to a hot-water converter, returning hot condensate back to the boiler. Another piping loop then carries hot water through the heating coils. Often, fixed-speed pumps are used with their control dedicated to chiller or boiler control. Dedicated control means that each pump is cycled on and off with the chiller or boiler that it serves. Systems with fixed-speed pumps and two-way cooling or heating coil valves often incorporate a water bypass valve to maintain relatively constant flow rates and reduce system pressure drop and pumping costs at low loads. The valve is typically controlled to maintain a fixed pressure difference between the main supply and return lines. This set point is termed the chilled- or hot-water loop differential pressure. Sometimes, primary systems use one or more variablespeed pumps to further reduce pumping costs at low loads. In this case, water bypass is not used and pumps are controlled directly to maintain a water loop differential pressure set point. Chiller or boiler plant: one or more chillers or boilers, typically ._ . arranged in parallel-with dedicated pumps, provide the primary source of cooling or heating for the system. Individual feedback controllers adjust the capacity &iller or boiler to maintain a specified supply water temperature (or header pressure for steam boilers). Additional control variables include the number of chillers or boilers operating and the relative loading for each. For a given total cooling or heating requirement, individual chiller or boiler loads can be controlled by using different water supply set

42.1

42.2 points for constant individual flow or by adjusting individual flows for identical set points. Chiller priority: control strategy for partial storage systems that uses the chiller to directly meet as much of the load as possible, normally by operating at full capacity most of the time. Thermal storage is used to supplement chiller operation only when the load exceeds the chiller capacity. Condenser water loop: consists of cooling towers, pumps, piping, and controls. Cooling towers reject heat to the environment through heat transfer and possibly evaporation (for wet towers) to the ambient air. Typically, large towers incorporate multiple cells sharing a common sump, with individual fans having two or more speed settings. Often, a feedback controller adjusts tower fan speeds to maintain a temperature set point for water leaving the cooling tower, termed the condenser water supply temperature. Typically, condenser water pumps are dedicated to individual chillers (i.e., each pump is cycled on and off with the chiller it serves). Demand limiting: a partial storage operating strategy that limits the capacity of the cooling system during the on-peak period. The cooling system capacity may be limited based on its cooling capacity, its electric demand, or the facility demand. Discharge capacity: maximum rate at which cooling can be supplied from a cool storage device. Discharging: using stored cooling capacity by adding thermal energy to a cool storage device or removing thermal energy from a heat storage device. Ice storage: types of ice storage systems include the following. An ice harvester is a machine that cyclically forms a layer of ice on a smooth cooling surface, utilizing the refrigerant inside the heat exchanger, then delivers it to a storage container by heating the surface of the cooling plate, normally by reversing the refrigeration process and delivering hot gases inside the heat exchanger. In iceon-coil-external melt, tubes or pipes (coil) are immersed in water and ice is formed on the outside of the tubes or pipes by circulating colder secondary medium or refrigerant inside the tubing or pipes, and is melted externally by circulation the unfrozen water outside the tubes or pipes to the load. Ice-on-coil-internal melt is similar, except the ice is melted internally by circulating the same secondary coolant or refrigerant to the load. Load leveling: a partial storage sizing strategy that minimizes storage equipment size and storage capacity. The system operates with the refrigeration equipment running at full capacity for 24 h to meet the normal cooling minimum load profile and, when the load is less than the chiller output, the excess cooling is stored. When the load exceeds the chiller capacity, the additional cooling requirement is obtained from the thermal storage system. Load profile: compilation of instantaneous thermal loads over a period of time, normally 24 hours. Nominal chiller capacity: (1) chiller capacity at standard ARI (Standard 5501590) rating conditions, or (2) chiller capacity at a given operating condition selected for the purpose of quick chiller sizing selections. Partial storage: a cool storage sizing strategy in which only a portion of the on-peak cooling load is met from thermal storage, with the remainder of the load being met by operating the chilling equipment. Precooling: a thermal energy storage (TES) strategy that allows a properly designed chiller system to operate more efficiently with lower condensing temperatures (low night ambient temperature) higher evaporating temperatures (15 to 20°C chilled water) and at or near its most efficient part-load point. Precooling can be applied to the conditioned space, or directly to mass by passing chilled air or water through building elements such as concrete floor decks. Primary/secondary chilled- or hot-water systems: systems designed specifically for variable-speed pumping. In the primary loop, fixed-speed pumps provide a relatively constant flow of water to the chillers or boilers. This design ensures good chiller or boiler

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Applications (SI)

performance and, for chilled-water systems, reduces the risk of freezing on evaporator tubes. The secondary loop incorporates one or more variable-speed pumps that are controlled to maintain a water loop differential pressure set point. The primary and secondary loops may be separated by a heat exchanger. However, it is more common to use direct coupling with a common pipe. Storage capacity: the maximum amount of cooling (or heating) that can be achieved by the stored medium in the thermal storage device. Nominal storage capacity is a theoretical capacity of the thermal storage device. In many cases, this may be greater than the usable storage capacity. This measure should not be used to compare usable capacities of alternative storage systems. Storage cycle: a period (usually one day) in which a substantial charge and discharge of a thermal storage device has occurred, beginning and ending at the same state or same time of day. Storage efficiency: the ratio of useful heating or cooling extracted during the discharge cycle to that imparted to storage during the charging cycle. One may also define an exergic efficiency that accounts for mixing and thermal destratification as well as conduction losses. Storage inventory: the amount of usable heating or cooling capacity remaining in a thermal storage device. Storage priority: a control strategy that uses stored cooling to meet as much of the load as possible. Chillers are operated only if the load exceeds the storage system’s available cooling capacity. Supply air temperature: temperature of air leaving an AHU or package unit. The temperature supplied to the zones may differ from the supply air temperature due to heat transfer in the ductwork and local reheat. A local-loop controller adjusts the flow of water through the air handler coolingiheating coil using a two- or threeway valve to maintain a specified set-point temperature for the air downstream of the coolingiheating coil. The value of the supply air temperature set-point will affect energy consumption and can be adjusted by the supervisory control system. System COP: ratio of cooling rate (kWthemal)to system input power (kWelectric)required to operate all distribution fans and pumps as well as compressors and condenser or cooling tower fans and pumps. Temperature set point: zone temperature set points are typically fixed values within the comfort zone during the occupied time, and zone humidity is allowed to “float” within a range dictated by the system design and choice of the supply air set-point temperature. Night setup is often used in summer to raise the zone temperature set points during unoccupied times and reduce the cooling requirements. Similarly, night setback is often used in winter to lower the zone temperature set points during unoccupied times and reduce the heating requirements. Setup and setbacks can also be used during occupied periods to temporarily curtail energy consumption. Thermal energy storage (TES): thermal energy storage systems are ofthree general types. Discrete (or active) TES uses atank of water (usually stratified), packed bed of rock or phase-change material, or a tank of ice and water with immersed coil. Intrinsic (or passive) TES uses the thermal capacitance of the building fabric, such as concrete columns, beams and decks, or wall board, possibly augmented by phase-change material. Thermally active building systems (TABS) cool floors or other elements directly with embedded pipes or ducts, giving storage capacity and efficiency substantially greater than can achieved by passive TES. System capacity: maximum amount of cooling that can be supplied by the entire cooling system, which may include the chillers and the thermal storage. Usable storage capacity is the total amount of beneficial cooling able to be discharged from a thermal storage device. (This may be less than the nominal storage capacity, because the distribution header piping may not allow discharging the entire cooling capacity of the thermal storage device.)

z

zyxwvuts

zyxwvutsrqp

Supervisory Control Strategies and Optimization

Total cooling load: The integrated thermal load that must be met by the cooling plant over a given period of time. VAV systems have a feedback controller that regulates the airflow to each zone to maintain zone temperature set point. The zone airflows are regulated using dampers located in VAV boxes in each zone. VAV systems also incorporate feedback control ofthe primary airflow through various means of fan capacity control. Typically, inputs to a fan outlet damper, inlet vanes, blade pitch, or variable speed motor are adjusted to maintain a duct static pressure set point in the supply duct, as described in Chapter 47.

CONTROL VARIABLES Systems and Controls Figures 1 and 2 show schematics of typical centralized cooling and heating systems for which control strategies are presented in this chapter. For cooling systems, the strategies generally assume that the equipment is electrically driven and that heat is rejected to the environment by cooling towers. For heating systems, boilers may be fired by a variety of fuels or powered by electricity, but are typically f r e d from either natural gas or #2 or #6 fuel oil. However, some strategies apply to any type of system (e.g., return from night setup or setback). For describing different systems and controls, it is useful to divide the system into the subsystems depicted in Figures 1 and 2: air distribution system, chilled-/hot-water loop, chiller/ boiler plant, condenser water loop. A variant of the chilled-water system shown in Figure 1 uses chilled water directly for sensible cooling by radiant panels, chilled beams, or radiant floors. Control of a VAV cooling system (Figure 1) responds to changes in building cooling requirements. As the cooling load increases, the zone temperature rises as energy gains to the zone air increase. The zone controller responds to higher temperatures by increasing local

Fig. 1 Schematic of Chilled-Water Cooling System

Fig. 2

Schematic of Hot-Water Heating System

42.3

flow of cool air by opening a damper. Opening a damper reduces static pressure in the primary supply duct, which causes the fan controller to create additional airflow. With greater airflow, the supply air temperature of the cooling coils increases, which causes the air handler feedback controller to increase the water flow by opening the cooling coil valves. This increases the chilled-water flow and heat transfer to the chilled water (i.e., the cooling load). Control of a radiant cooling system (a variant of Figure 1) responds directly to zone load by increasing the chilled-water flow rate. The chilled-water temperature may be controlled by the neediest zone or by an open-loop control. Control of a hot-water heating system (Figure 2) is similar. As the heating load increases, the zone temperature falls as energy gains to the zone air decrease. The zone controller responds to lower temperatures by opening a control valve and increasing the flow of hot water through the local reheat coil. The supply airflow rate is usually maintained at its minimum value when a VAV system is in heating mode. Increasing water flow through the reheat coils reduces the temperature of the water returned to the boiler. With lower return water temperature, the supply water temperature drops, which causes the feedback controller to increase the boiler firing rate to maintain the desired supply water temperature. For both heating and cooling, an increase in the building load results in an increase in water flow rate, which is ultimately propagated through the central system. For fixed-speed chilled- or hot-water pumps, the differential pressure controller closes the chilled- or hot-water bypass valve and keeps the overall flow relatively constant. For variable-speed pumping, the differential pressure controller increases pump speed. In a chilled-water system, the return water temperature andor flow rate to the chillers increases, leading to an increase in the chilled-water supply temperature. The chiller controller responds by increasing the chiller cooling capacity to maintain the chilled-water supply set point (and match the cooling coil loads). The increased energy removed by the chiller increases the heat rejected to the condenser water loop, which increases the temperature of water leaving the condenser. The increased water temperature entering the cooling tower increases the water temperature leaving the tower. The tower controller responds to the higher condenser water supply temperature and increases the tower airflow. At some load, the current set of operating chillers is not sufficient to meet the load (i.e., maintain the chilled-water supply set points) and an additional chiller is brought online. For a hotwater system, the return water temperature andor flow rate to the boilers decreases, leading to a decrease in the hot-water supply temperature. The boiler controller responds by increasing the boiler heating capacity to maintain the hot-water supply set point (and match the heating coil loads). For all-electric cooling without thermal storage, minimizing power at eachpoint in time is equivalent to minimizing energy costs. Therefore, supervisory control variables should be chosen to maximize the coefficient of performance (COP) of the system at all times while meeting the building load requirements. The COP is defined as the ratio of total cooling load to total system power consumption. In addition to the control variables, the COP depends primarily on the cooling load and the ambient wet- and dry-bulb temperatures. Often, the cooling load is expressed in a dimensionless form as a part-load ratio (PLR), which is the cooling load under a given condition divided by the design cooling capacity. For cooling or heating systems with thermal storage, performance depends on the time history of charging and discharging. In this case, controls should minimize operating costs integrated over the billing period or storage cycle. In addition, safety features that minimize the risk of prematurely depleting storage capacity may be important. For any of these scenarios, several local-loop controllers respond to load change to maintain specified set points. A supervisory controller establishes modes of operation and chooses (or resets) values

42.4

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of set points. At any given time, cooling or heating needs can be met with various combinations of modes of operation and set points. This chapter discusses several methods for determining supervisory control variables that provide good overall performance.

z

Sampling Intervals for Reset Controls Proper sampling intervals are required when resetting the set point for proportional-integral (PI) feedback control loops to prevent oscillation of the process variable in those loops. In general, the sampling time interval between reset commands should be greater than the settling time for the loop. For example, resetting both the chilled-water supply temperature set point and cooling coil discharge air temperature set point is necessary for optimal control. In this case, resetting the set points for chilled-water supply temperature and cooling coil discharge air temperature should not occur simultaneously, but at staggered intervals; the interval of reset for either loop should be greater than the settling time for the coil (the time for the discharge air temperature of the coil to reach a new steady-state temperature). For cascaded loops, the sampling interval between reset commands should be greater than the settling time for the slower loop. An example of a cascaded loop is a VAV box controller with its flow set point determined from the space temperature of its associated zone, and the box damper controlled to maintain the flow set point. For example, in resetting static pressure set point on a variablespeed air-handler fan based on VAV box damper position, the interval between resets should be greater than the settling time of the flow controlloop inapressure-independent VAVbox. (Settling time in this example is the time for the flow rate to reach a new steadystate value.)

OPTIMIZATION METHODS

Fig. 3

Schematic of Modular Optimization Problem

with respect to M and u, subject to equality constraints of the form

and inequality constraints of the form

STATIC OPTIMIZATION Optimal supervisory control of cooling equipment involves determining the control that minimizes the total operating cost. For an all-electric system without significant storage, cost optimization leads to minimization ofpower at each instant in time. Optimal control depends on time, albeit indirectly through changing cooling requirements and ambient conditions. Static optimization techniques applied to a general simulation can be used to determine optimal supervisory control variables. The simulation may be based on physical (Hiller and Glicksman 1977; Stoecker 1980) or empirical models. However, for control variable optimization, empirical and semiempirical models (where the model parameters are estimated from measurements) are often used. This section presents a framework for determining optimal control and a simplified approach for estimating control laws for cooling plants.

General Static OptimizationProblem

zyxw

zyx zyxwvut 20

(3)

where, for any component i,

zyxw zyxw

x, = vector of input stream variables y, = vector of output stream variables f, = vector of uncontrolled variables M, = vector of discrete control variables u, = vector of continuous control variables J, = operating cost g, = vector of equality constraints h, = vector of inequality constraints

zyx zyxwvuts

Figure 3 depicts the general nature of the static optimization problem for a system of interconnected components. Each component in a system is represented as a separate set of mathematical relationships organized into a computer model. Its output variables and operating cost are functions of parameter, input, output, uncontrolled, and controlledvariables. The structure ofthe complete set of equations to be solved for the entire system is dictated by the manner in which the components are interconnected. The problem is formally stated as the minimization of the sum of the operating costs of each component J,with respect to all discrete and continuous controls, or Minimize

Typical input and output stream variables for thermal systems are temperature and mass flow rate. Uncontrolled variables are measurable quantities that may not be controlled, but that affect component outputs andor costs, such as ambient dry- and wet-bulb temperature. Both equality and inequality constraints arise in the optimization of chilled-water systems. One example of an equality constraint that arises when two or more chillers are in operation is that the sum of their loads must equal the total load. The simplest type of inequality constraint is a bound on a control variable. For example, lower and upper limits are necessary for the chilled-water set temperature, to avoid freezing in the evaporator and to provide adequate dehumidification for the zones. Any equality constraint may be rewritten in the form of Equation (2) such that when it is satisfied, the constraint equation is equal to zero. Similarly, inequality constraints may be

Supervisory Control Strategies and Optimization

zyxwvz

expressed as Equation (3), so that the constraint equation is greater than or equal to zero to avoid violation. Braun (1988) and Braun et al. (1989a) presented a componentbased nonlinear optimization and simulation tool and used it to investigate optimal performance. Each component is represented as a separate subroutine with its own parameters, controls, inputs, and outputs. The optimization problem is solved efficiently by using second-order representations for costs that arise from curve-fits or Taylor-series approximations. Application of the component-based optimization led to many guidelines for control and a simplified system-based optimization methodology. In particular, the results showed that optimal set points could be correlated as a linear function of load and ambient wet-bulb temperature. Zakula et al. (2010) show that, for chillers with high part-load efficiency over a wide range of compressor speed, optimal condenser fan speed and chilled-water specific flow rate are highly nonlinear functions of cooling load, and without optimal control, transport power can be much greater than compressor power at partload and low-lift conditions. Gayeski et al. (2010a) demonstrated an empirical method for deriving near-optimal control laws from measured performance. Cumali (1988, 1994) presented a method for real-time global optimization of HVAC systems, including the central plant and associated piping and duct networks. The method uses a building load model for the zones, based on a coupled weighting-factor method similar to that used in DOE-2 (Winkelman et al. 1993). Variable time steps are used to predict loads over a 5 to 15 min period. The models are based on thermodynamic, heat transfer, and fluid mechanics fundamentals and are calibrated to match actual performance, using data obtained from the building and plant. Pipe and duct networks are represented as incidence and circuit matrices, and both dynamic and static losses are included. Fluid energy transfers are coupled with zone loads using custom weighting factors calibrated for each zone. The resulting equations are grouped to represent feasible equipment allocations for each range of building loads, and solved using a nonlinear solver. The objective function is the cost of delivering or removing energy to meet the loads, and is constrained by the comfort criteria for each zone. The objective function is minimized using the reduced gradient method, subject to constraints on comfort and equipment operation. Optimization starts with the feasible points as determined by a nonlinear equation solver for each combination of equipment allocation. The values of set points that minimize the objective function are determined; the allocation with the least cost is the desired operation mode. Results obtained from this approach have been applied to high-rise office buildings in San Francisco with central plants, VAV, dual-duct, and induction systems. Electrical demand reductions of 8 to 12% and energy savings of 18 to 23% were achieved.

Simplified System-Based OptimizationApproach The component-based optimization method presented by Braun et al. (1989a) was used to develop a simpler method for determining optimal control. The method involves correlating overall cooling plant power consumption using a quadratic functional form. Minimizing this function leads to linear control laws for control variables in terms of uncontrolled variables. The technique may be used to tune parameters of the cooling tower and chilled-water reset strategies presented in the section on Supervisory Control Strategies and Tools. It may also be used to defme strategies for supply air temperature reset for VAV systems and flow control for variable-speed condenser water pumps. In the vicinity of any optimal control point, plant power consumption may be approximated as a quadratic function of the continuous control variables for each of the operating modes (i.e., discrete control mode). A quadratic function also correlates power consumption in terms of uncontrolled variables (i.e., load, ambient temperature) over a wide range of conditions. This leads to the

42.5

zyx

following general functional relationship between overall cooling plant power and the controlled and uncontrolled variables: J(f, M, u) = uTAu + b T u + fTCf + d T f + f T E u + g

(4)

where J i s the total plant power, u is a vector of continuous and free control variables, f is a vector of uncontrolled variables, M is a vector of discrete control variables, and the superscript Tdesignates the transpose vector. A, C, and E are coefficient matrices, b and d are coefficient vectors, and g is a scalar. The empirical coefficients of this function depend on the operating modes so that these constants must be determined for each feasible combination of discrete control modes. A solution for the optimal control vector that minimizes power may be determined analytically by applying the first-order condition for a minimum. Equating the Jacobian of Equation (4) with respect to the control vector to zero and solving for the optimal control set points gives u*=k+Kf

(5)

k

= -A-I

(6)

K

= -A-’EI2

where b12

(7)

The cost associated with the unconstrained control of Equation (5) is

where

8 = K TAk+ EK + C

zyx

G = 2KAk+ Kb + E k + d T

= K T A k +b T k+g

(9)

(10) (11)

The control defined by Equation (5) results in a minimum power consumption if A is positive definite. If this condition holds and if the system power consumption is adequately correlated with Equation (4), then Equation (5) dictates that the optimal continuous, free control variables vary as a nearly linear function of the uncontrolled variables. However, a different linear relationship applies to each feasible combination of discrete control modes. The minimum cost associated with each mode combination must be computed from Equation (8) and compared to identify the minimum. Uncontrolled Variables. As discussed in the background section, optimal control variables primarily depend on ambient wetbulb temperature (or dry-bulb temperature in the case of air-cooled chillers) and total chilled-water load. The load affects the heat transfer requirements for all heat exchangers, whereas the wet-bulb temperature affects chilled- and condenser water temperatures necessary to achieve a given heat transfer rate. As discussed in the section on Supervisory Control Strategies and Tools, cooling coil heat transfer depends on the coil entering wet-bulb temperature. However, this reduces to an ambient wet-bulb temperature dependence for a given ventilation mode (e.g., minimum outside air or economizer) and fixed zone conditions. Thus, separate cost functions are necessary for each ventilation mode, with load and ambient wet bulb as uncontrolled variables. Alternatively, for a specified ventilation strategy (e.g., the economizer strategy from the section on Supervisory Control Strategies and Tools), three uncontrolled variables could be used for all ventilation modes: load, ambient wet-bulb temperature, and average cooling-coil inlet wet-bulb temperature.

42.6 For radiant cooling systems, if latent cooling is handled by package dehumidifying equipment (e.g., a dedicated outdoor air system), the chilled-water set point can be raised well above what is needed for dehumidification and the main chiller will operate more efficiently. Gayeski et al. (2010a) and Katipamula et al. (2010b) show that partload efficiency may benefit greatly from using optimal chilled-water flow rate and temperature in response to part-load ratio. Additional uncontrolled variables that could be important if varied over a wide range are the individual-zone latent-to-sensible load ratios and the ratios of individual sensible zone loads to the total sensible loads for all zones. However, these variables are difficult to determine from measurements and are of secondary importance. Free Control Variables. The number of independent or “free” control variables in the optimization can be reduced significantly by using the simplified strategies presented in the section on Supervisory Control Strategies and Tools. For instance, the optimal static pressure set point for a VAV system should keep at least one VAV box fully open and should not be considered as a free optimization variable. Similarly, supply air temperature for a constant-air-volume (CAV) system should be set to minimize reheat. Additional nearoptimal guidelines were presented for sequencing of cooling tower fans, sequencing of chillers, loading of chillers, reset of pressure differential set point for variable-speed pumping, and chilled-water reset with fixed-speed pumping. Furthermore, Braun et al. (1989b) showed that using identical supply air set points for multiple air handlers gives near-optimal results for VAV systems. For all variable-speed auxiliary equipment (i.e., pumps and fans), the free set-point variables to use in Equation (1) could be reduced to the following: (1) supply air set temperature, (2) chilledwater set temperature, (3) tower airflow relative to design capacity, and (4) condenser water flow relative to design capacity. All other continuous supervisory control variables are dependent on these variables with the simplified strategies presented in the section on Supervisory Control Strategies and Tools. Some of the dependent control variables may be discrete control variables. For instance, variable-flow pumping may be implemented with multiple fixed- and variable-speed pumps, where the number of operating pumps is a discrete variable that changes when a variable-speed pump reaches its capacity. These discrete changes could lead to discrete changes in cost because of changes in overall pump efficiency. However, this has arelatively small effect on overall power consumption and may be neglected in fitting the overall cost function to changes in the control variables. Some discrete control variables may also be independent variables. In general, different cost functions arise for all operating modes consisting of each possible combination of discrete control variables. With all variable-speed pumps and fans, the only significant discrete control variable is the number of operating chillers. Then, optimization involves determining optimal values of only four continuous control variables for each of the feasible chiller modes. A chiller mode defines which of the available chillers are to be online. The chiller mode giving the minimum overall power consumption represents the optimum. For a chiller mode to be feasible, the specified chillers must operate safely within their capacity and surge limits. In practice, abrupt changes in the chiller modes should also be avoided. Large chillers should not be cycled on or off except when the savings associated with the change are significant. Using fixed-speed equipment reduces the number of free continuous control variables. For instance, supply air temperature is removed as a control variable for CAV svstems. and chilled-water temperature is not included for fixed-speed chilled-water pumping. However, for multiple chilled-water pumps not dedicated to chillers, the number of operating pumps can become a free discrete control variable. Similarly, for multiple fixed-speed cooling tower fans and condenser water pumps, each of the discrete combinations can be considered as a separate mode. However, for multiple cooling tower cells with multiple fan speeds, the number of possible

201 1 ASHRAE Handbook-HVAC

Applications (SI)

combinations may be large. A simpler approach that works satisfactorily is to treat relative flows as continuous control variables during the optimization and to select the discrete relative flow that is closest to the optimal value. At least three relative flows (discrete flow modes) are necessary for each chiller mode to fit the quadratic cost function. The number of possible sequencing modes for fixed-speed pumps is generally much more limited than that for cooling tower fans, with two or three possibilities (at most) for each chiller mode. In fact, with many current designs, individual pumps are physically coupled with chillers, and it is impossible to operate more or fewer pumps than the number of operating chillers. Thus, it is generally best to treat the control of fixed-speed condenser water pumps with a set of discrete control possibilities rather than use a continuous control approximation. Training. The coefficients of Equation (4) must be determined empirically, and a variety of approaches have been proposed. One approach is to apply regression techniques directly to measurements of total power consumption. Because the cost function is linear with respect to the empirical coefficients, linear regression techniques may be used. A set of experiments can be performed over the expected range of operating conditions. Large amounts of data that include the entire range must be taken to account for measurement uncertainty. The regression could possibly be performed online using least-squares recursive parameter updating (Ljung and Soderstrom 1983). However, precautions should be taken to ensure that the matrix A is positive definite, which guarantees a minimum. If system power is relatively “flat,” automated methods could generate coefficients that produce a maximum in power consumption rather than a minimum (Brandemuehl and Bradford 1998). Rather than fitting empirical coefficients ofthe system-cost function of Equation (4), the coefficients of the optimal control Equation ( 5 ) and the minimum-cost function of Equation (8) may be estimated directly. At a limited set of conditions, optimal values of the continuous control and free variables may be estimated through trial-and-error variations. Only three independent conditions are necessary to determine coefficients of the linear control law given by Equation ( 5 ) if the load and wet bulb are the only uncontrolled variables. The coefficients ofthe minimum cost function can then be determined from system measurements with the linear control law in effect. The disadvantage of this approach is that there is no direct way to handle physical constraints on the controls. Summary and Constraint Implementation. The methodology for determining the near-optimal control of a chilled-water system may be summarized as follows: 1. Change the chiller operating mode if system operation is at the limits of chiller operation (near surge or maximum capacity). 2. For the current set of conditions (load and wet bulb), estimate the feasible modes of operation that avoid operating the chiller and condenser pump at their limits. 3. For the current operating mode, determine optimal values of the continuous controls using Equation ( 5 ) . 4. Determine a constrained optimum if controls exceed their bounds. 5 . Repeat steps 3 and 4 for each feasible operating mode. 6. Change the operating mode if the optimal cost associated with the new mode is significantly less than that associated with the current mode. 7. Change the values of the continuous control variables. When treating multiple-speed fan control with a continuous variable, use the discrete control closest to the optimal continuous value. If the linear optimal control Equation ( 5 ) is directly determined from optimal control results, then the constraints on controls may be handled directly. Otherwise, a simple solution is to constrain the individual control variables as necessary and neglect the effects of the constraints on the optimal values of the other controls and the minimum cost function. The variables of primary concern for constraints are the chilled-water and supply air set temperatures. These

z

zy

42.7

Supervisory Control Strategies and Optimization

Fig. 4

Comparisons of Optimal Supply Air Temperature

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controls must be bounded for proper comfort and safe operation of the equipment. On the other hand, cooling tower fans and condenser water pumps should be sized so the system performs efficiently at design loads, and constraints on control of this equipment should only occur under extreme conditions. The optimal value of the chilled-water supply temperature is coupled to the optimal value ofthe supply air temperature, so decoupling these variables in evaluating constraints is generally not justified. However, optimization studies indicate that when either control is operated at a bound, the optimal value of the other free control is approximately bounded at a value that depends only on the ambient wet-bulb temperature. The optimal value of this free control (either chilled-water or supply air set point) may be estimated at the load at which the other control reaches its limit. Coupling between optimal values of the chilled-water and condenser water loop controls is not as strong; interactions between constraints on these variables may be neglected. Case Studies. Braun et al. (1987) correlated the power consumption of the Dallas-Ft. Worth airport chiller, condenser pumps, and cooling tower fans with the quadratic cost function given by Equation (4) and showed good agreement with data. Because the chilledwater loop control was not considered, the chilled-water set point was treated as a known uncontrolled variable. The discrete control variables associated with the four tower cells with two-speed fans and the three condenser pumps were treated as continuous control variables. The optimal control determined by the near-optimal Equation (5) also agreed well with that determined using a nonlinear optimization applied to a detailed simulation of the system. In subsequent work, Braun et al. (1989a) considered complete system simulations (cooling plant and air handlers) to evaluate the performance of the quadratic, system-based approach. A number of different system characteristics were considered. Figures 4, 5, 22, and 23 show comparative results between the controls as determined with the component-based and system-based methods for a range of loads, for a relatively low and high ambient wet-bulb temperature (16°C and 27°C). In Figures 4 and 22, optimal values of the chilled-water and supply air temperatures are compared for a system with variable air and water flow. The near-optimal control equation provides a good fit to the optimization results for all conditions considered. The chilled-water temperature was constrained between 3 and 13"C, while the supply air set point was allowed to float freely. Figures 4 and 22 show that, for the conditions where the chilled-water temperature is constrained, the optimal supply air temperature is

Fig. 5

Comparisons of Optimal Condenser Pump Control

also nearly bounded at a value that depends on the ambient wet bulb. Optimal relative cooling tower air and condenser water flow rates are compared in Figures 5 and 23 for a system with variablespeed cooling tower fans and condenser water pumps. Although the optimal controls are not exactly linear functions of the load, the linear control equation provides an adequate fit. The differences in these controls result in insignificant differences in overall power consumption, because, as discussed in the background section, the optimum is extremely flat with respect to these variables. The nonlinearity of the condenser loop controls is partly due to the constraints imposed on the chilled-water set temperature. However, this effect is not very significant. Figures 5 and 23 also suggest that the optimal condenser loop control is not very sensitive to ambient wetbulb temperature.

DYNAMIC OPTIMIZATION Dynamic Optimization with Discrete Storage The optimal supervisory control for storage is a complex function of such factors as utility rates, load profile, chiller characteristics, storage characteristics, and weather. For a utility rate structure that includes both time-of-use energy and demand charges, the optimal strategy can depend on variables that extend over a monthly time scale. The overall problem of minimizing the utility cost over a billing period (e.g., a month) can be mathematically described as follows: Minimize

zyxwvu zyxw zyx N

J=

(EkPkA7)+Maxl

65

(LF) Rumble

Low-frequency range dominant (16 to 63 Hz)

5 dB < QAI < 10 dB OAI > 10 dB

Marginal Obi ectionable

(LFVB),Rumble,with moderately perceptible room surface vibration

Low-frequency range dominant (16 to 63 Hz)

QAI < 5 dB, 65 < L16, L31< 75 5 dB < QAI < 10 dB OAI > 10 dB

Marginal Marginal Obi ectionable

(LFV,) Rumble, with clearly perceptible room surface vibration

Low-frequency range dominant (16 to 63 Hz)

QAI < 5 dB,L16, L31 > 75 5 dB < QAI < 10 dB OAI > 10 dB

Marginal Marginal Obi ectionable

(MF) Roar

Mid-frequency range dominant (125 to 500 Hz)

5 dB < QAI < 10 dB QAI > 10 dB

Marginal Obi ectionable

(HF) Hiss

High-frequency range dominant (1000 to 4000 Hz)

5 dB < QAI < 10 dB QAI > 10 dB

Marginal Objectionable

Sound-Quality Descriptor

Probable Occupant Evaluation, Assuming Level of Specified Criterion is Not Exceeded Acceptable Marginal

level fluctuations, so none of these rating methods address these issues. Noise Criteria for Plumbing Systems. Acceptable noise levels from plumbing fixtures and piping have not been previously identified in the literature. Continuous noise from plumbing fixtures and piping systems with circulating fluids should meet the same noise criteria as HVAC systems. However, many sounds from plumbing fixtures and piping are of short duration or are transient, and typically have a somewhat higher threshold of acceptance. Examples of these sources include water flow noise associated with typical restroom fixtures; noise from waste lines connected to restroom, kitchen, andor laundry drains; and noise from jetted bathtubs. Table 5 presents suggested maximum A-weighted sound pressure levels for various transient plumbing noise sources in buildings with multiple occupancies. These criteria are minimum standards and are intended to apply to plumbing systems serving adjacent and nearby units in multifamily housing projects (apartments and condominiums), hospitals, educational facilities, and office buildings. Plumbing noise levels in high-end luxury condominiums or private homes should be 5 to 10 dB lower than levels shown in Table 5. Achieving the recommended plumbing noise criteria in the fmished space usually requires special attention to pipe installation details, selection of suitable piping materials, design flow velocities, and selection of appropriate fixtures. Determining Compliance. When taking field measurements to determine whether a space complies with the guidelines presented in Table 1, the following precautions must be taken:

Fig. 7 NCB Noise Criterion Curves

RNC: Room Noise Criteria Method. This rating method has been recently introduced and is described in detail in the American National Standards Institute (ANSI) Standard S12.2-2008. It is mentioned here for reference only and, at present, ASHRAE has no formal position on the use of this method. Table 4 summarizes the essential differences, advantages, and disadvantages of rating methods used to characterize HVAC-related background noise. Unfortunately, at this time there is no acceptable and simple process to characterize the effects of audible tones and

Measure the noise with an integrating sound level meter with a real-time frequency analyzer meeting type 1 or 2 specifications, asdefinedinANSIStandards S1.4, Sl.ll,andS1.43. Themeter should have been calibrated by an accredited calibration laboratory, with some assurance that the calibration accuracy has been maintained. Set the meter to display and save the equivalent energy sound pressure level (Leq)with the desired frequency filtering (e.g., octave bands, A-weighted, etc.). Each measurement should be a minimum of 15 s long. Place the measurement microphone in potential listening locations at least l m from room boundaries and noise sources and at least 0.5 m from furniture. More than one location may be measured, and the microphone may be moved during measurement; movement should not exceed 0.15 d s . Note the operational conditions ofthe HVAC system at the time of the test. Turn off all non-HVAC system noises during the test. If possible, measure in a normally furnished, unoccupied room.

48.7

Noise and Vibration Control Table 4

Comparison of Sound Rating Methods Considers Speech Interference Effects

Evaluates Sound Quality

Components Presently Rated by Each Method

No quality assessment Frequently used for outdoor noise ordinances

Yes

No

Cooling towers Water chillers Condensing units

NC

Can rate components Limited quality assessment Does not evaluate low-frequency rumble

Yes

Somewhat

Air terminals Diffusers

RC Mark I1

Used to evaluate systems Should not be used to evaluate components Evaluates sound quality Provides improved diagnostics capability

Yes

Yes

Not used for component rating

NCB

Can rate components Some quality assessment

Yes

Somewhat

See NC

RNC

Some quality assessment Attempts to quantify fluctuations

Method

Overview

dBA

Table 5 Receiving (listening) room

zy

zyxwvutsrqpon Yes

L,,

Not used for component rating

Outdoor Sound Criteria

Plumbing Noise Levels

Residential bedroodliving rooddining room Hospital patient roodclassroom Private office/conference room Residential bathroodkitchen Ooen office/lobbv/corridor

Somewhat

(slow response)

35 40 40 45 50

The test may be repeated with the entire HVAC system turned off, to determine whether the room’s ambient noise level from nonHVAC sources is contributing to the results. Record the sound level meter make, model, and serial number; measured sound pressure levels for each microphone location; HVAC system’s operating conditions; and microphone location(s).

Acceptable outdoor sound levels are generally specified by local noise ordinances or other government codes, which almost always use the A-weighted noise level (dBA) as their metric. The usual metric is either L,, (maximum noise level over aperiod), L,, (average noise level over a period), or Lp (no indication of the measure). The time constant (FAST or SLOW) used for L,, or Lp depends on the code. Some communities have no ordinance and depend on state regulations that often use the dayinight noise level descriptor LDN,which isacornbinationofthedaytime ( 7 : O O . m to 10:OO~~)andnighttime (1O:OO PM to 7 : O O AM) average noise levels (L,,) with a 10 dB penalty for nighttime. Other descriptors also exist; specific requirements should be identified at the outset of each project. In some cases, regulatory agencies may also impose project-specific noise conditions on the basis of community reaction and for maintaining an appropriate acoustic environment at the project vicinity. Measurement or estimation of community noise is based on a location, often at the receiver’s property line, from a height of approximately 1.2 m that represents ear height for a typical person seated at ground level to any height to address upper floor elevations, but can be anywhere within the property line, and often near the fagade of the closest dwelling unit. Alternatively, the measurement may be made at the property line of the noise source. In the absence of a local noise ordinance, county or state laws or codes or those of a similar community should be used. Even if activity noise levels do not exceed those specified by an ordinance, community acceptance is not ensured. Very low ambient levels or a noise source with an often-repeated, time-varying characteristic or strong tonal content may increase the likelihood of complaints. In the absence of local ordinances, noise levels between 45 and 5 5 dBA may be considered in residential zones and 5 5 to 65 dBA in commercial zones. These are for outdoor use areas and, with standard building constructions, they also typically result in acceptable interior noise levels. Often, daytime noise levels (the period of daytime to be defined) are 10 dB higher than nighttime levels. Although most ordinances are given as A-weighted pressure level, attenuation by distance, barriers, buildings, and atmosphere are all frequency-dependent. Thus, A-weighted levels do not give an accurate estimation of noise levels at distances from the source. If A-weighted sound levels of sources must be determined by means other than measurement, then octave band or one-third octave band measurements of source sound pressure level at a distance, or (preferably) sound power level, must be obtained before calculating the attenuation.

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When these levels are used as a basis for compliance verification, the following additional information must be provided:

What sound metrics are to be measured (specify L,, or L,, levels, etc., in each octave frequency band) Where and how the sound levels are to be measured (specify the space average over a defined area or specific points for a specified minimum time duration, etc.) What type(s) of instruments are to be used to make the sound measurements (specify ANSI or IEC Type 1 or Type 2 sound level meters with octave band filters, etc.) How sound measurements instruments are to be calibrated or checked (specify that instruments are to be checked with an acoustical calibrator both before and after taking sound level measurements, etc.) How sound level measurements are to be adjusted for the presence of other sound sources (specify that background sound level measurements be performed without other sound sources under consideration operating; if background sound levels are within 10 dB of operational sound levels, then corrections should be performed; etc.) How results of sound measurements are to be interpreted (specify whether octave band sound levels, NC, RC, dBA, dBC or other values are to be reported) Unless these six points are clearly stipulated, the specified sound criteria may be unenforceable. When applying the levels specified in Table 1 as a basis for design, sound from non-HVAC sources, such as traffic and office equipment, may establish the lower limit for sound levels in a space.

48.8 BASIC ACOUSTICAL DESIGN TECHNIQUES

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When selecting fans and other related mechanical equipment and when designing air distribution systems to minimize sound transmitted from system components to occupied spaces, consider the followinn: v Design the air distribution system to minimize flow resistance and turbulence. High flow resistance increases required fan pressure, which results in higher noise being generated by the fan, especially at low frequencies. Turbulence also increases flow noise generated by duct fittings and dampers, especially at low frequencies. Select a fan to operate as near as possible to its rated peak efficiency when handling the required airflow and static pressure. Also, select a fan that generates the lowest possible noise at required design conditions. Using an oversized or undersized fan that does not operate at or near rated peak efficiency can substantially increase noise levels. Design duct connections at both fan inlet and outlet for uniform and straight airflow. Both turbulence (at fan inlet and outlet) and flow separation at the fan blades can significantly increase fangenerated noise. Tuning vanes near fan outlets can also increase turbulence and noise, especially if airflow is not sufficiently uniform. Select duct silencers that do not significantly increase the required fan total static pressure. Selecting silencers with static pressure losses of 90 Pa or less can minimize regenerated noise from silencer airflow. Place fan-powered mixing boxes associated with variable-volume-air distribution systems away from noise-sensitive areas. Minimize flow-generated noise by elbows or duct branch takeoffs whenever possible by locating them at least four to five duct diameters from each other. For high-velocity systems, it may be necessary to increase this distance to up to 10 duct diameters in critical noise areas. Using flow straighteners or honeycomb grids, often called “egg crates,” in the necks of short-length takeoffs that lead directly to grilles, registers, and diffusers is preferred to using volume extractors that protrude into the main duct airflow. Keep airflow velocity in ducts serving sound-sensitive spaces as low as possible by increasing the duct size to minimize turbulence and flow-generated noise (see Tables 8 and 9, in the section on Aerodynamically Generated Sound in Ducts). Duct transitions should not exceed an included expansion angle of 15”, or the resulting flow separation may produce rumble noise. Use turning vanes in large 90” rectangular elbows and branch takeoffs. This provides a smoother directional transition, thus reducing turbulence. Place grilles, diffusers, and registers into occupied spaces as far as possible from elbows and branch takeoffs. Minimize use of volume dampers near grilles, diffusers, and registers in acoustically critical situations. Vibration-isolate all reciprocating and rotating equipment connected to structure. Also, it is usually necessary to vibrationisolate mechanical equipment in the basement of a building as well as piping supported from the ceiling slab of a basement, directly below tenant space. It may be necessary to use flexible piping connectors and flexible electrical conduit between rotating or reciprocating equipment and pipes and ducts that are connected to the equipment. Vibration-isolate ducts and pipes, using spring and/or neoprene hangers for at least the first 15 m from vibration-isolated equipment. Use barriers near outdoor equipment when noise associated with the equipment will disturb adjacent properties. In normal practice, barriers typically produce no more than 15 dB of sound attenuation in the midfrequency range. To be effective, the noise

201 1 ASHRAE Handbook-HVAC Applications (SI) barrier must at least block the direct “line of sight” between the source and receiver.

Table 6 lists several common sound sources associated with mechanical equipment noise. Anticipated sound transmission paths and recommended noise reduction methods are also listed. Airborne andor structureborne sound can follow any or all of the transmission paths associated with a specified sound source. Schaffer (2005) has more detailed information in this area.

SOURCE SOUND LEVELS Accurate acoustical analysis of HVAC systems depends in part on reliable equipment sound data. These data are often available from equipment manufacturers in the form of sound pressure levels at a specified distance from the equipment or, preferably, equipment sound power levels. Standards used to determine equipment and component sound data are listed at the end of this chapter. When reviewing manufacturers’ sound data, obtain certification that the data have been obtained according to one or more of the relevant industry standards. If they have not, the equipment should be rejected in favor of equipment for which data have been obtained according to relevant industry standards. See Ebbing and Blazier (1998) for further information.

Fans Prediction of Fan Sound Power. The sound power generated by a fan performing at a given duty is best obtained from manufacturers’ test data taken under approved test conditions (AMCA Standard 300 or ASHRAE Standard 68lAMCA Standard 330). Applications of air-handling products range from stand-alone fans to systems with various modules and attachments. These appurtenances and modules can have a significant effect on air-handler sound power levels. In addition, fans of similar aerodynamic performance can have significant acoustical differences. Predicting air-handling unit sound power from fan sound levels is difficult. Fan sound determined by tests may be quite different once the fan is installed in an air handler, which in effect creates a new acoustical environment. Proper testing to determine resulting sound power levels once a fan is installed is essential. Fan manufacturers are in the best position to supply information on their products, and should be consulted for data when evaluating the acoustic performance of fans for an air handler application. Similarly, air handler manufacturers are in the best position to supply acoustic information on air handlers. Air handler manufacturers typically provide discharge, inlet, and casing-radiated sound power levels for their units based on one of two methods. A common method is the fan-plus-algorithm method: the fan is tested as a stand-alone item, typically using AMCA Standard 300, and an algorithm is used to predict the effect of the rest of the air-handling unit on the sound as it travels from the fan to the discharge and intake openings or is radiated through a casing with known transmission loss values. Another method is described in AHRI Standard 260, in which the entire unit is tested as an assembly, including fans, filters, coils, plenums, casing, etc., and the sound power level at the inlet and discharge openings, as well as the radiated sound power, is measured in a qualified reverberant room. Whenever possible, data obtained by the AHRI 260 method should be used because it eliminates much of the uncertainty present in the fan-plus-algorithm method. For a detailed description of fan operations, see Chapter 20 in the 2008 ASHRAE Handbook-HVAC Systems and Equipment. Different fan types have different noise characteristics and within a fan type, several factors influence noise. Point of Fan Operation. The point of fan operation has a major effect on acoustical output. Fan selection at the calculated point of maximum efficiency is common practice to ensure minimum power consumption. In general, for a given design, fan sound

zy

zyxwv

Table 6

zy zy 48.9

Noise and Vibration Control Sound Sources, Transmission Paths, and Recommended Noise Reduction Methods Sound Source

Path No.

Circulating fans; grilles; registers; diffusers; unitary equipment in room 1 Induction coil and fan-powered VAV mixing units 1, 2 Unitary equipment located outside of room served; remotely located air-handling equipment, such as fans, blowers, dampers, 2, 3 duct fittings, and air washers Compressors, pumps, and other reciprocating and rotating equipment (excluding air-handling equipment) 4, 5 , 6 Cooling towers; air-cooled condensers 4, 5 , 6 7 Exhaust fans; window air conditioners 7, 8 Sound transmission between rooms 9, 10 No. Transmission Paths Noise Reduction Methods 1 Direct sound radiated from sound source to ear Direct sound can be controlled only. by. selecting _ quiet _ equipment. _ _ Reflected sound from walls, ceiling, and floor Reflected sound is controlled by adding sound absorption to room and to equipment location. 2 Air- and structureborne sound radiated from casings and through walls of Design duct and fittings for low turbulence; locate high-velocity ducts in ducts and plenums is transmitted through walls and ceiling into room noncritical areas; isolate ducts and sound plenums from structure with neoprene or spring hangers. 3 Airborne sound radiated through supply and return air ducts to diffusers in Select fans for minimum sound power; use ducts lined with soundabsorbing material; use duct silencers or sound plenums in supply and room and then to listener by Path 1 return air ducts. 4 Noise transmitted through equipment room walls and floors to adjacent Locate equipment rooms away from critical areas; use masonry blocks or rooms concrete for mechanical equipment room walls; use floating floors in mechanical rooms. 5 Vibration transmitted via building structure to adjacent walls and ceilings, Mount all machines on properly designed vibration isolators; design from which it radiates as noise into room by Path 1 mechanical equipment room for dynamic loads; balance rotating and reciprocating equipment. 6 Vibration transmission along pipes and duct walls Isolate pipe and ducts from structure with neoprene or spring hangers; install flexible connectors between pipes, ducts, and vibrating machines. I Noise radiated to outside enters room windows Locate equipment away from critical areas; use bamers and covers to interrupt noise paths; select quiet equipment. Indoor noise follows Path 1 8 Select quiet equipment. 9 Noise transmitted to an air diffuser in a room, into a duct, and out through Design and install duct attenuation to match transmission loss of wall an air diffuser in another room between rooms; use crosstalk silencers in ductwork. 10 Sound transmission through, over, and around room partition Extend partition to ceiling slab and tightly seal all around; seal all pipe, conduit, duct, and other partition penetrations.

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is at a minimum near the point of maximum efficiency. Noise increases as the operating point shifts to the right, as shown in Figure 8 (higher airflow and lower static pressure). Low-frequency noise can increase substantially at operating points to the left of maximum efficiency (lower airflow and higher static pressure). These operating points should be avoided

Blade-Pass Frequency. The blade-pass frequency is represented by the number of times per second a fans impeller passes a stationary item:fbp = (rpm x number of impeller blades)/60. All fans generate a tone at this frequency and its multiples (harmonics). Whether this tone is objectionable or barely noticeable depends on the type and design of the fan and the point of operation. Housed Centrifugal Fans. Forward-curved (FC) fans are commonly used in a wide range of standard air-handler products. The blade-pass of FC fans is typically less prominent and is at a higher frequency than other fans. The most distinguishing acoustical concern of FC fans is the prevalent occurrence of low-frequency rumble from airflow turbulence generated at blade tips, which can be exacerbated by nonideal discharge duct conditions (less than five diameters of straight duct). FC fans are commonly thought to have 16, 31.5, and 63 Hz (full octave band) rumble, particularly when operating to the left of the maximum efficiency point. Backward-inclined (BI) fans and airfoil (AF) fans are generally louder at the blade-pass frequency than a given FC fan selected for the same duty, but are much more energy-efficient at higher pressures and airflow. The blade-pass tone generally increases in prominence with increasing fan speed and is typically in a frequency range that is difficult to attenuate. Below the blade-pass frequency, these fans generally have lower sound amplitude than FC fans and are often quieter at high frequencies.

Fig. 8 Test Data for Plenum Fan, Comparing Operating Point (Static Pressure and Airflow), A-Weighted Sound Power Level Care should be taken with all types of housed fans to allow adequate clearance around the inlets. Also, note that belt guards and inlet screens may decrease airflow and increase sound generation. Plenum Fans. A plenum fan has no housing around the fan impeller and discharges directly into the chamber, pressurizing the plenum, and forcing air through the attached ductwork. Air flows into the fan impeller through an inlet bell located in the chamber

48.10 wall. These fans can substantially lower discharge sound power levels if the fan plenum is appropriately sized and acoustically treated with sound-absorptive material. The plenum discharge should be located away from the fan’s air blast, because blowing directly into the duct can aggravate the blade-pass sound. Avoid obstructing the inlet or crowding the coils or filters. Vaneaxial Fans. Generally thought to have the lowest amplitudes of low-frequency sound of any of the fan types, axial fans are often used in applications where the higher-frequency noise can be managed with attenuation devices. In the useful operating range, noise from axial fans is a strong function of the inlet airflow symmetry and blade tip speed. Propeller Fans. Sound from propeller fans generally has a lowfrequency-dominated spectrum shape; the blade-pass frequency is typically prominent and occurs in the low-frequency bands because of the small number of blades. Propeller fan blade-pass frequency noise is very sensitive to inlet obstructions. For some propeller fan designs, the shape of the fan venturi (inlet) is also a very important parameter that affects sound levels. In some applications, noise of a propeller fan is described as sounding like a helicopter. Propeller fans are most commonly used on condensers and for power exhausts. Minimizing Fan Noise. To minimize the required air distribution system sound attenuation, proper fan selection and installation are vital. The following factors should be considered: Design the air distribution system for minimum airflow resistance. High system resistance requires fans to operate at a higher wattage, which generates higher sound power levels. Carefully analyze system pressure losses. Higher-than-expected system resistance may result in higher sound power levels than originally estimated. Examine the sound power levels of different fan types and designs. Select a fan (or fans) that generates the lowest sound power levels while meeting other fan selection requirements. Many fans generate tones at the blade-pass frequency and its harmonics that may require additional acoustical treatment of the system. Amplitude of these tones can be affected by resonance within the duct system, fan design, and inlet flow distortions caused by poor inlet duct design, or by operation of an inlet volume control damper. When possible, use variable-speed volume control instead of volume control dampers. Design duct connections at both fan inlet and outlet for uniform and straight airflow. Avoid unstable, turbulent, and swirling inlet airflow. Deviation from acceptable practice can severely degrade both aerodynamic and acoustic performance of any fan and invalidate manufacturers’ ratings or other performance predictions.

Variable-Air-Volume (VAV) Systems General Design Considerations. As in other aspects of HVAC system design, ducts for VAV systems should be designed for the lowest practical static pressure loss, especially ductwork closest to the fan or air-handling unit (AHU). High airflow velocities and convoluted duct routing with closely spaced fittings can cause turbulent airflow that results in excessive pressure drop and fan instabilities that can cause excessive noise, fan stall, or both. Many VAV noise complaints have been traced to control problems. Although most problems are associated with improper installation, many are caused by poor design. The designer should specify high-quality fans or air handlers within their optimum ranges, not at the edge of their operation ranges where low system tolerances can lead to inaccurate fan flow capacity control. Also, in-duct static pressure sensors should be placed in duct sections having the lowest possible air turbulence (i.e., at least three equivalent duct diameters from any elbow, takeoff, transition, offset, or damper).

201 1 ASHRAE Handbook-HVAC Applications (SI)

Fig. 9

z

Basis for Fan Selection in VAV Systems

Balancing. VAV noise problems have also been traced to improper air balancing. For example, air balance contractors commonly balance an air distribution system by setting all damper positions without considering the possibility of reducing fan speed. The result is a duct system in which no damper is completely open and the fan delivers air at a higher static pressure than would otherwise be necessary. Ifthe duct system is balanced with at least one balancing damper wide open, fan speed and corresponding fan noise could be reduced. Lower sound levels occur if most balancing dampers are wide open or eliminated. The specified goal should be to balance the system at the lowest static pressure required to operate the box located at the farthest point in the system. Fan Selection. For constant-volume systems, fans should be selected to operate at maximum efficiency at design airflow. However, VAV systems must be selected to operate with efficiency and stability throughout the operating range. For example, a fan selected for peak efficiency at full output may aerodynamically stall at an operating point of 50% of full output, resulting in significantly increased low-frequency noise and unstable airflow. A stalling fan can indicate operation in the surge region, a region of operational instability where airflow reverses direction at the fan blade because of insufficient air entering the fan wheel. Similarly, a fan selected to operate most efficiently at the 50% output point may be very inefficient at full output, resulting in substantially increased fan noise at all frequencies. In general, a fan for a VAV system should be selected for peak efficiency at an operating point between 70 and 80% of the maximum required system capacity, which is where the fan will operate most of the time. This usually means selecting a fan that is one size smaller than that required for peak efficiency at 100% of maximum required system capacity (Figure 9). When the smaller fan operates at higher capacities, it produces up to 5 dB more noise. This occasional increase in sound level is usually more tolerable than stall-related sound problems that can occur with a larger fan operating at less than 100% design capacity most of the time. Air Modulation Devices. The control method selected to vary the air capacity of a VAV system is important. Variable-capacity control methods can be divided into three general categories: (1) variable inlet vanes (sometimes called inlet guide vanes) or discharge dampers that yield a new fan system curve at each vane or damper setting, (2) variable-pitch fan blades (usually used on axial fans) that adjust the blade angle for optimum efficiency at varying capacity requirements, and (3) variable-speed motor drives in which motor speed is varied by modulation of the power line frequency or by mechanical means such as gears or continuous belt adjustment.

zy

z zyxwvutsrqp 48.11

Noise and Vibration Control

Inlet vane and discharge damper volume controls can add noise to a fan system at reduced capacities, whereas variable-speed motor drives and variable-pitch fan blade systems are quieter at reduced air output than at full air output.

Variable-Inlet Vanes and Discharge Dampers. Variable-inlet vanes vary airflow capacity by changing inlet airflow to a fan wheel. This type of air modulation varies the total air volume and pressure at the fan, but fan speed remains constant. Although fan pressure and air volume reductions at the fan reduce duct system noise by reducing air velocities and pressures in the duct work, there is an associated increase in fan noise caused by airflow turbulence and flow distortions at the inlet vanes. Fan manufacturers’ test data show that, on airfoil centrifugal fans, as vanes mounted inside the fan inlet (nested inlet vanes) close, the sound level at the blade-pass frequency of the fan increl lases by 2 to 8 dB, depending on the percent of total air volume restricted. For externally mounted inlet vanes, the increase is on the order of 2 to 3 dB. The increase for forwardcurved fan wheels with inlet vanes is about 1 to 2 dB less than that for airfoil fan wheels. In-line axial fans with inlet vanes generate increased noise levels of 2 to 8 dB in the low-frequency octave bands for a 25 to 50% closed vane position. Discharge dampers, typically located immediately downstream of the supply air fan, reduce airflow and increase pressure drop across the fan while fan speed remains constant. Because of air turbulence and flow distortions created by the high pressure drop across discharge dampers, there is a high probability of duct rumble near the damper location. If the dampers are throttled to a very low flow, a stall condition can occur at the fan, resulting in an increase in low-frequency noise. Variable-Pitch Fans f o r Capacity Control. Variable-pitch fan blade controls vary the fan blade angle to reduce airflow. This type of system is predominantly used in axial fans. As air volume and pressure are reduced at the fan, there is a corresponding noise reduction. In the 125 to 4000 Hz octave bands, this reduction usually varies between 2 to 5 dB for a 20% reduction in air volume, and between 8 to 12 dB for a 60% reduction in air volume. Variable-Speed-Motor-ControlledFan. Three types of electronic variable-speed control units are used with fans: (1) current source inverter, (2) voltage source inverter, and (3) pulse-width modulation (PWM). The current source inverter and third-generation PWM control units are usually the quietest of the three controls. In all three types, matching motors to control units and the quality of the motor windings determine the motor’s noise output. The motor typically emits a pure tone with an amplitude that depends on the smoothness of the waveform from the line current. The frequency of the motor tone depends on the motor type, windings, and speed, but is typically at the drive’s switching frequency. Some drives allow adjustment to a higher frequency that does not carry as well, but at a cost of lower drive efficiency. Both inverter control units and motors should be enclosed in areas, such as mechanical rooms or electrical rooms, where the noise effect on surrounding rooms is minimal. The primary acoustic advantage of variable-speed fans is reduction of fan speed, which translates into reduced noise; dB reduction is approximately equal to 50 x log (higher speed/lower speed). Because this speed reduction generally follows the fan system curve, a fan selected at optimum efficiency initially (lowest noise) does not lose efficiency as the speed is reduced. When using variable-speed controllers, Select fan vibration isolators on the basis of the lowest practical speed of the fan. For example, the lowest rotational speed might be 600 rpm for a 1000 rpm fan in a commercial system. Select a controller with a feature typically called “critical frequency jump band.” This feature allows a user to program the controller to avoid certain fan or motor rpm settings that might excite vibration isolation system or building structure resonance

frequencies, or correspond to speeds of other fans in the same system. Check the intersection of the fan’s curve at various speeds against the duct system curve. When selecting a fan controlled by a variable-speed motor controller, keep in mind that the system curve does not go to zero static pressure at no flow. The system curve is asymptotic at the static pressure control set point, typically 250 to 370 Pa. An improperly selected fan may be forced to operate in its stall range at slower fan speeds.

Terminal Units. Fans and pressure-reducing valves in VAV units should have manufacturer-published sound data indicating sound power levels that (1) are discharged from the low-pressure end of the unit and (2) radiate from the exterior shell of the unit. These sound power levels vary as a function of valve position and fan point of operation. Sound data for VAV units should be obtained according to the procedures specified by the latest ARI Standard 880. In critical situations, a mock-up test should be conducted of a production terminal box under project conditions and space finishes. The test is required because minor changes in box motor, fan, or valve components can affect the noise generated by such equipment. If the VAV unit is located in noncritical areas (e.g., above a storeroom or corridor), sound radiated from the shell of the unit may be of no concern. If, however, the unit is located above a critical space and separated from the space by a ceiling with little or no sound transmission loss at low frequencies, sound radiated from the shell into the space below may exceed the desired noise criterion. In this case, it may be necessary to relocate the unit to a noncritical area or to enclose it with a high-transmission-loss construction. Room sound levels can be estimated using attenuation factors detailed in AHRI Standard 885. In general, fan-powered VAV units should not be placed above or near any room with a required sound criterion rating of less than RC 40(N) (Schaffer 2005). For further information, see the section on Indoor Sound Criteria. Full shutoff of VAV units can produce excessive duct system pressure at low flow, sometimes causing a fan to go into stall, resulting in accompanying roar, rumble, and surge. Systems providing more than 30% of their air to VAV devices should be provided with a means of static pressure control. Variable-frequency drives are preferred, but in the case of constant-volume air handlers, some means of bypass pressure control should be used to relieve system pressure as VAV devices close down (Schaffer 2005).

Rooftop-Mounted Air Handlers Rooftop air handlers can have unique noise control requirements because these units are often integrated into a low-mass roof construction. Large roof openings are often required for supply and return air duct connections. These ducts run directly from noisegenerating rooftop air handlers to the building interior. Generally, there is insufficient space or distance between roof-mounted equipment and the closest occupied spaces below the roof to apply standard sound control treatments. Rooftop units should be located above spaces that are not acoustically sensitive and should be placed as far as possible from the nearest occupied space. This measure can reduce the amount of sound control treatment necessary to achieve an acoustically acceptable installation. The common sound transmission paths associated with rooftop air handlers (Figure 10) are Flanking-path-borne sound from condenser fans, or compressors breaking in through low-mass roofs or through windows Airborne through bottom of rooftop unit to spaces below Structureborne from vibrating equipment in rooftop unit to building structure Ductborne through supply air duct from air handler Ductborne through return air duct to air handler Duct breakout noise (see the section on Sound Radiation Through Duct Walls)

201 1 ASHRAE Handbook-HVAC

48.12 Flanking-path noise can enter through low-mass roof structures, adjacent walls, and windows. Avoid placing rooftop units on light structure over sensitive spaces or close to higher sidewalls with windows or other lightly constructed building elements. If it is necessary to place the rooftop unit over sensitive spaces or lightly constructed walls, then lagging with additional layers of gypsum board or other similar material may be required in these areas. Using proper vibration isolation can minimize structureborne sound and vibration from vibrating equipment in a rooftop unit. Special curb mounting bases are available to support and provide vibration isolation for rooftop units. For roofs constructed with open web joists, thin long-span slabs, wooden construction, and any unusually light construction, evaluate all equipment with a mass of more than 130 kg to determine the additional deflection of the structure at mounting points caused by the equipment. Isolator deflection should be a minimum of 10 times the additional static deflection. If the required spring isolator deflection exceeds commercially available products, stiffen the supporting structure or change the equipment location. Airborne paths are associated with casing-radiated sound that passes through the air-handler enclosure and roof structure to the spaces below. Airborne sound can result from air-handler noise or from other equipment components in the rooftop unit. Rooftop units should not be placed on open curbs or over a large opening in the roof structure through which both supply and return air ducts pass. Roof penetrations should be limited to two openings sized to accommodate only the supply and return air ducts. These openings should be properly sealed after installation of the ducts. If a large single opening exists under the rooftop unit, it should be structurally, acoustically, and flexibly sealed with one or more layers of gypsum board or other similar material around the supply and return air ducts. Airborne sound transmission to spaces below a rooftop unit can be greatly reduced by placing the rooftop unit on a structural support extending above the roof structure, and running supply and return air ducts horizontally along the roof for several duct diameters before the ducts turn to penetrate the roof. The roof deck/ ceiling system below the unit can be constructed to adequately attenuate sound radiated from the bottom of the unit. Ductborne transmission of sound through the supply air duct consists of two components: sound transmitted from the air handler through the supply air duct system to occupied areas, and sound transmitted via duct breakout through a section or sections of the supply air duct close to the air handler to occupied areas. Sound transmission below 250 Hz through duct breakout is often a major acoustical limitation for many rooftop installations. Excessive lowfrequency noise associated with fan noise and air turbulence in the region of the discharge section of the fan (or air handler) and the frst duct elbow results in duct rumble, which is difficult to attenuate. This

Fig. 10

Sound Paths for Typical Rooftop Installations

Applications (SI)

problem is often worsened by the presence of a high-aspect-ratio duct at the discharge section of the fan (or air handler). Rectangular ducts with duct lagging are often ineffective in reducing duct breakout noise. Using either a single- or dual-wall round duct with a radiused elbow coming off the discharge section of the fan can reduce duct breakout. If space does not allow for the use of a single duct, the duct can be split into several parallel round ducts. Another effective method is using an acoustic plenum chamber constructed of a minimum 50 mm thick, dual-wall plenum panel, lined with fiberglass and with a perforated inner liner, at the discharge section of the fan. Either round or rectangular ducts can be taken off the plenum as necessary for the rest of the supply air distribution system. Table 7 shows 12 possible rooftop discharge duct configurations with their associated low-frequency noise reduction potential (Beatty 1987; Harold 1986, 1991). Ductborne transmission of sound through the return air duct of a rooftop unit is often a problem because there is generally only one short return air duct section between the plenum space above a ceiling and the return air section of the air handler. This does not allow for adequate sound attenuation between the fan inlet and spaces below the air handler. Sound attenuation through the return air duct system can be improved by adding at least one (more if possible) branch division where the return air duct is split into two sections that extend several duct diameters before they terminate into the plenum space above the ceiling. The inside surfaces of all return air ducts should be lined with a minimum of 25 mm thick duct liner. If conditions permit, duct silencers in duct branches or an acoustic plenum chamber at the air-handler inlet section give better sound conditions.

Aerodynamically Generated Sound in Ducts Aerodynamic sound is generated when airflow turbulence occurs at duct elements such as duct fittings, dampers, air modulation units, sound attenuators, and room air devices. For details on air modulation units and sound attenuators, see the sections on Variable-AirVolume Systems and Duct Silencers. Although fans are a major source of sound in HVAC systems, aerodynamically generated sound can often exceed fan sound because of close proximity to the receiver. When making octave-band fan sound calculations using a source-path-receiver analysis, aerodynamically generated sound must be added in the path sound calculations at the location of the element. Duct Velocities. The extent of aerodynamic sound is related to the airflow turbulence and velocity through the duct element. The sound amplitude of aerodynamically generated sound in ducts is proportional to the fifth, sixth, and seventh power of the duct airflow velocity in the vicinity of a duct element (Bullock 1970; Ingard et al. 1968). Therefore, reducing duct airflow velocity significantly reduces flow-generated noise. Tables 8 (Schaffer 2005) and 9 (Egan 1988) give guidelines for recommended airflow velocities in duct sections and duct outlets to avoid problems associated with aerodynamically generated sound in ducts. Fixed Duct Fittings. Fixed duct fittings include elbows, tees, transitions, fixed dampers, and branch takeoffs. In all cases, less generated air turbulence and lower airflow velocities result in less aerodynamic sound. Figures 11 and 12 show typical frequency spectra for specific sizes of elbows and transitions. Data in these figures are based on empirical data obtained from ASHRAE RP-37 (Ingard et al. 1968). Normalized data from ASHRAE RP-37 and others, which can apply to all types of duct fittings and dampers, have been published (Bullock 1970) and presented in ASHRAE RP-265 (Ver 1983a). When multiple duct fittings are installed adjacent to each other, aerodynamic sound can increase significantly because of the added air turbulence and increased velocity pressures. Note that the magnitude of the field-measured static pressure drop across fixed duct fittings does not relate to the aerodynamic generated sound. However, total pressure drop across a duct fitting,

z

48.13

Noise and Vibration Control

zyxwvutsrqpo zy

Table 7 Duct Breakout Insertion Loss-Potential

Low-Frequency Improvement over Bare Duct and Elbow Duct Breakout Insertion Loss at Low Frequencies, dB

Discharge Duct Configuration, 3660 mm of Horizontal Supply Duct

63Hz

125Hz

250Hz

Rectangular duct: no turning vanes (reference)

0

0

0

Rectangular duct: one-dimensional turning vanes

0

1

1

Rectangular duct: two-dimensional turning vanes

0

1

1

Rectangular duct: wrapped with foam insulation and two layers of lead

4

3

5

Rectangular duct: wrapped with glass fiber and one layer 16 mm gypsum board

4

7

6

Rectangular duct: wrapped with glass fiber and two layers 16 mm gypsum board

7

9

9

Rectangular plenum drop (12 ga.): three parallel rectangular supply ducts (22 ga.)

1

2

4

Rectangular plenum drop (12 ga.): one round supply duct (18 ga.)

8

10

6

Rectangular plenum drop (12 ga.): three parallel round supply ducts (24 ga.)

11

14

8

Rectangular (14 ga.) to multiple drop: round mitered elbows with turning vanes, three parallel round supply ducts (24 ga.)

18

12

13

Rectangular (14 ga.) to multiple drop: round mitered elbows with turning vanes, three parallel round lined double-wall, 560 mm OD supply ducts (24 ga.1

18

13

16

Round drop: radiused elbow (14 ga.), single 940 mm diameter supply duct

15

17

10

which includes the velocity pressure change resulting from air turbulence, does affect aerodynamically generated sound. Operable Volume Dampers. Operable damper aerodynamic sound is created because the damper is an obstacle in the airstream, and air turbulence increases as the damper closes. Because total pressure drop across the damper also increases with closure, the aerodynamic sound is related to the total pressure drop. Both singleblade and multiblade dampers, used to balance and control the airflow in a duct system and at room air devices, have similar frequency spectra. Figure 13 shows the frequency spectrum for a 45" damper in a 600 by 600 nnn duct (Ingard et al. 1968). Depending on its location relative to a room air device, a damper can generate sound that is transmitted down the duct to the room air device, or radiate sound through the ceiling space into the occupied space below. When an operable control damper is installed close to an air device to achieve system balance, the acoustic performance of the air outlet must be based not only on the air volume handled, but also on the magnitude of the air turbulence generated at the damper.

Side View

End View

-

The sound level produced by closing the damper is accounted for by adding a correction to the air device sound rating. As the damper is modulated for air balance, this quantity is proportional to the pressure ratio (PR), that is, the throttled total pressure drop across the damper divided by the minimum total pressure drop across the damper. Table 10 provides decibel corrections to determine the effect of damper location on linear diffuser sound ratings. Volume dampers in sound-critical spaces should always be a minimum of 5 to 10 duct diameters from air device, with an acoustically lined duct between the damper and air device. Acoustically lined plenums may also be used between the damper and room air device to reduce damper sound. Linear air devices with around duct connected to an insulated plenum have been successfully used for damper sound control. However, acoustical lining in this type of plenum does not minimize the sound generated by air flowing through a short section of the linear air device. If multiple inlets/ outlets are used to spread airflow uniformly over the lined plenum and air device, then the linear slot generates less sound.

zyxwvu

Next Page

201 1 ASHRAE Handbook-HVAC Applications (SI)

48.14

Fig. 13 Velocity-Generated Sound of 600 by 600 mm Volume Damper

zy zy zyxwvuts Table 8 Maximum Recommended Duct Airflow Velocities to Achieve Specified Acoustic Design Criteria Maximum Airflow Velocity, m / s

Design Rectangular RC(N) Duct

Main Duct Location

In shaft or above drywall ceiling

Fig. 11 Velocity-Generated Sound of Duct Transitions

Above suspended acoustic ceiling

Duct located within occupied space

45 35 25 45 35 25 45 35 25

17.8 12.7 8.6 12.7 8.9 6.1 10.2 7.4 4.8

Circular Duct

25.4 17.8 12.7 22.9 15.2 10.2 19.8 13.2 8.6

Notes: Branch ducts should have airflow velocities of about 80% ofvalues listed. Velocities in final runouts to outlets should be 50% ofvalues or less. Elbows and other fittings can increase airflow noise substantially, depending on type. Thus, duct airflow velocities should be reduced accordingly.

Table 9 Maximum Recommended Air Velocities at Neck of Supply Diffusers or Return Registers to Achieve Specified Acoustical Design Criteria Type of Opening

Design RC(N)

“Free” Opening Airflow Velocity, m / s

Supply air outlet

45 40 35 30 25 45 40 35 30 25

3.2 2.8 2.5 2.2 1.8 3.8 3.4 3.0 2.5 2.2

Return air opening

Fig. 12 Velocity-Generated Sound of Elbows

Note: Table intended for use when no sound data are available for selected grilles or diffusers, or no diffuser or grille is used. The number of diffusers or grilles increases sound levels, depending on proximity to receiver. Allowable outlet or opening airflow velocities should be reduced accordingly in these cases.

zyx zyxwvutsrqp CHAPTER 49

WATER TREATMENT

Water Characteristics

Biological Growth Control.......................................................

49.1 49.2 49.4 49.5

Suspended Solids and Depositation Contro 49.7 Start-up and Shutdown of Cooling Tower ................. 49.8 Selection of Water Treatment 49.9 Terminology............................................................................ 49.11

T

Table 1 Alkalinity Interpretation for Watersa

HIS chapter covers the fundamentals of water treatment and some of the common problems associated with water in heating and air-conditioning equipment.

Then, Carbonate PAlk=O P Alk < 0.5M Alk

WATER CHARACTERISTICS

Bicarbonate

Free CO, Present

2P Alk

Chemical Characteristics When rain falls, it dissolves carbon dioxide and oxygen in the atmosphere. The carbon dioxide mixes with the water to form carbonic acid (H,CO,). When carbonic acid contacts soil that contains limestone (CaCO,), it dissolves the calcium to form calcium carbonate. Calcium carbonate in water used in heating or air-conditioning applications can eventually become scale, which can increase energy costs, maintenance time, equipment shutdowns, and could eventually lead to equipment replacement. The following paragraphs discuss typical chemical and physical properties of water used for HVAC applications. Alkalinity is ameasure ofthe capacity to neutralize strong acids. In natural waters, the alkalinity almost always consists of bicarbonate, although some carbonate may also be present. Borate, hydroxide, phosphate, and other constituents, if present, are included in the alkalinity measurement in treated waters. Alkalinity also contributes to scale formation. Alkalinity is measured using two different end-point indicators. The phenolphthalein alkalinity (P alkalinity) measures the strong alkali present; the methyl orange alkalinity (M alkalinity), or total alkalinity, measures the total alkalinity in the water. Note that the total alkalinity includes the phenolphthalein alkalinity. For most natural waters, in which the concentration of phosphates, borates, and other noncarbonated alkaline materials is small, the actual chemical species present can be estimated from the two alkalinity measurements (Table 1). Alkalinity or acidity is often confused with pH. Such confusion may be avoided by keeping in mind that the pH is a measure of hydrogen ion concentration expressed as the logarithm of its reciprocal. Chlorides have no effect on scale formation but do contribute to corrosion because of their conductivity and because the small size of the chloride ion permits the continuous flow of corrosion current when surface films are porous. The amount of chlorides in the water is a useful measuring tool in evaporative systems. Virtually all other constituents in the water increase or decrease when common treatment chemicals are added or because of chemical changes that take place in normal operation. With few exceptions, only evaporation affects chloride concentration, so the ratio of chlorides in a water sample from an operating system to those of the makeup water provides a measure of how much the water has been concentrated. (Note: Chloride levels will change if the system is continuously chlorinated.) Dissolved solids consist of salts and other materials that combine with water as a solution. They can affect the formation of corrosion and scale. Low-solids waters are generally corrosive because they have less tendency to deposit protective scale. If a high-solids The preparation of this chapter is assigned to TC 3.6, Water Treatment.

a P Alk = Phenolphthalein alkalinity. M Alk =Methyl orange (total) alkalinity

Treated waters only. Hydroxide also present.

water is nonscaling, it tends to produce more intensive corrosion because of its high conductivity. Dissolved solids are often referred to as total dissolved solids (TDS). Conductivity or specific conductance measures the ability of a water to conduct electricity. Conductivity increases with the total dissolved solids. Specific conductance can be used to estimate total dissolved solids. Silica can form particularly hard-to-remove deposits if allowed to concentrate. Fortunately, silicate deposition is less likely than other deposits. Soluble iron in water can originate from metal corrosion in water systems or as a contaminant in the makeup water supply. The iron can form heat-insulating deposits by precipitation as iron hydroxide or iron phosphate (if a phosphate-based water treatment product is used or if phosphate is present in the makeup water). Sulfates also contribute to scale formation in high-calcium waters. Calcium sulfate scale, however, forms only at much higher concentrations than the more common calcium carbonate scale. High sulfates also contribute to increased corrosion because of their high conductivity. Suspended solids include both organic and inorganic solids suspended in water (particularly unpurified water from surface sources or those that have been circulating in open equipment). Organic matter in surface supplies may be colloidal. Naturally occurring compounds such as lignins and tannins are often colloidal. At high velocities, hard suspended particles can abrade equipment. Settled suspended matter of all types can contribute to concentration cell corrosion. Turbidity can be interpreted as a lack of clearness or brilliance in a water. It should not be confused with color. A water may be dark in color but still clear and not turbid. Turbidity is due to suspended matter in a fmely divided state. Clay, silt, organic matter, microscopic organisms, and similar materials are contributing causes of turbidity. Although suspended matter and turbidity are closely related they are not synonymous. Suspended matter is the quantity of material in a water that can be removed by filtration. The turbidity of water used in HVAC systems should be as low as possible. This is particularly true of boiler feedwater. The turbidity can concentrate in the boiler and may settle out as sludge or mud and lead to deposition. It can also cause increased boiler blowdown, plugging, overheating, priming, and foaming.

Biological Characteristics Bacteria, algae, and fungi can be present in water systems, and their growth can cause operating, maintenance, and health problems.

49.1

201 1 ASHRAE Handbook-HVAC Microorganism growth is affected by temperature, food sources, and water availability. Biological growth can occur in most water systems below 65°C. Problems caused by biological materials range from green algae growth in cooling towers to slime formation from bacteria in secluded and dark areas. The result can be plugging of equipment where flow is essential. Dead algae are often characterized by foul odors and mud-like deposits, which are often high in silica from the cell walls of the diatoms. These problems can be eliminated, or at least reduced to reasonable levels, by mechanical or chemical treatment.

CORROSION CONTROL Corrosion is the destruction of a metal or alloy by chemical or electrochemical reaction with its environment. In most instances, this reaction is electrochemical in nature, much like that in an electric battery. For corrosion to occur, a corrosion cell consisting of an anode, a cathode, an electrolyte, and an electrical connection must exist. Metal ions dissolve into the electrolyte (water) at the anode. Electrically charged particles (electrons) are left behind. These electrons flow through the metal to other points (cathodes) where electron-consuming reactions occur. The result of this activity is the loss of metal and often the formation of a deposit.

Types of Corrosion Corrosion can often be characterized as general, localized or pitting, galvanic, caustic cracking, corrosion fatigue, erosion corrosion, and microbiological corrosion. General corrosion is uniformly distributed over the metal surface. The considerable amount of iron oxide produced by generalized corrosion contributes to fouling. Localized or pitting corrosion exists when only small areas of the metal corrode. Pitting is the most serious form of corrosion because the action is concentrated in a small area. Pitting may perforate the metal in a short time. Galvanic corrosion can occur when two different metals are in contact. The more active (less noble) metal corrodes rapidly. Common examples of galvanic corrosion in water systems are steel and brass, aluminum and steel, zinc and steel, and zinc and brass. If galvanic corrosion occurs, the metal named first corrodes. Corrosion fatigue may occur by one of two mechanisms. In the first mechanism, cyclic stresses (for example, those created by rapid heating and cooling) are concentrated at points where corrosion has roughened or pitted the metal surface. In the second type, cracks often originate where metal surfaces are covered by a dense protective oxide film,and cracking occurs from the action of applied cyclic stresses. Caustic cracking occurs when metal is stressed, water has a high caustic content, a trace of silica is present, and a mechanism of concentration occurs. Stress corrosion cracking can occur in alloys exposed to a characteristic corrosive environment and subject to tensile stress. The stress may be either applied, residual (from processing), or a combination. The resulting crack formation is generally intergranular. Erosion corrosion occurs as a result of flow or impact that physically removes the protective metal oxide surface. This type of corrosion usually takes place due to altered flow patterns or a flow rate that is above design. Microbiologically influenced corrosion occurs when bacteria secrete corrosive acids on the metal surface. Often bacteria commingle with dirt and silt that protect the bacteria from biocides.

Factors That Contribute to Corrosion Moisture. Corrosion does not occur in dry environments. However, some moisture is present as water vapor in most environments. In pure oxygen, almost no iron corrosion occurs at relative humidities up to 99%. However, when contaminants such as sulfur dioxide or solid particles of charcoal are present, corrosion can proceed at

Applications (SI)

relative humidities of 50% or more. The corrosion reaction proceeds on surfaces of exposed metals such as iron and unalloyed steel as long as the metal remains wet. Many alloys develop protective corrosion-product films or oxide coatings and are thus unaffected by moisture. Oxygen. In electrolytes consisting of water solutions of salts or acids, the presence of dissolved oxygen accelerates the corrosion rate of ferrous metals by depolarizing the cathodic areas through reaction with hydrogen generated at the cathode. In many systems, such as boilers or water heaters, most of the dissolved oxygen and other dissolved gases are removed from the water by deaeration to reduce the potential for corrosion. Solutes. In ferrous materials such as iron and steel, mineral acids accelerate the corrosion rate, whereas alkalies decrease it. The likelihood of cathodic polarization, which slows down corrosion, decreases as the concentration of hydrogen ions (i.e., the acidity of the environment) increases. Relative acidity or alkalinity of a solution is defmed as pH; a neutral solution has a pH of 7. The corrosivity of most salt solutions depend on their pH. Because alkaline solutions are generally less corrosive to ferrous systems, it is practical in many closed water systems to minimize corrosion by adding alkali or alkaline salt to raise the pH to 9 or higher. Differential Solute Concentration. For the corrosion reaction to proceed, a potential difference between anode and cathode areas is required. This potential difference can be established between different locations on a metal surface because of differences in solute concentration in the environment at these locations. Corrosion caused by such conditions is called concentration cell corrosion. These cells can be metal ions or oxygen concentration cells. In the metal ion cell, the metal surface in contact with the higher concentration of dissolvedmetal ion becomes the cathodic area, and the surface in contact with the lower concentration becomes the anode. The metal ions involved may be a constituent of the environment or may come from the corroding surface itself. The concentration differences may be caused by the sweeping away of the dissolved metal ions at one location and not at another. In an oxygen concentration cell, the surface area in contact with the surface environment of higher oxygen concentration becomes the cathodic area, and the surface in contact with the surface environment of lower oxygen concentration becomes the anode. Crevices or foreign deposits on the metal surface can create conditions that contribute to corrosion. The anodic area, where corrosion proceeds, is in the crevice or under the deposit. Although they are manifestations of concentration cell corrosion, crevice corrosion and deposit attack are sometimes referred to as separate forms of corrosion. Galvanic or Dissimilar Metal Corrosion. Another factor that can accelerate the corrosion process is the difference in potential of dissimilar metals coupled together and immersed in an electrolyte. The following factors control the severity of corrosion resulting from such dissimilar metal coupling:

z

zyxwvu Relative differences in position (potential) in the galvanic series, with reference to a standard electrode. The greater the difference, the greater the force of the reaction. The galvanic series for metals in flowing aerated seawater is shown in Table 2. Relative area relationship between anode and cathode areas. Because the amount of current flow and, therefore, total metal loss is determined by the potential difference and resistance of the circuits, a small anodic area corrodes more rapidly; it is penetrated at a greater rate than a large anodic area. Polarization of either the cathodic or anodic area. Polarization can reduce the potential difference and thus reduce the rate of attack of the anode. The mineral content of water. As mineral content increases, the resulting higher electrical conductivity increases the rate of galvanic corrosion.

Water Treatment Table 2

49.3

zyxwvutsrq

Galvanic Series of Metals and Alloys in Flowing Aerated Seawater at 4 to 27OC

Corroded End (Anodic or Least Noble) Magnesium alloys Zinc Beryllium Aluminum alloys Cadmium Mild steel, wrought iron Cast iron, flake or ductile Low-alloy high-strength steel Ni-Resist, Types 1 & 2 Naval Brass (CA464), yellow brass (CA268), A1 brass (CA687), red brass (CA230), admiralty brass (CA443), Mn Bronze Tin Copper (CA102, 1lo), Si Bronze (CA655) Lead-tin solder Tin bronze (G & M) Stainless steel, 12 to 14% Cr (AISI types 410,416) Nickel silver (CA 732,735, 745,752, 764,770, 794) 90/10 Copper-nickel (CA 706) 80/20 Copper-nickel (CA 710) Stainless steel, 16 to 18% Cr (AISI Types 430) Lead 70/30 Copper-nickel (CA 715) Nickel-aluminum bronze Silver braze alloys Nickel 200 Silver Stainless steel, 18% Cr, 8% Ni (AISI Types 302,304, 321,347) Stainless steel, 18% Cr, 12% Ni-Mo (AISI Types 316, 317) Titanium Graphite, graphitized cast iron Protected End (Cathodic or Most Noble)

Stress. Stresses in metallic structures rarely have significant effects on the uniform corrosion resistance of metals and alloys. Stresses in specific metals and alloys can cause corrosion cracking when the metals are exposed to specific corrosive environments. The cracking can have catastrophic effects on the usefulness of the metal. Almost all metals and alloys exhibit susceptibility to stress corrosion cracking in at least one environment. Common examples are steels in hot caustic solutions, high zinc content brasses in ammonia, and stainless steels in hot chlorides. Metal manufacturers have technical details on specific materials and their resistance to stress corrosion. Temperature. According to studies of chemical reaction rates, corrosion rates double for every 10 K rise in temperature. However, such a ratio is not necessarily valid for nonlaboratory corrosion reactions. The effect of temperature on a particular system is difficult to predict without specific knowledge of the characteristics of the metals involved and the environmental conditions. An increase in temperature may increase the corrosion rate, but only to a point. Oxygen solubility decreases as temperature increases and, in an open system, may approach zero as water boils. Beyond a critical temperature level, the corrosion rate may decrease due to a decrease in oxygen solubility. However, in a closed system, where oxygen cannot escape, the corrosion rate may continue to increase with an increase in temperature. For those alloys, such as stainless steel, that depend on oxygen in the environment for maintaining a protective oxide film, the reduction in oxygen content due to an increase in temperature can accelerate the corrosion rate by preventing oxide film formation. Temperature can affect corrosion potential by causing a salt dissolved in the environment to precipitate on the metal surface as a protective layer of scale. One example is calcium carbonate scale in hard waters. Temperature can also affect the nature of the corrosion product, which may be relatively stable and protective in certain temperature ranges and unstable and non protective in others. An example of this is zinc in distilled water; the corrosion product is

non protective from 60 to 80°C but reasonably protective at other temperatures. Pressure. Where dissolved gases such as oxygen and carbon dioxide affect the corrosion rate, pressure on the system may increase their solubility and thus increase corrosion. Similarly, a vacuum on the system reduces the solubility of the dissolved gas, thus reducing corrosion. In a heated system, pressure may rise with temperature. It is difficult and impractical to control system corrosion by pressure control alone. Flow Velocity. The effect of flow velocity on the corrosion rate of systems depends on several factors, including Amount of oxygen in the water Type of metal (iron and steel are most susceptible) Flow rate

In metal systems where corrosion products retard corrosion by acting as a physical barrier, high flow velocities may cause the removal of those protective barriers and increase the potential for corrosion. A turbulent environment may cause uneven attack, from both erosion and corrosion. This corrosion is called erosion corrosion. It is commonly found in piping with sharp bends where the flow velocity is high. Copper and softer metals are more susceptible to this type of attack.

Preventive and Protective Measures Materials Selection. Any piece of heating or air-conditioning equipment can be made of metals that are virtually corrosion-proof under normal and typical operating conditions. However, economics usually dictate material choices. When selecting construction materials the following factors should be considered: Corrosion resistance of the metal in the operating environment Corrosion products that may be formed and their effects on equipment operation Ease of construction using a particular material Design and fabrication limitations on corrosion potential Economics of construction, operation, and maintenance during the projected life of the equipment, (i.e., expenses may be minimized in the long run by paying more for a corrosion-resistant material and avoiding regular maintenance). Use of dissimilar metals should be avoided. Where dissimilar materials are used, insulating gaskets andor organic coatings must be used to prevent galvanic corrosion. Compatibility of chemical additives with materials in the system

Protective Coatings. The operating environment has a significant role in the selection of protective coatings. Even with a coating suited for that environment, the protective material depends on the adhesion of the coating to the base material, which itself depends on the surface preparation and application technique. Maintenance. Defects in a coating are difficult to prevent. These defects can be either flaws introduced into the coating during application or mechanical damage sustained after application. In order to maintain corrosion protection, defects must be repaired. Cycles of Concentration. Some corrosion control may be achieved by optimizing the cycles of concentration (the degree to which soluble mineral solids in the makeup water have increased in the circulating water due to evaporation). Generally, adjustment of the blowdown rate and pH to produce a slightly scale-forming condition (see section on Scale Control) will result in an optimum condition between excess corrosion and excess scale. Chemical Methods. Chemical protective film-forming chemical inhibitors reduce or stop corrosion by interfering with the corrosion mechanism. Inhibitors usually affect either the anode or the cathode. Anodic corrosion inhibitors establish a protective film on the anode. Though these inhibitors can be effective, they can be dangerous-if insufficient anodic inhibitor is present, the entire corrosion

49.4

zyxwvutsrqpo 201 1 ASHRAE Handbook-HVAC

Table 3 Typical Corrosion Inhibitors Anodic Corrosion Inhibitors Molybdate Nitrite Orthophosphate Silicate Mainly Cathodic Corrosion Inhibitors Bicarbonate Polyphosphate Phosphonate Zinc Polysilicate General Soluble oils Other organics, such as azole or carboxylate

Applications (SI)

normally protects the galvanized steel for many years. Passivation is best accomplished by controlling pH during initial operation of the cooling tower. Control of the cooling water pH in the range of 7 to 8 for 45 to 60 days usually allows passivation of galvanized surfaces to occur. In addition to pH control, operation with moderate hardness levels of 100 to 300 mgikg as CaC0, and alkalinity levels of 100 to 300 mgikg as CaCO, will promote passivation. Where pH control is not possible, certain phosphate-based inhibitors may help protect galvanized steel. A water treatment company should be consulted for specific formulations.

SCALE CONTROL Scale is a dense coating of predominantly inorganic material formed from the precipitation of water-soluble constituents. Some common scales are

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potential occurs at the unprotected anode sites. This causes severe localized (or pitting) attack. Cathodic corrosion inhibitors form a protective film on the cathode. These inhibitors reduce the corrosion rate in direct proportion to the reduction of the cathodic area. General corrosion inhibitors protect by forming a film on all metal surfaces whether anodic or cathodic. Table 3 lists typical corrosion inhibitors. The most important factor in an effective corrosion inhibition program is the consistent control of both the corrosion inhibition chemicals and the key water characteristics. No program will work without controlling these factors. Cathodic Protection. Sacrificial anodes reduce galvanic attack by providing a metal (usually zinc, but sometimes magnesium) that is higher on the galvanic series than either of the two metals that are coupled together. The sacrificial anode thereby becomes anodic to both metals and supplies electrons to these cathodic surfaces. Proper design and placement of these anodes are important. When properly used, they can reduce loss of steel from the tube sheet of exchangers using copper tubes. Sacrificial anodes have helped supplement chemical programs in many cooling water and process water systems. Impressed-current protection is a similar corrosion control technique that reverses the corrosion cell’s normal current flow by impressing a stronger current of opposite polarity. Direct current is applied to an anode-inert (platinum, graphite) or expendable (aluminum, cast iron)-reversing the galvanic flow and converting the steel from a corroding anode to a protective cathode. The method is very effective in protecting essential equipment such as elevated water storage tanks, steel tanks, or softeners.

White Rust on Galvanized Steel Cooling Towers White rust is a zinc corrosion product that forms on galvanized surfaces. It appears as a white, waxy or fluffy deposit composed of loosely adhering zinc carbonate. The loose crystal structure allows continued access of the corrosive water to exposed zinc. Unusually rapid corrosion of galvanized steel, as evidenced by white rust, can affect galvanized steel cooling towers under certain conditions. Before chromates in cooling tower water were banned, the common treatment system consisted of chromates for corrosion control and sulfuric acid for scale control. This control method generally has been replaced by alkaline treatment involving scale inhibitors at a higher pH. Alkaline water chemistry is naturally less corrosive to steel and copper, but create an environment where white rust on galvanized steel can occur. Also, some scale prevention programs soften the water to reduce hardness, rather than use acid to reduce alkalinity. The resulting soft water is corrosive to galvanized steel. Prevention. White rust can be prevented by promoting the formation of a nonporous surface layer of basic zinc carbonate. This barrier layer is formed during a process called passivation and

Calcium carbonate Calcium phosphate Magnesium salts Silica

The following principal factors determine whether or not a water is scale forming: Temperature Alkalinity or acidity (pH) Amount of scale-forming material present Influence of other dissolved materials, which may or may not be scale-forming As any of these factors changes, scaling tendencies also change. Most salts become more soluble as temperature increases. However, some salts, such as calcium carbonate, become less soluble as temperature increases. Therefore, they often cause deposits at higher temperatures. A change in pH or alkalinity can greatly affect scale formation. For example, as pH or alkalinity increases, calcium carbonate-the most common scale constituent in cooling systemsdecreases in solubility and deposits on surfaces. Some materials, such as silica (SiO,), are less soluble at lower alkalinities. When the amount of scale-forming material dissolved in water exceeds its saturation point, scale may result. In addition, other dissolved solids may influence scale-forming tendencies. In general, a higher level of scale-forming dissolved solids results in a greater chance for scale formation. Indices such as the Langelier Saturation Index (Langelier 1936) and the Ryznar Stability Index ( R y n a r 1944) can be useful tools to predict the calcium carbonate scaling tendency of water. These indices are calculated using the pH, alkalinity, calcium hardness, temperature, and total dissolved solids of the water, and indicate whether the water will favor precipitating or dissolving of calcium carbonate. Methods used to control scale formation include Limit the concentration of scale-forming minerals by controlling cycles of concentration or by removing the minerals before they enter the system (see the section on External Treatments later in this section). Cycles of concentration is the ratio of makeup rate to the sum of blowdown and drift rates. The cycles of concentration can be monitored by calculating the ratio of chloride ion, which is highly soluble, in the system water to that in the makeup water. Make mechanical changes in the system to reduce the chances for scale formation. Increased water flow and exchangers with larger surface areas are examples. Feed acid to keep the common scale forming minerals (e.g., calcium carbonate) dissolved. Treat with chemicals designed to prevent scale. Chemical scale inhibitors work by the following mechanisms:

Water Treatment

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1. Threshold inhibition chemicals prevent scale formation by keeping the scale forming minerals in solution and not allowing a deposit to form. Threshold inhibitors include organic phosphates, polyphosphates, and polymeric compounds. 2. Scale conditioners modify the crystal structure of scale, creating a bulky, transportable sludge instead of a hard deposit. Scale conditioners include lignins, tannins, and polymeric compounds.

Nonchemical Methods Equipment based on magnetic, electromagnetic, or electrostatic technology has been used for scale control in boiler water, cooling water, and other process applications. Magnetic systems are designed to cause scale-forming minerals to precipitate in a low-temperature area away from heat exchanger surfaces, thus producing nonadherent particles (e.g., aragonite form of calcium carbonate versus the hard, adherent calcite form). The precipitated particles can then be removed by blowdown, mechanical means, or physical flushing. The objective of electrostatics is to prevent scale-forming reactions by imposing a surface charge on dissolved ions that causes them to repel. Results of side-by-side comparative tests with conventional water treatment have been mixed. A Federal Technology Alert report regarding these technologies (DOE 1998) stresses that success of the application depends largely on the experience of the installer. The report includes a discussion of the potential benefits achieved and the necessary precautions to consider when applying these systems. ASHRAE Research Project RP-1155 (Cho 2002) studied physical water treatment (PWT). For this study, a PWT device was defmed as a nonchemical method of water treatment for scale prevention or mitigation. Bulk precipitation was proposed as the mechanism of scale prevention. Three different devices described as permanent magnets, a solenoid coil device, and a high-voltage electrode were tested under laboratory conditions. Fouling resistance data obtained in a heat transfer test section supported the benefit of all three devices when configured in optimum conditions.

External Treatments Minerals may also be removed by various external pretreatment methods such as reverse osmosis and ion exchange. Zeolite softening, demineralization, and dealkalization are examples of ion exchange processes.

BIOLOGICAL GROWTH CONTROL Biological growth (algae, bacteria, and fungi) can interfere with a cooling operation due to fouling or corrosion, and may present a health hazard if present in aerosols produced by the equipment. Heating equipment operates above normal biological limits and therefore has fewer microbial problems. When considering biological growth in a cooling system, it is important to distinguish between free-living planktonic organisms and sessile (attached) Organisms. Sessile organisms cause the majority of the problems, though they may have entered and multiplied as planktonic organisms. Biological fouling can be caused by a wide variety of organisms that produce biofihn and slime masses. Slimes can be formed by bacteria, algae, yeasts, or molds and frequently consist of a mixture of these organisms combined with organic and inorganic debris. Organisms such as barnacles and mussels may cause fouling when river, estuarine, or sea water is used. Biological fouling can significantly reduce the efficiency of cooling by reducing heat transfer, increasing back pressure on recirculation pumps, disrupting flow patterns over cooling media, plugging heat exchangers, and blocking distribution systems. In extreme cases the additional mass of slime has caused the cooling media to collapse.

49.5

Microorganisms can dramatically enhance, accelerate or, in some cases, initiate localized corrosion (pitting). Microorganisms can influence localized corrosion directly by their metabolism or indirectly by the deposits they form. Indirect influence may not be mediated by simply killing the microorganisms; deposit removal is usually necessary, while direct influence can be substantially mediated by inhibiting microorganism metabolism. Algae use energy from the sun to convert bicarbonate or carbon dioxide into biomass. Masses of algae can block piping, distribution holes, and nozzles. A distribution deck cover, which drastically reduces the sunlight reaching the algae, is one of the most costeffective control devices for a cooling tower. Biocides are also used to assist in the control of algae. Algae can also provide nutrients for other microorganisms in the cooling system, increasing the biomass in the water. Bacteria can grow in systems even when nutrient levels are relatively low. Yeasts and fungi are much slower growing than bacteria and fmd it difficult to compete in bulk waters for the available food. Fungi do thrive in partially wetted and high humidity areas such as the cooling media. Wood-destroying species of fungi can be a major concern for wooden cooling towers as the fungi consume the cellulose andor lignin in the wood, reducing its structural integrity. Most waters contain organisms capable of producing biological slime, but optimal conditions for growth are poorly understood. Equipment near nutrient sources or that has process leaks acting as a food source is particularly susceptible to slime formation. Even a thin layer of biofilm significantly reduces heat transfer rates in exchangers.

Control Measures Eliminating sunlight from wetted surfaces such as distribution troughs, cooling media, and sumps significantly reduces algae growth. Eliminating deadlegs and low flow areas in the piping and the cooling loop reduces biological growth in those areas. Careful selection of materials of construction can remove nutrient sources and environmental niches for growth. Maintaining a high quality makeup water supply with low bacteria counts also helps minimize biological growth. Equipment should also be designed with adequate access for inspection, sampling, and manual cleaning. Sometimes the effective control of slime and algae requires a combination of mechanical and chemical treatments. For example, when a system already contains a considerable accumulation of slime, a preliminary mechanical cleaning makes the subsequent application of a biocidal chemical more effective in killing the growth and more effective in preventing further growth. A buildup of scale deposits, corrosion product, and sediment in a cooling system also reduces the effectiveness of chemical biocides. Routine manual cleaning of cooling towers, including the use of high level chlorination and a biodispersant (surfactant), helps control Legionella bacteria as well as other microorganisms. Microbiocides. Chemical biocides used to control biological growth in cooling systems fall into two broad categories: oxidizing and nonoxidizing biocides. Oxidizing biocides (chlorine, chlorine-yielding compounds, bromine, bromochlorodimethylhydantoin (BCDMH, or BCD), ozone, iodine, and chlorine dioxide) are among the most effective microbiocidal chemicals. However, they are not always appropriate for control in cooling systems with a high organic loading. In air washers, the odor may become offensive; in wooden cooling towers, excessive concentrations of oxidizing biocides can cause delignification; and overdosing of oxidizing biocides may cause corrosion of metallic components. In systems large enough to justify the cost of equipment to control feeding of oxidizing biocides accurately, the application may be safe and economical. The most effective use of oxidizing biocides is to maintain a constant low level residual in the system. However, if halogen-based oxidizing biocides are fed intermittently (slug dosed), a pH near 7 is advantageous because, at this

49.6 neutral pH, halogens are present as the hypohalous acid (HOR, where R represents the halogen) form over the hypohalous ion (OR-) form. The effectiveness of this shock feeding is enhanced due to the faster killing action of hypohalous acid over that of hypohalous ion. The residual biocide concentration should be tested, using a field test kit, on a routine basis. Most halogenation programs can benefit from the use of dispersants or surfactants (chlorine helpers) to break up microbiological masses. Chlorine has been the oxidizing biocide of choice for many years, either as chlorine gas or in the liquid form as sodium hypochlorite. Other forms of chlorine, such as powders or pellets, are also available. Use of chlorine gas is declining due to the health and safety concerns involved in handling this material and in part due to environmental pressures concerning the formation of chloramines and trihalomethane. Bromine is produced either by the reaction of sodium hypochlorite with sodium bromide on site, or by release from pellets. Bromine has certain advantages over chlorine: it is less volatile, and bromamines break down more rapidly than chloramines in the environment. Also, when slug feeding biocide in high pH systems, hypobromous acid may have an advantage because its dissociation constant is lower than that of chlorine. This effect is less important when biocides are fed continuously. Ozone has several advantages compared to chlorine: it does not produce chloramines or trihalomethane, it breaks down to nontoxic compounds rapidly in the environment, it controls biofilm better, and it requires significantly less chemical handling. The use of ozone-generating equipment in an enclosed space however, requires care be taken to protect operators from the toxic gas. Also, research by ASHRAE has shown that ozone is only marginally effective as a scale and corrosion inhibitor (Gan et al. 1996; Nasrazadani and Chao 1996). Water conditions should be reviewed to determine the need for scale and corrosion inhibitors and then, as with all oxidizing biocides, inhibitor chemicals should be carefully selected to ensure compatibility. To maximize the biocidal performance of the ozone, the injection equipment should be designed to provide adequate contact of the ozone with the circulating water. In larger systems, care should be taken to ensure that the ozone is not depleted before the water has circulated through the entire system. Iodine is provided in pelletized form, often from a rechargeable cartridge. Iodine is a relatively expensive chemical for use on cooling towers and is probably only suitable for use on smaller systems. Nonoxidizing Biocides. When selecting a nonoxidizing microbiocide, the pH of the circulating water and the chemical compatibility with the corrosion a n d o r scale inhibitor product must be considered. The following list, while not exhaustive, identifies some of these products: Quaternary ammonium compounds Methylene bis(thiocyanate) (MBT) Isothiazolones Thiadiazine thione Dithiocarbamates Decyl thioethanamine (DTEA) Glutaraldehyde Dodecylguanidine Benzotriazole Tetrakis(hydroxymethy1)phosphonium sulfate (THPS) Dibromo-nitrilopropionamide (DBNPA) Bromo-nitropropane-do1 Bromo-nitrostyrene (BNS) Proprietary blends The manner in which nonoxidizing biocides are fed is important. Sometimes the continuous feeding of low dosages is neither effective nor economical. Slug feeding large concentrations to achieve a toxic level of the chemical in the water for a sufficient time to kill the

201 1 ASHRAE Handbook-HVAC

Applications (SI)

organisms present can show better results. Water blowdown rate and biocide hydrolysis (chemical degradation) rate affect the required dosage. The hydrolysis rate of the biocide is affected by the type of biocide, along with the temperature and pH of the system water. Dosage rates are proportional to system volume; dosage concentrations should be sufficient to ensure that the contact time of the biocide is long enough to obtain a high kill rate of microorganisms before the minimum inhibitory concentration of the biocide is reached. The period between nonoxidizing biocide additions should be based on the system half life, with sequential additions timed to prevent regrowth of bacteria in the water. Handling Microbiocides. All microbiocides must be handled with care to ensure personal safety. In the United States, cooling water microbiocides are approved and regulated through the EPA and, by law, must be handled in accordance with labeled instructions. Maintenance staff handling the biocides should read the material safety data sheets and be provided with all the appropriate safety equipment to handle the substance. Automatic feed systems should be used that minimize and eliminate the handling of biocides by maintenance personnel. Other Biocides. Ultraviolet irradiation deactivates the microorganisms as the water passes through a quartz tube. The intensity of the light and thorough contact with the water are critical in obtaining a satisfactory kill of microorganisms. Suspended solids in the water or deposits on the quartz tube significantly reduce the effectiveness of this treatment method. Therefore, a filter is often installed upstream of the lamp to minimize these problems. Because the ultraviolet light leaves no residual material in the water, sessile organisms and organisms that do not pass the light source are not affected by the ultraviolet treatment. Ultraviolet irradiation may be effective on humidifiers and air washers where the application of biocidal chemicals is unacceptable and where 100% of the recirculating water passes the lamp. Ultraviolet irradiation is less effective where all the microorganisms cannot be exposed to the treatment, such as in cooling towers. Ultraviolet lamps require replacement after approximately every 8000 h of operation. Metallic ions, namely copper and silver, effectively control microbial populations under very specific circumstances. Either singularly or in combination, copper and silver ions are released into the water via electrochemical means to generate 1 to 2 mgikg of copper andor 0.5 to 1.O mgikg of silver. The ions assist in the control ofbacterial populations in the presence of a free chlorine residual of at least 0.2 mgikg. Copper, in particular, effectively controls algae. Liu et al. (1994) reported control of Legionellapneumophila bacteria in a hospital hot water supply using copper-silver ionization. In this case, Legionella colonization decreased significantly when copper and silver concentrations exceeded 0.4 and 0.04 mgikg, respectively. Also, residual disinfection prevented Legionella colonization for two months after the copper-silver unit was inactivated. Significant limitations exist in the use of copper and silver ion for cooling systems. Many states are restricting the discharge of these ions to surface waters, and if the pH of the system water rises above 7.8, the efficacy of the treatment is significantly reduced. Systems that have steel or aluminum heat exchangers should not be treated by this method, as the potential for the deposition of the copper ion and subsequent galvanic corrosion is significant.

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Legionnaires' Disease Like other living things, Legionella pneumophila, the bacterium that causes Legionnaires' disease (legionellosis), requires moisture for survival. Legionella bacteria are widely distributed in natural water systems and are present in many drinking water supplies. Potable hot water systems between 27 and 50°C, cooling towers, certain types of humidifiers, evaporative condensers, whirlpools and spas, and the various components of air conditioners are considered to be amplifiers. These bacteria are killed in a matter of minutes when exposed to temperatures above 60°C.

Water Treatment

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Legionellosis can be acquired by inhalation of Legionella organisms in aerosols. Aerosols can be produced by cooling towers, evaporative condensers, decorative fountains, showers, and misters. It has been reported that the aerosol from cooling towers can be transmitted over a distance of up to 3 km. If air inlet ducts of nearby air conditioners draw the aerosol from contaminated cooling towers into the building, the air distribution system itself can transmit the disease. When an outbreak of Legionnaires’ disease occurs, cooling towers are often the suspected source. However, other water systems may produce an aerosol and should not be neglected. Amplification of Legionella within protozoans has been demonstrated, and Legionella bacteria are thought to be protected from biocides while growing intracellularly. Amplification of Legionella bacteria in biofilm and slime masses has been shown by a number of researchers. Microbial control programs should consider the effectiveness of the products against slimes as part of the Legionella control program. Humidifiers. Units that generate a water aerosol for humidity control can become amplifiers of bacteria if their reservoirs are poorly maintained. Manufacturers’ recommendations on cleaning and maintenance should be followed closely. Steam humidifiers should not pose a bacterial problem because the steam does not contain bacteria. Whirlpools and Spas. These units pose a potential hazard to users if not properly maintained. The complexity of some units makes cleaning difficult, so a firm that specializes in cleaning these devices may need to be hired. Manufacturers’ instructions should be followed carefully. Decorative Fountains. If these systems become contaminated, Legionella may multiply and pose a hazard to those nearby. The recirculating water should be kept clean and clear with proper filtration. Continuous chlorination or use of another biocide with EPA approval for decorative fountains is recommended. Indoor decorative fountains with ponds containing fish and other aquatic life cannot be chlorinated or treated; steps should be taken to ensure that water does not become airborne via sprays or cascading waterfalls. Roof Ponds. These are used to lower the roof temperature and thus the demand on the air conditioning. If contaminated, such ponds can pose a risk to the staff and general public. Roof ponds should be monitored and treated in the same manner as recirculating cooling water systems (see the section on Selection of Water Treatment). Safety Showers. Safety showers are mandated for safety, but they are used infrequently. Standing reservoirs of nonsterile water at room temperature should be avoided. A preventative maintenance program that includes flushing is suggested. Vegetable Misters or Sprays. Although an older-style ultrasonic mist machine has been implicated in at least one case of this disease, once-through cool-water sprayers, (directly connected to a cold, potable water line with no reservoir) do not appear to be a problem. Machine Shop Cooling. Water used in machining operations may be mixed with oil or other ingredients to improve cooling and cutting efficiency. It is typically stored in holding tanks that are subject to bacterial contamination, including by Legionella. Bacterial activity should be monitored and controlled. Ice-Making Machines. While Legionella bacteria are not likely to amplify in this cold environment, bacterial amplification can occur prior to freezing the water. Graman et al. (1997) described a case in which Legionella were presumed to have been transmitted by aspiration of ice or ice water from an ice machine. Prevention and Control. The Legionella count required to cause illness has not been firmly established because many factors are involved, including (1) virulence and number of Legionella in the air, ( 2 ) rate at which the aerosol dries, (3) wind direction, and (4) susceptibility to the disease of the person breathing the air. The organism is often found in sites not associated with an outbreak of the disease. It has been shown that it is feasible to operate cooling

49.7

systems with Legionella bacteria below the limit of detection and that the only method to prove that a system is operating at these levels is to specifically test for Legionella bacteria, rather than to infer from total bacteria count measurements. Periodic monitoring of circulating water for total bacteria count and Legionella count can be accomplished using culture methods. However, routine culturing of samples from building water systems may not yield an accurate prediction of the risk of Legionella transmission. Monitoring system cleanliness and using a microbial control agent that has proven efficacy or is generally regarded as effective in controlling Legionella populations are also important. Other measures to decrease risk include optimizing cooling tower design to minimize drift, eliminating deadlegs or low flow areas, selecting materials that do not promote the growth of Legionella, and locating the tower so that drift is not injected into the air handlers. The Legionellosis Position Statement, an ASHRAE Position Paper (1 998) has further information on this topic.

SUSPENDED SOLIDS AND DEPOSITATION CONTROL

Mechanical Filtration Strainers, filters, and separators may be used to reduce suspended solids to an acceptable low level. Generally, if the screen is 200 mesh, with an aperture of 74 pm, it is called a strainer; if it is finer than 200 mesh, it is called a filter. Strainers. A strainer is a closed vessel with a cleanable screen designed to remove and retain foreign particles down to 25 pm diameter from various flowing fluids. Strainers extract material that is not wanted in the fluid, and allow saving the extracted product if it is valuable. Strainers are available as single-basket or duplex units, manual or automatic cleaning units, and may be made of cast iron, bronze, stainless steel, copper-nickel alloys, or plastic. Magnetic inserts are available where microscopic iron or steel particles are present in the fluid. Cartridge Filters. These are typically used as fmal filters to remove nearly all suspended particles from about 100 pm down to 1 pm or less. Cartridge filters are typically disposable (i.e., once plugged, they must be replaced). The frequency of replacement, and thus the economical feasibility of their use, depends on the concentration of suspended solids in the fluid, the size of the smallest particles to be removed, and the removal efficiency of the cartridge filter selected. In general, cartridge filters are favored in systems where contamination levels are less than 0.01% by mass (< 100 mgikg). They are available in many different materials of construction and configurations. Filter media materials include yams, felts, papers, nonwoven materials, resin-bonded fabric, woven wire cloths, sintered metal, and ceramic structures. The standard configuration is a cylinder with an overall length of approximately 250 mm, an outside diameter of approximately 65 to 70 mm, and an inside diameter of about 25 to 40 mm, where the filtered fluid collects in the perforated internal core. Overall lengths from 0.1 to 1 m are readily available. Cartridges made of yams, resin-bonded, or melt-blown fibers normally have a structure that increases in density towards the center. These depth-type filters capture particles throughout the total media thickness. Thin media, such as pleated paper (membrane types), have a narrow pore size distribution design to capture particles at or near the surface of the filter. Surface-type filters can normally handle higher flow rates and provide higher removal efficiency than equivalent depth filters. Cartridge filters are rated according to manufacturers’ guidelines. Surface-type filters have an absolute rating, while depth-type filters have a nominal rating that reflects their general classification function. Higher efficiency meltblown depth filters are available with absolute ratings as needed. Sand Filters. A downflow filter is used to remove suspended solids from a water stream. The degree of suspended solids removal

49.8 depends on the combinations and grades of the medium being used in the vessel. During the filtration mode, water enters the top of the filter vessel. After passing through a flow impingement plate, it enters the quiescent (calm) freeboard area above the medium. In multimedia downflow vessels, various grain sizes and types of media are used to filter the water. This design increases the suspended solids holding capacity of the system, which in turn increases the backwashing interval. Multimedia vessels might also be used for low suspended solids applications, where chemical additives are required. In the multimedia vessel, the fluid enters the top layer of anthracite media, which has an effective size of 1 mm. This relatively coarse layer removes the larger suspended particles, a substantial portion of the smaller particles, and small quantities of free oil. Flow continues down through the next layer of fine garnet material, which has an effective size of 0.3 mm. A more finely divided range of suspended solids is removed in this polishing layer. The fluid continues into the fmal layer, a coarse garnet material that has an effective size of 2 mm. Contained in this layer is the header/ lateral assembly that collects the filtered water. When the vessel has retained enough suspended solids to develop a substantial pressure drop, the unit must be backwashed either manually or automatically by reversing the direction of flow. This operation removes the accumulated solids out through the top of the vessel. Centrifugal-Gravity Separators. In this type of separator, liquidsisolids enter the unit tangentially, which sets up a circular flow. Liquidsisolids are drawn through tangential slots and accelerated into the separation chamber. Centrifugal action tosses the particles heavier than the liquid to the perimeter of the separation chamber. Solids gently drop along the perimeter and into the separator’s quiescent collection chamber. Solids-free liquid is drawn into the separator’s vortex (low-pressure area) and up through the separator’s outlet. Solids are either purged periodically or continuously bled from the separator by either a manual or automatic valve system. Bag-Type Filters. These filters are composed of a bag of mesh or felt supported by a removable perforated metal basket, placed in a closed housing with an inlet and outlet. The housing is a welded, tubular pressure vessel with a hinged cover on top for access to the bag and basket. Housings are made of carbon or stainless steel. The inlet can be in the cover, in the side (above the bag), or in the bottom (and internally piped to the bag). The side inlet is the simplest type. In any case, the liquid enters the top of the bag. The outlet is located at the bottom of the side (below the bag). Pipe connections can be threaded or flanged. Single-basket housings can handle up to 14 Lis, multibaskets up to 220 Lis. The support basket is usually of 304 stainless steel perforated with 3 mm holes. (Heavy wire mesh baskets also exist.) The baskets can be lined with fine wire mesh and used by themselves as strainers, without adding a filter bag. Some manufacturers offer a second, inner basket (and bag) that fits inside the primary basket. This provides for two-stage filtering: f r s t a coarse filtering stage, then a finer one. The benefits are longer service time and possible elimination of a second housing to accomplish the same function. The filter bags are made of many materials (cotton, nylon, polypropylene, and polyester) with a range of ratings from 0.01 mm to 0.85 mm. Most common are felted materials because of their depthfiltering quality, which provides high dirt-loading capability, and their fine pores. Mesh bags are generally coarser, but are reusable and, therefore, less costly. The bags have a metal ring sewn into their opening; this holds the bag open and seats it on top ofthe basket rim. In operation, the liquid enters the bag from above, flows out through the basket, and exits the housing cleaned of particulate down to the desired size. The contaminant is trapped inside the bag, making it easy to remove without spilling any downstream. Special Methods. Localized areas frequently can be protected by special methods. Thus, pump-packing glands or mechanical shaft seals can be protected by fresh water makeup or by circulating

201 1 ASHRAE Handbook-HVAC Applications (SI) water from the pump casing through a cyclone separator or filter, then into the lubricating chamber. In smaller equipment, a good dirt-control measure is to install backflush connections and shutoff valves on all condensers and heat exchangers so that accumulated settled dirt can be removed by backflushing with makeup water or detergent solutions. These connections can also be used for acid cleaning to remove calcium carbonate scale. In specifying filtration systems, third-party testing by a qualified university or private test agency should be requested. The test report documentation should include a description of methods, piping diagrams, performance data, and certification. Filters described in this section may also be used where industrial process cooling water is involved. For this type of service, consultation with the filtration equipment manufacturer is essential to ensure proper application.

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START-UP AND SHUTDOWN OF COOLING TOWER SYSTEMS The following guidelines are for start-up (or recommissioning) and shutdown of cooling tower systems:

Start-up and Recommissioning for Drained Systems

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Clean all debris, such as leaves and dirt from the cooling tower. Close building air intakes in the area of the cooling tower to prevent entrainment of biocide and biological aerosols in the building air handling systems. Fill the system with water. While operating the condensing water pump(s) and prior to operating the cooling tower fans, execute one of the following two biocidal treatment programs:

Resume treatment with the biocide that had been used prior to shutdown. Use the services of the water treatment supplier. Maintain the maximum recommended biocide residual (for the specific biocide) for a period sufficient to bring the system under good biological control (residual and time varies with the biocide). Treat the system with sodium hypochlorite at a level of 4 to 5 mgikg free chlorine residual at a pH of 7.0 to 7.6. The residual level of free chlorine must be held at 4 to 5 mgikg for 6 h. Commercially available test kits can be used to measure the residual of free chlorine. Once one of the two biocidal treatment programs has been successfully completed, turn on the fan and the put the system in service. The standard water treatment program (including biocidal treatment) should be resumed at this time.

Start-up and Recommissioning for Undrained (Stagnant) Systems Remove accessible solid debris from bulk water storage vessel. Close building air intakes in the area of the cooling tower to prevent entrainment of biocide and biological aerosols in the building air handlers. Perform one of the two biocide pretreatment procedures (described in the section on Start-up for Drained Systems) directly to the bulk water storage vessel (cooling tower sump, draindown tank, etc.). Do not circulate stagnant bulkcooling water over cooling tower311 or operate cooling towerfans during pretreatment. Stagnant cooling water may be circulated with condenser water pumps if tower fill is bypassed. Otherwise, add approved biocide directly to the bulk water source and mix with manual or sidestream flow methods. Take care to prevent the creation of aerosol spray from the stagnant cooling water from any point in the cooling water system. When one of the two biocidal pretreatments has been successfully completed, the cooling water should be circulated over the tower

49.9

Water Treatment fill. If biocide residual is maintained at a satisfactory level for at least 6 h, the cooling tower fans may then be operated safely. Shutdown When the system is to be shut down for an extended period, the entire system (cooling tower, system piping, heat exchangers, etc.) should be flushed and drained using the following procedure: Add a dispersant and biocide to the system and recirculate for 12 to 24 h. Confer with a water treatment consultant for suitable chemicals and dosage levels. Shut down pumps and completely drain all water distribution piping and headers, as well as the cooling loop. Remove water and debris from dead heads and low areas in the piping, which may not have completely drained. Rinse silt and debris from the sump. Pay special attention to corners and crevices. Add a mild solution of detergent and disinfectant to the sump and rinse. If the sump does not completely drain, pump out the remaining water and residue. If the equipment cannot be completely drained and is exposed to cold temperatures, freeze protection may be required.

Automation capabilities Environmental requirements Water treatment supplier (some technologies are superior to others in terms of economics, ease of use, safety, and impact on the environment) An open recirculating system is typically treated with a scale Inhibitor, corrosion Inhibitor, oxidizing biocide, nonoxidizing biocide, and possibly a dispersant. The exact treatment program depends on the previously mentioned conditions. A water treatment control scheme for a cooling tower might include Chemistry and cycles of concentration control using a conductivity controller Alkalinity control using automatic injection of sulfuric acid based on pH Scale control using contacting water meters, proportional feed, or traced control technology Oxidizing biocide control using an ORP (oxidation-reduction potential) controller Nonoxidizing biocide control using timers and pump systems

SELECTION OF WATER TREATMENT As discussed in the nrevious sections.,manv , methods are available to prevent or correct water-caused problems. The selection of the proper water treatment method, and the chemicals and equipment necessary to apply that method, depends on many factors. The chemical characteristics of the water, which change with the operation of the equipment, are important. Other factors contributing to the selection of proper water treatment are Economics Chemistry control mechanisms Dynamics of the operating system Design of major components (e.g., the cooling tower or boiler) Number of operators available Training and qualifications of personnel Preventive maintenance program

Once-Through Systems Economics is an overriding concern in treating water for oncethrough systems (in which a very large volume of water passes through the system only once). Protection can be obtained with relatively little treatment per unit mass of water because the water does not change significantly in composition while passing through equipment. However, the quantity of water to be treated is usually so large that any treatment other than simple filtration or the addition of a few parts per million of a polyphosphate, silicate, or other inexpensive chemical may not be practical or affordable. Intermittent treatment with polyelectrolytes can help maintain clean conditions when the cooling water is sediment-laden. In such systems, it is generally less expensive to invest more in corrosion-resistant construction materials than to attempt to treat the water.

Open Recirculating Systems In an open recirculating system with chemical treatment, more chemical must be present because the water composition changes significantly by evaporation. Corrosive and scaling constituents are concentrated. However, treatment chemicals also concentrate by evaporation; therefore, after the initial dosage, only moderate dosages maintain the higher level of treatment needed. The selection of a water treatment program for an open recirculating system depends on the following major factors: Economics Water quality Performance criteria (e.g., corrosion rate, bacteria count, etc.) System metallurgy Available staffing

Air Washers and Sprayed-Coil Units A water treatment program for an air washer or a sprayed-coil unit is usually complex and depends on the purpose and function of the system. Some systems, such as sprayed coils in office buildings, are used primarily to control the temperature and humidity. Other systems are intended to remove dust, oil vapor, and other airborne contaminants from an airstream. Unless the water is properly treated, the fouling characteristics of the contaminants removed from the air can cause operating problems. Scale control is important in air washers or sprayed coils providing humidification. The minerals in the water may become concentrated (by evaporation) enough to cause problems. Inhibitor/ dispersant treatment commonly used in cooling towers are often used in air washers to control scale formation and corrosion. Suitable dispersants and surfactants are often needed to control oil and dust removed from the airstream. The type of dispersant depends on the nature of the contaminant and the degree of contamination. For maximum operating efficiency, dispersants should produce minimal amounts of foam. Control of slime and bacterial growth is also necessary in the treatment of air washers and sprayed coils. The potential for biological growth is enhanced, especially if the water contains contaminants that are nutrients for the microorganisms. Due to variations in conditions and applications of air-washing installations and the possibility of toxicity problems, individual treatment options should be discussed with water treatment experts before a program is chosen. All microbiocides applied in air washers must have specific regulatory approval.

Ice Machines Lime scale formation, cloudy or “milky” ice, objectionable taste and odor, and sediment are the most frequently encountered water problems in ice machines. Lime scale formation is probably the most serious problem because it interferes with the harvest cycle by forming on the freezing surfaces, preventing the smooth release of ice from the surface to the harvest bin. Scale is caused by dissolved minerals in the water. Water freezes in a pure state and dissolved minerals concentrate in the unfrozen water; some eventually deposit on the machine’s freezing surfaces as scale. As shown in Table 4, the probability of scale formation in an ice machine varies directly with the concentrations of carbonate and bicarbonate in the water circulating in the machine. Dirty or scaled-up ice makers should be thoroughly cleaned before the water treatment program is started. Water distributor

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201 1 ASHRAE Handbook-HVAC

49.10 Table 4 Amount of Scale in an Ice Machine Total Alkalinity as Bicarbonate, mg/kg

0 to 49

0 to 49 50 to 99 100 to 199 200 and UD

None Very light Very light Verv lieht

Hardness as Calcium Carbonate, mg/kg

50 to 99

100 to 199

Very light Very light Moderate Moderate Troublesome Troublesome Troublesome Heavv

200 and up Very light Moderate Heavy Verv heavv

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holes should be cleared, and all loose sediment and other material should be flushed from the system. Existing scale can be removed by circulating an acid solution through the system. Slowly soluble food-grade polyphosphates inhibit scale formation on freezing surfaces during normal operation by keeping hardness in solution. Although polyphosphates can inhibit lime scale in the ice-making section and help prevent sludge deposits of loose particles of lime scale in the sump, they do not eliminate the soft, milky, or white ice caused by a high concentration of dissolved minerals in the water. Even with proper chemical treatment, recirculating water having a mineral content above 500 to 1000 mgikg cannot produce clear ice. Increasing bleed off or reducing the thickness of the ice slab or the size of the cubes may mitigate the problem. However, demineralizing or distillation equipment is usually needed to prevent white ice production. Another problem frequently encountered with ice machines is objectionable taste or odor. When water containing a material having an offensive taste or odor is used in an ice machine, the taste or odor is trapped in the ice. An activated carbon filter on the makeup water line can remove the objectionable material from the water. Carbon filters must be serviced or replaced regularly to avoid organic buildup in the carbon bed. Occasionally, slime growth causes an odor problem in an ice machine. This problem can be controlled by regularly cleaning the machine with a food-grade acid. If slime deposits persist, sterilization of the ice machine may be helpful. Feedwater often contains suspended solids such as mud, rust, silt, and dirt. To remove these contaminants, a sediment filter of appropriate size can be installed in the feed lines.

Closed Recirculating Systems In a closed recirculating system, water composition remains fairly constant with very little loss of either water or treatment chemical. Closed systems are often defmed as those requiring less than 5% makeup per year. The need for water treatment in such systems (i.e., water heating, chilled water, combined cooling and heating, and closed loop condenser water systems) is often ignored based on the rationalization that the total amount of scale from the water initially filling the system would be insufficient to interfere significantly with heat transfer, and that corrosion would not be serious. However, leakage losses are common, and corrosion products can accumulate sufficiently to foul heat transfer surfaces. Therefore, all systems should be adequately treated to control corrosion. Systems with high makeup rates should be treated to control scale as well. The selection of a treatment program for closed systems should consider the following factors: Economics System metallurgy Operating conditions Makeup rate System size Possible treatment technologies include

Applications (SI)

Buffered nitrite Molybdate Silicates Polyphosphates Oxygen scavengers Organic blends

Before new systems are treated, they must be cleaned and flushed. Grease, oil, construction dust, dirt, and mill scale are always present in varying degrees and must be removed from the metallic surfaces to ensure adequate heat transfer and to reduce the opportunity for localized corrosion. Detergent cleaners with organic dispersants are available for proper cleaning and preparation of new closed systems.

Water Heating Systems Secondary and Low-Temperature. Closed, chilled-water systems that are converted to secondary water heating during winter and primary low-temperature water heating, both of which usually operate in the range of 60 to 120°C, require sufficient inhibitors to control corrosion to less than 125 pm per year. Ethylene glycol or propylene glycol may be used as antifreeze in secondary hot water systems. Such glycols are available commercially, with inhibitors such as sodium nitrite, potassium phosphate, and organic inhibitors for nonferrous metals added by the manufacturer. These require no further treatment, but softened water should be used for all filling and makeup requirements. Samples should be checked periodically to ensure that the inhibitor has not been depleted. Analytical services are available from the glycol manufacturers and others for this purpose. Environment-and High-Temperature.Environment-temperature water heating systems (120 to 175°C) and high-temperature, highpressure hot water systems (above 175°C) require careful consideration of treatment for corrosion and deposit control. Makeup water for such systems should be demineralized or softened to prevent scale deposits. For corrosion control, oxygen scavengers such as sodium sulfite can be added to remove dissolved oxygen. Electrode boilers are sometimes used to supply low- or hightemperature hot water. Such systems use heat generated due to the electrical resistance of the water between electrodes. The conductivity of the recirculating water must be in a specific range depending on the voltage used. Treatment of this type of system for corrosion and deposit control varies. In some cases oil-based corrosion inhibitors that do not contribute to the conductivity of the recirculating water are used.

Brine Systems Systems containing brine, a strong solution of sodium chloride or calcium chloride, must be treated to control corrosion and deposits. Sodium nitrite at a minimum 3000 mgikg in calcium brines or 4000 mgikg in sodium brines, and a pH between 7.0 and 8.5 should provide adequate protection. Organic inhibitors are available that may provide adequate protection where nitrites cannot be used. Molybdates should not be used with calcium brines because insoluble calcium molybdate will precipitate.

Boiler Systems Many treatment methods are available for steam-producing boilers; the method selected depends on Makeup water quality Makeup water quantity (or percentage condensate return) Pretreatment equipment Boiler operating conditions Steam purity requirements Economics Pretreatment for makeup water could consist of Water softeners (for removal of calcium and magnesium hardness)

49.11

Water Treatment Deaerators (for removal of dissolved gases; especially oxygen and carbon dioxide) Dealkalizers (to remove alkalinity in systems with high makeup rates and high alkalinity makeup water) Demineralizers (to remove almost all the hardness, alkalinity, and solids, depending on the application) Reverse osmosis (can remove up to 99% of minerals and dissolved solids from the water leaving almost pure H,O) Contaminants that are not removed mechanically by pretreatment equipment must be treated chemically. Once in the feedwater, dissolved gases, hardness, and dissolved minerals must be treated to prevent deposition and corrosion. ASME (1994) and ABMA (1995) have published recommended water chemistry limits for boiler water. Treatment of the boiler water is often determined by the end use of the steam. Treatment regimens may include reduction of alkalinity; hardness removal; silica removal; oxygen reduction; and the feed of scale and corrosion inhibitors, oxygen scavengers, condensate treatment chemicals, and antifoams. These regimens are described in the following paragraphs. Prevention of Scale. After the feedwater is pretreated, scale is controlled with phosphates, acrylates, polymers, chelates, and coagulation programs. Chelates, polymers, and acrylates work by binding the hardness, thereby preventing precipitation and scale formation. Phosphates and coagulation programs work in combination with sludge conditioners (tannins, lignins, starches, and synthetic polymers) to produce a softened precipitate that is removed by blowdown of the boiler. Prevention of Corrosion and Oxygen Pitting. While boilers can corrode as the result of low boiler water pH or misuse of certain chemicals, corrosion is primarily caused by oxygen. After mechanical deaeration, boiler feedwater must be treated chemically. Effective deaeration removes most of the dissolved oxygen. (Most properly operating deaerators can remove oxygen down to 0.007 mgikg and deaerating heaters can remove oxygen down to 0.04 mgikg.) Oxygen scavengers such as catalyzed sodium sulfite and proprietary organic oxygen scavengers should then be fed to react with the residual oxygen in feedwater after deaeration. Oxygen scavengers will not only provide added protection to the boiler but to the steam and condensate system as well. Oxygen at levels as low as 0.005 mgikg can cause oxygen pitting in the steam and condensate system if not chemically reduced by oxygen scavengers. Most of the corrosion damage to boilers and associated equipment occurs during idle periods. The corrosion is caused by the exposure of wet metal to oxygen in the air or water. For this reason, special precautions must be taken to prevent corrosion while boilers are out of service. Wet Boiler Lay-Up. This is a method of storing boilers full of water so that they can be returned to service. It involves adding extra chemicals (usually something to increase alkalinity, an oxygen scavenger, and a dispersant) to the boiler water. The water level is raised in the idle boiler to eliminate air spaces, and the boiler is kept completely full of treated water. Superheaters require special protection. Nitrogen gas can also be used on airtight boilers to maintain a positive pressure on the boiler, thereby preventing oxygen in-leakage. Dry Boiler Lay-Up. This method of lay-up is usually for longer boiler outages. It involves draining, cleaning, and drying the boiler. A material that absorbs moisture, such as hydrated lime or silica gel, is placed in trays inside the boiler. The boiler is then sealed carefully to keep out air. Periodic inspection and replacement of the drying chemical are required during long storage periods.

Steam and Condensate Systems Two problems associated with steam and condensate systems include general corrosion and pitting corrosion. In order to prevent

condensate corrosion, the systems must be protected from acidic conditions, which lead to general corrosion, and oxygen, which leads to pitting corrosion. Protection can be by mechanical or chemical means or a combination of both. The following methods are commonly used for condensate system protection.

Protection from General Corrosion

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Mechanical Protection. Reduce alkalinity from boiler feedwater to minimize the amount of carbon dioxide in the system. Carbon dioxide reacts with water (condensate) and forms carbonic acid that will corrode condensate system metal. Alkalinity can be reduced by dealkalization, demineralization, and reverse osmosis. Note: In many cases mechanical reduction of alkalinity is not needed due to low alkalinity makeup water andor feedwater. Chemical Protection. Use volatile amines, such as morpholine, diethylaminoethanol (DEAE), and cyclohexylamine, to neutralize carbonic acid and keep the condensate pH between 8.0 and 9.0. Protection from Oxygen Corrosion Mechanical Protection. Reduce oxygen from all boiler feedwater to prevent oxygen carryover to the steam and condensate system (via mechanical methods and chemical oxygen scavengers). Chemical Protection. Feed filming amines, such as octadecylamine, to the steam to form a thin, hydrophobic film on the condensate system surfaces. Chemical Protection. Feed a volatile oxygen scavenger to the steam to scavenge the oxygen. The need for chemical treatment can be reduced by designing and maintaining tight return systems so that the condensate is returned to the boiler and less makeup is required in the boiler feedwater. The greater the amount of makeup, the more the system requires increased chemical treatment.

TERMINOLOGY The following terms are commonly used in the water treatment industry as they pertain to corrosion, scale formation and fouling. Alkalinity. The sum of bicarbonate, carbonate, and hydroxide ions in water. Other ions, such as borate, phosphate, or silicate, can also contribute to alkalinity. Anion. A negatively charged ion of an electrolyte that migrates toward the anode influenced by an electric potential gradient. Anode. The electrode of an electrolytic cell at which oxidation occurs. Biological deposits. Water-formed deposits of biological organisms or the products of their life processes, such as barnacles, algae, or slimes. Cathode. The electrode of an electrolytic cell at which reduction occurs. Cation. A positively charged ion of an electrolyte that migrates toward the cathode influenced by an electric potential gradient. Corrosion. The deterioration of a material, usually a metal, by reaction with its environment. Corrosivity. The capacity of an environment or environmental factor to bring about destruction of a specific metal by the process of corrosion. Electrolyte. A solution through which an electric current can flow. Filtration. Process of passing a liquid through a porous material in such a manner as to remove suspended matter from the liquid. Galvanic corrosion. Corrosion resulting from the contact of two dissimilar metals in an electrolyte or from the contact of two similar metals in an electrolyte of nonuniform concentration. Hardness. The sum of the calcium and magnesium ions in water; usually expressed in mgikg as CaC03.

49.12

zyxwvutsrqp 201 1 ASHRAE Handbook-HVAC Applications (SI)

Inhibitor. A chemical substance that reduces the rate of corrosion, scale formation, fouling, or slime production. Ion. An electrically charged atom or group of atoms. Passivity. The tendency of a metal to become inactive in a given environment. pH. The logarithm of the reciprocal of the hydrogen ion concentration of a solution. pH values below 7 are increasingly acidic; those above 7 are increasingly alkaline. Polarization. The deviation from the open circuit potential of an electrode resulting from the passage of current. ppm. Parts per million by mass. In water, ppm are essentially the same as milligrams per liter (mgiL); 10 000 ppm (mgiL) = 1%. Scale. 1. The formation at high temperature of thick corrosion product layers on a metal surface. 2. The precipitation of waterinsoluble constituents on a surface. Sludge. A sedimentary water-formed deposit, either of biological origin or suspended particles from the air. Tuberculation. The formation over a surface of scattered, knoblike mounds of localized corrosion products. Water-formed deposit. Any accumulation of insoluble material derived from water or formed by the reaction with water on surfaces in contact with it.

REFERENCES

ASHRAE. 1998. Legionellosis position statement and Legionellosis position paper. ASME. 1994. Consensus on operating practices for the control of feedwater and boiler water chemistry in modem industrial boilers. Research Committee on Water in Thermal Power Systems, Industrial Boiler Subcommittee. American Society of Mechanical Engineers, New York. Cho, Y.I. 2002. Efficiency of physical water treatments in controlling calcium scale accumulation in recirculating open cooling water system. ASHRAE Research Project RP-1155, Final Report. DOE. 1998. Non-chemical technologies for scale and hardness control. Federal Technology Alert DOE/EE-0162. U S . Department of Energy. Gan, F., D.-T. Chin, and A. Meitz. 1996. Laboratoly evaluation of ozone as a corrosion inhibitor for carbon steel, copper, and galvanized steel in cooling water. ASHRAE Transactions 102(1). Graman, P.S., G.A. Quinlan, and J.A. Rank. 1997. Nosocomial legionellosis traced to a contaminated ice machine. Infection Control and Hospital Epidemiology 18(9):637-640. Langelier, W.F. 1936. The analytical control of anticorrosion water treatment. Journal of the American Water Works Association 28: 1500. Liu, Z., J.E. Stout, L. Tedesco, M. Boldin, C. Hwang, W.F. Diven, and V.L Yu. 1994. Controlled evaluation of copper-silver ionization in eradicating Legionellapneumophila from a hospital water distribution system. The Journal ofhfectious Diseases 169:919-922. Nasrazadani, S. and T.J. Chao. 1996. Laboratoly evaluations of ozone as a scale inhibitor for use in open recirculating cooling systems. ASHRAE Transactions 102(2). Ryznar, J.W. 1944. A new index for determining amount of calcium carbonate scale formed by a watel: Journal of the American Water Work Association 36:472.

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ABMA. 2005. Boiler water quality requirements and associated steam quality for industrial/commercial and institutional boilers. Publication 402. American Boiler Manufacturers Association, Arlington, VA.

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CHAPTER 50

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SERVICE WATER HEATING ..................................................... Water-Heating Equipment ........................................................ Design Considerations............................................................. Distribution .............................................................................. Terminal Hot- Water Usage Devices .........................................

50.1 50.1 50.2 50.2 50.4 50.5 50.9

Water Quality, Scale, and Corrosion Safety Devicesfo Special Concerns Hot- Water Requirements and Storage Equipment Sizing ................................................................ Boilers for Indirect Water Heating ......................................... Water-Heating Energy Use ....................................................

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ATER HEATING energy use is second only to space conditioning in most residential buildings, and is also significant in many commercial and industrial settings. In some climates and applications, water heating is the largest energy use in a building. Moreover, quick availability of adequate amounts of hot water is an important factor in user satisfaction. Both water and energy waste can be significant in poorly designed service water-heating systems: from over- or undersizing pipes and equipment, from poor building layout, and from poor system design and operating strategies. Good service water-heating system design and operating practices can often reduce frst costs as well as operating costs. The information in this chapter is thus critical for the sustainable design and operation of many buildings.

SYSTEM ELEMENTS A service water-heating system has (1) one or more heat energy sources, (2) heat transfer equipment, (3) a distribution system, and (4) terminal hot-water usage devices. Heat energy sources may be (1) fuel combustion; (2) electrical conversion; (3) solar energy; (4) geothermal, air, or other environmental energy; andor (5) recovered waste heat from sources such as flue gases, ventilation and air-conditioning systems, refrigeration cycles, and process waste discharge. Heat transfer equipment is direct, indirect, or a combination of the two. For direct equipment, heat is derived from combustion of fuel or direct conversion of electrical energy into heat and is applied within the water-heating equipment. For indirect heat transfer equipment, heat energy is developed from remote heat sources (e.g., boilers; solar energy collection; air, geothermal, or other environmental source; cogeneration; refrigeration; waste heat) and is then transferred to the water in a separate piece of equipment. Storage tanks may be part of or associated with either type of heat transfer equipment. Distribution systems transport hot water produced by waterheating equipment to terminal hot-water usage devices. Water consumed must be replenished from the building water service main. For locations where constant supply temperatures are desired, circulation piping or a means of heat maintenance must be provided. Terminal hot-water usage devices are plumbing fixtures and equipment requiring hot water that may have periods of irregular flow, constant flow, and no flow. These patterns and their related water usage vary with different buildings, process applications, and personal preference. In this chapter, it is assumed that an adequate supply of building service water is available. If this is not the case, alternative strategies such as water accumulation, pressure control, and flow restoration should be considered. The preparation of this chapter is assigned to TC 6.6, Service Water Heating Systems.

50.11 50.28 50.28

WATER-HEATING TERMINOLOGY Recovery efficiency. Heat absorbed by the water divided by heat input to heating unit during the period that water temperature is raised from inlet temperature to fmal temperature (includes heat losses from water heater jacket and/or tank). Recovery rate. The amount of hot water that a residential water heater can continually produce, usually reported as flow rate in litres per hour that can be maintained for a specified temperature rise through the water heater. Fixture unit. A number, on an arbitrarily chosen scale, that expresses the load-producing effects on the system of different kinds of fixtures. Thermal efficiency. Heat in water flowing from the heater outlet divided by the energy input to the heating unit over a specific period of steady-state conditions (includes heat losses from the water heater jacket and/or tank). Input efficiency. Heat entering water in the heating device divided by energy input to the heating unit over a specific period of steady-state conditions, or while heating from cold to hot, depending on how stated (steady-state versus average input efficiency); it does not include heat losses from the water heater jacket andor tank. When used with fossil-fuel-fired equipment, this is commonly called combustion efficiency. Energy factor. The delivered efficiency of a residential water heater when operated as specified in U.S. Department of Energy (DOE) test procedures (DOE 2001). See also ASHRAE Standard 118.2. First-hour rating. An indicator of the maximum amount of hot water a residential water heater can supply in 1 h. This rating is used by the Federal Trade Commission (FTC) for comparative purposes. Because peak draws taken over periods less than 1 h frequently drive residential equipment sizing, frst-hour rating alone should not be used for equipment sizing. As for larger systems, storage tank volume and heating rate also play important roles. Standby loss. As applied to a tank water heater (under test conditions with no water flow), the average hourly energy consumption divided by the average hourly heat energy contained in stored water, expressed as a percent per hour. This can be converted to the average watts energy consumption required to maintain any wateriair temperature difference by taking the percent times the temperature difference, times 1.15 k W ( m 3 . K) (a nominal specific heat for water), times the tank capacity, and then dividing by 100. Standby loss coefficient. The heat input (in WIK) into a storage water heater when operated as specified in U.S. Department of Energy (DOE) test procedures (DOE 2001). This value is essentially the standby loss divided by the difference in temperature between the average stored water temperature and the surrounding air temperature, and also includes the effect of recovery efficiency for providing the necessary heat energy to offset the heat loss.

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50.2

Hot-water distribution efficiency. Heat contained in the water at points of use divided by heat delivered at the heater outlet at a given flow. Heatedsystem efficiency. Heat contained in the water at points of use divided by the heat input to the heating unit at a given flow rate (thermal efficiency times distribution efficiency). Heat trap. A device to counteract the natural convection of heated water in a vertical pipe. Commercially available heat traps for large equipment are generally 360" loops of tubing; heat traps can also be constructed of pipes connected to the water heater (inlet or outlet) that direct flow downward before connecting to the vertical supply or hot-water distribution system. Tubing or piping heat traps should have a loop diameter or length of downward piping of at least 300 mm. Various prefabricated check-valve-like heat traps are available for residential-sized equipment, using balls, flexible flaps, or moving disks. Overall system efficiency. Heat energy in the water delivered at points of use divided by the total energy supplied to the heater for any selected period. System standby loss. The amount of heat lost from the waterheating system and the auxiliary power consumed during periods of nonuse of service hot water.

SYSTEM PLANNING The goals of system planning are to (1) size the system properly; (2) optimize system efficiency; and (3) minimize frst, operating, and overall life-cycle costs. It is important to design systems so that they perform well from both functional and energy-use perspectives. Flow rate, temperature, and total flow over specific time periods are the primary factors to be determined in the hydraulic and thermal design of a water-heating and piping system. Operating pressures, time of delivery, and water quality are also factors to consider. Separate procedures are used to select water-heating equipment and to design the piping system. However, water-heating equipment sizing and piping system design should be considered together for best system design. Oversized or excessively long piping exacerbates delivery delay andor energy waste. Water-heating equipment, storage facilities, and piping should (1) have enough capacity to provide the required hot water while minimizing waste of energy or water and (2) allow economical system installation, maintenance, and operation. Water-heating equipment types and designs are based on the (1) energy source, (2) application of the developed energy to heat the water, and (3) control method used to deliver the necessary hot water at the required temperature under varying water demand conditions. Application of water-heating equipment within the overall design of the hot-water system is based on (1) location of the equipment within the system, (2) related temperature requirements, (3) volume of water to be used, and (4) flow rate. Consideration of peak demand effects on utilities is also of growing importance. Additional planning is required when the system providing the potable hot water is also used for space heating or other purposes. Some special water heater designs are made for this purpose, but this end can also be achieved by combining needed components in an appropriate manner.

Energy Sources

Applications (SI)

WATER-HEATING EQUIPMENT

Gas-Fired Systems Automatic storage water heaters incorporate the burner(s), storage tank, outer jacket, and controls such as a thermostat in a single unit and have an input-to-storage capacity ratio of less than 300 W per litre. Automatic instantaneous water heaters are produced in two distinctly different types. Tank-type instantaneous heaters have an input-to-storage capacity ratio of 300 W per litre or more and a thermostat to control energy input to the heater. Water-tube instantaneous heaters have minimal water storage capacity. They usually have a flow switch that controls the burner, and may have a modulating fuel valve that varies fuel flow as water flow changes. Tankless water heaters have almost no storage capacity, and heat water as it flows once through the water heater. Heating rate required varies with water flow rate and needed temperature rise. Most modern gas-fred tankless water heaters have a flow switch or equivalent to confirm flow before the burner activates. Some have advanced multistage or modulating burners to better control outlet temperature. Some also incorporate fixed or modulating water flow rate controls to ensure that water temperature reaches at least a minimum outlet temperature (i.e., it restricts flow rate, possibly below that which the user requested, to avoid undesirably cool outlet water temperature if burners are already operating at maximum heating rate). Most advanced designs also incorporate electronic ignition controls, thus minimizing standby energy losses compared to having a tank and continuously burning pilot light. Properly applied tankless water heaters thus have lower overall energy use and higher efficiency compared to minimum-efficiency tank types serving the same loads. Note, however, that tankless gas water heaters have odoff cycling-rate-related energy losses that, under some draw patterns, may reduce their apparent efficiency advantage. They may also have minimum flow rate requirements before they activate, which may require users to modify their behavior (e.g., use a higher flow rate than they normally would andor leave water running when they would normally turn it off) to obtain hot water. Sometimes, it may be beneficial to reduce the hot-water delivery temperature to reduce point-of-use mixing with cold water, thereby increasing hot-water flow rate. Circulating tank water heaters are classified in two types: (1) automatic, in which the thermostat is located in the water heater, and (2) nonautomatic, in which the thermostat is located within an associated storage tank. Hot-water supply boilers are capable of providing service hot water. They are typically installed with separate storage tanks and applied as an alternative to circulating tank water heaters. Outdoor models are wind- and rain-tested. They are available in most of the classifications previously listed. Direct-vent models are to be installed inside, but are not vented through a conventional chimney or gas vent and do not use ambient air for combustion. They must be installed with the means specified by the equipment manufacturer for venting (typically horizontal) and for supplying combustion air from outside the building. Power vent equipment uses a powered fan or blower to move combustion products, allowing horizontal as well as vertical venting. Direct-fired equipment passes cold water through a stainless steel or other heat exchange medium, which breaks up the water into very small droplets. These droplets then come into direct contact with heat rising from a flame, which heats the water directly. Residential water-heating equipment is usually the automatic storage type, although increasing numbers of tankless water heaters are being installed. For industrial and commercial applications, commonly used types of heaters are (1) automatic storage, (2) circulating tank, (3) instantaneousitankless and (4) hot-water supply boilers.

zyxwvutsrqpo

The choice of energy source(s) is influenced by equipment type and location. These decisions should be made only after evaluating purchase, installation, operating, and maintenance costs. A lifecycle analysis is highly recommended. In making energy conservation choices, consult the ANSI/ ASHRAEiIESNA Standards 90.1 and 90.2, or the sections on Service Water Heating of ANSIiASHRAEiIESNA Standard 100, as well as the section on Design Considerations in this chapter.

Service Water Heating

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Installation guidelines for gas-fred water heaters can be found in the National Fuel Gas Code, NFPA Standard 54IANSI Standard 2223.1. This code also covers sizing and installation of venting equipment and controls.

Oil-Fired Systems Oil-fred water heaters are generally the storage tank type. Models with a storage tank of 200 L or less with an input rating of 30 kW or less are usually considered residential models. Commercial models are offered in a wide range of input ratings and tank sizes. There are models available with combination gasioil burners, which can be switched to burn either fuel, depending on local availability. Installation guidelines for oil-fired water heaters can be found in NFPA Standard 31IANSI Standard Z95.1.

Electric Electric water heaters are generally the storage type, consisting of a tank with one or more immersion heating elements. The heating elements consist of resistance wire embedded in refractories having good heat conduction properties and electrical insulating values. Heating elements are fitted into a threaded or flanged mounting for insertion into a tank. Thermostats controlling heating elements may be of the immersion or surface-mounted type. Residential storage tank water heaters range up to 450 L with input up to 12 kW. They have a primary resistance heating element near the bottom and often a secondary element located in the upper portion of the tank. Each element is controlled by its own thermostat. In dual-element heaters, the thermostats are usually interlocked so that the lower heating element cannot operate if the top element is operating. Thus, only one heating element operates at a time to limit the current draw. Commercial storage tank water heaters are available in many combinations of element quantity, wattage, voltage, and storage capacity. Storage tanks may be horizontal or vertical. Compact, low-volume models are used in point-of-use applications to reduce hot-water piping length. Locating the water heater near the point of use makes recirculation loops unnecessary. Instantaneous or tankless electric water heaters have almost no storage capacity and heat water as it flows once through the water heater. Heating rate required varies with water flow rate and needed temperature rise. Tankless electric water heaters for residential applications are available in heating capacities from a low of about 1.5 kW to a high of about 38 kW. Smaller-capacity units (typically 12 kW or less, but this varies with geographic location and entering cold-water temperature) are sometimes used in lavatory (sink) and other point-of-use applications such as remote low-use showers, small hot tubs, whirlpool baths, and other lowflow-rate applications. Larger sizes (above 18 kW) can sometimes be used in whole-house applications, depending on geographic location (and hence entering cold water temperature) and site hotwater use profiles (see Table 15). Tankless water heaters can, if equipped with appropriate controls, be used in booster a n d o r recirculating water-heating systems. Note that not all models can be used to heat already partially warmed water: this capability varies among models. Heat pump water heaters (HPWHs) use a vapor-compression refrigeration cycle to extract energy from an air, ground, or water source to heat water. HPWHs may be add-on or integrated devices. Integrated units include a storage tank and supplemental heating. Add-on units can be connected to a storage tank. The heat pump cycle of some HPWHs has a maximum output temperature of 52 to 60°C, although other cycles can deliver temperatures in the range of 82°C. Where a higher delivery temperature is required than the HPWH can produce, a supplemental or booster water heater downstream of the storage tank should be used. HPWHs function most efficiently where inlet water temperature is low and source

temperature is w m . Systems should be sized to allow high HPWH run time, which in some cases can require additional storage tank capacity above that normal for the application. As the HPWH collects heat, it provides a potentially useful cooling effect and, in airsource units, also dehumidifies the air. The effect of HPWH cooling output on the building’s energy balance should be considered. Cooling output should be directed to provide occupant comfort and avoid interfering with temperature-sensitive equipment (EPRI 1990). Demand-controlled water heating can significantly reduce the cost ofheating water electrically. Demand controllers operate on the principle that a building’s peak electrical demand exists for a short period, during which heated water can be supplied from storage rather than through additional energy applications. Shifting the use of electricity for service water heating from peak demand periods allows water heating at the lowest electric energy cost in many electric rate schedules. The building electrical loadmust be detected and compared with peak demand data. When the load is below peak, the control device allows the water heater to operate. Some controllers can program deferred loads in steps as capacity is available. The priority sequence may involve each of several banks of elements in (1) a water heater, (2) multiple water heaters, or (3) water-heating and other equipment having a deferrable load, such as pool heating and snow melting. When load controllers are used, hot-water storage must be sized appropriately. Electric off-peak storage water heating is a water-heating equipment load management strategy whereby electrical demand to a water-heating system is time-controlled, primarily in relation to the building or utility electrical load profile. This approach may require increased tank storage capacity and/or stored-water temperature to accommodate water use during peak periods. Sizing recommendations in this chapter apply only to water heating without demand or off-peak control. When demand control devices are used, the storage and recovery rate may need to be increased to supply all the hot water needed during the peak period and during the ensuing recovery period. Manian and Chackeris (1974) include a detailed discussion on load-limited storage heating system design.

Indirect Water Heating In indirect water heating, the heating medium is steam, hot water, or another fluid that has been heated in a separate generator or boiler. The water heater extracts heat through an external or internal heat exchanger. When the heating medium is at a higher pressure than the service water, the service water may be contaminated by leakage of the heating medium through a damaged heat transfer surface. In the United States, some national, state, and local codes require doublewall, vented tubing in indirect water heaters to reduce the possibility of cross-contamination. When the heating medium is at a lower pressure than the service water, other jurisdictions allow single-wall tubing heaters because any leak would be into the heating medium. If the heating medium is steam, high rates of condensation occur, particularly when a sudden demand causes an inflow of cold water. The steam pipe and condensate return pipes should be of ample size. Condensate may be cooled by preheating the cold-water supply to the heater. Corrosion is minimized on the heating medium side of the heat exchanger because no makeup water, and hence no oxygen, is brought into that system. The metal temperature ofthe service water side of the heat exchanger is usually less than that in direct-fired water heaters. This minimizes scale formation from hard water. Storage water heaters are designed for service conditions where hot-water requirements are not constant (i.e., where a large volume of heated water is held in storage for periods of peak load). The amount of storage required depends on the load’s nature and water heater’s recovery capacity. An individual tank or several tanks joined by a manifold may be used to provide the required storage.

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Applications (SI)

The basic elements of a solar water heater include solar collectors, a storage tank, piping, controls, and a transfer medium. The system may use natural or forced circulation. Auxiliary heat energy sources may be added, if needed. Collector design must allow operation in below-freezing conditions, where applicable. Antifreeze solutions in a separate collector piping circuit arrangement are often used, as are systems that allow water to drain back to heated areas when low temperatures occur. Uniform flow distribution in the collector or bank of collectors and stratification in the storage tank are important for good system performance. Application of solar water heaters depends on (1) auxiliary energy requirements; (2) collector orientation; ( 3 ) temperature of the cold water; (4) general site, climatic, and solar conditions; ( 5 ) installation requirements; (6) area of collectors; and (7) amount of storage. Chapter 35 has more detailed design information.

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Fig. 1 Indirect, External Storage Water Heater

External storage water heaters are designed for connection to a separate tank (Figure 1). Boiler water circulates through the heater shell, while service water from the storage tank circulates through the tubes and back to the tank. Circulating pumps are usually installed in both the boiler water piping circuit and the circuits between the heat exchanger and the storage tank. Steam can also be used as the heating medium in a similar scheme. Instantaneous indirect water heaters (tankless coils) are best used for a steady, continuous supply of hot water. In these units, the water is heated as it flows through the tubes. Because the heating medium flows through a shell, the ratio of hot-water volume to heating medium volume is small. As a result, variable flow of the service water causes uncertain temperature control unless a thermostatic mixing valve is used to maintain the hot-water supply to the plumbing fixtures at a more uniform temperature. Some indirect instantaneous water heaters are located inside a boiler. The boiler is provided with a special opening through which the coil can be inserted. Although the coil can be placed in the steam space above the water line of a steam boiler, it is usually placed below the water line. The water heater transfers heat from the boiler water to the service water. The gross output of the boiler must be sufficient to serve all loads.

Semi-Instantaneous These water heaters have limited storage to meet the average momentary surges of hot-water demand. They usually consist of a heating element and control assembly devised for close control of the temperature of the leaving hot water.

Circulating Tank These water heaters are instantaneous or semi-instantaneous types used with a separate storage tank and a circulating pump. The storage acts as a flywheel to accommodate variations in the demand for hot water.

Blending Injection

Waste Heat Use

Waste heat recovery can reduce energy cost and the energy requirement of the building heating and service water-heating equipment. Waste heat can be recovered from equipment or processes by using appropriate heat exchangers in the hot gaseous or liquid streams. Heat recovered is frequently used to preheat water entering the service water heater. A conventional water heater is typically required to augment the output of a waste heat recovery device and to provide hot water during periods when the host system is not in operation.

Refrigeration Heat Reclaim These systems heat water with heat that would otherwise be rejected through a refrigeration, air-conditioning, or heat pump condenser. Refrigeration heat reclaim uses refrigerant-to-water heat exchangers connected to the refrigeration circuit between the compressor and condenser of a host refrigeration or air-conditioning system to extract heat. Water is heated only when the host is operating. Because many simple systems reclaim only superheat energy from the refrigerant, they are often called desuperheaters. However, some units are also designed to provide partial or full condensing. The refrigeration heat reclaim heat exchanger is generally of vented, double-wall construction to isolate potable water from refrigerant. Some heat reclaim devices are designed for use with multiple refrigerant circuits. Controls are required to limit high water temperature, prevent low condenser pressure, and provide for freeze protection. Refrigeration systems with higher run time and lower efficiency provide more heat reclaim potential. Most systems are designed with a preheat water storage tank connected in series with a conventional water heater (EPRI 1992). In all installations, care must be taken to prevent inappropriately venting refrigerants.

Combination Heating A combo system provides hot water for both space heating and domestic use. A space-heating coil and a space-cooling coil are often included with the air handler to provide year-round comfort. Combo systems also can use other types of heat exchangers for space heating, such as baseboard convectors or floor heating coils. A method of testing combo systems is given in ASHRAE Standard 124. The test procedures allow the calculation of combined annual efficiency (CAE), as well as space- and water-heating efficiency factors. Kweller (1992), Pietsch and Talbert (1989), Pietsch et al. (1994), Subherwal (1986), and Talbert et al. (1992) provide additional design information on these heaters.

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These water heaters inject steam or hot water directly into the process or volume of water to be heated. They are often associated with point-of-use applications (e.g., certain types of commercial laundry, food, and process equipment). Caution: Cross-contamination of potable water is possible.

Solar Availability of solar energy at the building site, efficiency and cost of solar collectors, system installation costs, and availability and cost of other fuels determine whether solar energy collection units should be used as a primary heat energy source. Solar energy equipment can also be included to supplement other energy sources and conserve fuel or electrical energy.

DESIGN CONSIDERATIONS Hot-water system design should consider the following: Water heaters of different sizes and insulation may have different standby losses, recovery efficiency, thermal efficiency, or energy factors.

Service Water Heating

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A distribution system should be properly laid out, sized, and insulated to deliver adequate water quantities at temperatures satisfactory for the uses served. This reduces standby loss and improves hot-water distribution efficiency. Locating fixtures or usage devices close to each other and to the water-heating equipment is particularly important for minimizing piping lengths and diameters, and thus reducing wait times as well as water and energy waste. Heat traps between recirculation mains and infrequently used branch lines reduce convection losses to these lines and improve heaterisystem efficiency. In small residential systems, heat traps can be applied directly to the water heater for the same purpose. Controlling circulating pumps to operate only as needed to maintain proper temperature at the end of the main reduces losses on return lines. Provision for shutdown of circulators during building vacancy reduces standby losses.

DISTRIBUTION

Supply Piping

Table 16, Figures 25 and 26, and manufacturers’ specifications for fixtures and appliances can be used to determine hot-water demands. These demands, together with procedures given in Chapter 22 of the 2009 ASHRAE Handbook-Fundamentals, are used to size the mains, branches, and risers. Allowance for pressure drop through the heater should not be overlooked when sizing hot-water distribution systems, particularly where instantaneous water heaters are used and where the available pressure is low.

Pressure Differential Sizing both cold- and hot-water piping requires that the pressure differential at the point of use of blended hot and cold water be kept to a minimum. This is particularly important for tubs and showers, because sudden changes in flow at fixtures cause discomfort and a possible scalding hazard. Pressure-compensating devices are available.

Piping Heat Loss and Hot-Water Delivery Delays

Piping Material Traditional piping materials include galvanized steel used with galvanized malleable iron screwed fittings. Copper piping and copper water tube types K, L, or M have been used with brass, bronze, or wrought copper water solder fittings. Legislation or plumbing code changes have banned the use of lead in solders or pipe-jointing compounds in potable water piping because of possible lead contamination of the water supply. See ASHRAE Standard 90 series for pipe insulation requirements. Today, most potable water supplies require treatment before distribution; this may cause the water to become more corrosive. Therefore, depending on the water supply, traditional galvanized steel piping or copper tube may no longer be satisfactory, because of accelerated corrosion. Galvanized steel piping is particularly susceptible to corrosion (1) when hot water is between 60 and 80°C and (2) where repairs have been made using copper tube without a nonmetallic coupling. Note that plumbing can be either piping (relatively thick wall) or tubing (relatively thin wall), althoughpiping is used in this chapter for both. Before selecting any water piping material or system, consult the local code authority. The local water supply authority should also be consulted about any history of water aggressiveness causing failures of any particular material. Alternative piping materials that may be considered are (1) stainless steel tube and (2) various plastic piping and tubes. Particular care must be taken to ensure that the application meets the design limitations set by the manufacturer, particularly regarding temperature and pressure limits, and that the correct materials and methods of joining are used. These precautions are easily taken with new projects, but become more difficult during repairs of existing work. Using incompatible piping, fittings, and jointing methods or materials must be avoided, because they can cause severe problems, such as corrosion or leakage caused by differential thermal expansion.

Good hot-water distribution system layout is very important, for both user satisfaction and energy use. This has become increasingly important with the mandated use of low-flow fixtures, which can cause lengthy delays and increased water waste while waiting for hot water to arrive at fixtures compared to higher-flow designs. In general, it is desirable to put fixtures close to each other and close to the water heater(s) that serve them. This minimizes both the diameter and length of the hot-water piping required. Recent work has shown that energy loss from hot-water piping due to both heat loss and water waste waiting for hot water to arrive at fixtures can be a significant percentage of total water-heating system energy use (Hiller 2005a; Klein 2004a, 2004b, 2004c; Lutz 2005). Energy losses from hot-water distribution systems usually amount to at least 10-20% of total hot-water system energy use in most potable water-heating systems (Hiller 2005a), and are often as high as 50%; losses of over 90% have been found in some installations (Hiller and Miller 2002; Hiller et al. 2002). Hiller (2005a, 2005b, 2006a, 2006b) measured both piping heat loss and time, water, and energy waste while waiting for hot water to arrive at fixtures. This research measured piping heat loss UA factors for several commonly used piping sizes, types, and insulation levels. UAjOwing values are a slight function of water flow rate and temperature difference between the hot water and the surroundings. However, for many practical calculation purposes, UA can be considered constant at the values shown in Table 1. Hiller (2008) found that bare copper piping buried in damp sand (typical of under-slab piping) exhibited heat loss rates over eight times higher than the same pipe in air. This much higher heat loss rate is believed to be caused by moisture in the sand near the pipe behaving like a heat pipe by evaporating, recondensing (thus transferring heat to sand particles a short distance away much faster than conduction would), and then wicking back to the pipe. Adding insulation to buried piping dramatically reduced the heat-pipe effect by lowering the surface temperature seen by the moisture. Hence, as can be seen in Table 1, adding 19 nnn foam pipe insulation to copper piping reduces the heat loss rate in air to around one-half of the uninsulated value, but adding the same insulation to pipe buried in damp sand reduces the heat loss rate to only around 6% of its uninsulated value, a reduction by a factor of around 16. Thus adding pipe insulation is highly beneficial for buried piping, and is recommended. Table 1 also shows that all of the plastic pipes tested to date exhibit moderately to significantly higher heat loss rates than comparably sized copper pipes when tested uninsulated in air. However, when insulated, they exhibit moderately to significantly lower heat loss rates than comparably sized copper pipes with the same insulation. Adding 19 nnn foam reduces plastic pipe heat loss rates to

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Pipe Sizing Sizing hot-water supply pipes from a hydraulic (pressure drop) perspective involves the same principles as sizing cold-water supply pipes (see Chapter 22 ofthe 2009 ASHRAE Handbook-Fundamentals). The water distribution system must be correctly sized for the total hot-water system to function properly. Hot-water demand varies with the type of establishment, usage, occupancy, and time of day. The piping system should be able to meet peak demand at an acceptable pressure loss. It is important not to oversize hot-water supply pipes, because this adversely affects system heat loss and overall energy use.

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Table 1 Piping Heat Loss Factors for Foam In Piping Heat Loss Factors for Foam Insulation with Thermal Conductivity of 0.114 W/(m2.K)

Nominal Pipe Size

13 mm rigid copper

19 mm rigid copper

19 mm rolled copper 19 mm roll CU-sand 19 mm PEX-AL-PEXa

19 mm PEXb 13 mm PEX 10 mm PEX 19 mm CPVC

Foam Insulation Thickness, mm 0 13 19 0 13 19 0 19 0 19 0 13 19 0 19 0 19 0 0 19

For water flowing in pipes in a constant-air-temperature environment,

High-Value

u&roflow,

UAflowinp

W/(m.K)

W/(m.K)

0.391 0.222 0.201 0.672 0.260 0.246 0.579 0.239 2.08 0.269 0.952 0.344 0.273 0.927 0.276 0.759 0.225

0.623 0.346 0.329 0.762 0.433 0.415 0.579 0.277 4.89 0.307 0.945 0.344 0.312 1.01 0329 0.759 0.225

0.762 (0.257

0.901 0.295

AT,,

=

in - ' a i r ) - ('hot

[('hot

out- 'air)]

(3)

h [ ( T h o t in - T a i r ) / ( T h o t out - ' a i r ) ]

When UAflowing,water flow rate, air temperature, and entering water temperature are known, Equations (1) to (3) can be combined and rearranged to determine pipe-exiting water temperature as follows:

where AT,, = log mean temperature difference, K Q =heat loss rate, W m = water flow rate, kg/s cp = specific heat of water, 4.1868 kJ/(kg.K) That In = water temperature entering pipe, "C That = water temperature leaving pipe, "C UAJmIng = flowing heat loss factor per metre of pipe, W/(m.K) Lplpe = length of hot-water pipe, m

zyxwvutsrq Note that the quantity (UAflpwing)(Lpi ,)/(mc )water must be nondimensional, so appropriate umts must &e u s e 8

Note: Results are for horizontal in-air tests unless otherwise noted. Sources: Hiller (2005a, 2005b, 2006b, 2008,2009). aHigh-density cross-linked polyethylene, aluminum, high-density cross-linked polyethylene multilayer pipe. bHigh-density cross-linked polyethylene.

around 30% of their uninsulated values when tested in air. This is a reduction in heat loss rate by a factor of three, compared to a factor of two for insulation on copper piping. This result suggests that plastic pipes have higher emissivity for radiation heat loss from the piping than does copper. Theoretical analysis suggests that, for the pipe sizes tested, radiation heat loss from the pipes represents between 30% and 70% of total heat loss rate from the pipes, depending on pipe type and size. It has been suggested that the emissivity of copper pipe may increase with age as the outer surface oxidizes to its normal dull-brown appearance from its original bright, shiny surface. Repeat tests on aged copper pipe have not yet been performed. The UA factors of Table 1 are used in Equations (1) to (8) to determine heat loss rates from piping during both flowing and zeroflow (cooldown) conditions, and to find temperature drop while water is flowing through pipe, and pipe temperature at any time during cooldown. Note that piping heat loss and pipe temperature drop are not constant with length under flowing conditions, because the temperature of each successive length of pipe is less than the one before it. The same is true for zero-flow pipe cooldown with respect to time, because the pipe is at a progressively lower temperature at each successive time interval. The result is that pipe temperatures decay inverse-exponentially with length under flowing conditions and with time under cooldown conditions. This is why log-mean temperature difference must be used in heat loss calculations instead of a simple linear temperature difference (Rohsenow and Choi 1961). Under flowing conditions,

and

- p J ' 4 z e r o . f l o w ) ( t 2- tl)] ' h o t t2 = ' a i r

+

('hot

t l - 'air)'

where = initial time t2 =final time Q = average heat loss rate from time tl to time t2,W ( M C ~ = ) sum ~ ~ of , ~mass times specific heat for water, pipe, and insulation, kJ/(m.K) That t , =pipe temperature at tl, "C That =pipe temperature at t2,"C UAzerO.JOw = zero-flow heat loss factor per metre of pipe, W/(m.K)

tl

Note that the quantity (UAzerogow)(t2 ~ J ( M C must ~ ) ~be~non, ~ dimensional, so appropriate units must be used. Pipe temperature at any time during the cooldown process is determined by Equation (8). Total energy lost from piping during zero-flow cooldown is determined by calculating the pipe temperature at time t2 and multiplying the average heat loss rate between tl and t2 determined by Equation (5) times the duration of the cooldown period (t2 t l ) .An alternative is to calculate heat loss over short time periods using Equation (6) and sum the results. Table 2 contains earlier piping heat loss data, and shows computed piping UA values based on those data. Hiller (2005a, 2005b, 2006b) also produced tables of water/ energy wasted while waiting for hot water to anive at fixtures. Waste is a strong function ofpipe material, interior fmish, diameter, fittings present, flow rate, initial pipe temperature, and entering hot-water ~

~

Service Water Heating Table 2

zyxwvuts 50.7

zyxwvut zyxwvuts zyxwvutsrqpon

Approximate Heat Loss from Piping at 6OoC Inlet, 21OC Ambient

13 mm Glass 13 m m Glass Nominal Bare Copper Bare Copper Fiber Insulated Fiber Insulated Size, Tubing, UA, Copper Tubing, Copper UA, mm W/m W/(m.K) W/m W/(m.K)

19 25 32 38 50 64 75 100

29 37 43 51 63 77 90 115

0.74 0.93 1.11 1.32 1.63 1.97 2.32 2.96

17.0 19.5 22.5 24.4 28.5 32.5 38.0 46.5

0.43 0.50 0.57 0.62 0.73 0.83 0.96 1.19

temperature. The amount of water wasted to drain is generally an amount greater than pipe volume because temperature of some of the frst hot water traveling through the pipe is degraded to below a usable temperature. Initial flow of hot water into a pipe full of cooler water often does not behave as predicted by steady-state flow theory, because both hot and cold water are flowing simultaneously in the same pipe (a non-steady-state condition). At least three different flow regimes were identified: (1) stratified flow (at low flow rates in horizontal pipes, hot water flows farther along the top side of the pipe than on the bottom side; this can happen even in small-diameter pipes), (2) normal turbulent flow, and (3) shear flow (a relatively sharp hot/ cold interface with little turbulence-induced mixing of hot and cold water because the normal boundary layer is slow to develop under some conditions). These flow regimes are important because each causes different amounts of temperature degradation as hot water flows through the pipe. For detailed information on time, water, and energy waste while waiting for hot water to arrive at fixtures, see Hiller (2005b). Simply summarized here, the amount of water waste can be expressed as the ratio of the actual amount of water (actual flow or AF) wasted while waiting for hot-enough-to-use water to arrive at fixtures (defmed as 40.5"C by Hiller) divided by pipe volume (PV). When the pipe cools below a usable temperature, AFiPV ratios are usually in the range of 1.O to 2.0, but can go to infmity at low flow rates in long, uninsulated pipe in cold or otherwise adverse (e.g., damp) heat transfer environments. The critical length of pipe at which AFiPV goes to infinity can be calculated for any flow rate and temperature conditions, using the piping UAJowing factors and Equations (1) to (4). For preliminary engineering design and energy use calculations, Hiller recommends assuming AFiPV values of 1.25 to 1.75. For more refined analyses, accounting better for temperature effects on AFI PV ratio, the data tables in the original reference should be consulted. More such data on a larger variety of pipe sizes, types, and environments would be beneficial, but are not currently available. Examples 11 to 14 demonstrate how to use piping heat loss and delivery water waste information to calculate hot-water system energy use.

temperature range. This thermostat can significantly reduce both heat loss and pumping energy in some applications. An automatic time switch or other control should turn water circulation off when hot water is not required. Other, more advanced circulating pump control schemes, such as on-demand types using manual initiation, flow switches, or occupancy sensors, are also available. Because hot water is corrosive, circulating pumps should be made of corrosionresistant material. For small installations, a simplified pump sizing method is to allow 3 mLis for every fixture unit in the system, or to allow 30 mLis for each 20 or 25 mm riser; 60 mL/s for each 32 or 40 mm riser; and 130 mLis for each riser 50 mm or larger. D m et al. (1959) and Werden and Spielvogel (1969a, 1969b) discuss heat loss calculations for large systems. For larger installations, piping heat losses become significant. A quick method to size the pump and return for larger systems is as follows: 1. Determine total length of all hot-water supply and return piping. 2. Choose an appropriate value for piping heat loss from Tables 1 or 2 or other engineering data (usually supplied by insulation companies, etc.). Multiply this value by the total length of piping involved. A rough estimation can be made by multiplying the total length of covered pipe by 30 Wim or uninsulated pipe by 60 Wim. Table 2 gives actual heat losses in pipes at a service water temperature of 60°C and ambient temperature of 21°C. The values of 30 or 60 Wim are only recommended for ease in calculation. 3. Determine pump capacity as follows:

zyxw

Q=- 4 Pep At

(9)

where Q, q

= =

p = cp = At =

pump capacity, L/s heat loss, W density of water = 0.99 kg/L (50°C) specific heat of water = 4186.8 J/(kg.K) allowable temperature drop, K

For a 10 K allowable temperature drop, 4 0.99 x 4186.8 x 10

zyxwvutsr

Hot-Water Recirculation Loops and Return Piping Hot-water recirculation loops are commonly used where piping lengths are long and hot water is desired immediately at fixtures. In recirculation-loop systems, return piping and a circulation device are provided. Some recirculation-loop systems use buoyancy-driven natural convection forces to circulate flow, but most are equipped with circulating pumps to force water through the piping and back to the water heater, thus keeping water in the piping hot. The water circulation pump may be controlled by a thermostat (in the return line) set to start and stop the pump over an acceptable

~

Caution: This calculation assumes that a 10 K temperature drop is acceptable at the last fixture. 4. Select a pump to provide the required flow rate, and obtain from the pump curves the pressure created at this flow. 5. Check that the pressure does not exceed the allowable friction loss per metre of pipe. 6. Determine the required flow in each circulating loop, and size the hot water return pipe based on this flow and the allowable friction loss.

Where multiple risers or horizontal loops are used, balancing valves with means of testing are recommended in the return lines. A swing-type check valve should be placed in each return to prevent entry of cold water or reversal of flow, particularly during periods of high hot-water demand. Three common methods of arranging circulation lines are shown in Figure 2. Although the diagrams apply to multistory buildings, arrangements (A) and (B) are also used in residential designs. In circulation systems, air venting, pressure drops through the heaters and storage tanks, balancing, and line losses should be considered. In Figures 2A and 2B, air is vented by connecting the circulating line below the top fixture supply. With this arrangement, air is eliminated from the system each time the top fixture is opened. Generally, for small installations, a nominal pipe size (NPS) 15 or 20 mm hot-water return is ample.

50.8

zyxwvutsrqp 201 1 ASHRAE Handbook-HVAC

Applications (SI)

zyxwvuts zyxwvutsrq

Fig. 2 Arrangements of Hot-Water Circulation Lines

All storage tanks and piping on recirculating systems should be insulated as recommended by the ASHRAE Standard 90 series and Standard 100.

Heat-Traced, Nonreturn Piping In this system, the fixtures can be as remote as in the hot-water recirculation loops and return piping section. The hot-water supply piping is heat traced with electric resistance heating cable preinstalled under the pipe insulation. Electrical energy input is self-regulated by the cable’s construction to maintain the required water temperature at the fixtures. No return piping system or circulation pump is required.

Multiple Water Heaters Depending on fixture spacing, required pipe lengths, and draw spacing, it may be more energy-efficient (and sometimes provide lower first cost) to use more than one water heater rather than using extensive piping runs. Energy losses from high-efficiency water heaters can be lower than recirculation-loop piping heat losses if the distance from water heaters to fixtures exceeds 10 to 20 m (Hiller 2005a). Although there are considerations beyond energy use, such as installation, maintenance, and space requirements, using more than one water heater should always be evaluated when designing water heating systems, even in residences, because of the potentially large energy savings.

Special Piping-Commercial Dishwashers Adequate flow rate and pressure must be maintained for automatic dishwashers in commercial kitchens. To reduce operating difficulties, piping for automatic dishwashers should be installed according to the following recommendations: The cold-water feed line to the water heater should be no smaller than NPS 25 mm. The supply line that carries 82°C water from the water heater to the dishwasher should not be smaller than NPS 19 mm. No auxiliary feed lines should connect to the 82°C supply line. A return line should be installed if the source of 82°C water is more than 1.5 m from the dishwasher. Forced circulation by a pump should be used if the water heater is installed on the same level as the dishwasher, if the length of return piping is more than 18 m, or if the water lines are trapped. If a circulating pump is used, it is generally installed in the return line. It may be controlled by (1) the dishwasher wash switch, (2) a manual switch located near the dishwasher, or (3) an immersion or strap-on thermostat located in the return line. A pressure-reducing valve should be installed in the lowtemperature supply line to a booster water heater, but external to a recirculating loop. It should be adjusted, with the water flowing, to the value stated by the washer manufacturer (typically 140 kPa).

Fig. 3 National Sanitation Foundation (NSF) Plumbing Requirements for Commercial Dishwasher

A check valve should be installed in the return circulating line. If a check-valve water meter or a backflow prevention device is installed in the cold-water line ahead of the heater, it is necessary to install a properly sized diaphragm-type expansion tank between the water meter or prevention device and the heater. National Sanitation Foundation (NSF) standards require an NPS 6 mm IPS connection for a pressure gage mounted adjacent to the supply side of the control valve. They also require a waterline strainer ahead of any electrically operated control valve (Figure 3). NSF standards do not allow copper water lines that are not under constant pressure, except for the line downstream of the solenoid valve on the rinse line to the cabinet.

Water Pressure-Commercial Kitchens Proper flow pressure must be maintained to achieve efficient dishwashing. NSF standards for dishwasher water flow pressure are 100 kPa (gage) minimum, 170 kPa (gage) maximum, and 140 kPa (gage) ideal. Flow pressure is the line pressure measured when water is flowing through the rinse arms of the dishwasher. Low flow pressure can be caused by undersized water piping, stoppage in piping, or excess pressure drop through heaters. Low water pressure causes an inadequate rinse, resulting in poor drying and sanitizing of the dishes. If flow pressure in the supply line to the dishwasher is below 100 kPa (gage), a booster pump or other means should be installed to provide supply water at 140 kPa (gage). Flow pressure over 170 kPa (gage) causes atomization of the 82°C rinse water, resulting in excessive temperature drop (which can be as much as 8 K between rinse nozzle and dishes). A pressure regulator should be installed in the supply water line adjacent to the dishwasher and external to the return circulating loop (if used). The regulator should be set to maintain a pressure of 140 kPa (gage).

Two-Temperature Service Where multiple temperature requirements are met by a single system, the system temperature is determined by the maximum temperature needed. Where the bulk of the hot water is needed at the higher temperature, lower temperatures can be obtained by mixing hot and cold water. Automatic mixing valves reduce the temperature of the hot water available at certain outlets to prevent injury or damage (Figure 4). Applicable codes should be consulted for mixing valve requirements. Where predominant use is at a lower temperature, the common design heats all water to the lower temperature and then uses a

Service Water Heating

zyxwvuts

Fig. 4 Two-Temperature Service with Mixing Valve

50.9

Fig. 7 Reverserneturn Manifold System

TERMINAL HOT-WATER USAGE DEVICES Details on the vast number of devices using service hot water are beyond the scope of this chapter. Nonetheless, they are important to a successful overall design. Consult the manufacturer’s literature for information on required flow rates, temperature and pressure limits, andor other operating factors for specific items.

Fig. 5

Fig. 6

Two-Temperature Service with Primary Heater and Booster Heater in Series

WATER QUALITY, SCALE, AND CORROSION A complete water analysis and an understanding of system requirements are needed to protect water-heating systems from scale and corrosion. Analysis shows whether water is hard or soft. Hard water, unless treated, causes scaling or liming of heat transfer and water storage surfaces; soft water may aggravate corrosion problems and sacrificial anode consumption (Talbert et al. 1986). Scale formation is also affected by system requirements and equipment. As shown in Figure 8, the rate of scaling increases with temperature and use because calcium carbonate and other scaling compounds lose solubility at higher temperatures. In water tubetype equipment, scaling problems can be offset by increasing water velocity over the heat transfer surfaces, which reduces the tube surface temperature. Also, flow turbulence, if high enough, works to keep any scale that does precipitate off the surface. When water hardness is over 140 mg/L, water softening or other water treatment is often recommended. Corrosion problems increase with temperature because corrosive oxygen and carbon dioxide gases are released from the water. Electrical conductivity also increases with temperature, enhancing electrochemical reactions such as rusting (Taborek etal. 1972). A deposit of scale provides some protection from corrosion; however, this deposit also reduces the heat transfer rate, and it is not under the control of the system designer (Talbert et al. 1986). Steel vessels can be protected to varying degrees by galvanizing or by lining with copper, glass, cement, electroless nickel-phosphorus, or other corrosion-resistant material. Glass-lined vessels are almost always supplied with electrochemical protection. Typically, one or more anode rods of magnesium, aluminum, or zinc alloy are installed in the vessel by the manufacturer. This electrochemically active material sacrifices itself to reduce or prevent corrosion of the tank (the cathode). Higher temperature, softened water, and high water use may lead to rapid anode consumption. Manufacturers recommend periodic replacement of the anode rod(s) to prolong the life of the vessel. Some waters have very little electrochemical activity. In this instance, a standard anode shows little or no activity, and the vessel is not adequately protected. If this condition is suspected, consult the equipment manufacturer on the possible need for a high-potential anode, or consider using vessels made of nonferrous material. Water heaters and hot-water storage tanks constructed of stainless steel, copper, or other nonferrous alloys are protected against oxygen corrosion. However, care must still be taken, as some stain-

zyxwvutsrq zyxwvutsrqp

Two-Temperature Service with Separate Heater for Each Service

separate booster heater to further heat the water for the highertemperature service (Figure 5 ) . This method offers better protection against scalding. A third method uses separate heaters for the higher-temperature service (Figure 6). It is common practice to cross-connect the two heaters, so that one heater can serve the complete installation temporarily while the other is valved off for maintenance. Each heater should be sized for the total load unless hot-water consumption can be reduced during maintenance periods.

Manifolding Where one heater does not have sufficient capacity, two or more water heaters may be installed in parallel. If blending is needed, a single mixing valve of adequate capacity should be used. It is difficult to obtain even flow through parallel mixing valves. Heaters installed in parallel should have similar specifications: the same input and storage capacity, with inlet and outlet piping arranged so that an equal flow is received from each heater under all demand conditions. An easy way to get balanced, parallel flow is to use reverse/ return piping (Figure 7). The unit having its inlet closest to the coldwater supply is piped so that its outlet is farthest from the hot-water supply line. Quite often this results in a hot-water supply line that reverses direction (see dashed line, Figure 7) to bring it back to the first unit in line; hence the name reverseireturn.

201 1 ASHRAE Handbook-HVAC

50.10

zyx

Applications (SI)

element located in the top 150 mm of the tank (i.e., where the water is hottest). To reduce scald hazards, discharge temperature at fixtures accessible to the occupant should not exceed 50°C. Thermostatically controlled mixing valves can be used to blend hot and cold water to maintain safe service hot-water temperatures. A relief valve should be installed in any part of the system containing a heat input device that can be isolated by valves. The heat input device may be solar water-heating panels, desuperheater water heaters, heat recovery devices, or similar equipment.

SPECIAL CONCERNS

zyx

Legionella pneumophila (Legionnaires’ Disease)

Fig. 8

Lime Deposited Versus Temperature and Water Use (Based on data from Purdue University Bulletin No. 74)

Legionnaires’ disease (a form of severe pneumonia) is caused by inhaling the bacteria Legionella pneumophila. It has been discovered in the service water systems of various buildings throughout the world. Infection has often been traced to L. pneumophila colonies in shower heads. Ciesielski et al. (1984) determined that L. pneumophila can colonize in hot water maintained at 46°C or lower. Segments of service water systems in which water stagnates (e.g., shower heads, faucet aerators, unused or infrequently used piping branches, some sections of storage water heaters) provide ideal breeding locations. Service water temperature in the 60°C range is recommended to limit the potential for L. pneumophila growth. This high temperature increases the potential for scalding, so care must be taken such as installing an anti-scald or mixing valve. Supervised periodic flushing of fixture heads with 77°C water is recommended in hospitals and health care facilities because the already weakened patients are generally more susceptible to infection. Although higher temperatures are required for eradication of Legionella, lower temperatures may be adequate for prevention. Note, too, that Legionella colonies can grow on the cold-water side of the system in stagnant flow areas, especially if those areas can rise in temperature because of heat input from the surroundings. Note that susceptibility to Legionnaire’s disease varies among individuals. People with compromised immune systems (organ transplant patients or otherwise on immunosuppressant drugs, AIDS patients, smokers, elderly, those with other chronic health conditions or injuries) are at greater risk of contracting the disease at lower exposure levels. More information on this subject can be found in ASHRAE Guideline 12-2000.

zyxwvut

less steel may be adversely affected by chlorides, and copper may be attacked by ammonia or carbon dioxide.

SAFETY DEVICES FOR HOT-WATER SUPPLIES Regulatory agencies differ as to the selection of protective devices and methods of installation. It is therefore essential to check and comply with the manufacturer’s instructions and the applicable local codes. In the absence of such instructions and codes, the following recommendations may be used as a guide: Water expands when it is heated. Although the water-heating system is initially under service pressure, the pressure rises rapidly if backflow is prevented by devices such as a check valve, pressurereducing valve, or backflow preventer in the cold-water line or by temporarily shutting off the cold-water valve. When backflow is prevented, the pressure rise during heating may cause the safety relief valve to weep to relieve the pressure. However, if the safety relief valve is inadequate, inoperative, or missing, pressure rise may rupture the tank or cause other damage. Systems having this potential problem must be protected by a properly sized expansion tank located on the cold-water line downstream of and as close as practical to the device preventing backflow. Temperature-limiting devices (energy cutoffihigh limit) prevent water temperatures from exceeding 99°C by stopping the flow of fuel or energy. These devices should be listed and labeled by a recognized certifying agency. Safety relief valves open when pressure exceeds the valve setting. These valves are typically applied to water-heating and hot-water supply boilers. The set pressure should not exceed the maximum allowable working pressure of the boiler. The heat input pressure steam rating (in kW) should equal or exceed the maximum out-put rating for the boiler. The valves should comply with current applicable standards or the ASME Boiler and Pressure Vessel Code. Temperature and pressure safety relief valves also open if the water temperature reaches 99°C. These valves are typically applied to water heaters and hot-water storage tanks. The heat input temperatureisteam rating (in kW) should equal or exceed the heat input rating of the water heater. Combination temperature- and pressurerelief valves should be installed with the temperature-sensitive

Scalding Scalding is an important concern in design and operation of potable hot-water systems. Figure 9 (Moritz 1947) shows plots of exposure time versus water temperature that results in both first-degree (pain, redness, swelling, minor tissue damage) and full-thickness third-degree (permanent damage, scarring) skin burns in adults. Children burn even more rapidly. Note that, at the high temperatures required to eradicate Legionella bacteria (60°C and above), burns can occur almost instantaneously (3 s or less exposure). Safety dictates some tradeoffs to limit scalding injuries (e.g., during pressure transients that may inhibit proper operation of temperature regulating valves) while minimizing risk of Legionnaire’s disease.

zyxwvutsrqp Temperature Requirement

Typical temperature requirements for some services are shown in Table 3. A 60°C water temperature minimizes flue gas condensation in the equipment.

Hot Water from Tanks and Storage Systems With storage systems, 60 to 80% of the hot water in a tank is assumed to be usable before dilution by cold water lowers the temperature below an acceptable level. However, better designs can

50.11

Service Water Heating

entering cold-water temperature is 16"C, the water will be heated to only 28"C, too cold to be useful, so the heating rate cannot contribute to effective storage tank capacity under a prolonged draw at this flow rate. In reality, draw rates are rarely constant during peak draw or other times. Computer simulation models allow equipment sizing under these more realistic conditions (Hiller 1992). Maximum usable hot water from an unfred tank is

v,

=

MS,

where

V , = usable water available from unfired tank, L S,

capacity of unfired tank, L

Note: Assumes tank water at required temperature. Hot water obtained from a water heater using a storage heater with an auxiliary storage tank is

zyxwvutsrqponml zyxwvutsrqponm Fig. 9

Time for Adult Skin Burns in Hot Water

Table 3 Representative Hot-Water Temperatures

Temperature,

Use

=

zy zyxw

O C

Lavatory Hand washing Shaving Showers and tubs Therapeutic baths Commercial or institutional laundry, based on fabric Residential dish washing and laundry Surgical scrubbing Commercial spray-type dish washinga Single- or multiple-tank hood or rack type Wash Final rinse Single-tank conveyor type Wash Final rinse Single-tank rack or door type Single-temperature wash and rinse Chemical sanitizing typesb Multiple-tank conveyor type Wash Pumped rinse Final rinse Chemical sanitizing glass washer Wash Rinse

v, v,+ v, =

(13)

where V, =total hot water available during one peak, in litres.

40 45 43 35 up to 82 60 43

65 min. 82 to 90 71 min. 82 to 90 74 min. 60 65 min. 71 min. 82 to 90 60 24 min.

Placement of Water Heaters

Many types of water heaters may be expected to leak at the end of their useful life. They should be placed where leakage will not cause damage. Alternatively, suitable drain pans piped to drains must be provided. Water heaters not requiring combustion air may generally be placed in any suitable location, as long as relief valve discharge pipes open to a safe location. Water heaters requiring ambient combustion air must be located in areas with air openings large enough to admit the required combustioddilution air (see NFPA Standard 541ANSI 2223.1). For water heaters located in areas where flammable vapors are likely to be present, precautions should be taken against ignition. For water heaters installed in residential garages, additional precautions should be taken. Consult local codes for additional requirements or see sections 5.1.9 through 5.1.12 of NFPA Standard 541 ANSI 2223.1. Outdoor models with a weather-proofed jacket are available. Direct-vent gas- and oil-fred models are also available; they are to be installed inside, but are not vented through a conventional chimney or gas vent. They use outdoor air for combustion. They must be installed with the means specified by the manufacturer for venting (typically horizontal) and for supplying air for combustion from outside the building. Air-source heat pump water heaters require access to an adequate air supply from which heat can be extracted. For residential units, a room of at least 27 m3 or ducted air is recommended. See manufacturer's literature for more information.

zyxwvutsrqp

aAs required by NSF. bSee manufacturer for actual temperature required

exceed 90%. Thus, the maximum hot water available from a selfcontained storage heater is usually

P'=Rd+MS,

where

(1 1)

HOT-WATER REQUIREMENTS AND STORAGE EQUIPMENT SIZING

zyxwvutsr

V, = available hot water, L R = recovery rate at required temperature, L/s d = duration of peak hot-water demand, s A4 = ratio of usable water to storage tank capacity S, = storage capacity of heater tank, L

However, Equation (1 1) only applies if the water draw rate is less than the available reheat rate. Otherwise, the tank cannot heat the flowing water to a usable temperature during the draw, and V, drops to the same as an unfired tank. For example, a fossil-fuel-fred heater with a fuel input rate of 13 kW and an input efficiency of 80% can raise the temperature of water being drawn through a storage tank at a rate of 200 mL1s by approximately 13 K. If the

Methods for sizing storage water heaters vary. Those using recovery versus storage curves are based on extensive research. All methods provide adequate hot water if the designer allows for unusual conditions. To serve a hot-water load adequately, the needs of both the peak energy withdrawal rate and total integrated energy delivery for end uses must be met. Meeting these needs can be done either by providing a heating rate large enough to meet the peak energy withdrawal rate of the system (and modulating that heating input for smaller loads), or by providing a lower heating rate combined with storage (from which the peak rates can be satisfied). Lower costs are usually achieved by using at least some storage. A variety of different heating rateistorage volume combinations can be used to meet the needs of a given water-heating load profile (Hiller 1998).

zyxwvutsrq zyx 201 1 ASHRAE Handbook-HVAC

50.12 Load Diversity

The greatest difficulty in designing water-heating systems comes from uncertainty about design hot-water loads, especially for buildings not yet built. Although it is fairly simple to test maximum flow rates of various hot-water fixtures and appliances, actual flow rates and durations are user-dependent. Moreover, the timing of different hot-water use events varies from day to day, with some overlap, but almost never will all fixtures be used simultaneously. As the number of hot-water-using fixtures and appliances grows, the percent of those fixtures used simultaneously decreases. Some of the hot-water load information in this chapter is based on limited-scale field testing combined with statistical analysis to estimate load demand or diversity factors (percent of total possible load that is ever actually used at one time) versus number of end use points, number of people, etc. Much of the work to provide these diversity factors dates from the 1930s to the 1960s; it remains, however, the best information currently available (with a few exceptions, as noted). Of greatest concern is the fact that most of the data from those early studies were for fixtures that used water at much higher flow rates than modern energy-efficient fixtures (e.g., lowflow shower heads and sink aerators, energy-efficient washing machines and dishwashers). Some research has provided limited information on hot-water use by more modern fixtures, and on their use diversity (Becker et al. 1991; Goldner 1994a, 1994b; Goldner and Price 1999; Hiller 1998; Hiller and Lowenstein 1996, 1998; Thrasher and DeWerth 1994), but much more information in a variety of applications is needed before the design procedures can be updated. Using the older load diversity information usually results in a water-heating system that adequately serves the loads, but often results in substantial oversizing. Oversizing can be a deterrent to using modern high-efficiency water-heating equipment, which may have higher frst cost per unit of capacity than less efficient equipment. Sustainable design must consider these effects.

periods of considerably less than 1 h, often as short as 15 minutes. (Hiller 1998) Over these short periods, storage tank volume is a better indicator of hot-water delivery capability than frst-hour rating for residential applications. Another factor to consider when sizing water heaters is the setpoint temperature. At lower storage tank water temperatures, the tank volume andor energy input rate may need to be increased to meet a given hot-water demand. Currently, manufacturers ship residential water heaters with a recommendation that the initial set point be approximately 50°C to minimize the potential for scalding. Reduced set points generally lower standby losses and increase the water heater’s efficiency and recovery capacity, but may also reduce the amount of hot water available. The structure and lifestyle of a typical family (variations in family size, age of family members, presence and age of children, hot-water use volume and temperature, and other factors) cause

zyxwvuts zyxwvutsrq

Residential

Table 4 shows typical hot-water usage in a residence, including usage rates of modern ultralow-use appliances and fixtures. It is more difficult to show typical values for newer devices, because some automatically adjust the amount of hot water they use based on sensed load or cycle setting. In its Minimum Property Standards for Housing, the U.S. Department of Housing and Urban Development (HUD 1994) established minimum permissible water heater sizes (Table 5). Storage water heaters may vary from the sizes shown if combinations of recovery and storage are used that produce the required 1 h draw. The frst-hour rating (FHR) is the theoretical maximum amount of hot water that the water heater can supply in 1 h of operation under specific test conditions (DOE 1998). The linear regression lines shown in Figure 10 represent the FHR for 1556 electric heaters and 2901 gas heaters [GAMA (Continuous Maintenance); Hiller 19981. Regression lines are not included for oil-fired and heat-pump water heaters because of limited data. The FHR represents water-heater performance characteristics that are similar to those represented by the 1 h draw values listed in Table 5. Residential water-heating equipment sizing is frequently driven by amounts of water used over

Table 4

Applications (SI)

Fig. 10 First Hour Rating (FHR) Relationships for Residential Water Heaters

Typical Residential Use of Hot Water

Use Food preparation Hand dish washing Automatic dishwasher Clothes washer Shower or bath Face and hand washing

High Flow, LitredTask

Low Flow (Water Savers Used), LitredTask

Ultralow Flow, Litred Task

19 15 51 121 16 15

11 15 51 80 51 8

11 11 11 to 38 19 to 51 38 to 51 4 to 8

Fig. 11 Residential Average Hourly Hot-Water Use

50.13

Service Water Heating

zyxwvutsrqponm Table 5

HUD-FHA Minimum Water Heater Capacities for One- and Two-Family Living Units

Number of Baths

Number of Bedrooms Gasa Storage, L kW input 1 h draw, L Recovery, mL/s Electrica Storage, L kW input 1 h draw, L Recovery, mL/s 0ila Storage, L kW input 1 h draw, L Recovery, mL/s Tank-type indirectb,c I-W-H-rated draw, L in 3 h, 55 K rise Manufacturer-rated draw, L in 3 h, 55 K rise Tank capacity, L Tankless-type indirect c,d I-W-H-rated draw, &Is, 55 K rise Manufacturer-rated draw, L in 5 min, 55 K rise

1

1 to 1.5 2

3

2

2 to 2.5 3 4

76 7.9 163 24

114 10.5 227 32

114 10.5 227 32

114 10.5 227 32

150 10.5 265 32

76 2.5 114 10

114 3.5 167 15

150 4.5 220 19

150 4.5 220 19

114 20.5 337 62

114 20.5 337 62

114 20.5 337 62

114 20.5 337 62

150 186 250

170 57

3 to 3.5 4 5

5

3

6

150 11.1 273 36

190 13.8 341 42

150 11.1 273 34

190 11.1 311 34

190 13.8 341 42

190 14.6 350 44

190 5.5 273 23

190 5.5 273 23

250 5.5 334 23

190 5.5 273 23

250 5.5 334 23

250 5.5 334 23

300 5.5 387 23

114 20.5 337 62

114 20.5 337 62

114 20.5 337 62

114 20.5 337 62

114 20.5 337 62

114 20.5 337 62

114 20.5 337 62

150 186 250

250 284 250

250e 284e 250e

250 284 3 10

250 284 250

250 284 310

250 284 310

250 284 310

170 57

200 95

200e 95e

240 133

200 95

240 133

240 133

240 133

zyxwvutsrqp zy

Note: Applies to tank-type water heaters only 5torage capacity, input, and recovely requirements indicated are typical and may valy with manufacturer. Any combination of requirements to produce stated 1 h draw is satisfactoly. bBoiler-connected water heater capacities (82°C boiler water, internal or external connection).

hot-water consumption demand patterns to fluctuate widely in both magnitude and time distribution. Perlman and Mills (1985) developed the overall and peak average hot-water use volumes shown in Table 6. Average hourly patterns and 95% confidence level profiles are illustrated in Figures 11 and 12. Samples ofresults from the analysis of similarities in hotwater use are given in Figures 13 and 14.

CHeatercapacities and inputs are minimum allowable. Variations in tank size are permitted when recovely is based on 4.2 mL/(s.kW) at 55 K rise for electrical, AGA recovely ratings for gas, and IBR ratings for steam and hot-water heaters. dBoiler-connected heater capacities (93 “C boiler water, internal or external connection). eAlso for 1 to 1.5 baths and 4 bedrooms for indirect water heaters.

Table 6

Overall (OVL) and Peak Average Hot-Water Use Average Hot-Water Use, L Hourly Daily Weekly Monthly OVL Peak OVL Peak OVL Peak OVL Peak

Grouo All families “Typical”fami1ies

9.8 9.9

17.3 21.9

236 239

254 252

1652 1873 7178 7700 1673 1981 7270 7866

Commercial and Institutional Most commercial and institutional establishments use hot or warm water. The specific requirements vary in total volume, flow rate, duration of peak load period, and temperature. Water heaters and systems should be selected based on these requirements. This section covers sizing recommendations for central storage water-heating systems. Hot-water usage data and sizing curves for dormitories, motels, nursing homes, office buildings, food service establishments, apartments, and schools are based on EEI-sponsored research (Werden and Spielvogel 1969a, 1969b). Caution must be taken in applying these data to small buildings. Also, within any given category there may be significant variation. For example, the motel category encompasses standard, luxury, resort, and convention motels. When additional hot-water requirements exist, increase the recovery andor storage capacity accordingly. For example, if there is food service in an office building, the recovery and storage capacities required for each additional hot-water use should be added when sizing a single central water-heating system. Peak hourly and daily demands for various categories of commercial and institutional buildings are shown in Table 7. These demands for central-storage hot water represent the maximum flows metered in this 129-building study, excluding extremely high and very infrequent peaks. Table 7 also shows average hot-water consumption figures for these buildings. Averages for schools and food service establishments are based on actual days of operation; all others are based on total days. These averages can be used to estimate monthly consumption of hot water, but are not intended

Fig. 12 Residential Hourly Hot-Water Use, 95% Confidence Level for sizing purposes because they do not show the time distribution of draws. Research conducted for ASHRAE (Becker et al. 1991; Thrasher and DeWerth 1994) and others (Goldner 1994a, 1994b) included a compilation and review of service hot-water use information in commercial and multifamily structures along with new monitoring data. Some of this work found consumption comparable to those

zyx

201 1 ASHRAE Handbook-HVAC Applications (SI)

50.14 Table 7

Hot-Water Demands and Use for Various Types of Buildings*

Type of Building

Maximum Hourly

Maximum Daily

Average Daily

Men’s dormitories Women’s dormitories Motels: Number of unitsa 20 or less 60 100 or more Nursing homes Office buildings Food service establishments: Type A: Full-meal restaurants and cafeterias Tvoe B: Drive-ins. grills. luncheonettes. sandwich and snack shoos Apartment houses: Number of apartments 20 or less 50 75 100 200 or more Elementary schools Junior and senior high schools

14.4 L/student 19 L/student

83.3 L/student 100 L/student

49.7 L/student 46.6 L/student

23 L/unit 20 L/unit 15 L/unit 17 L/bed 1.5 L/person

132.6 L/unit 94.8 L/unit 56.8 L/unit 114 L/bed 7.6 L/person

75.8 L/unit 53.1 L/unit 37.9 L/unit 69.7 L/bed 3.8 L/person

5.7 L/max meals/h 2.6 L/max meals/h

41.7 L/max mealsdday 22.7 L/max mealsddav

45.5 L/apartment 37.9 L/apartment 32.2 L/apartment 26.5 L/apartment 19 L/apartment 2.3 L/student 3.8 L/student

*Data predate modern low-flow fixtures and appliances.

aInterpolate for intermediate values.bPer day of operation

303.2 L/apartment 276.7 L/apartment 250 L/apartment 227.4 L/apartment 195 L/apartment 5.7 L/student 13.6 L/student

9.1 L/average meals/dayb 2.6 L/averaee meals/davb 159.2 L/apartment 151.6 L/apartment 144 L/apartment 140.2 L/apartment 132.7 L/apartment 2.3 L/studentb 6.8 L/studentb

zyxw

Fig. 13 Residential Hourly Hot-Water Use Pattern for Selected High Morning and High Evening Users

Fig. 14 Residential Average Hourly Hot-Water Use Pattern for Low and High Users

shown in Table 7; however, many of the studies showed higher consumption. Dormitories. Hot-water requirements for college dormitories generally include showers, lavatories, service sinks, and clothes washers. Peak demand usually results from the use of showers. Load profiles and hourly consumption data indicate that peaks may last 1 or 2 h and then taper off substantially. Peaks occur predominantly in the evening, mainly around midnight. The figures do not include hot water used for food service. Military Barracks. Design criteria for military barracks are available from the engineering departments of the U.S. Department of Defense. Some measured data exist for hot-water use in these facilities. For published data, contact the U.S. Army Corps of Engineers or Naval Facilities Engineering Command. Motels. Domestic hot-water requirements are for tubs and showers, lavatories, and general cleaning purposes. Recommendations are based on tests at low- and high-rise motels located in urban, suburban, rural, highway, and resort areas. Peak demand, usually from shower use, may last 1 or 2 h and then drop off sharply. Food service, laundry, and swimming pool requirements are not included.

Nursing Homes. Hot water is required for tubs and showers, wash basins, service slnks, kitchen equipment, and general cleaning. These figures include hot water for kitchen use. When other equipment, such as that for heavy laundry and hydrotherapy purposes, is to be used, its hot-water requirement should be added. Office Buildings. Hot-water requirements are primarily for cleaning and lavatory use by occupants and visitors. Older office buildings often use hot-water recirculation-loop systems and are thus good candidates for water-heating distribution system efficiency upgrades through more modern controls and/or addition of point-of-use water heaters. Hot-water use for food service in office buildings is not included. Food Service Establishments. Hot-water requirements are primarily for dish washing. Other uses include food preparation, cleaning pots and pans and floors, and hand washing for employees and customers. Recommendations are for establishments serving food at tables, counters, booths, and parked cars. Establishments that use disposable service exclusively are not covered in Table 7. Dish washing, as metered in these tests, is based on normal practice of dish washing after meals, not on indiscriminate or continuous

zyxwvuts z Next Page

Service Water Heating

use of machines irrespective of the flow of soiled dishes. Recommendations include hot water supplied to dishwasher booster heaters. Apartments. Hot-water requirements for both garden-type and high-rise apartments are for one- and two-bath apartments, for showers, lavatories, kitchen sinks, dishwashers, clothes washers, and general cleaning purposes. Clothes washers can be either in individual apartments or centrally located. These data apply to central water-heating systems only. Elementary Schools. Hot-water requirements are for lavatories, cafeteria and kitchen use, and general cleaning purposes. When showers are used, their additional hot-water requirements should be added. Recommendations include hot water for dishwashers but not for extended school operation such as evening classes. High Schools. Senior high schools, grades 9 or 10 through 12, require hot water for showers, lavatories, dishwashers, kitchens, and general cleaning. Junior high schools, grades 7 through 8 or 9, have requirements similar to those of the senior high schools. Junior high schools without showers follow the recommendations for elementary schools. Requirements for high schools axe based on daytime use. Recommendations do not take into account hot-water use for additional activities such as night school. In such cases, the maximum hourly demand remains the same, but the maximum and average daily use increase, usually by the number of additional people using showers and, to a lesser extent, eating and washing facilities. Additional Data. Fast Food Restaurants. Hot water is used for food preparation, cleanup, and rest rooms. Dish washing is usually not a significant load. In most facilities, peak usage occurs during the cleanup period, typically soon after opening and immediately before closing. Hot-water consumption varies significantly among individual facilities. Fast food restaurants typically consume 1000 to 2000 L per day (EPRI 1994). Supermarkets. The trend in supermarket design is to incorporate food preparation and food service functions, substantially increasing the usage of hot water. Peak usage is usually associated with cleanup periods, often at night, with a total consumption of 1100 to 3800 L per day (EPRI 1994). Apartments. Table 8 shows cumulative hot-water use over time for apartment buildings, taken from a series of field tests by Becker et al. (1991), Goldner (1994a, 1994b), Goldner and Price (1999), and Thrasher and DeWerth (1994). These data include use diversity information, and enable use of modern water-heating equipment sizing methods for this building type, making it easy to understand the variety of heating rate and storage volume combinations that can serve a given load profile (see Example 1). Unlike Table 7, Table 8 presents lowimediumihigh (LMH) guidelines rather than specific singular volumes, and gives better time resolution of peak hot-water use information. The same information is shown graphically in Figure 15.Note that these studies showed that occupants on average use more hot water when water-heating costs are included in the rent, than if the occupants pay directly for water-heating energy use. The low-use peak hot-water consumption profile represents the lowest peak profile seen in the tests, and is generally associated with apartment buildings having mostly a mix of the following occupant demographics:

50.15

Table 8 Hot-Water Demand and Use Guidelines for Apartment Buildings (Litres per Person at 49OC Delivered to Fixtures) Peak Minutes

Guideline Low Medium High

5 1.5 2.6 4.5

15

30

60

120

180

3.8 6.4 10.6 17.0 23.1 6.4 11.0 18.2 30.3 41.6 11.4 19.3 32.2 54.9 71.9

Maximum Average Daily Daily

76 185 340

53 114 204

zyxwvutsrqpo

All occupants working One person working, while one stays at home Seniors Couples Middle income Higher population density The medium-use peak hot-water consumption profile represents the overall average highest peak profile seen in the tests, and is generally associated with apartment buildings having mostly a mix of the following occupant demographics:

Fig. 15 Apartment Building Cumulative Hot-Water Use Versus Time (from Table 8)

Families Singles On public assistance Single-parent households The high-use peak hot-water consumption profile represents the highest peak profile seen in the tests, and is generally associated with apartment buildings having mostly a mix of the following occupant demographics: High percentage of children Low income On public assistance No occupants working Families Single-parent households In applying these guidelines, the designer should note that a building may outlast its current use. This may be a reason to increase the design capacity for domestic hot water or allow space and connections for future enhancement of the service hot-water system. Building management practices, such as the explicit prohibition (in the lease) of apartment clothes washers or the existence of bathikitchen hook-ups, should be factored into the design process. A diversity factor that lowers the probability of coincident consumption should also be used in larger buildings. The information in Table 8 and Figure 15 generates a waterheating equipment sizing method for apartment buildings. The cumulative total hot-water consumption versus time (which includes all necessary load diversity information) can be used to select a range of heating rate and storage volume options, all of which will satisfy the load. The key is that plots of cumulative total hot-water consumption versus time as shown in Figure 15 also represent, by the slope of a line drawn from zero time through the cumulative volume used at any given time, the average hot-water flow rate up to that point in time. Up to any point in time, the minimum average heating rate needed to satisfy the load is one that can heat the average hot-water flow rate through that time from the local

CHAPTER 51

zy zyx

SNOW MELTING AND FREEZE PROTECTION Snow-Melting Heat Flux Requirement Slab Design ......................................... Control ........................................................................................................................................ Hydronic System Design Electric System Design.. .............................................................................................................. Freeze Protection Systems ..........................................................................................................

T

HE practicality of melting snow or ice by supplying heat to the exposed surface has been demonstrated in many installations, including sidewalks, roadways, ramps, bridges, access ramps, and parking spaces for the handicapped, and runways. Melting eliminates the need for snow removal by chemical means, provides greater safety for pedestrians and vehicles, and reduces the labor and cost of slush removal. Other advantages include eliminating piled snow, reducing liability, and reducing health risks of manual and mechanized shoveling. This chapter covers three types of snow-melting and freeze protection systems: 1. Hot fluid circulated in slab-embedded pipes (hydronic) 2. Embedded electric heater cables or wire 3. Overhead high-intensity infrared radiant heating Detailed information about slab heating can be found in Chapter 6 of the 2008 ASHRAE Handbook-HVACSystems and Equipment. More information about infrared heating can be found in Chapter 15 of the same volume. Components of the system design include (1) heat requirement, (2) slab design, (3) control, and (4) hydronic or electric system design.

Sensible and Latent Heat Fluxes. The sensible heat flux q, is the heat flux required to raise the temperature of snow falling on the slab to the melting temperature plus, after the snow has melted, to raise the temperature of the liquid to the assigned temperature tfof the liquid film. The snow is assumed to fall at air temperature t,. The latent heat flux qm is the heat flux required to melt the snow. Under steady-state conditions, both q, and qm are directly proportional to the snowfall rate s. Snow-Free Area Ratio. Sensible and latent (melting) heat fluxes occur on the entire slab during snowfall. On the other hand, heat and mass transfer at the slab surface depend on whether there is a snow layer on the surface. Any snow accumulation on the slab acts to partially insulate the surface from heat losses and evaporation. The insulating effect of partial snow cover can be large. Because snow may cover a portion of the slab area, it is convenient to thlnk of the insulating effect in terms of an effective or equivalent snow-covered area A,, which is perfectly insulated and from which no evaporation and heat transfer occurs. The balance is then considered to be the equivalent snow-free area AT This area is assumed to be completely covered with a thin liquid film; therefore, both heat and mass transfer occur at the maximum rates for the existing environmental conditions. It is convenient to defme a dimensionless snow-free area ratio A,:

SNOW-MELTING HEAT FLUX REQUIREMENT The heat required for snow melting depends on five atmospheric factors: (1) rate of snowfall, (2) snowfall-coincident air dry-bulb temperature, (3) humidity, (4) wind speed near the heated surface, and (5) apparent sky temperature. The dimensions of the snowmelting slab affect heat and mass transfer rates at the surface. Other factors such as back and edge heat losses must be considered in the complete design.

51.10 51.10 5 1.13 5 1.17

where Af A, A,

zyxwvu

equivalent snow-free area, m2 equivalent snow-covered area, m2 = Af + A, = total area, m2 = =

Therefore.

Heat Balance The processes that establish the heat requirement at the snowmelting surface can be described by terms in the following equation, which is the steady-state energy balance for required total heat flux (heat flow rate per unit surface area) qo at the upper surface of a snow-melting slab during snowfall.

where

OIA,Il To satisfy A, = 1, the system must melt snow rapidly enough that no accumulation occurs. For A, = 0, the surface is covered with snow of sufficient thickness to prevent heat and evaporation losses. Practical snow-melting systems operate between these limits. Earlier studies indicate that sufficient snow-melting system design information is obtained by considering three values of the free area ratio: 0, 0.5, and 1.0 (Chapman 1952). Heat Flux because of Surface Convection, Radiation, and Evaporation. Using the snow-free area ratio, appropriate heat and mass transfer relations can be written for the snow-free fraction of the slab A,. These appear as the third and fourth terms on the righthand side of Equation (1). On the snow-free surface, maintained at film temperature heat is transferred to the surroundings and mass is transferred from the evaporating liquid film.Heat flux qh includes convective losses to the ambient air at temperature t, and radiative losses to the surroundings, which are at mean radiant temperature TMR.The convection heat transfer coefficient is a function of wind

zyxwvutsrqpo z zyxwv

qo = heat flux required at snow-melting surface, W/m2 q, = sensible heat flux, W/m2 qm = latent heat flux, W/m2 A, = snow-free area ratio, dimensionless qh = convective and radiative heat flux from snow-free surface, W/m2 qe = heat flux of evaporation, W/m2

tf,

The preparation of this chapter is assigned to TC 6.5, Radiant Heating and Cooling.

51.1

51.2

201 1 ASHRAE Handbook-HVAC

speed and a characteristic dimension of the snow-melting surface. This heat transfer coefficient is also a function of the thermodynamic properties of the air, which vary slightly over the temperature range for various snowfall events. The mean radiant temperature depends on air temperature, relative humidity, cloudiness, cloud altitude, and whether snow is falling. The heat flux qe from surface film evaporation is equal to the evaporation rate multiplied by the heat of vaporization. The evaporation rate is driven by the difference in vapor pressure between the wet surface of the snow-melting slab and the ambient air. The evaporation rate is a function of wind speed, a characteristic dimension of the slab, and the thermodynamic properties of the ambient air.

VL ReL = -c2

Sensible Heat Flux. The sensible heat flux qs is given by the following equation:

4s = PwaterS [Cp,ice(ts where

tu)

+ Cp,water(tf

ts)l/cl

,,,c ,, = specific heat of ice, J/(kg.K) c~,~,~,, = specific heat of water, J/(kg.K) s = snowfall rate water equivalent, m d h t, = ambient temperature coincident with snowfall, "C tf = liquid film temperature, "C t, = melting temperature, "C pwuter = density of water, k4m3 c1 = 1000 mmlm x 3600 s/h = 3.6 x lo6

(3)

qm = Pwatershif/Cl

(4)

where hif = heat of fusion of snow, Jikg. Convective and Radiative Heat Flux from a Snow-Free Surface. The corresponding heat flux qh is given by the following equation:

where

V = design wind speed near slab surface, k d h v,,, = kinematic viscosity of air, m2/s c2 = 1000 d k m x 1 h/3600 s = 0.278

Without specific wind data for winter, the extreme wind data in Chapter 14 of the 2009 ASHRAE Handbook-Fundamentals may be used; however, it should be noted that these wind speeds may not correspond to actual measured data. If the snow-melting surface is not horizontal, the convection heat transfer coefficient might be different, but in many applications, this difference is negligible. From Equations (6) and (7), it can be seen that the turbulent convection heat transfer coefficient is a function of L-o.2. Because of this relationship, shorter snow-melting slabs have higher convective heat transfer coefficients than longer slabs. For design, the shortest dimension should be used (e.g., for a long, narrow driveway or sidewalk, use the width). A snow-melting slab length L = 6.1 m is used in the heat transfer calculations that resulted in Tables 1 , 2 , and 3. The mean radiant temperature TMR in Equation (5) is the equivalent blackbody temperature of the surroundings of the snowmelting slab. Under snowfall conditions, the entire surroundings are approximately at the ambient air temperature (i.e., TMR = T,). When there is no snow precipitation (e.g., during idling and after snowfall operations for A, < l), the mean radiant temperature is approximated by the following equation:

where F,,

fraction of radiation exchange that occurs between slab and clouds Tcloud= temperature of clouds, K TsQ clear= temperature of clear sky, K =

The equivalent blackbody temperature of a clear sky is primarily a function of the ambient air temperature and the water content of the atmosphere. An approximation for the clear sky temperature is given by the following equation, which is a curve fit of data in Ramsey et al. (1982): Z&

=

T,

-

(1 .105 8 x 1O3

+ 1.333 x

(5)

-

7.5 62 T,

10-2T2- 31.2924 + 14.5842)

(9)

where

where convection heat transfer coefficient for turbulent flow, W/(m2.K) Tf = liquid film temperature, K TMR= mean radiant temperature of surroundings, K CT = Stefan-Boltzmann constant = 5.670 x 10" W/(m2.K4) E, = emittance of surface, dimensionless =

zyxwvuts

The convection heat transfer coefficient over the slab on a plane horizontal surface is given by the following equations (Incropera and DeWitt 1996):

where

and

(7)

V,ir

zyxwvuts

The density of water, specific heat of ice, and specific heat of water are approximately constant over the temperature range of interest and are evaluated at 0°C. The ambient temperature and snowfall rate are available from weather data. The liquid film temperature is usually taken as 0.56"C. Melting Heat Flux. The heat flux qm required to melt the snow is given by the following equation:

k,,, L Pr Re,

z

zyxwvutsrqpo zyxwvutsr zyxwvu zyxwvutsrqponmlk

Heat Flux Equations

h,

Applications (SI)

= = = =

thermal conductivity of air at t,, W/(m.K) characteristic length of slab in direction of wind, m Prandtl number for air, taken as Pr = 0.7 Reynolds number based on characteristic length L

T,

=

ambient temperature, K

4 = relative humidity of air at elevation for which typical weather measurements are made, decimal

The cloud-covered portion of the sky is assumed to be at Tcloud. The height of the clouds may be assumed to be 3000 m. The temperature of the clouds at 3000 m is calculated by subtracting the product ofthe average lapse rate (rate of decrease of atmospheric temperature with height) and the altitude from the atmospheric temperature T,. The average lapse rate, determined from the tables of U.S. Standard Atmospheres (COESA 1976), is 6.4 K per 1000 m of elevation (Ramsey et al. 1982). Therefore, for clouds at 3000 m,

Under most conditions, this method of approximating the temperature of the clouds provides an acceptable estimate. However, when the atmosphere contains a very high water content, the temperature calculated for a clear sky using Equation (9) may be warmer than the cloud temperature estimated using Equation (10). When that condition exists, Tcloudis set equal to the calculated clear sky temperature Tskv

zyxwvutsrqp zyxwvutsrq zyxwvutsrqpo 51.3

Snow Melting and Freeze Protection

Evaporation Heat Flux. The heat flux qe required to evaporate water from a wet surface is given by q e = Pdry aiThndWf

where

~

Waa)hfg

(1 1)

h, = mass transfer coefficient, d s W, = humidity ratio of ambient air, kgvupol/kga~r Wf = humidity ratio of saturated air at film surface temperature, kgvupo~kg,,, hfg = heat of vaporization (enthalpy difference between saturated water vapor and saturated liquid water), J/kg pdv , = density of dry air, kg/m3

Determination of the mass transfer coefficient is based on the analogy between heat transfer and mass transfer. Details of the analogy are given in Chapter 5 of the 2009 ASHRAE Handbook-Fundamentals. For external flow where mass transfer occurs at the convective surface and the water vapor component is dilute, the following equation relates the mass transfer coefficient h, to the heat transfer coefficient h, [Equation (6)]:

other measure of humidity). By computing the heat flux for each snowfall hour over a period of several years, a frequency distribution of hourly heat fluxes can be developed. Annual averages or maximums for climatic factors should never be used in sizing a system because they are unlikely to coexist. Finally, it is critical to note that the preceding analysis only describes what is happening at the upper surface of the snow-melting surface. Edge losses and back losses have not been taken into account.

Example 1. During the snowfall that occurred during the 8 PM hour on December 26, 1985, in the Detroit metropolitan area, the following simultaneous conditions existed: air dry-bulb temperature = -8.3"C, dew-point temperature = -1O"C, wind speed = 3 1.7 k d h , and snowfall rate = 2.54 mm of liquid water equivalent per hour. Assuming L = 6.1 m, Pr = 0.7, and Sc = 0.6, calculate the surface heat flux qo for a snow-free area ratio of A, = 1.0. The thermodynamic and transport properties used in the calculation are taken from Chapters 1 and 33 of the 2009 ASHRAE Handbook-Fundamental. The emittance of the wet surface of the heated slab is 0.9. Solution: By Equation (3),

zyxwv

qs= 1000 x 2'54 [2100(0 + 8.3) + 4290(0.56 3.6 x lo6

-

O)]

=

14.0 W/m2

By Equation (4),

where Sc = Schmidt number. In applying Equation (1 l ) , the values Pr = 0.7 and Sc = 0.6 were used to generate the values in Tables 1 through 4. The humidity ratios both in the atmosphere and at the surface of the water film are calculated using the standard psychrometric relation given in the following equation (from Chapter 1 of the 2009 ASHRAE Handbook-Fundamentals):

=

1000 x 2'54 x 334 000 = 235.6 W/m2 3.6 x lo6

By Equation (7), ReL =

31.7 x 6.1 x 0.278

=

4,13

106

1.3 x 10

zyxwvutsr zyxwvutsrq W = 0.622 [P?PJ

where

q,

By Equation (6),

h, = 0.037

i 1 O.0235

(4.13 x 106)('8(0.7)''3 = 24.8 W/(m2.K)

6.1

p = atmospheric pressure, kPa pv = partial pressure of water vapor, kPa

The atmospheric pressure in Equation (13) is corrected for altitude using the following equation (Kuehn et al. 1998):

By Equation (5),

qh = 24.8(0.56 =

+ 8.3) + (5.670 x

10")(0.9)(273.74 -264.94)

258.8 W/m2

By Equation (12), I

where

\2/3

24'8 1.33 x 1005

pstd = standard atmospheric pressure, kPa A = 0.0065 K/m z = altitude of the location above sea level, m To = 288.2 K

Altitudes of specific locations are found in Chapter 14 of the 2009 ASHRAE Handbook-Fundamentals . The vapor pressure pv for the calculation of W, is equal to the saturation vapor pressurep, at the dew-point temperature of the air. Saturated conditions exist at the water film surface. Therefore, the vapor pressure used in calculating Wf is the saturation pressure at the film temperature 9.The saturation partial pressures of water vapor for temperatures above and below freezing are found in tables of the thermodynamic properties of water at saturation or can be calculated using appropriate equations. Both are presented in Chapter 1 of the 2009 ASHRAE Handbook-Fundamentals. Heat Flux Calculations. Equations (1) to (14) can be used to determine the required heat fluxes of a snow-melting system. However, calculations must be made for coincident values of snowfall rate, wind speed, ambient temperature, and dew-point temperature (or an-

=

0.0206 d s

Obtain the values of the saturation vapor pressures at the dew-point temperature -10°C and the film temperature 0.56"C from Table 3 in Chapter 1 of the 2009 ASHRAE Handbook-Fundamental. Then, use Equation (13) to obtain W , = 0.00160 kgvup0,/kg,,, and W f = 0.00393 kgvup0,/kg,,,. BY Equation (1 11,

zyxwvutsr qe = 1.33 x 0.0206(0.00393

-

0.00160) x 2499 x lo3 = 159.5 W/m2

By Equation (l),

qo = 14.0 + 235.6 + 1.0(258.8 + 159.5) = 664 W/m2

Note that this is the heat flux needed at the snow-melting surface of the slab. Back and edge losses must be added as discussed in the section on Back and Edge Heat Losses.

Weather Data and Heat Flux Calculation Results Table 1 shows frequencies of snow-melting loads for 46 cities in the United States (Ramsey et al. 1999).For the calculations, the temperature of the surface of the snow-melting slab was taken to be 0.56"C. Any time the ambient temperature was below 0°C and it

201 1 ASHRAE Handbook-HVAC Applications (SI)

51.4

zyxwvutsr zyxwvutsr zy zyxwvutsrqponmlk zyxwvut

Table 1 Frequencies of Snow-Melting Surface Heat Fluxes at Steady-State Conditions*

Location Albany, NY

Snowfall Hours per Year 156

Albuquerque, NM

44

Amanllo, TX

64

Billinns. MT

225

Bismarck. ND

158

V

I

Boise, ID

85

Boston, MA

112

Buffalo, NY

292

Burlington, VT

204

Cheyenne, WY

224

Chicago, IL, O'Hare International Airport

124

Cleveland, OH

188

Colorado Springs, CO

159

Columbus, OH, International Airport

92

Des Moines, IA

127

Detroit, MI, Metro Airport

153

Duluth, MN

23 8

Ely, NV

153

Eugene, OR Fairbanks, AK Baltimore, MD, BWI Airport

18 288 56

Great Falls, MT

233

Indianapolis, IN

96

Heat Fluxes Not Exceeded During Indicated Percentage of Snowfall Hours from 1982 Through 1993, W/m2

Snow-Free Area Ratio.

4

15Yo

90%

95%

98%

99%

100%

1 0.5 0 1 0.5 0 I 0.5 0 1 0.5 0 1 0.5 0 1 0.5 0 1 0.5 0 1 0.5 0 1 0.5 0 1 0.5 0 1 0.5 0 1 0.5 0 1 0.5 0 1 0.5 0 1 0.5 0 1 0.5 0 1 0.5 0 1 0.5 0 1 0.5 0

282 189 118

395 270 194

47 1 348 262

588 436 376

668 535 46 1

1011 870 870

35x

4l L

223 76 353 203 71 476 263 50 183 118 71 303 207 118 364 214 72 288 182 72 375 219 52 303 184 72 267 165 71 28 1 178 72 223 143 49 379 235 74 290 178 71 388 225 71 212 140 72 1x5 149 95

279 145 517 282 104 627 338 95 250 165 97 43 1 299 235 522 305 123 410 247 125 542 305 118 396 242 120 391 229 118 425 258 141 317 190 95 550 323 144 41 1 243 120 540 306 101 307 208 143

I

LX I

0.5 0 1 0.5 0 1 0.5 0 1 0.5 0

165 49 276 219 145 389 224 51 300 184 71

LL2

372

52Y

603

762

1241

161 95

256 144

304 191 53 I 340 195 589 322 142 729 390 122 314 207 127 519 353 292 664 399 174 485 289 173 63 5 35 1 165 482 297 168 494 29 1 149 525 311 191 389 223 141 655 377 216 49 1 297 147 63 5 36 1 145 365 26 1 212

368 282

492 29 1

723 611

66X

IIX

IUU4

390 282 669 366 188 867 466 189 398 254 166 636 470 380 873 517 294 580 358 247 72 1 415 241 586 358 235 615 373 217 637 392 274 47 1 276 188 804 47 1 298 605 371 235 752 413 213 423 350 306 5LU 375 321

449 363 748 403 215 969 520 230 460 280 195 724 60 1 544 1040 594 355 632 40 5 298 823 469 317 740 43 1 262 726 46 5 289 692 442 354 553 298 195 913 567 340 668 424 282 790 448 244 512 407 353

963 922 1072 566 355 1506 767 569 640 5 17 5 17 1152 1152 1152 1799 1227 781 1081 1081 1081 1117 908 900 1643 835 474 1363 741 711 1031 687 521 1035 580 426 1307 977 729 1136 715 611 1167 671 620 764 761 758

53Y

7ux

385 379

5 17 5 17 IL3L 630 273 1361 1162 964 1237 662 452 897 658 658

zyxwvut 347

43x

242 166

292 220

3XL

454

54Y

63Y

214 74 439 342 264 538 292 98 42 1 254 118

247 99 542 46 5 374 610 337 141 49 8 304 165

297 126 740 63 1 571 734 407 190 613 366 26 1

342 152 89 1 75 1 677 869 453 218 678 39 1 312

*Heat fluxes are at the snow-melting surface only. See text for calculation ofback and edge heat loss fluxes.

Snow Melting and Freeze Protection

zyxwvu zyxw 51.5

zyxwvutsr zy

Table 1 Frequencies of Snow-Melting Surface Heat Fluxes at Steady-State Conditions* (Continued)

Location Lexington, KY

Snowfall Hours per Year 50

Heat Fluxes Not Exceeded During Indicated Percentage of Snowfall Hours from 1982 Through 1993, W/m2

Snow-Free Area Ratio.

4

15Yo

90%

95%

98%

99%

100%

1 0.5 0

257 153 50

340 204 95

389 234 122

473 270 145

537 301 173

734 622 5 10

1

312

437

51X

64Y

760

141X

Madison, WI

161

0.5 0

191 72

258 123

310 189

407 287

513 358

773 611

I

335

445

54L

63L

65 I

6/1

Memphis, TN

13

Milwaukee. WI

161

Minneauolis-St. Paul. MN

199

0.5 0 1 0.5 0 1 0.5 0 1 0.5 0 1 0.5 0 1 0.5 0 1 0.5 0 1 0.5 0 1 0.5 0

235 126 318 194 73 376 230 74 287 199 119 370 226 74 342 204 72 299 183 72 296 204 119 262 160 49

303 235 425 263 145 532 3 12 141 423 294 214 529 320 145 468 281 121 439 260 119 406 282 197 393 238 97

363 240 516 320 214 608 360 192 518 372 270 677 389 213 598 330 189 525 313 167 487 353 249 502 297 144

373 285 618 404 309 722 434 286 654 457 356 781 419 247 702 405 283 634 375 239 655 511 350 613 349 214

410 307 654 465 379 80 1 485 155 700 517 420 820 453 355 817 425 315 717 410 29 1 777 582 474 690 406 244

495 388 1359 777 752 1048 904 771 1052 1024 995 882 655 598 1145 586 429 1376 789 718 1038 842 711 1335 681 428

New York. NY, JFK Aimort

61

Oklahoma City, OK

35

Omaha, NE

94

Peoria, IL Philadelphia, PA, International Airport

91

56

Pittsburgh, PA, International Airport

168

Portland, ME

157

Portland. OR

15

Rapid City, SD Reno, NV

177 63

Salt Lake City, UT

142

Sault Ste. Marie, MI

42 5

Seattle, WA Spokane, WA

27 144

Springfield, MO

58

St. Louis, MO, International Airport

62

Tooeka. KS

61

Wichita. KS

60

I

,

~

~

~

1

377

530

615

73x

x37

1349

0.5 0 1 0.5 0 1 0.5 0 1 0.5 0 1 0.5 0 1 0.5 0 1 0.5 0 1 0.5 0

239 122 159 122 72 438 245 49 158 115 72 165 122 94 353 207 71 177 142 118 210 141 72

342 212 246 175 141 641 349 95 227 174 143 243 196 188 484 278 118 339 226 165 308 191 118

418 285 321 256 188 793 416 121 280 235 215 282 240 235 577 327 148 434 307 235 366 229 141

530 409 558 360 246 984 5 19 166 365 331 288 346 301 282 681 394 214 539 3 84 302 444 266 170

628 479 755 41 1 321 1107 578 204 43 1 363 355 379 329 329 785 447 26 1 647 420 386 500 300 210

1185 1021 934 627 404 1519 773 564 604 543 502 541 541 541 1384 753 594 664 551 477 716 459 353

1

34x

4Y0

566

677

707

Y 20

0.5 0 1 0.5 0 1 0.5 0 1 0.5 0

220 101 307 207 97 323 201 73 364 225 74

299 171 463 284 169 482 291 122 515 302 143

368 238 537 330 214 607 347 165 660 367 179

449 362 608 399 306 738 415 213 782 432 237

538 407 715 454 329 773 43 8 264 900 48 1 260

757 715 1084 847 611 919 582 526 1027 529 498

*Heat fluxes are at the snow-melting surface only. See text for calculation ofback and edge heat loss fluxes.

201 1 ASHRAE Handbook-HVAC

51.6 was not snowing, it was assumed that the system was idling (i.e., that heat was supplied to the slab so that melting would start immediately when snow began to fall). Weather data were taken for the years 1982 through 1993. These years were selected because of their completeness of data. The weather data included hourly values of the precipitation amount in equivalent depth of liquid water, precipitation type, ambient dry-bulb and dew-point temperatures, wind speed, and sky cover. All weather elements for 1982 to 1990 were obtained from the Solar andMeteorological Surface Observation Network 1961 to 1990 (SAMSON), Version 1.0 (NCDC 1993). For 1991 to 1993, all weather elements except precipitation were taken from DATSAV2 data obtained from the National Climatic Data Center as described in Colliver et al. (1998). The precipitation data for these years were taken from NCDC’s Hourly Cooperative Dataset (NCDC 1990). All wind speeds used were taken directly from the weather data. Wind speed Vmetis usually measured at height of approximately 10 m. As indicated in the section on Heat Balance, the heat and mass transfer coefficients are functions of a characteristic dimension of the snow-melting slab. The dimension used in generating the values of Table 1 was 6.1 m. Sensitivity of the load to both wind speed and the characteristic dimension is included in Table 2. During snowfall, the sky temperature was taken as equal to the ambient temperature. The frst data column in Table 1 presents the average number of snowfall hours per year for each location. All surface heat fluxes were computed for snow-free arearatios of 1,0.5, and 0, and the frequencies of snow-melting loads are presented. The frequency indicates the percentage of time that the required snow-melting surface heat flux does not exceed the value in the table for that ratio. This table is used to design a snow-melting system for a given level of customer satisfaction depending on criticality of function. For example, although a heliport at the rooftop of a hospital may

Applications (SI)

require almost 100% satisfactory operation at a snow-free ratio of 1, a residential driveway may be considered satisfactory at 90% and A, = 0.5 design conditions. To optimize cost, different percentiles may be applied to different sections of the slab. For example, train station slab embalddisembark areas may be designed for a higher percentile and A, than other sections.

z

zyxwvutsrq Figures 1 and 2 show the distribution in the United States of snowmelting surface heat fluxes for snow-free area ratios of 1.O and 0, respectively. The values presented satisfy the loads 99% of the time (as listed in the 99% column of Table 1). Local values can be approximated by interpolating between values given on the figure; however, extreme care must be taken because special local climatological conditions exist formany areas (e.g., lake effect snow). Both altitude and geography should be considered in making interpolations. Generally, locations in the northern plains of the United States require the maximum snow-melting heat flux (Chapman 1999).

Example for Surface Heat Flux CalculationUsing Table 1 Example 2. Consider the design of a system for Albany, New York, which has an installed heat flux capacity at the top surface of approximately 471 W/m2. Based on data in Table 1, this system will keep the surface completely free of snow 95% of the time. Because there are 156 snowfall hours in an average year, this design would have some accumulation of snow approximately 8 h per year (the remaining 5% of the 156 h). This design will also meet the load for more than 98% of the time (i.e., more than 153 of the 156 snowfall hours) at an area ratio of 0.5 and more than 99% of the time for an area ratio of 0. A, = 0.5 means that there is a thin layer of snow over all or part of the slab such that it acts as though half the slab is insulated by a snow layer; A, = 0 means that the snow layer is sufficient to insulatethe surface from heat and evaporation losses, but that snow is melting at the base of this layer at the same rate that it is falling on the top of the layer.

zyx

Fig. 1 Snow-Melting Surface Heat Fluxes Required to Provide Snow-Free Area Ratio of 1.0 for 99% of Time

51.7

Snow Melting and Freeze Protection Therefore, the results for this system can be interpreted to mean the following (all times are rounded to the nearest hour): (a) For all but 8 h of the year, the slab will be snow-free. (b) For the less than 5 h between the 95% and 98% nonexceedance values, there will be a thin build-up of snow on part of the slab. (c) For the less than 2 h between the 98% and 99% nonexceedance values, snow will accumulate on the slab to a thickness at which the snow blanket insulates the slab, but the thickness will not increase beyond that level. (d) For less than 2 h, the system cannot keep up with the snowfall. An examination of the 100% column shows that to keep up with the snowfall the last 1% of the time, in this case less than 2 h for an average year, would require a system capacity of approximately 870 W/m2; to attempt to keep the slab completely snow-free the entire season requires a capacity of 1011 W/m2. Based on this interpretation, the designer and customer must decide the acceptable operating conditions. Note that the heat flux values in this example do not include back or edge losses, which must be added in sizing energy source and heat delively systems.

Sensitivity of Design Surface Heat Flux to Wind Speed and Surface Size Some snow-melting systems are in sheltered areas, whereas others may be in locations where surroundings create a wind tunnel effect. Similarly, systems vary in size from the baseline characteristic length of 6.1 m. For example, sidewalks exposed to a crosswind may have a characteristic length on the order of 1.5 m. In such cases, the wind speed will be either less than or greater than the meteorological value Vmetused in Table 1. To establish the sensitivity of the surface heat flux to wind speed and characteristic length, calculations were performed at combinations of wind speeds 0.5 Vmet,Vmet,and 2Vmet and L values of 1.5 m and 6.1 m for area ratios A, of 1.0 and 0.5. Wind speed and system size do not affect the load values for A, = 0

because the calculations assume that no heat or mass transfer from the surface occurs at this condition. Table 2 presents a set of mean values of multipliers that can be applied to the loads presented in Table 1; these multipliers were established by examining the effect on the 99% nonexceedance values. The ratio of V to Vmetin a given design problem may be determined from information given in Chapter 24 of the 2009 ASHRAE Handbook-Fundamentals. The closest ratio in Table 2 can then be selected. The designer is cautioned that these are to be used only as guidelines on the effect of wind speed and size variations.

z

Back and Edge Heat Losses The surface heat fluxes in Table 1 do not account for heat losses from the back and edges of the slab. Adlam (1950) demonstrated that these back and edge losses may vary from 4 to 50%, depending on factors such as slab construction, operating temperature, ground temperature, and back and edge insulation and exposure. With the construction shown in Figure 3 or Figure 5 and ground temperature of 4.5"C at a depth of 600 mm, back losses are approximately 20%. Higher losses occur with (1) colder ground, (2)more cover over the slab, or (3) exposed back, such as on bridges or parking decks.

zyxwvutsrqpon

Fig. 2

Transient Analysis of System Performance

Determination of snow-melting surface heat fluxes as described in Equations (1) to (14) is based on steady-state analysis. Snowmelting systems generally have heating elements embedded in material of significant thermal mass. Transient effects, such as occur when the system is started, may be significant. A transient analysis method was developed by Spitler et al. (2002)and showed that particular storm conditions could change the snow-melting surface heat flux requirement significantly, depending on the precipitation rate at a particular time in the storm. It is therefore

Snow-Melting Surface Heat Fluxes Required to Provide Snow-Free Area Ratio of 0 for 99% of Time

zyxwvuts zyxwvutsr 201 1 ASHRAE Handbook-HVAC

51.8 Table 2

Mean Sensitivity of Snow-Melting Surface Heat Fluxes to Wind Speed and Slab Length

table may only be used to predict annual operating costs. Use Table 1 for system sizing.

For loads not exceeded during 99% of snowfall hours, 1982 through 1993 SnowFree Area Ratio, A,

1 0.5 0

Ratio of Flux at Stated Condition to Flux at L = 6.1 m and V = V,,,

L = 6.1 m

L = 1.5 m

V = O.5Vm,, V = 2V,,, 0.7 0.8 1.o

V = V,,,

1.6 1.4 1.o

Note: Based on data fr0mU.S. locations. L = characteristic length Vmet= meteorological wind speed from NCDC

1.2 1.2 1.o

2.0 1.7 1.0

Annual Operating Cost Example

Example 3. A snow-melting system of 200 m2 is to be installed in Chicago. The application is considered critical enough that the system is designed to remain snow-free 99% of the time. Table 3 shows that the annual energy requirement to melt the snow is 26.8 kWWm2. Assuming a fossil fuel cost of $9 per GJ, an electric cost of $0.07 per kWh, and back loss at 30%, find and compare the annual cost to melt snow with hydronic and electric systems. For the hydronic system, boiler combustion efficiency is 0.85 and energy distribution efficiency is 0.90.

zyxwvutsr

V = O.5Vm,, V = 2V,,, 0.8 0.9 1.0

Applications (SI)

difficult to find simple general design rules that account for transient effects. To keep slab surfaces clear from snow during the frst hour of the snowstorm, when the system is just starting to operate, heat fluxes up to five times greater than those indicated by steady-state analysis could be required. In general, greater heat input is required for greater spacing and greater depth of the heating elements in the slab; however, because of transient effects, this is not always true. Transient analysis (Spitler et al. 2002) has also been used to examine back and edge losses. Heat fluxes because of back losses in systems without insulation ranged from 10 to 30% of the surface heat flux, depending primarily on the particular storm data, though higher losses occurred where heating elements were embedded deeper in the slab. In cases where 50 nnn of insulation was applied below the slab, back losses were significantly reduced, to 1 to 4%. Although peak losses were reduced, the surface heat fluxes required to melt the snow were not significantly affected by the presence of insulation, because transient effects at the start of system operation drive the peak design surface heat fluxes. Edge losses ranged from 15 to 35% of the heat delivered by the heating element nearest the edge. This may be converted to an approximately equivalent surface heat flux percentage by reducing the snow-melting surface length and width by an amount equal to two-thirds of the heating element spacing in the slab. Then the design surface heat flux may be adjusted by the ratio of the actual snow-melting surface area to the reduced surface area as described here. The effect of edge insulation was found to be similar to that at the back of the slab. Although edge insulation does not reduce the surface heat flux requirement significantly, increased snow accumulation at the edges should be expected.

Solution: Operating cost 0 may be expressed as follows:

where 0 = annual operating cost $/yr At = total snow-melting area, m2 Q, = annual snow-melting or idling energy requirement, kWh/m2 F = primary energy cost $/kWh B = back heat loss percentage, % qb = combustion efficiency of boiler (or COP of a heat pump in heating mode), dimensionless. If a waste energy source is directly used for snow-melting or idling purposes, the combustion efficiency term is neglected. qd = energy distribution efficiency, dimensionless (in an electric system, efficiencies may be taken to be 1j

zyxwvutsr

Annual Operating Data Annual operating data for the cities in Table 1 are presented in Table 3. Melting and idling hours are summarized in this table along with the energy per unit area needed to operate the system during an average year based on calculations for the years 1982 to 1993. Back and edge heat losses are not included in the energy values in Table 3. Data are presented for snow-free area ratios of 1.0,0.5, and 0. The energy per unit area values are based on systems designed to satisfy the loads 99% of the time (i.e., at the levels indicated in the 99% column in Table 1) for each A, value. The energy use for each melting hour is taken as either (1) the actual energy required to maintain the surface at 0.56"C or (2) the design output, whichever is less. The design snow-melting energy differs, of course, depending on whether the design is for A, = 1.O, 0.5, or 0; therefore, the a n n u l melting energy differs as well. The idling hours include all non-snowfall hours when the ambient temperature is below 0°C. The energy consumption for each idling hour is based on either (1) the actual energy required to maintain the surface at 0°C or (2) the design snow-melting energy, whichever is less. In Table 3, the column labeled "2% Min. Snow Temp." is the temperature below which only 2% of the snowfall hours occur. This

Operating cost for a hydronic system is

['

-

[%I]

1 (0.85 j(0.90 j]

Operating cost for an electric system is O = 200(26'8)(0'07) 1 -(30/100)

=

$536/yr

It is desirable to use waste or alternative energy resources to minimize operating costs. If available in large quantities, low-temperature energy resources may replace primary energy resources, because the temperature requirement is generally moderate (Kilkis 1995). Heat pipes may also be used to exploit ground heat (Shirakawa et al. 1985).

SLAB DESIGN Either concrete or asphalt slabs may be used for snow-melting systems. The thermal conductivity of asphalt is less than that of concrete; pipe or electric cable spacing and required fluid temperatures are thus different. Hot asphalt may damage plastic or electric (except mineral-insulated cable) snow-melting systems unless adequate precautions are taken. For specific recommendations, see the sections on Hydronic System Design and Electric System Design. Concrete slabs containing hydronic or electric snow-melting apparatus must have a subbase, expansion-contraction joints, reinforcement, and drainage to prevent slab cracking; otherwise, crackinduced shearing or tensile forces could break the pipe or cable. The pipe or cable must not run through expansion-contraction joints, keyed construction joints, or control joints (dummy grooves); however, the pipe or cable may be run under 3 nnn score marks or saw cuts (block and other patterns). Sleeved pipe is allowed to cross expansion joints (see Figure 4). Control joints must be placed wherever the slab changes size or incline. The maximum distance between control joints for ground-supported slabs should be less than 4.6 m, and the length should be no greater than twice the width, except for ribbon driveways or sidewalks. In ground-supported slabs, most cracking occurs during the early cure. Depending on the

Next Page

51.9

Snow Melting and Freeze Protection

zyxwvuts zy

Table 3 Annual Operating Data at 99% Satisfaction Level of Heat Flux Requirement

Annual Energy Requirement per Unit Area at Steady-State Conditions,* kWh/m2

2% Min. Snow Temp.,

Time, City

System Designed for A,=l

System Designed for A, = 0.5

System Designed for A,=O

Melting

Idling

OC

Melting

Idling

Melting

Idling

Melting

Idling

Albany, NY Albuquerque, NM Amarillo, TX

156 44 64

1883 954 1212

-12.6 -8.8 -14.0

32.0 7.7 16.6

344.5 121.4 197.3

22.9 5.5 10.5

343.8 121.4 196.0

13.8 3.1 4.3

342.0 120.9 192.9

Billings, MT Bismarck, ND Boise, ID Boston, MA Buffalo, NY

225 158 85 112 292

1800 2887 1611 1273 1779

-23.8 -22.6 -14.9 -8.8 -15.7

54.6 51.4 11.2 24.3 75.5

368.9 655.7 235.7 246.0 333.8

33.2 29.4 7.7 17.2 46.5

352.6 635.7 230.3 245.7 332.8

11.7 7.3 4.2 10.1 17.5

288.1 496.8 215.9 245.2 321.5

Burlington, VT Cheyenne, WY Chicago, IL, O’Hare International Airport Cleveland, OH Colorado Springs, CO Columbus, OH, International Airport Des Moines, IA Detroit, MI, Metro Airport Duluth, MN

204 224 124

2215 2152 1854

-15.4 -26.5 -15.7

41.6 63.3 26.8

464.0 399.7 368.0

26.8 37.6 17.0

453.6 396.3 355.7

11.9 11.9 7.1

424.6 381.4 316.7

188 159 92

1570 1925 1429

-12.9 -22.6 -10.7

36.0 35.1 14.4

272.9 306.1 224.1

23.2 22.4 9.4

269.6 305.5 214.5

10.1 9.5 4.3

255.0 303.6 195.7

127 153 23 8

1954 1781 3206

-18.8 -11.5 -17.6

34.3 32.2 65.7

404.2 329.3 792.3

21.4 20.4 39.2

397.2 322.6 746.4

8.4 8.5 12.5

367.6 302.1 592.4

Ely, NV Eugene, OR Fairbanks, AK Baltimore, MD, BWI Airport Great Falls, MT

153 18 288 56 233

2445 48 1 4258 957 1907

-10.4 -9.0 -26.5 -8.8 -26.5

23.4 2.7 62.5 12.1 62.1

445.6 53.7 1083.9 142.3 390.5

16.6 2.0 36.9 9.4 37.0

439.2 53.6 1005.7 142.3 380.4

9.8 1.4 11.2 6.7 11.8

431.8 53.6 612.6 142.3 320.8

Indianapolis, IN Lexington, KY Madison, WI Memphis, TN Milwaukee, WI

96 50 161 13 161

1473 1106 2308 473 1960

-11.8 -10.4 -14.9 -10.7 -13.8

20.7 8.5 36.0 3.2 36.8

255.3 170.6 471.1 68.6 401.3

13.0 5.4 23.0 2.2 23.9

247.7 164.9 464.0 67.9 391.0

5.4 2.3 9.8 1.2 10.8

239.5 144.6 441.9 66.6 378.3

Minneapolis-St. Paul, MN New York, NY, JFK Airport Oklahoma City, OK Omaha, NE

199 61 35 94

2513 885 686 1981

-17.6 -7.6 -14.0 -19.0

52.1 13.2 9.3 23.4

580.3 159.8 129.2 392.0

32.6 9.4 5.8 14.5

563.0 159.2 125.3 377.1

12.9 5.7 2.3 5.6

526.5 157.9 120.8 355.5

Peoria, IL Philadelphia, PA, Internation:11 Airport Pittsburgh, PA, International Airport Portland, ME Portland, OR

91 56

1748 992

-16.5 -7.6

20.6 11.9

329.2 159.3

12.9 8.4

317.2 159.0

5.1 5.0

296.6 158.3

168

1514

-12.6

31.6

250.1

20.0

245.2

8.3

228.2

157 15

1996 329

-13.8 -5.7

42.0 2.0

363.5 42.3

28.3 1.5

363.3 41.6

14.6 1.o

362.2 40.7

Rapid City, SD Reno, NV Salt Lake City, UT Sault Ste. Marie, MI Seattle, WA

177 63 142 425 27

2154 1436 1578 273 1 260

-20.4 -8.8 -8.8 -17.9 -7.9

53.3 7.2 16.6 108.0 3.8

433.7 172.6 221.6 556.7 33.1

30.7 5.7 13.5 65.5 3.0

425.9 172.5 220.5 550.4 33.0

8.0 4.1 10.4 22.9 2.1

334.6 172.5 220.5 490.5 33.0

Spokane, WA Springfield, MO St. Louis, MO, International Airport Topeka, KS Wichita, KS

144 58 62

1832 1108 1150

-11.8 -14.0 -14.0

21.8 13.9 14.2

255.5 180.3 204.0

14.9 9.3 9.4

249.7 179.6 200.1

7.9 4.7 4.6

238.6 177.4 191.7

61 60

1409 1223

-18.8 -17.6

14.2 15.6

238.4 218.2

8.9 9.8

233.5 213.9

3.6 3.9

215.7 192.4

*Does not include back and edge heat losses

zyxw zyx zyxwvutsrqp CHAPTER 52

EVAPORATIVE COOLING

General Applications 52.1 Indirect Evaporative Cooling Systems f o r Comfort Cooling ............................................................. 52.2 Booster Refrigeration ............................................................... 52.8 Residential or Commercial Cooling ........................................ 52.9 Exhaust Required ................................................................... 52.10 Two-Stage Cooling................................................................. 52.10

Industrial Applications Other Applications ................................................................. Control Strategy to Optimize Energy Recovery ..................... Air Cleaning ........................................................................... Economic Factors .................................................................. Psychrometrics ....................................................................... Entering Air Considerations ..................................................

E

vaporization. If water is recirculated in the direct evaporative cooling apparatus, the water temperature in the reservoir approaches the wetbulb temperature of the air entering the process. By defdtion, no heat is added to, or extracted from, an adiabatic process; the initial and fmal conditions fall on a line of constant wet-bulb temperature, which nearly coincides with a line of constant enthalpy. The maximum reduction in dry-bulb temperature is the difference between the entering air dry- and wet-bulb temperatures. If air is cooled to the wet-bulb temperature, it becomes saturated and the process would be 100% effective. Effectiveness is the depression of the dry-bulb temperature of the air leaving the apparatus divided by the difference between the dry- and wet-bulb temperatures of the entering air. Theoretically, adiabatic direct evaporative cooling is less than 100% effective, although evaporative coolers are 85 to 95% (or more) effective. When a direct evaporative cooling unit alone cannot provide desired conditions, several alternatives can satisfy application requirements and still be energy-effective and economical to operate. The recirculating water supplying the direct evaporative cooling unit can be increased in volume and chilled by mechanical refrigeration to provide lower leaving wet- and dry-bulb temperatures and lower humidity. Compared to the cost of using mechanical refrigeration only, this arrangement reduces operating costs by as much as 25 to 40%. Indirect evaporative cooling applied as a first stage, upstream from a second, direct evaporative stage, reduces both the entering dry- and wet-bulb temperatures before the air enters the direct evaporative cooler. Indirect evaporative cooling may save as much as 60 to 75% or more of the total cost of operating mechanical refrigeration to produce the same cooling effect. Systems may combine indirect evaporative cooling, direct evaporative cooling, heaters, and mechanical refrigeration, in any combination. The psychrometric chart in Figure 1 illustrates what happens when air is passed through a direct evaporative cooler. In the example shown, assume an entering condition of 35°C db and 24°C wb. The initial differenceis 35 24 = 11 K. Ifthe effectivenessis SO%, the depression is 0.80 x 11 = 8.8 K db. The dry-bulb temperature leaving the direct evaporative cooler is 35 8.8 = 26.2"C. In the adiabatic evaporative cooler, only part of the water recirculated is assumed to evaporate and the water supply is recirculated. The recirculated water reaches an equilibrium temperature approximately the same as the wet-bulb temperature of the entering air. The performance of an indirect evaporative cooler can also be shown on a psychrometric chart (Figure 1). Many manufacturers define effectiveness similarly for both direct and indirect evaporative cooling equipment. In indirect evaporative cooling, the cooling process in the primary airstream follows a line of constant moisture content (constant dew point). Indirect evaporative cooling effectiveness is the dry-bulb depression in the primary airstream divided by the difference between the entering dry-bulb temperature of the primary airstream and the entering wet-bulb temperature of the secondary air. Depending on heat exchanger design and relative

VAPORATIVE cooling is energy-efficient, environmentally friendly, and cost-effective in many applications and all climates. Applications range from comfort cooling in residential, agricultural, commercial, and institutional buildings, to industrial applications for spot cooling in mills, foundries, power plants, and other hot environments. Several types of apparatus cool by evaporating water directly in the airstream, including (1) direct evaporative coolers, (2) spray-filled and wetted-surface air washers, (3) sprayedcoil units, and (4) humidifiers. Indirect evaporative cooling equipment combines the evaporative cooling effect in a secondary airstream with a heat exchanger to produce cooling without adding moisture to the primary airstream. Direct evaporative cooling reduces the dry-bulb temperature and increases the relative humidity of the air. It is most commonly applied to dry climates or to applications requiring high air exchange rates. Innovative schemes combining evaporative cooling with other equipment have resulted in energy-efficient designs. When temperature a n d o r humidity must be controlled within narrow limits, heat and mechanical refrigeration can be combined with evaporative cooling in stages. Evaporative cooling equipment, including unitary equipment and air washers, is covered in Chapter 40 of the 2008 ASHRAE Handbook-HVAC Systems and Equipment.

GENERAL APPLICATIONS Cooling Evaporative cooling is used in almost all climates. The wet-bulb temperature of the entering airstream limits direct evaporative cooling. The wet-bulb temperature of the secondary airstream limits indirect evaporative cooling. Design wet-bulb temperatures are rarely higher than 25"C, making direct evaporative cooling economical for spot cooling, kitchens, laundries, agricultural, and industrial applications. At lower wet-bulb temperatures, evaporative cooling can be effectively used for comfort cooling, although some climates may require mechanical refrigeration for part of the year. Indirect applications lower the air wet-bulb temperature and can produce leaving dry-bulb temperatures that approach the wet-bulb temperature of the secondary airstream. Using room exhaust as secondary air or incorporating precooled air in the secondary airstream lowers the wet-bulb temperature of the secondary air and further enhances the cooling capability of the indirect evaporative cooler. Direct evaporative cooling is an adiabatic exchange of heat. Heat must be added to evaporate water. The air into which water is evaporated supplies the heat. The dry-bulb temperature is lowered, and sensible cooling results. The amount of heat removed from the air equals the amount of heat absorbed by the water evaporated as heat of The preparation of this chapter is assigned to TC 5.7, Evaporative Cooling.

52.1

~

~

52.10 52.13 52.15 52.15 52.16 52.17 52.18

52.2

201 1 ASHRAE Handbook-HVAC

Fig. 1 Psychrometrics of Evaporative Cooling

Applications (SI)

temperature. Typical saturation or humidifying effectiveness of various air washer spray arrangements is between 50 and 98%. The degree of saturation depends on the extent of contact between air and water. Other conditions being equal, low-velocity airflow is conducive to higher humidifying effectiveness. Preheated Air. Preheating air increases both the dry- and wetbulb temperatures and lowers the relative humidity; it does not, however, alter the humidity ratio (i.e., mass ratio of water vapor to dry air) or dew-point temperature of the air. At a higher wet-bulb temperature, but with the same humidity ratio, more water can be absorbed per unit mass of dry air in passing through the direct evaporative humidifier. Analysis of the process that occurs in the direct evaporative humidifier is the same as that for recirculated water. The desired conditions are achieved by heating to the desired wet-bulb temperature and evaporatively cooling at constant wet-bulb temperature to the desired dry-bulb temperature and relative humidity. Relative humidity of the leaving air may be controlled by (1) bypassing air around the direct evaporative humidifier or (2) reducing the number of operating spray nozzles or the area of media wetted. Heated Recirculated Water. Heating humidifier water increases direct evaporative humidifier effectiveness. When heat is added to the recirculated water, mixing in the direct evaporative humidifier may still be modeled adiabatically. The state point of the mixture should move toward the specific enthalpy of the heated water. By raising the water temperature, the air temperature (both dry- and wet-bulb) may be raised above the dry-bulb temperature of entering air. The relative humidity of leaving air may be controlled by methods similar to those used with preheated air.

zyxwvuts

quantities of primary and secondary air, effectiveness ratings may be as high as 85%. Assuming 60% effectiveness, and assuming both primary and secondary air enter the apparatus at the outside condition of 35°C db and 24°C wb, the dry-bulb depression is 0.60(35 - 24) = 6.6 K. The dry-bulb temperature leaving the indirect evaporative cooling process is 35 - 6.6 = 28.4"C. Because the process cools without adding moisture, the wet-bulb temperature is also reduced. Plotting on the psychrometric chart shows that the fmal wet-bulb temperature is 22.1"C. Because both wet- and dry-bulb temperatures in the indirect evaporative cooling process are reduced, indirect evaporative cooling can substitute for part of the refrigeration load in many applications.

Humidification Air can be humidified with a direct evaporative cooler by three methods: (1) using recirculated water without prior treatment of the air, (2) preheating the air and treating it with recirculated water, or (3) heating recirculated water. Air leaving an evaporative cooler used as either a humidifier or a dehumidifier is substantially saturated when in operation. Usually, the spread between leaving dry- and wet-bulb temperatures is less than 1 K. The temperature difference between leaving air and leaving water depends on the difference between entering dry- and wet-bulb temperatures and on certain physical features, such as the length and height of a spray chamber, cross-sectional area and depth of the wetted media used, quantity and velocity of air, quantity of water, and spray pattern. In any direct evaporative humidifier installation, air should not enter with a dry-bulb temperature of less than 4°C; otherwise, the water may freeze. Recirculated Water. Except for the small amount of energy added by shaft work from the recirculating pump and the small amount of heat leakage into the apparatus through the unit enclosure, evaporative humidification is strictly adiabatic. As the recirculated liquid evaporates, its temperature approaches the thermodynamic wet-bulb temperature of the entering air. The airstream cannot be brought to complete saturation, but its state point changes adiabatically along a line of constant wet-bulb

Dehumidification and Cooling

Direct evaporative coolers may also be used to cool and dehumidify air. If the entering water temperature is cooled below the entering wet-bulb temperature, both the dry- and wet-bulb temperatures of the leaving air are lowered. Dehumidification results if the leaving water temperature is maintained below the entering air dew point. Moreover, the final water temperature is determined by the sensible and latent heat absorbed from the air and the amount of circulated water, and it is 0.5 to 1 K below the final required dew-point temperature. The air leaving a direct evaporative cooler being used as a dehumidifier is substantially saturated. Usually, the spread between dry- and wet-bulb temperatures is less than 0.5 K. The temperature difference between leaving air and leaving water depends on the difference between entering dry- and wet-bulb temperatures and on certain design features, such as the cross-sectional area and depth of the media or spray chamber, quantity and velocity of air, quantity of water, and the water distribution.

Air Cleaning Direct evaporative coolers of all types perform some air cleaning. See the section on Air Cleaning later in this chapter for detailed information.

INDIRECT EVAPORATIVE COOLING SYSTEMS FOR COMFORT COOLING Five types of indirect evaporative cooling systems are most commonly used for commercial, institutional, and industrial cooling applications. Figures 2 to 6 show schematics of these dry evaporative cooling systems. Indirect evaporative cooling efficiency is measured by the approach of the outdoor air dry-bulb condition to either the room return air or scavenger outdoor air wet-bulb condition on the wet side ofthe air-to-air heat exchanger. The indirect evaporative cooling percent effectiveness (IEE) is expressed as follows:

Evaporative Cooling

IEE

zyxwvutsr zy zyxwvutsrq 52.3

t1-t2 x

100

tl - t 3

where tl = supply air inlet dry-bulb temperature, "C t2 = supply air outlet dry-bulb temperature, "C t3 = wet-side air inlet wet-bulb temperature, "C

The heat pipe air-to-air heat exchanger in Figure 2 uses a direct water spray from a recirculation sump on the wet side of the heat pipe tubes (Scofield and Taylor 1986). When either room return or scavenger outdoor air passes over the wet surface, outdoor air entering the building is dry-cooled and produces an approach to the wetside wet-bulb temperature in the range of 60 to 80% IEE for equal mass flow rates on both sides of the heat exchanger. The IEE is a function of heat exchanger surface area, face velocity, and completeness of wetting achieved for the wet-side heat exchanger surface. Face velocities on the wet side are usually selected in the range of 2 to 2.3 d s . Figure 3 shows a cross-flow plate type air-to-air indirect evaporative cooling heat exchanger (Yellott and Gamero 1984). In this configuration, outdoor air is supplied for both wet- and dry-side flows through the heat exchanger. Recirculation water from the sump below the heat exchanger is sprayed downward through the vertical wet-side air path, counterflow to the air which moves vertically up through the heat exchanger. The horizontal airflow path is dry-cooled with a 60 to 80% IEE for equal mass flows on both sides of the heat exchanger. Again, the approach to the ambient wet bulb

is a function of heat exchanger surface area and the effectiveness of the water spray system at completely wetting the wet-side surface of the air-to-air heat exchanger. The heat wheel (Figure 4) and the run-around coil (Figure 5) both use a direct evaporative cooling component on the cold side to enhance the dry-cooling effect on the makeup air side. The heat wheel (sensible transfer), when sized for 2.5 d s face velocity with equal mass flows on both sides, has an IEE around 60 to 70%. The run-around coil system at the same conditions produces an IEE of 35 to 50%. The adiabatic cooling component is usually selected for an effectiveness of 85 to 95%. Water coil freeze protection is required in cold climates for the run-around coil loop. Air-to-air heat exchangers that are directly wetted produce a closer approach to the cold-side wet-bulb temperature, all things being equal. First cost, physical size, and parasitic losses are also reduced by direct wetting of the heat exchanger. In applications having extremely hard makeup water conditions, using a direct evaporative cooling device in lieu of directly wetting the air-to-air heat exchanger may reduce maintenance costs and extend the useful life of the system. All ofthe air-to-air heat exchangers (Figures 2 to 5) produce beneficial winter heat recovery when using building return air with the sprays or adiabatic cooling component turned off.

Fig. 4

Fig. 2

Rotary Heat Exchanger with Direct Evaporative Cooling

Heat Pipe Air-to-Air Heat Exchanger with Sump Base

Fig. 3 Cross-Flow Plate Air-to-Air Indirect Evaporative Cooling Heat Exchanger with Direct Evaporative Cooling Second Stage

Fig. 5

Coil Energy Recovery Loop with Direct Evaporative Cooling

201 1 ASHRAE Handbook-HVAC

52.4

Fig. 6

Applications (SI)

Cooling-Tower-to-Coil Indirect Evaporative Cooling

zyxwvuts zyxw zyxwvutsrqponm Table 1 Indirect Evaporative Cooling Systems Comparison

System Typea

IEE,b Yo

Coolingtower 40 to 60 to coil

Heat Recovery Wet-Side Efficiency, Air AP, Pa Yo

Dry-Side Pump Parasitic Loss Equipment Air AP, power, W Range,eWl3517 Cost Range: Pa per 4720 Lls W of Cooling US $ per Lls Notes

NA

NA

99.5 to 174.1

Vanes

Vanes

1.06 to 2.12

Crossflow plate

60 to 85

40 to 50

174.2 to 248.8

99.5 to 174.1

74.6 to 149.2

120 to 200

2.54 to 3.60

Heat pipeC

65 to 75

50 to 60

174.2 to 248.8

124.4 to 174.1

149.2 to 298.4

150 to 259

3.18 to 5.30

Heat wheeld

60 to 70

70 to 80

149.3 to 223.9

99.5 to 161.7

74.6 to 149.2

200 to 300

3.18 to 5.30

Runaround coild

35 to 50

40 to 60

149.3 to 199.0

99.5 to 161.7

Vanes

> 350

Best for serving multiple AHUs from a single cooling tower. No winter heat recovery. Most cost-effective for lower airflows. Some cross contamination possible. Low winter heat recovery. Most cost-effective for large airflows. Some cross contamination possible. Medium winter heat recovery. Best for high airflows. Some cross contamination. Highest winter heat recovery rates. Best for applications where supply and return air ducts are separated. Lowest summer WBDE.

zyxwvutsrqponm zyxw

IEE = indirect evavorative effectiveness Notes: aAll air-to-air heat exchangers have equal mass flow on supply and exhaust sides. bPlate and heat pipe are direct spray on exhaust side. Heat wheel and runaround coil systems use 90% WBDE direct evaporative cooling media on exhaust air side.

Figure 6 shows a cooling-tower-to-coil indirect evaporative cooling system with IEE in the range of 50 to 75% (Colvin 1995). This system is sometimes referred as a water-side economizer. The cooling tower is selected for a close approach to the ambient wet-bulb temperature, with sump water from the tower then pumped to precooling coils in an air-handling unit. Provision for water filtration to remove solids from sump water is needed, and water coils may need to be cleanable. Freeze protection of the water coil loop is required in cold climates. No winter heat recovery is available with this design. Table 1 gives the designer some performance predictions and application limits that may be helpful in determining the indirect evaporative cooling system that best solves the design problem at hand. If winter heat recovery is a priority, the heat wheel system may provide the quickest payback. Runaround coil systems are applied where supply air and exhaust air ducts are remote from each other. The heat pipe adapts well to high-volume air-handling systems where cooling energy reduction is the priority. The plate heat

2.12 to 4.24

CAssumessix-row heat pipe, 2.3 mm fin spacing, with 2.54 n d s face velocity on both sides. dAssumes 2.54 n d s face velocity. Parasitic loss includes wheel rotational power. ‘3ncludes air-side static pressure and pumping penalty. Qxcludes cooling tower cost and assumes less than 60 m piping between components.

exchanger fits smaller-volume systems with high cooling requirements but with lower winter heat recovery potential.

Indirect Evaporative Cooling Controls Where the heat exchanger is directly wetted, a water hardness monitor for the recirculation water sump is recommended. Water hardness should be kept within 200 to 500 parts per million (ppm) to minimize plating out of dissolved solids from the sump. To maintain its set point, the hardness monitor may initiate a sump dump cycle when it detects increased water hardness. In addition, the sump should have provisions for a fixed bleed so that extra makeup water is continuously introduced to dilute dissolved solids left behind when water evaporates from the wetted heat exchanger surface. Sumps should always be drained at the end of a duty cycle and refilled the next day when the system is turned on. For rooftop applications, sumps should be drained for freeze protection during low ambient temperatures.

Evaporative Cooling

zyxwvutsz

Air-side control for a cooling system with a 13°C supply air set point may be set up as follows. The heat exchanger's cold-side sprays or direct evaporative cooling component should be activated whenever ambient dry-bulb temperatures exceed 18"C, if room return air is used on the wet side ofthe air-to-air heat exchanger. Airconditioned buildings have a stable return air wet-bulb condition in therangeof 15.5 to 18°C. Valuableprecoolingofoutdoorairmaybe achieved when ambient dry-bulb temperatures exceed the return air wet-bulb condition. Where outdoor air is used on the cold-air side of the heat exchanger, cooling may begin at ambient temperatures above 13"C, because the wet-bulb condition of outdoor air is always lower than its dry-bulb condition. Parasitic losses generated by the heat exchanger static pressure penalty to supply and return air fans and by the water pump need to be evaluated. These losses may be mitigated by opening bypass dampers around the heat exchanger for pressure relief and shutting off the pump in the ambient temperature range of 13 to 18°C db. Where scavenger outdoor air is used on the cold side of an air-to-air heat exchanger, this temperature range may be reduced somewhat. A comparison of the energy penalty to the precooling energy avoided determines the optimum range of ambient conditions for this control strategy. For variable-air-volume (VAV) supply and return fan systems, the static penalty reduces by the square of the airflow reduction from full design flow at summer peak design condition. As airflow rates decrease across an air-to-air heat exchanger, the IEE increases, thereby providing better precooling. Where scavenger outdoor air is used for indirect evaporative cooling, the wet-side airflow rate is usually constant volume. Winter heat recovery may be initiated at ambient temperatures below the 13°C supply air set point. Where building return air is used with an air-to-air heat exchanger, the 2 1 to 24°C return air condition is used to preheat makeup air for the building. For a VAV supply air system, Figure 7 shows the increased ventilation potential of a heat pipe air-to-air heat exchanger that uses face and bypass dampers on the supply air side to mix unheated outdoor air with preheated outdoor air to maintain the 13°C building supply air set point (Scofield and Bergman 1997). The heat pipe leaving air temperature may also be controlled with a tilt control (see Chapter 25 of the 2008 ASHRAE Handbook-HVACSystems andEquipment). With a heat pipe economizer, a minimum outdoor air ventilation rate of 20% would not be breached until ambient temperatures dropped below -26°C.

52.5

Runaround coils control leaving supply air temperature with a three-way valve (see Figure 5). Because of their higher parasitic losses, these systems may require a wider range of ambient conditions where pressure-relief bypass dampers are open and the pump system shut down. Some projects limit activation of these recovery systems to ambient temperatures above 29°C to below 4°C.

Indirect/Direct Evaporative Cooling with VAV Delivery Coupling indirect and direct evaporative cooling to a variable-airvolume (VAV) delivery system in arid climates can effectively eliminate requirements for mechanical refrigeration cooling in many applications. Many cities in the western United States have summer design conditions suitable to deliver 13°C or lower supply air to a building using a 70% IEE indirect and a 90% effective direct evaporative cooling system. Figure 8 shows plan and elevation views of an air-handling unit using a sprayed heat pipe air-to-air heat exchanger and a wettedmedia direct evaporative cooling section augmented by a final-stage chilled-water cooling coil (Scofield and Bergman 1997). The 70% indirect IEE is achieved with a direct-sprayed heat pipe using a sump and a recirculation water system on the building return air side of the heat exchanger. The 90% effective direct evaporative cooling medium is split into two sections for two-stage cooling capacity control of the 13°C leaving air temperature. The direct evaporative cooling system also uses a sump and water recirculation. Supplyside heat pipe face and bypass dampers control the final supply air temperature (13°C) in both summer (when indirect sprays are on) and winter, to control the heat pipe's heat recovery capacity. Heat pipe dampers on both sides of the heat exchanger are powered to full open to mitigate system parasitic losses during ambient temperature conditions when the value of energy recovered is exceeded by the fan energy penalty. The recirculation damper is used for morning w m - u p of the building and for blending building return air with preheated outdoor air during extreme cold ambient conditions (see Figure 7). Table 2 uses ASHRAE bin weather data for the semi-arid climate of Sacramento, California, to illustrate potential cooling energy savings for a 4.7 m3is VAV design that turns down to 2.4 m3isat winter design (Scofield and Bergman 1997). Compared to a conventionalrefrigeration cooling VAV design with a 25% minimum outdoor air economizer, the two-stage evaporative cooling system reduces peak cooling load by 49% while introducing 100% outdoor air. For a buildingduty cycleof8760 hperyear, thekWhsavingsis$l19 712, or a 60% reduction compared to the conventional air-side economizer system with mechanical cooling only. Within ambient bin conditions of 17°C dbil2"C wb to 14°C dbil1"C wb, there are 2376 cooling hours per year (27% of the annual cooling hours) where a 90% wet-bulb depression efficiency (WBDE) direct evaporative cooling system may be used for the 13°C supply air requirement without refrigeration. Figure 9 uses typical meteorological year (TMY) data for 14 cities in the western United States to illustrate the evaporative cooling m u a l refrigeration avoidance per 4.7 mis of VAV supply air, compared to a 25% minimum outdoor air economizer (Scofield and Bergman 1997). For thermal energy storage (TES) applications, the two-stage evaporative cooling design may significantly reduce chiller plant storage capacity and refrigeration equipment first cost. Benefits of this design in dry climates include the following:

zyxwvutsrqpon

zyxw

Fig. 7

Increased Winter Ventilation

Indoor air quality is improved by using all outdoor air during cooling, and increased ventilation in winter through the heat pipe economizer (see Figure 7). Energy demand is in the range of 0.04 to 0.07 kW per kilowatt of cooling, versus air-cooled refrigeration at 0.3 to 0.4 kW per kilowatt. Peak building electrical cooling and gas heating demand requirements are reduced, especially for applications that require higher amounts of outdoor air.

201 1 ASHRAE Handbook-HVAC

52.6

Applications (SI)

zyxwvutsrq zy Fig. 8 Heat Pipe Air-Handling Unit

Because VAV pinchdown terminals may reduce their minimum airflow settings and comply with ASHRAE Standard 62.1, supply and return fan energy savings are possible in cooler weather when using an all-outdoor-air design. VAV turndown of fans during cooler ambient conditions decreases fan parasitic energy losses because of the evaporative cooling system components. VAV turndown increases the IEE of both the air-to-air heat exchanger and direct evaporative cooling system. In semi-arid climates where a chilled-water final cooling stage is required, two-stage evaporative cooling allows central chilledwater plants to be turned off earlier in the fall and reactivated later in the spring. This results in significant maintenance and cooling energy cost savings. In cooler weather, resetting supply air down to 10°C and using only the direct evaporative cooler extends free cooling hours and reduces fan energy. When using building return air, winter heat recovery provides increased outdoor air quantities during the period when fan

turndown can result in loss of proper ventilation rates for VAV systems (see Figure 7). During mild winter daytime ambient conditions, the 100 nnn deep wetted media section may be used for beneficial building humidification (see Table 3).

Beneficial Humidification Areas with mild winter climates (e.g., the western U.S. coast) may use the heat available in building return air, through the airto-air heat exchanger, to overheat supply air and add building humidification during the driest season of the year. The 100 nnn section of direct evaporative cooling media (see Figure 8) is used in cool ambient conditions as a humidifier. Table 3 (Scofield and Bergman 1997) extends the Table 2 bin weather data for the Sacramento, California, site into winter ambient conditions. The table shows that 100% outdoor air may be introduced and humidity controlled between 54 and 32% for ambient conditions down to 2 3 ° C with a 60% heat pipe recovery effectiveness. ASHRAE Standard 62.1 recommends that humidities in occupied areas be maintained between

52.7

Evaporative Cooling Table 2

zy zyxwvu

Sacramento, California, Cooling Load Comparison

100% Outdoor Air Indirect-Direct Evaporative Cooling Outdoor Air VAV Supply, Hours Per Indirect LAT dblwb, OC Lls Yea@ dblwb, OC

25% Outdoor Air Economizer

Direct LAT Refrigeration,aRefrigeration,bMixed Air dbl Refrigeration,aRefrigeration,b dblwb, OC kW kWh wb, OC kW kWh

41.6/2 1.1 3 8.9/2 1.1 36.1/20.0 33.3M8.9 30.5/18.34 27.8M7.2 25/16.1 22.2/15.0 19.4/13.88

4720 4602 4425 4277 4130 3983 3835 3687 3540

7 59 144 242 30 1 397 497 64 1 82 1

25/15.5 24/16.2 23.3/15.6 22.3/15.0 2 1.6m5.2 20.6/14.8 20M4.2 18.U13.9 18.3/13.3

16.5/15.5 17.0M6.2 16.4/15.6 15.7/15.0 15.W15.2 15.4/14.8 14.W14.2 14.4/13.9 13.W13.3

49.9 61.2 49.2 40.4 36.9 33.4 23.6 18.6 13.7

16.7/12.2 13.8/11.1

3393 3245

1086 1290

16.7/12.2 13.8111.1

12.6/12.2 11.4/11.1

0 0

349 3 611 7 085 9 777 11 107 13 260 11 729 11 923 11 248 0 0

28.3M8.8 27.7/18.8 27.2/18.3 26.1M8.4 25.5/18.4 24.9/17.7 25.2/17.4 22.2/l5.Ob 19.4/13.Bb

102.7 99.5 91.1 83.4 78.4 71.4 64.4 45.4 31.6

719 5 871 13 118 20 183 23 598 28 346 32 007 29 101 25 944

16.7/12.2b 13.8111.1

15.1 3.5

16 399c 4 515c

Total kWh = 80 089 LAT = leaving-air temperature Notes: aAmount of cooling required to reach 12.8"C db supply air requirements. bAmbient conditions when dampers for air-side economizer introduce 100% outdoor air in arid climates.

Table 3 Outdoor Air VAV Supply,a dblwb, OC LIS

11.1/9.4 8.4/6.7 5.1/4.4 3.9/2.2 O/-0.6 -2.8/-3.3

3097 2950 2803 2655 2507 2360

Total kWh = 199 801

CAmbientconditions when 90% saturation efficiency direct evaporative cooler may be used to eliminate refrigeration cooling. Heat pipe bypass dampers should be open to minimize parasitic losses. Indirect water sprays should be off. dBin hours at each condition based on 24 hlday, 365 daylyear duty cycle.

Sacramento, California, Heat Recovery and Humidification

Hours Per Yearb

Heat Recovery Leaving Air dblwb, OC

1199 924 660 333 116 30

17.2/11.6 16.1/10.5 15/8.9 13.9/7.8 12.W6.1 11.6/5.0

Source: Scofield and Bergman (1997). V A V turndown airflow is assumed linear from summer design (4720 Lls) to winter design (2360 Lls). bBin hours at each condition based on 24 hlday, 365 dayslyear duty cycle. CHeatpipe overheats outdoor air to allow direct evaporative humidifier to add moisture.

Direct Evaporative Humidifier Energy Savings? Leaving Air db/wb,C OC W

12.W11.6 12.8/10.0 12.W8.9 12.W7.7 OFF OFF

21 637 26 379 28 978 35 256 38 338 73 502

Resultant Room rh

54% 47% 3 8% 32% 25%e 21%e

dRecirculated building heat used for preheating 100% outdoor air and increasing humidity levels. eAdditional heat is required or recirculation damper must open during these bin conditions, to maintain both acceptable 30% indoor relative humidity and reach the 12.79"C supply air set point.

30 and 60% rh. There are only 146 bin hours below the 2 3 ° C ambient threshold during which the building recirculation air damper (see Figure 8) would have to open or additional heat be added with the hot-water coil to maintain the 12.8"C air delivery set point. The average winter temperature in Sacramento is 11.5"C, which is fairly typical for this region.

Indirect Evaporative Cooling With Heat Recovery

Fig. 9

Refrigeration Reduction with Two-Stage Evaporative Cooling Design

In indirect evaporative cooling, outside supply air passes through an air-to-air heat exchanger and is cooled by evaporatively cooled air exhausted from the building or application. The two airstreams never mix or come into contact, so no moisture is added to the supply airstream. Cooling the building's exhaust air results in a larger overall temperature difference across the heat exchanger and a greater cooling of the supply air. Indirect evaporative cooling requires only fan and water pumping power, so the coefficient of performance tends to be high. The principle of indirect evaporative cooling is effective in most air-conditioned buildings, because evaporative cooling is applied to exhaust air rather than to outside air. Indirect evaporative cooling has been applied in a number of heat recovery applications (Mathur et al. 1993), such as plate heat exchangers (Scofield and DesChamps 1984; Wu and Yellot 1987), heat pipe exchangers (Mathur 1998; Scofield 1986), rotary regenerative heat exchangers, and two-phase thermosiphon loop heat exchangers (Mathur 1990). In residential air conditioning, the outside condensing unit can be evaporatively cooled to performance (Mathur 1997; Mathur and Goswami 1995; Mathur et al.

201 1 ASHRAE Handbook-HVAC

52.8

Applications (SI)

zyxwvutsr zyxwvut zyxwvutsrqp zyxwvuts zyx Indirect/Direct Performance (Supply Air = 1.55 kJ/m3)

City

Outdoor Air Design Indirect db/wb, db/wb, OC OC

Two-Stage Supply Sensible Air db, Capacity, OC W

TwoStage Sensible EUC, EER Yo

Los Angeles, CA

29.4/17.8

22.4/15.3

16.6

2303

8.2

San Francisco, CA

28.3M7.2

21.7/14.8

16.1

2421

8.6

30.5

29.0

Seattle, WA

29.4/18.3

22.U16.1

17.3

2142

7.7

32.6

Albuquerque, NM

35.6/15.6

23.6/11.4

13.2

3080

11.3

22.3

Denver, CO

33.9/15.6

22.9/11.8

13.4

Salt Lake City, UT

35.5/16.7

24.2/12.8

14.5

Phoenix, AZ

43.3/21.1

30.0/16.9

18.8

3018 2774 1796

1.3 10.1 6,6

22.3 24.7 38,0

El Paso, TX Santa Rosa. CA

38.3M7.8 29.4/19.4

26.0/13.7 23.4/17.5

15.5 18.6

2549 1834

9.4 6.6

36.8 37.7

Spokane, WA

33.3M6.7

23.3/13.2

14.7

2728

9.8

25.5

Boise. ID

35.6/17.2

24.6/13.4

15.1

Billings, MT

33.9/17.2

23.9/13.9

15.4

2638 2565

9.6 9,3

26.7 26,8

Portland, OR Sacramento, CA

32.2/19.4 37.W20.6

24.6/16.9 27.4/17.2

18.2 18.8

1930 1799

6.9 6.5

36.0 38.5

Fresno, CA

39.4/21.7

28.8/18.4

19.9

Austin, TX

36.7/23.3

28.7/21.1

22.4

1528 977

5'6 3.7

44'5 66.6

Notes: IUD effectiveness: Indirect = 60% or 0.6 (dry bulb wet bulb); Direct = 90% or 0.9 (dry bulb wet bulb). Outdoor air design condition: 0.4% drybulb/mean coincident wet bulb (2009 ASHRAE Hundbook-Fundumentul, Chapter 14). Fan heat is added to two-stage supply air dry bulb (0.5 K) Assume 0.6 W per L/s for the direct and 0.4 W per L/s* for the inmrect section (200 W total). AC is 1000 W in all cases. Sensible capacity = 1.08 x L/s* x At. For AC, this is 2530 W in all cases. based on 11 K At. EER = energy efficiency ratio = watts cooling output per watt of electrical input. Comparison base to conventional refrigeration with 15.5"C suuulv air and 11 K temuerature drou. Sensible EER= Sensible cooling capacity t wattage. EUC = Energy Use Comparison to conventional refrigeration with EER = 8.6 (watt cooling per watt input). Psvchrometric routines are calculated using site atmosuheric uressure. ~

~

I I

zyxwvut

2

*At 20'Cand 101.325 H a

Fig. 10 Indirect/Direct Two-Stage System Performance

Fig. 11 Two-Stage Evaporative Cooling with Third-Stage Integral DX Cooling Design 1993). Indirect evaporative cooling with heat recovery is covered in detail in Chapter 25 of the 2008 ASHRAE Handbook-HVAC Systems and Equipment.

BOOSTER REFRIGERATION Staged evaporative coolers can completely cool office buildings, schools, gymnasiums, sports facilities, department stores, restaurants, factory space, and other buildings. These coolers can control room dry-bulb temperature and relative humidity, even though one stage is a direct evaporative cooling stage. In many cases, booster refrigeration is not required. Supple (1982) showed that even in higher-humidity areas with a 1% mean wet-bulb design temperature of 24"C, 42% of the annual cooling load can be satisfied by

two-stage evaporative cooling. Refrigerated cooling need supply only 58% of the load. Figure 10 shows indirectidirect two-stage performance for 16 cities in the United States. Performance is based on 60% effectiveness of the indirect stage and 90% for the direct stage. Supply air temperatures (leaving the direct stage) at the 0.4% design dry-bulb mean coincident wet-bulb condition range from 13.4 to 22.4"C. Energy use ranges from 16.4 to 51.8%, compared to conventional refrigerated equipment. Booster mechanical refrigeration provides inside design comfort conditions regardless of the outside wet-bulb temperature without having to size the mechanical refrigeration equipment for the total cooling load. If the inside humidity level becomes uncomfortable, the quantity of moisture introduced into the airstream must be limited to control room humidity. Where the upper relative humidity design level is critical, a life-cycle cost analysis favors a design with an indirect cooling stage and a mechanical refrigeration stage. Figure 11 shows an air-handling unit design that uses building return air instead of outdoor air to develop the indirect (dry) evaporative cooling effect with a direct-sprayed, heat pipe, air-to-air, heat exchanger (Felver et al. 2001). The humid, cool air off the heat pipe is then used to reject the heat of refrigeration at a condenser coil downstream of the exhaust fan. The direct expansion (DX) cooling coil, the last component in the supply air, develops the final building supply air temperature when the two-stage evaporative cooling components cannot meet the design cooling requirements. Figure 12 shows the process points for both supply and exhaust airstreams, using the Stockton, California, ASHRAE 0.4% summer dry-bulb design ambient condition. Several benefits accrue from this evaporative cooling design: Building return air has a more predictable and stable wet-bulb condition (15.5 to 18°C) than ambient air for use in generating the first stage of indirect (dry) evaporative cooling. Daytime absorption of moisture inside most buildings further enhances the firststage cooling effect.

z zyxwvu Next Page

Evaporative Cooling Locating a DX condenser coil in sprayed exhaust offthe heat pipe results in a more efficient rejection of refrigeration heat than a condenser coil located outdoors in the ambient air. Lower refrigeration condensing temperatures increase compressor capacity and compressor life, and reduce energy consumption. Central chilled-water plant or remote chiller installation and piping costs are eliminated. Evaporative cooling components provide back-up cooling capability in case of compressor failure. Figure 12 shows equilibrium conditions in the occupied area with indirectldirect evaporative cooling only. Peak refrigeration demand can be reduced 14 to 40% in California's semi-arid climate (Scofield 1994). Blow-through supply fan and draw-through exhaust fans provide: Reduced supply fan heat addition for DX cooling system. Reduced risk of cross contamination of supply air with exhaust air for hospital or laboratory applications. Reduced fan noise breakout into building duct system.

-

There are several desim considerations for the successful integration of DX refrigeration with two-stage evaporative cooling airhandling units, as shown in Figure 11. For both constant-volume (CV) and variable-air-volume (VAV) units, the return air must closely match the supply airflow to ensure adequate heat rejection at the condenser coil. Buildings with large fixed-exhaust systems may not provide sufficient building return airflow for absorption of refrigeration heat at acceptable refrigerant condensing temperatures. Face-and-bypass dampers are required around the condenser coil for control of the refrigerant condensing pressure and temperature. Note that peak refrigeration requirements always occur during the highest ambient humidity (dew-point design) conditions. In

52.9

semi-arid climates, this design condition occurs during reduced summer ambient dry-bulb temperatures (Ecodyne Corp. 1980). Review of site ASHRAE dew-point design conditions (Chapter 14 of the 2009 ASHRAE Handbook-Fundamentals) is required to determine the peak refrigeration cooling capacity needed to maintain the specified supply air temperature set point to the building.

RESIDENTIAL OR COMMERCIAL COOLING In dry climates, evaporative cooling is effective at lower air velocities than those required in humid climates. Packaged direct evaporative coolers are used for residential and commercial application. Cooler capacity may be determined from standard heat gain calculations (see Chapters 17 and 18 of the 2009 ASHRAE Handbook-Fundamentals). Detailed calculation of heat load, however, is usually not economically justified. Instead, one of several estimates gives satisfactory results. In one method, the difference between dry-bulb design temperature and coincident wet-bulb temperature multiplied by 10 is equal to the number of seconds needed for each air change. This or any other arbitrary method for equating cooling capacity with airflow depends on a direct evaporative cooler effectiveness of 70 to 80%. Obviously, the method must be modified for unusual conditions such as large unshaded glass areas, uninsulated roof exposure, or high internal heat gain. Also, such empirical methods make no attempt to predict air temperature at specific points; they merely establish an air quantity for use in sizing equipment. Example 1. An indirect evaporative cooler is to be installed in a 15 by 24.4 m one-story office building with a 3 m ceiling and a flat roof. Outside design conditions are assumed to be 35°C db and 18.3"C wb. The following heat gains are to be used in the design:

Fig. 12 Psychrometrics of 100% OA, Two-Stage Evaporative Cooling Design (9440 L/s Supply, 8496 L/s Return) Compared with 10% OA Conventional System Operating at Stockton, California, ASHRAE 0.4% db Design Condition

zyxw zy zyxwvut CHAPTER 53

FIRE AND SMOKE MANAGEMENT Fire Management ..................................................................... 53.1 Smoke Movement ..................................................................... 53.2 Smoke Management ................................................................. 53.4 Smoke Control System Design ................................................. 53.6 Fire and Smoke Dampers ......................................................... 53.8 Pressurized Stairwells .............................................................. 53.9 Elevators ................................................................................ 53.11

Zone Smoke Control ............................................................... Computer Analysis f o r Pressurization Systems ...................... Smoke Management in Large Spaces ..................................... Tenability Systems .................................................................. Acceptance Testing................................................................. Special Inspector .................................................................... Extraordinay Incidents .........................................................

53.1 1 53.12 53.13 53.18 53.18 53.19 53.19

I

N building fires, smoke often flows to locations remote from the fre, threatening life and damaging property. Stairwells and elevators frequently fill with smoke, thereby blocking or inhibiting evacuation. Smoke causes the most deaths in fires. Smoke includes airborne solid and liquid particles and gases produced when a material undergoes pyrolysis or combustion, together with air that is entrained or otherwise mixed into the mass. The idea of using pressurization to prevent smoke infiltration of stairwells began to attract attention in the late 1960s. This concept was followed by the idea of the pressure sandwich (i.e., venting or exhausting the fire floor and pressurizing the surrounding floors). Frequently, a building’s ventilation system is used for this purpose. Smoke control systems use fans to pressurize appropriate areas to limit smoke movement in fire situations. Smoke management systems include pressurization and all other methods that can be used singly or in combination to modify smoke movement. This chapter discusses f r e protection and smoke control systems in buildings as they relate to HVAC. For a more complete discussion, refer to Principles of Smoke Management (Klote and M i k e 2002). National Fire Protection Association (NFPA) Standard 204 provides information about venting large industrial and storage buildings. For further information, refer to NFPA Standards 92A and 92B. The objective of fire safety is to provide some degree of protection for a building’s occupants, the building and property inside it, and neighboring buildings. Various forms of analysis have been used to quantify protection. Specific life safety objectives differ with occupancy; for example, nursing home requirements are different from those for office buildings. Two basic approaches to f r e protection are (1) to prevent f r e ignition and (2) to manage f r e effects. Figure 1 shows a decision tree for f r e protection. Building occupants and managers have the primary role in preventing f r e ignition. The building design team may incorporate features into the building to assist the occupants and managers in this effort. Because it is impossible to prevent f r e ignition completely, managing f r e effect has become significant in f r e protection design. Examples include compartmentation, suppression, control of construction materials, exit systems, and smoke management. The Fire Protection Handbook (NFPA 2008) and Smoke Movement and Control in High-Rise Buildings (Tamura 1994) contain detailed fire safety information. Historically, f r e safety professionals have considered the HVAC system a potentially dangerous penetration of natural building membranes (walls, floors, etc.) that can readily transport smoke and f r e . For this reason, HVAC has traditionally been shut down when f r e is discovered; this prevents fans from forcing smoke flow, but does not prevent ducted smoke movement caused by buoyancy, stack effect, or wind. To solve the problem of smoke movement, The preparation of this chapter is assigned to TC 5.6, Control of Fire and Smoke.

Fig. 1 Simplified Fire Protection Decision Tree methods of smoke control have been developed; however, smoke control should be viewed as only one part of the overall building f r e protection system.

FIRE MANAGEMENT Although most of this chapter discusses smoke management, f r e management at HVAC penetrations is an additional concern for the HVAC engineer. The most efficient way to limit f r e damage is through compartmentation. Fire-rated assemblies, such as the floor or walls, keep the f r e in a given area for a specific period. However, f r e can easily pass through openings for plumbing, HVAC ductwork, communication cables, or other services. Therefore, f r e stop systems are installed to maintain the rating of the fre-rated assembly. The rating of a f r e stop system depends on the number, size, and type of penetrations, and the construction assembly in which it is installed. Performance of the entire f r e stop system, which includes the construction assembly with its penetrations, is tested under f r e conditions by recognized independent testing laboratories. ASTM Standard E814 and UL Standard 1479 describe ways to determine performance of through-penetration fire stopping (TPFS). TPFS is required by building codes under certain circumstances for specific construction types and occupancies. In the United States, model building codes require that most penetrations meet the ASTM E814 test standard. TPFS classifications are published by testing laboratories. Each classification is proprietary, and each applies to use with a specific set of conditions, so numerous types are usually required on any given project. The construction manager and general contractor, not the architects and engineers, make work assignments. Sometimes they assign f r e stopping to the discipline making the penetration; other times, they assign it to a specialty fre-stopping subcontractor. The Construction Specifications Institute (CSI) assigns fire-stopping specifications to Division 7, which

53.1

201 1 ASHRAE Handbook-HVAC Applications (SI)

53.2 Encourages continuity of fire-stopping products on the project by consolidating their requirements (e.g., TPFS, expansion joint f r e stopping, floor-to-wall joint fire stopping, etc.) Maintains flexibility of work assignments for the general contractor and construction manager Encourages prebid discussions between the contractor and subcontractors regarding appropriate work assignments

SMOKE MOVEMENT A smoke control system must be designed so that it is not overpowered by the driving forces that cause smoke movement, which include stack effect, buoyancy, expansion, wind, and the HVAC system. During a fire, smoke is generally moved by a combination of these forces.

Stack Effect When it is cold outside, air tends to move upward within building shafts (e.g., stairwells, elevator shafts, dumbwaiter shafts, mechanical shafts, mail chutes). This normal stack effect occurs because air in the building is warmer and less dense than outside air. Normal stack effect is large when outside temperatures are low, especially in tall buildings. However, normal stack effect can exist even in a onestory building. When outside air is warmer than building air, there is a natural tendency for downward airflow, or reverse stack effect, in shafts. At standard atmospheric pressure, the pressure difference caused by either normal or reverse stack effect is expressed as

zyxwvutsrqponm zyxwvutsrq zyxwvutsrqpo i: 11

Ap=3460 - - - h

where

movement in buildings caused by both normal and reverse stack effect. Figure 4 can be used to determine the pressure difference caused by stack effect. For normal stack effect, Apih is positive, and the pressure difference is positive above the neutral plane and negative below it. For reverse stack effect, Apih is negative, and the pressure difference is negative above the neutral plane and positive below it. In unusually tight buildings with exterior stairwells, Klote (1980) observed reverse stack effect even with low outside air temperatures. In this situation, the exterior stairwell temperature is considerably lower than the building temperature. The stairwell represents the cold column of air, and other shafts within the building represent the wann columns of air. If leakage paths are uniform with height, the neutral plane is near the midheight of the building. However, when the leakage paths are not uniform, the location of the neutral plane can vary considerably, as in the case of vented shafts. McGuire and Tamura (1975) provide methods for calculating the location of the neutral plane for some vented conditions. Smoke movement from a building fire can be dominated by stack effect. In a building with normal stack effect, the existing air currents (as shown in Figure 3) can move smoke considerable distances from the f r e origin. If the f r e is below the neutral plane, smoke moves with building air into and up the shafts. This upward smoke flow is enhanced by buoyancy forces due to the temperature of the smoke. Once above the neutral plane, smoke flows from the shafts into the upper floors of the building. If leakage between floors is

(1)

A p = pressure hfference, Pa To = absolute temperature of outside air, K T, = absolute temperature of air inside shaft, K h = distance above neutral plane, m

For a building 60 m tall with a neutral plane at midheight, an outside temperature of -18°C (255 K), and an inside temperature of 21 "C (294 K), the maximum pressure difference from stack effect is 54 Pa. This means that, at the top of the building, pressure inside a shaft is 54 Pa greater than the outside pressure. At the base of the building, pressure inside a shaft is 54 Pa lower than the outside pressure. Figure 2 diagrams the pressure difference between a building shaft and the outside. A positive pressure difference indicates that shaft pressure is higher than the outside pressure, and a negative pressure difference indicates the opposite. Figure 3 illustrates air

Fig. 2 Pressure Difference Between Building Shaft and Outdoors Caused by Normal Stack Effect

Fig. 3 Air Movement Caused by Normal and Reverse Stack Effect

Fig. 4

Pressure Difference Caused by Stack Effect

53.3

Fire and Smoke Management negligible, floors below the neutral plane (except the f r e floor) remain relatively smoke-free until more smoke is produced than can be handled by stack effect flows. Smoke from a f r e located above the neutral plane is carried by building airflow to the outside through exterior openings in the building. If leakage between floors is negligible, all floors other than the f r e floor remain relatively smoke-free until more smoke is produced than can be handled by stack effect flows. When leakage between floors is considerable, smoke flows to the floor above the fire floor. Air currents caused by reverse stack effect (see Figure 3) tend to move relatively cool smoke down. In the case of hot smoke, buoyancy forces can cause smoke to flow upward, even during reverse stack effect conditions.

methods. However, the example illustrates the extent to which Equation (2) can be applied. In sprinkler-controlled fres, the temperature in the f r e room remains at that of the surroundings except for a short time before sprinkler activation. Sprinklers are activated by the ceiling jet, a thin (50 to 100 mm) layer of hot gas under the ceiling. The maximum temperature of the ceiling jet depends on the location of the fire, the activation temperature of the sprlnkler, and the thermal lag of the sprinkler heat-responsive element. For most residential and commercial applications, the ceiling jet is between 80 and 150°C. In Equation (2), Tf is the average temperature of the f r e compartment. For a sprlnkler-controlled fire,

T s ( H - H j ) + 7;Hj Tf

Buoyancy

\

I:, k ,

Ap=3460 - - - h

H

(3)

where

H HI

= = =

floor-to-ceiling height, m thickness of ceiling jet, m absolute temperature of ceiling jet, K

zyxwvutsrq zyxwvutsrqp For example, for H = 2.5 m, Hj = 0.1 m, T, = 20 + 273 = 293 K, and = 150 + 273 = 423 K,

3

Tf= [293(2.5 - 0.1) + 423 x 0.1112.5 = 298 K or 25°C

where Ap

=

zyxw zyxwv

High-temperature smoke has buoyancy because of its reduced density. At sea level, the pressure difference between a fire compartment and its surroundings can be expressed as follows: /

pressure difference, Pa absolute temperature of surroundings, K average absolute temperature of fire compartment, K distance above neutral plane, m

In Equation (2), this results in a pressure difference of 0.5 Pa, which is insignificant for smoke control applications.

The pressure difference caused by buoyancy can be obtained from Figure 5 for surroundings at 20°C (293 K). The neutral plane is the plane of equal hydrostatic pressure between the fire compartment and its surroundings. For a fire with a f r e compartment temperature at 800°C (1073 K), the pressure difference 1.5 m above the neutral plane is 13 Pa. Fang (1980) studied pressures caused by room f r e s during a series of full-scale f r e tests. During these tests, the maximum pressure difference reached was 16 Pa across the burn room wall at the ceiling. Much larger pressure differences are possible for tall f r e compartments where the distance h from the neutral plane can be larger. If the fire compartment temperature is 700°C (993 K), the pressure difference 10 m above the neutral plane is 83 Pa. This is a large fire, and the pressures it produces are beyond present smoke control

Energy released by a fire can also move smoke by expansion. In a fire compartment with only one opening to the building, building air will flow in, and hot smoke will flow out. Neglecting the added mass of the fuel, which is small compared to airflow, the ratio of volumetric flows can be expressed as a ratio of absolute temperatures:

=

T, =

Tf = h

z

=

Expansion

!din

where Q,,, Q,, To,,

= = =

q, =

zyxwv 1In .

(4)

volumetric flow rate of smoke out of fire compartment, m3/s volumetric flow rate of air into fire compartment, m3/s absolute temperature of smoke leaving fire compartment, K absolute temperature of air into fire compartment, K

For smoke at 700°C (973 K) and entering air at 20°C (293 K), the ratio of volumetric flows is 3.32. Note that absolute temperatures are used in the calculation. In such a case, if air enters the compartment at 1.5 m3/s, then smoke flows out at 5.0 m3/s, with the gas expanding to more than three times its original volume. For a fire compartment with open doors or windows, the pressure difference across these openings caused by expansion is negligible. However, for a tightly sealed f r e compartment, the pressure differences from expansion may be important.

Wind Wind can have a pronounced effect on smoke movement within a building. The pressure wind exerts on a surface can be expressed as

p,

=

0.5C,p0V2

(5)

where p, = C, = p, = V=

Fig. 5

Pressure Difference Caused by Buoyancy

pressure exerted by wind, Pa pressure coefficient, dimensionless outside air density, kg/m3 wind velocity, d s

The pressure coefficients C, are in the range of -0.8 to 0.8, with positive values for windward walls and negative values for leeward walls. The pressure coefficient depends on building geometry and varies locally over the wall surface. In general, wind velocity increases with height from the surface of the earth. Houghton and Carruther (1976), MacDonald (1975), Sachs (1972), and Simiu and

53.4

zyxwvutsrqpz 201 1 ASHRAE Handbook-HVAC

Applications (SI)

zyxwvutsrqpon

Scanlan (1978) give detailed information concerning wind velocity variations and pressure coefficients. Shaw and Tamura (1977) developed specific information about wind data with respect to air infiltration in buildings. With a pressure coefficient of 0.8 and air density of 1.20 kg/m3, a 15 d s wind produces a pressure on a structure of 100 Pa. The effect of wind on air movement within tightly constructed buildings with all exterior doors and windows closed is slight. However, wind effects can be important for loosely constructed buildings or for buildings with open doors or windows. Usually, the resulting airflows are complicated, and computer analysis is required. Frequently, a window breaks in the f r e compartment. If the window is on the leeward side of the building, the negative pressure caused by the wind vents the smoke from the f r e compartment. This reduces smoke movement throughout the building. However, if the broken window is on the windward side, wind forces the smoke throughout the fire floor and to other floors, which endangers the lives of building occupants and hampers fire fighting. Wind-induced pressure in this situation can be large and can dominate air movement throughout the building.

Dilution Remote from Fire

Smoke dilution is sometimes referred to as smoke purging, smoke removal, smoke exhaust, or smoke extraction. Dilution can be used to maintain acceptable gas and particulate concentrations in a compartment subject to smoke infiltration from an adjacent space. It can be effective if the rate of smoke leakage is small compared to either the total volume of the safeguarded space or the rate of purging air supplied to and removed from the space. Also, dilution can be beneficial to the f r e service for removing smoke after a fire has been extinguished. Sometimes, when doors are opened, smoke flows into areas intended to be protected. Ideally, the doors are only open for short periods during evacuation. Smoke that has entered spaces remote from the fire can be purged by supplying outside air to dilute the smoke. The following is a simple analysis of smoke dilution for spaces in which there is no fire. Assume that at time zero (0 = 0), a compartment is contaminated with some concentration of smoke and that no more smoke flows into the compartment or is generated within it. Also, assume that the contaminant is uniformly distributed throughout the space. The concentration of contaminant in the space can be expressed as

HVAC Systems Before methods of smoke control were developed, HVAC systems were shut down when fires were discovered because the systems frequently transported smoke during fres. In the early stages of a fre, the HVAC system can aid in fire detection. When a f r e starts in an unoccupied portion of a building, the system can transport the smoke to a space where people can smell it and be alerted to the fire. However, as the fire progresses, the system transports smoke to every area it serves, thus endangering life in all those spaces. The system also supplies air to the f r e space, which aids combustion. Although shutting the system down prevents it from supplying air to the fre, it does not prevent smoke movement through the supply and return air ducts, air shafts, and other building openings because of stack effect, buoyancy, or wind.

SMOKE MANAGEMENT In this chapter, smoke management includes all methods that can be used singly or in combination to modify smoke movement for the benefit of occupants or frefighters or for reducing property damage. Barriers, smoke vents, and smoke shafts are traditional methods of smoke management. The effectiveness of barriers is limited by the extent to which they are free of leakage paths. Smoke vents and smoke shafts are limited by the fact that smoke must be sufficiently buoyant to overcome any other driving forces that could be present. In the last few decades, fans have been used to overcome the limitations of traditional approaches. Compartmentation, dilution, pressurization, airflow, and buoyancy are used by themselves or in combination to manage smoke conditions in fire situations. These mechanisms are discussed in the following sections.

Compartmentation Barriers with sufficient f r e endurance to remain effective throughout a f r e exposure have long been used to protect against f r e spread. In this approach, walls, partitions, floors, doors, and other barriers provide some level of smoke protection to spaces remote from the fre. This section discusses passive compaxtmentation; using compaxtmentation with pressurization is discussed in the section on Pressurization (Smoke Control). Many codes, such as NFPA Standard 101 and the InternationalBuilding Code@(ICC 2009), provide specific criteria for construction of smoke barriers (including doors) and their smoke dampers. The extent to which smoke leaks through such barriers depends on the size and shape of the leakage paths in the barriers and the pressure difference across the paths.

L O

zyxwv zy

The dilution rate can be determined from the following equation:

(7)

where

C, = initial concentration of contaminant

C = concentration of contaminant at time 8 a = dilution rate, air changes per minute t = time after smoke stops entering space or smoke production has stopped, min e = base of natural logarithm (approximately 2.718)

Concentrations Co and C must be expressed in the same units, but can be any units appropriate for the particular contaminant being considered. McGuire et al. (1970) evaluated the maximum levels of smoke obscuration from a number of f r e tests and a number of proposed criteria for tolerable levels of smoke obscuration. Based on this evaluation, they state that the maximum levels of smoke obscuration are greater by a factor of 100 than those relating to the limit of tolerance. Thus, they indicate that a space can be considered “reasonably safe” with respect to smoke obscuration if the concentration of contaminants in the space is less than about 1% of the concentration in the immediate fire area. This level of dilution increases visibility by aboutafactorof 100(e.g.,frornO.l5mto 15m)andreducestheconcentrations of toxic smoke components. Toxicity is a more complex problem, and no parallel statement has been made regarding dilution needed to obtain a safe atmosphere with respect to toxic gases. In reality, it is impossible to ensure that the concentration of the contaminant is uniform throughout the compartment. Because of buoyancy, it is likely that higher concentrations are near the ceiling. Therefore, exhausting smoke near the ceiling and supplying air near the floor probably dilutes smoke even more quickly than indicated by Equation (7). Supply and exhaust points should be placed to prevent supply air from blowing into the exhaust inlet, thereby short-circuiting the dilution.

zyxw

E:xample 1. A space is isolated from a fire by smoke bamers and self-closing

zyxwv

doors, so that no smoke enters the compartment when the doors are closed. When a door is opened, smoke flows through the open doorway into the space. If the door is closed when the contaminant in the space is 20% of the bum room concentration, what dilution rate is required to reduce the concentration to 1% of that in the bum room in 6 min? The time t = 6 min and CJC = 20. From Equation (7), the dilution rate is about 0.5 air changes per minute, or 30 air changes per hour.

Fire and Smoke Management

zyxwvut zyxwvutsrq 53.5

Caution about Dilution near Fire. Many people have unrealistic expectations about what dilution can accomplish in the fire space. Neither theoretical nor experimental evidence indicates that using a building’s HVAC system for smoke dilution will significantly improve tenable conditions in a f r e space. The exception is an unusual space where the fuel is such that fire size cannot grow above a specific limit; this occurs in some tunnels and underground transit situations. Because HVAC systems promote a considerable degree of air mixing in the spaces they serve and because very large quantities of smoke can be produced by building fres, it is generally believed that smoke dilution by an HVAC system in the f r e space does not improve tenable conditions in that space. Thus, any attempt to improve hazard conditions in the fire space, or in spaces connected to the f r e space by large openings, with smoke purging will be ineffective.

Pressurization (Smoke Control)

Q= C= A= Ap = p=

Airflow has been used extensively to manage smoke from fres in subway, railroad, and highway tunnels (see Chapter 15). Large airflow rates are needed to control smoke flow, and these flow rates can supply additional oxygen to the fre. Because of the need for complex controls, airflow is not used as extensively in buildings. The control problem consists of having very small flows when a door is closed and then significantly increased flows when that door is open. Furthermore, it is a major concern that the airflow supplies oxygen to the fre. This section presents the basics of smoke control by airflow and demonstrates why this technique is rarely recommended. Thomas (1970) determined that in a corridor in which there is a fire, airflow can almost totally prevent smoke from flowing upstream of the fre. Molecular diffusion is believed to transfer trace amounts of smoke, which are not hazardous but which are detectable as the smell of smoke upstream. Based on work by Thomas, the critical air velocity for most applications can be approximated as

zyxwvutsrqpon where

volumetric airflow rate, m3/s flow coefficient flow area (leakage area), m2 pressure difference across flow path, Pa density of air entering flow path, kg/m3

The flow coefficient depends on the geometry of the flow path, as well as on turbulence and friction. In the present context, the flow coefficient is generally 0.6 to 0.7. For p = 1.2 kg/m3 and C = 0.65, Equation (8) can be expressed as Q = 0.839A & (9) The flow area is frequently the same as the cross-sectional area of the flow path. A closed door with a crack area of 0.01 m2 and a pressure difference of 2.5 Pa has an air leakage rate of approximately 0.013 m3/s. If the pressure difference across the door is increased to 75 Pa, the flow is 0.073 m3/s. Frequently, in field tests of smoke control systems, pressure differences across partitions or closed doors have fluctuated by as

Fig. 6

Airflow

zyxwvutsr

Systems that pressurize an area using mechanical fans are referred to as smoke control in this chapter and in NFPA Standard 92A. A pressure difference across a barrier can control smoke movement, as illustrated in Figure 6. Within the barrier is a door. The high-pressure side of the door can be either a refuge area or an egress route. The low-pressure side is exposed to smoke from a fre. Airflow through gaps around the door and through construction cracks prevents smoke infiltration to the high-pressure side. For smoke control analysis, the orifice equation can be used to estimate the flow through building flow paths:

where

much as 5 Pa. These fluctuations have generally been attributed to wind, although they could have been due to the HVAC system or some other source. To control smoke movement, the pressure difference produced by a smoke control system must be large enough to overcome pressure fluctuations, stack effect, smoke buoyancy, and wind pressure. However, the pressure difference should not be so large that the door is difficult to open.

Smoke Control System Preventing Smoke Infiltration to High-pressure Side of Barrier

Vk = critical air velocity to prevent smoke backflow, m/s qc = heat release rate into comdor, W W = comdor width, m

This relation can be used when the f r e is in the corridor or when smoke enters the corridor through an open doorway, air transfer grille, or other opening. Although critical velocities calculated from Equation (10) are general and approximate, they indicate the kind of air velocities required to prevent smoke backflow from fres of different sizes. For specific applications, other equations may be more appropriate: for tunnel applications, see Chapter 15; for smoke management in atriums and other large spaces, see Klote and Milke (2002) and NFPA Standard 92B. Although Equation (10) can be used to estimate the airflow rate necessary to prevent smoke backflow through an open door, the oxygen supplied is a concern. Huggett (1980) evaluated the oxygen consumed in the combustion of numerous natural and synthetic solids. He found that, for most materials involved in building fres, the energy released is approximately 13.1 MJ per kilogram of oxygen. Air is 23.3% oxygen by mass. Thus, if all the oxygen in a kilogram of air is consumed, 3.0 MJ is liberated. If all the oxygen in 1 m3/s of air with a density of 1.2 kg/m3 is consumed by fire, 3.6 MW is liberated. Examples 2 and 3 demonstrate that the air needed to prevent smoke backflow can support an extremely large f r e . Most commercial and residential buildings contain enough fuel (paper, cardboard, furniture, etc.) to support very large fres. Even when the amount of fuel is normally very small, short-term fuel loads (during building renovation, material delivery, etc.) can be significant. Therefore, using airflow for smoke control is not recommended, except when the f r e is suppressed or in the rare cases when fuel can be restricted with confidence. Example 2. What airflow at a doorway is needed to stop smoke bac!dlow from a room fully involved in fire, and how large a fire can this airflow support? A room fully involved in fire can have an energy release rate on the order of 2.4 MW. Assume the door is 0.9 m wide and 2.1 m high. From Equation (lo), Vk = 0.0292(2.4 x 106/0.9)1’3= 4.0 d s . A flow through

z zyxwvutsrqpon 201 1 ASHRAE Handbook-HVAC

53.6

Applications (SI)

the doorway of 4.0 x 0.9 x 2.1 = 7.6 m3/s is needed to prevent smoke from bacmowing into the area. If all the oxygen in this airflow is consumed in the fire, the heat liberated is 7.6 m3/s x 3.6 MW per m3/s of air = 27 MW. This is over 10 times more than the heat generated by the fully involved room fire and indicates why airflow is generally not recommended for smoke control in buildings. Example 3. What airflow is needed to stop smoke backflow from a wastebasket fire, and how large a fire can this airflow support? A wastebasket fire can have an energy release rate on the order of 150 kW. As in Example 2, Vk = 0.0292(150 x 103/0.9)1’3= 1.6 d s . A flow through the doorway of 1.6 x 0.9 x 2.1 = 3.0 m3/s is needed to prevent smoke bacmow. If all the oxygen in this airflow is consumed in the fire, the heat liberated is 3 m3/s x 3.6 MW per m3/s of air = 10.8 MW. This is still many times greater than the fully involved room fire and further indicates why airflow is generally not recommended for smoke control in buildings.

Buoyancy The buoyancy of hot combustion gases is used in both fanpowered and non-fan-powered venting systems. Fan-powered venting for large spaces is commonly used for atriums and covered shopping malls, and non-fan-powered venting is commonly used for large industrial and storage buildings. There is a concern that sprinkler flow will cool the smoke, reducing buoyancy and thus the system effectiveness. Research is needed in this area. Refer to Klote and M i k e (2002) and NFPA Standards 92B and 204 for detailed design information about these systems.

SMOKE CONTROL SYSTEM DESIGN Door-Opening Forces The door-opening forces resulting from the pressure differences produced by a smoke control systemmust be considered. Unreasonably high door-opening forces can make it difficult or impossible for occupants to open doors to refuge areas or escape routes. The force required to open a door is the sum of the forces to overcome the pressure difference across the door and to overcome the door closer. This can be expressed as F=Fdc+

WA Ap 2(W-d)

However, ifthis door is installed with a 20 mm undercut, the leakage area is 0.033 m2, a significant difference. The leakage area of elevator doors is in the range of 0.051 to 0.065 m2 per door. For open stairwell doorways, Cresci (1973) found complex flow patterns; the resulting flow through open doorways was considerably below that calculated using the doorway’s geometric area as the flow area in Equation (8). Based on this research, it is recommended that the design flow area of an open stairwell doorway be h a y the geometric area (door height x width) of the doorway. An alternative for open stairwell doorways is to use the geometric area as the flow area and use a reduced flow coefficient. Because it does not allow the direct use of Equation (8), this approach is not used here. Typical leakage areas for walls and floors of commercial buildings are tabulated as area ratios in Table 1. These data are based on a relatively small number of tests performed by the National Research Council of Canada (Shaw et al. 1993; Tamura and Shaw 1976a, 1976b, 1978; Tamura and Wilson 1966). Actual leakage areas depend primarily on workmanship rather than on construction materials, and in some cases, the flow areas in particular buildings may vary from the values listed. Data concerning air leakage through building components are also provided in Chapter 16 of the 20 09 ASHRAE Handboo k-Fundamentals . Because a vent surface is usually covered by a louver and screen, a vent’s flow area is less than its area (vent height x width). Calculation is further complicated because the louver slats are frequently slanted. Manufacturer’s data should be used for specific information.

zyxwvutsrqpon ~

where F = total door-opening force, N Fdc = force to overcome door closer, N W= A= Ap = d =

Fig. 7 Door-Opening Force Caused by Pressure Difference

door width, m door area, m2 pressure difference across door, Pa distance from doorknob to edge of knob side of door, m

This relation assumes that the door-opening force is applied at the knob. Door-opening force Fp caused by pressure difference can be determined from Figure 7 for a value of d = 75 mm. The force to overcome the door closer is usually greater than 13 N and, in some cases, can be as great as 90 N. For a door that is 2.1 m high and 0.9 m wide and subject to a pressure difference of 75 Pa, the total door-opening force is 130 N, if the force to overcome the door closer is 53 N.

Flow Areas In designing smoke control systems, airflow paths must be identified and evaluated. Some leakage paths are obvious, such as cracks around closed doors, open doors, elevator doors, windows, and air transfer grilles. Construction cracks in building walls are less obvious, but they are equally important. The flow area of most large openings, such as open windows, can be calculated easily. However, flow areas of cracks are more difficult to evaluate. The area of these leakage paths depends on such features as workmanship, door fit, and weatherstripping. A 0.9 by 2.1 m door with an average crack width of 3 mm has a leakage area of 0.018 m2.

Effective Flow Areas The concept of effective flow areas is useful for analyzing smoke control systems. The paths in the system can be in parallel with one another, in series, or a combination of parallel and series. The effective area of a system of flow areas is the area that gives the same flow as the system when it is subjected to the same pressure difference over the total system of flow paths. This is similar to the effective resistance of a system of electrical resistances. The effective flow area A, for parallel leakage areas is the sum of the individual leakage paths:

zyxw n

A,

=

CAi i=l

where n is the number of flow areas Ai in parallel.

53.7

Fire and Smoke Management Table 1

Typical Leakage Areas for Walls and Floors of Commercial Buildings Wall Tightness

Area Ratio

Tight Average Loose Very Loose

AIA, 0.50 x lo4 0.17 x 10-3 0.35 x 10-3 0.12 x 10-2

Stairwell wallsa (includes construction cracks but not cracks around windows or doors)

Tight Average Loose

0.14 x lo4 0.11 x 10-3 0.35 x 10-3

Elevator shaft wallsa (includes construction cracks but not cracks around doors)

Tight Average Loose

0.18 x 10-3 0.84 x 10-3 0.18 x lo-,

Construction Element Exterior building wallsa (includes construction cracks and cracks around windows and doors)

zyxwvuts zyxwvutsr Fig. 9 Leakage Paths in Series

AIAf

zyxwvutsrqponml

Floorsb (includes construction cracks and gaps around penetrations)

Tight Average Loose

0.66 x 10-5 0.52 x lo4 0.17 x 10-3

A = leakage area; A , = wall area; Ar= floor area Leakage areas evaluated at a75 Pa; b25 Pa.

Fig. 10

Fig. 8 Leakage Paths in Series

For example, the effective area A , for the three parallel leakage areas in Figure 8 is A,=A,+A,+A, (13) If A , is 0.10 m2 and A , and A , are each 0.05 m2, then the effective flow area A , is 0.20 m2. The general rule for any number of leakage areas in series is

Combination of Leakage Paths in Parallel and Series

Example 4. Calculate the effective leakage area of two equal flow paths in series. Let A =A, =A, = 0.02 m2. From Equation (16), A,=

=0.014m2 42A2

zyx zyxwvutsrq r

..

Example 5. Calculate the effective flow area of two flow paths in series, where A, = 0.02 m2 and A, = 0.2 m2. From Equation (16),

7-0.5

A,=

where IZ is the number of leakage areas Ai in series. Three leakage areas in series from a pressurized space are illustrated in Figure 9. The effective flow area of these paths is

A

=

id?

- + - +1A;

-0.5

1;)

(15)

~

JA:+A,2

=

Example 5 illustrates that when two paths are in series, and one is much larger than the other, the effective flow area is approximately equal to the smaller area. Developing an effective area for a system of both parallel and series paths requires combining groups of parallel paths and series paths systematically. The system illustrated in Figure 10 is analyzed as an example. The figure shows that A , and A , are in parallel; therefore, their effective area is

zyxwvutsr Jm

In smoke control analysis, there are frequently only two paths in series, and the effective leakage area is

=

A,

=

0.0199 m2

'41'42

(16)

+

Areas A,, A,, and A , are also in parallel, so their effective area is (A456)e =

+

+

53.8

z zyxwvutsrqp zyxwvutsrq 201 1 ASHRAE Handbook-HVAC

Applications (SI)

These two effective areas are in series with A,. Therefore, the effective flow area of the system is given by

zyxwvutsrqpon

Example 6. Calculate the effective area of the system in Figure 10, if the leakage areas are A , = A , = A 3 = 0.02 m2 and A, = A , = A, = 0.01 m2.

(Az3), = 0.04m2

(A,,,), A,

= =

0.03 m2 0.015 m2

Design Weather Data Little weather information has been developed specifically for smoke control system design. Design temperatures for heating and cooling found in Chapter 14 of the 2009 ASHRAE Handbook-Fundamentals (on the CD-ROM accompanying that volume) may be used. Extreme temperatures can be considerably lower than the winter design temperatures. For example, the 99% design temperature for Tallahassee, Florida, is -2.1°C, but the lowest temperature observed there was -19°C (NOAA 1979). Temperatures are generally below the design values for short periods, and because of the thermal lag of building materials, these short intervals of low temperature usually do not cause problems with heating. However, there is no time lag for a smoke control system; it is therefore subjected to all the extreme forces of stack effect that exist the moment it operates. If the outside temperature is below the system's winter design temperature, stack effect problems may result. A similar situation can occur with summer design temperatures and reverse stack effect. Extreme wind data for smoke management design are listed in Chapter 14 of the 2009 ASHRAE Handbook-Fundamentals.

Design Pressure Differences Both the maximum and minimum allowable pressure differences across the boundaries of smoke control should be considered. The maximum allowable pressure difference should not cause excessive door-opening forces. The minimum allowable pressure difference across a boundary of a smoke control system might be the difference such that no smoke leakage occurs during building evacuation. In this case, the smoke control system must produce sufficient pressure differences to overcome forces of wind, stack effect, or buoyancy of hot smoke. Pressure differences caused by wind and stack effect can be large in the event of a broken window in the fire compartment. Evaluation of these pressure differences depends on evacuation time, rate of f r e growth, building configuration, and the presence of a fire suppression system. NFPA Standard 92A suggests values of minimum and maximum design pressure difference.

Open Doors Another design concern is the number of doors that could be opened simultaneously when the smoke control system is operating. A design that allows all doors to be open simultaneously may ensure that the system always works, but often adds to system cost. The number of doors that may be open simultaneously depends largely on building occupancy. For example, in a densely populated building, it is likely that all doors will be open during evacuation. However, if a staged evacuation plan or refuge area concept is incorporated in the building fire emergency plan, or if the building is sparsely occupied, only a few of the doors may be open during a fire.

FIRE AND SMOKE DAMPERS Openings for ducts in walls and floors with f r e resistance ratings should be protected by fire dampers and ceiling dampers, as

Fig. 11

Smoke Control System Damper Recommendation

required by local codes. Air transfer openings should also be protected. These dampers should be classified and labeled in accordance with Underwriters Laboratories (UL) Standard 555. Figure 11 shows recommended damper positions for smoke control. A smoke damper can be used for either traditional smoke management (smoke containment) or smoke control. In smoke management, a smoke damper inhibits passage of smoke under the forces of buoyancy, stack effect, and wind. However, smoke dampers are only one of many elements (partitions, floors, doors) intended to inhibit smoke flow. In smoke management applications, the leakage characteristics of smoke dampers should be selected to be appropriate with the leakage of the other system elements. In a smoke control system, a smoke damper inhibits the passage of air that may or may not contain smoke. A damper does not need low leakage characteristics when outdoor (fresh) air is on the highpressure side of the damper, as is the case for dampers that shut off supply air from a smoke zone or that shut off exhaust air from anonsmoke zone. In these cases, moderate leakage of smoke-free air through the damper does not adversely affect control of smoke movement. It is best to design smoke control systems so that only smoke-free air is on the high-pressure side of a closed smoke damper. Smoke dampers should be classified and listed in accordance with UL Standard 5553 for temperature, leakage, and operating velocity. The velocity rating of a smoke damper is the velocity at which the actuator will open and close the damper. At locations requiring both smoke and f r e dampers, combination dampers meeting the requirements of both UL Standards 555 and 5553 can be used. The combination frelsmoke dampers must close when they reach their UL Standard 5553 temperature rating to maintain the integrity of the firewall. Fire, ceiling, and smoke dampers should be installed in accordance with the manufacturers' instructions. NFPA Standard 90A gives general guidelines on locations requiring these dampers. The supply and returdsmoke dampers should be a minimum of Class I1 leakage at 120°C. The return air damper should be a minimum of Class I leakage at 120°C to prevent recirculation of smoke exhaust. The operating velocity of the dampers should be evaluated when the dampers are in smoke control mode. To minimize velocity build-up, only zones adjacent to the fire need to be pressurized. The exhaust ductwork and fan must be designed to handle the temperature of the exhaust smoke. This temperature can be lowered by making the smoke control zones large or by pressurizing only the zones adjacent to the fire zone and leaving all the other zones operatingnormally.

zyxwvutsr 53.9

Fire and Smoke Management Fans Used to Exhaust Smoke

Understanding building code requirements for high-temperature fans in smoke control systems is important for both designers, who must select fans that can operate satisfactorily at elevated temperatures, and manufacturers, who can then design suitable off-the-shelf fans rather than customizing fans for each application. Only fans designed for use under elevated temperatures should be used in smoke management applications; other types may fail, or their performance may change because of component deformation or altered clearances among components. Also, some smoke exhaust applications (e.g., transit tunnels) require that smoke-handling fans reverse direction repeatedly on demand. Until recently, standards did not address reversibility or airflow performances of high-temperature fans at ambient and elevated temperatures. To allow manufacturers to provide suitable off-the-shelf products, a standard method of test (MOT) and ratings scale have been developed. ANSUASHRAE Standard 149 provides testing laboratories with standard testing methods for fan characteristics specific to smoke exhaust functions, including (1) aerodynamic performance, (2) operation at specified elevated temperature, (3) reversal, and (4) damper performance (for dampers included with the fan). AMCA Publication 212 establishes ratings to allow consistent comparison among catalog test data. Model code requirements for elevated temperature and duration of operation are charted on a graph, which is divided into several fan performance groups. Manufacturers can request that laboratories test fans according to ANSI/ ASHRAE Standard 149; those data can then be incorporated into catalogs for off-the-shelf products according to AMCA Publication 212 ratings, allowing designers to select the most appropriate models and performances for their specific applications. This allows designers and code officials to compare different manufacturers’ products more easily, and enhances confidence that products will perform as intended; it also allows manufacturers to provide more cost-efficient off-the-shelf products rather than custom-designing fans for each application.

Stairwell Compartmentation

Compartmentation of the stairwell into a number of sections is one alternative to multiple injection (Figure 14). When the doors between compartments are open, the effect of compartmentation is lost. For this reason, compartmentation is inappropriate for densely populated buildings where total building evacuation by the stairwell is planned in the event of fire. However, when a staged evacuation plan is used and the system is designed to operate successfully with the maximum number of doors between compartments open, compartmentation can effectively pressurize tall stairwells,

zyxwvutsrqpo Stairwell Analysis

This section presents an analysis for a pressurized stairwell in a building without vertical leakage. This method closely approximates the performance of pressurized stairwells in buildings without elevators. It is also useful for buildings with vertical leakage because it yields conservative results. For evaluating vertical leakage through the building or with open stairwell doors, computer analysis is recommended. The analysis is for buildings where the leakage areas are the same for each floor of the building and where

PRESSURIZED STAIRWELLS Many pressurized stairwells have been designed and built to provide a smoke-free escape route in the event of a building f r e . They also provide a smoke-free staging area for frefighters. On the fire floor, a pressurized stairwell must maintain a positive pressure difference across a closed stairwell door to prevent smoke infiltration. During building fres, some stairwell doors are opened intermittently during evacuation and fire fighting, and some doors may even be blocked open. Ideally, when the stairwell door is opened on the f r e floor, airflow through the door should be sufficient to prevent smoke backflow. Designing a system to achieve this goal is difficult because of the many combinations of open stairwell doors and weather conditions affecting airflow. Stairwell pressurization systems may be single- or multipleinjection systems. A single-injection system supplies pressurized air to the stairwell at one location, usually at the top. Associated with this system is the potential for smoke to enter the stairwell through the pressurization fan intake. Therefore, automatic shutdown during such an event should be considered. For tall stairwells, single-injection systems can fail when a few doors are open near the air supply injection point, especially in bottom-injection systems when a ground-level stairwell door is open. For tall stairwells, supply air can be supplied at a number of locations over the height of the stairwell, Figures 12 and 13 show two examples of multiple-injection systems that can be used to overcome the limitations of single-injection systems. In these figures, the supply duct is shown in a separate shaft. However, systems have been built that eliminated the expense of a separate duct shaft by locating the supply duct in the stairwell itself. In such a case, care must be taken that the duct does not obstruct orderly building evacuation.

Fig. 12

Stairwell Pressurization by Multiple Injection with Fan Located at Ground Level

Fig. 13 Stairwell Pressurization by Multiple Injection with Roof-Mounted Fan

Next Page

201 1 ASHRAE Handbook-HVAC

53.10

Fig. 14

zyxwvuts zyxwvutsrqpo zyxw zyxwvutsrq

Compartmentation of Pressurized Stairwell

the only significant driving forces are the stairwell pressurization system and the indoor-outdoor temperature difference. The pressure difference Ap,, between the stairwell and the building can be expressed as

pressure difference between stairwell and building at stairwell bottom, Pa B = 3460(1/T, UT') at sea level standard pressure y = distance above stairwell bottom, m As, = flow area between stairwell and building (per floor), m2 A,, = flow area between building and outside (per floor), m2 To = temperature of outside air, K T' = temperature of stairwell air, K =

~

For a stairwell with no leakage directly to the outside, the flow rate of pressurization air is

where Q N Ap,,,

Fig. 15 Stairwell Pressurization with Vents to Building at Each Floor

difference Ap,,, is calculated from Equation (17) at 82.6 Pa, using y = 15(3.3) = 49.5 m. Thus, Apsb,does not exceed the maximum allowable pressure. The flow rate of pressurization air is calculated from Equation (18) at 2.7 m3/s.

where Ap,,,

Applications (SI)

= = =

volumetric flow rate, m3/s number of floors pressure difference from stairwell to building at stairwell top, Pa

Example 7. Each story of a 15-story stairwell is 3.3 m high. The stairwell has a single-leaf door at each floor leading to the occupant space and one ground-level door to the outside. The exterior of the building has a wall area of 560 m2 per floor. The exterior building walls and stairwell walls are of average leakiness. The stairwell wall area is 52 m2 per floor. The area of the gap around each stairwell door to the building is 0.024 m2. The exterior door is well gasketed, and its leakage can be neglected when it is closed. Outside design temperature To = 263 K; stairwell temperature T, = 294 K; maximum design pressure differences when all stairwell doors are closed is 87 Pa; the minimum allowable pressure difference is 13 Pa. Using the leakage ratio for an exterior building wall of average tightness from Table 1, A,, = 560(0.17 x = 0.095 m2. Using the leakage ratio for a stairwell wall of average tightness from Table 1, the leakage area of the stairwell wall is 52(0.11 x = 0.006 m2. The value of A , equals the leakage area of the stairwell wall plus the gaps around the closed doors: As, = 0.006 + 0.024 = 0.030 m2. The temperature factor B is calculated at 1.39 Pa/m. The pressure difference at the stairwell bottom is selected as Ap,,, = 20 Pa to provide an extra degree of protection above the minimum allowable value of 13 Pa. The pressure

The flow rate depends strongly on the leakage area around the closed doors and on the leakage area in the stairwell walls. In practice, these areas are difficult to evaluate and even more difficult to control. If flow area A,, in Example 7 were 0.050 m2 rather than 0.030 m2, Equation (18)would give a flow rate of pressurization air of 3.1 m3/s. A fan with a sheave allows adjustment of supply air to offset for variations in actual leakage from the values used in design calculations.

Stairwell Pressurization and Open Doors The simple pressurization system discussed in the previous section has two limitations regarding open doors. First, when a stairwell door to the outside and building doors are open, the simple system cannot provide enough airflow through building doorways to prevent smoke backflow. Second, when stairwell doors are open, pressure difference across the closed doors can drop to low levels. Two systems used to overcome these problems are overpressure relief (Tamura 1990) and supply fan bypass. Overpressure Relief. The total airflow rate is selected to provide the minimum air velocity when a specific number of doors are open. When all the doors are closed, part of this air is relieved through a vent to prevent excessive pressure build-up, which could cause excessive door-opening forces. This excess air should be vented from the stairwell to the street-level floor. Fire and relief dampers should be the low-leakage type. Stairwell doors should have gasket seals at sides and top, leaving the bottom gap open for relief. Barometric dampers that close when pressure drops below a specified value can minimize air loss through the vent when doors are open. Figure 15 illustrates a pressurized stairwell with overpressure relief vents to the building at each floor. In systems with vents between stairwell and building, the vents typically have a fire damper in series with the barometric damper. To conserve energy, these fire dampers are normally closed, but they open when the pressurization system is activated. This arrangement also reduces the possibility of the annoying damper chatter that frequently occurs with barometric dampers.

zyxw zy zyxwvut

CHAPTER 54

RADIANT HEATING AND COOLING Low-, Medium-, and High-Intensity Infrared Heating. ............ Panel Heating and Cooling ...................................................... Elementary Design Relationships ............................................ Design Criteriafor Acceptable Radiant Heating Design for Beam Radiant Heating ...........................................

54.1 54.1 54.1 54.3 54.4

R

ADIANT heating and cooling applications are classified as panel heating or cooling if the panel surface temperature is below 150°C, and as low-, medium-, or high-intensity radiant heating if the surface or source temperature exceeds 150°C. In thermal radiation heat is transferred by electromagnetic waves that travel in straight lines, and can be reflected. Thermal radiation principally occurs between surfaces or between a source and a surface. In a conditioned space, air is not heated or cooled in this process. Because of these characteristics, radiant systems are effective for both spot heating and space heating or cooling requirements for an entire building. Sensible heating loads may be reduced by 4 to 16% compared to ASHRAE standard design load. Percent reduction increases with the air change rate (Suryanarayana and Howell 1990).

LOW-, MEDIUM-, AND HIGH-INTENSITY INFRARED HEATING Low-, medium-, and high-intensity infrared heaters are compact, self-contained direct-heating devices used in hangars, warehouses, factories, greenhouses, and gymnasiums, as well as in areas such as loading docks, racetrack stands, outdoor restaurants, animal breeding areas, swimming pool lounge areas, and areas under marquees. Infrared heating is also used for snow melting and freeze protection (e.g., on stairs and ramps) and process heating (e.g., paint baking and drying). An infrared heater may be electric, gas-fired, or oilfred and is classified by the source temperature as follows: Low-intensity (source temperatures to 650°C) Medium-intensity (source temperatures to 980°C) High-intensity (source temperatures to 2800°C)

Radiation Patterns .................................................................... Design for Total Space Heating ............................................... Testing Instruments for Radiant Heating. ................................ Applications Symbols ....................................................................................

54.5 54.6 54.7 54.7 54.9

In these systems, generally more than 50% of the heat transfer between the temperature-controlled surface and other surfaces is by thermal radiation. Panel heating and cooling systems are used in residences, office buildings, classrooms, hospital patient rooms, swimming pool areas, repair garages, and in industrial and warehouse applications. Additional information is available in Chapter 6 of the 2008 ASHRAE Handbook-HVAC Systems and Equipment. Some radiant panel systems, referred to as hybrid HVAC systems, combine radiant heating and cooling with central air conditioning (Scheatzle 2003). They are used more for cooling than for heating (Wilkins and Kosonen 1992). The controlled-temperature surfaces may be in the floor, walls, or ceiling, with temperature maintained by electric resistance or circulation of water or air. The central station can be a basic, one-zone, constant-temperature, or constant-volume system, or it can incorporate some or all the features of dual-duct, reheat, multizone, or variable-volume systems. When used in combination with other waterlair systems, radiant panels provide zone control of temperature and humidity. Metal ceiling panels may be integrated into the central heating and cooling system to provide individual room or zone heating and cooling. These panels can be designed as small units to fit the building module, or they can be arranged as large continuous areas for economy. Room thermal conditions are maintained primarily by direct transfer of radiant energy, normally using four-pipe hot and chilled water. These systems have generally been used in hospital patient rooms. Metal ceiling panel systems are discussed in Chapter 6 of the 2008 ASHRAE Handbook-HVACSystems and Equipment.

zyxw

ELEMENTARY DESIGN RELATIONSHIPS

The source temperature is determined by such factors as the source of energy, the configuration, and the size. Reflectors can be used to direct the distribution of thermal radiation in specific patterns. Chapter 15 of the 2008 ASHRAE Handbook-HVAC Systems and Equipment covers radiant equipment in detail.

When considering radiant heating or cooling for human comfort, the following terms describe the temperature and energy characteristics of the total radiant environment:

PANEL HEATING AND COOLING Panel heating and cooling systems provide a comfortable environment by controlling surface temperatures and minimizing air motion within a space. They include the following designs: Ceiling panels Embedded hydronic tubing or attached piping in ceilings, walls, or floors Air-heated or cooled floors or ceilings Electric ceiling or wall panels Electric heating cable or wire mats in ceilings or floors Deep heat, a modified storage system using electric heating cable or embedded hydronic tubing in ceilings or floors The preparation of this chapter is assigned to TC 6.5, Radiant Heating and Cooling.

54.1

Mean radiant temperature (MRT) Tr is the temperature of an imaginary isothermal black enclosure in which an occupant would exchange the same amount of heat by radiation as in the actual nonuniform environment. Ambient temperature t, is the temperature of the air surrounding the occupant. Operative temperature to is the temperature of a uniform isothermal black enclosure in which the occupant would exchange the same amount of heat by radiation and convection as in the actual nonuniform environment. For air velocities less than 0.4 d s and mean radiant temperatures less than 50°C, the operative temperature is approximately equal to the adjusted dry-bulb temperature, which is the average of the air and mean radiant temperatures. Adjusted dry-bulb temperature is the average of the air temperature and the mean radiant temperature at a given location. The adjusted dry-bulb temperature is approximately equivalent to the operative temperature for air motions less than 0.4 d s and mean radiant temperatures less than 50°C.

zyxwvutsrqp zyxwvutsrqp zyxwvutsrq zyxwvu zyxw zyxwvutsrq 201 1 ASHRAE Handbook-HVAC Applications (SI)

54.2

Effective radiant flux (ERF) is defined as the net radiant heat exchanged at ambient temperature t, between an occupant, whose surface is hypothetical, and all enclosing surfaces and directional heat sources and slnks. Thus, ERF is the net radiant energy received by the occupant from all surfaces and sources whose temperatures differ from t,. ERF is particularly useful in highintensity radiant heating applications.

The relationship between these terms can be shown for an occupant at surface temperature tJfi exchanging sensible heat H, in a room with ambient air temperature t, and mean radiant temperature . The linear radiative and convective heat transfer coefficients are h, and he, respectively; the latter is a function of the relative movement between the occupant and air movement V. The heat balance equation is

c

where

h, j&

= =

CT =

linear radiative heat transfer coefficient, W/(m2.K) ratio of radiating surface of the human body to its total DuBois surface areaAD = 0.71 Stefan-Boltzmann constant = 5.67 x 10-8 W/(m2.K4)

The convective heat transfer coefficient for an occupant depends on the relative velocity between the occupant and the surrounding air, as well as the occupant’s activity: If the occupant is walking in still air, he

During thermal equilibrium, H, is equal to metabolic heat minus work and evaporative cooling by sweating. By defmition of operative temperature,

H,

=

(h,+ h,)(tsf - t o )

=

h(ts f - t o )

The combined heat transfer coefficient is h, where h = h, Equations (1) and (2) to solve for to yields

(2)

+ he. Using

8.6V

=

0.53

{ 0.5 < V < 2.0 d s }

(-1

where V is the occupant’s walking speed. If the occupant is sedentary with moving air, he

=

he

8.3 V,0.6

=

3.1

{ 0.2 < v, < 4 d s }

(12b)

{ 0 < V, < 0.23 d s }

More information about he may be found in Chapter 9 of the 2009 ASHRAE Handbook-Fundamentals. heat is When & > t,, ERF adds heat to the body; when t, > lost from the body because of thermal radiation. ERF is independent of the occupant’s surface temperature and can be measured directly by a black globe thermometer or any blackbody radiometer or flux meter using the ambient air t, as its heat sink. In these defmitions and for radiators below 925°C (1200 K), the body clothing and skin surface are treated as blackbodies, exchanging radiation with an imaginary blackbody surface at temperature 37 kW) motors’ residual voltage to decay before connection to the other source. Other timers are usually available to provide ride-through for one or two recloser operations (used by utilities to keep their system operational during momentary faults caused by falling limbs, high winds, etc.). An in-phase monitor can be preset and used in conjunction with or in place of the delayed transition to protect large motors during the transfer process. Can be two-, three- or four-pole, depending on phase and grounding scenario. Results in at least two momentary power outages: when utility service is lost and when the system switches back to the utility. Closed-Transition ATS (Figure 9)

Provides momentary (less than six cycles) connection of load to both power sources within acceptable phase angle for seamless transfer when both sources are available.

Fig. 8

Break-Before-Make Design for Standard ATS

Fig. 9

Closed-Transition ATS

Parallel-Transfer (PT) Switch (Figure 10)

Parallel switchgear in a simple one- or two-breaker design allows for parallel connection of the load to both power sources for an indefmite time period. Should include all protective relay devices as required by the local utility and generator supplier. Can include some of the features of a standard ATS, because most can also be operatedas an open-transfer(break-before-make)switch.

Switch selection can profoundly affect the electrical system, especially if an existing back-up system is upgraded for an expandedrole. For example, it may be necessary to completely replace the existing switchgear of a building if an original generator system with a small generator and a standard ATS is replaced with a larger generator and a closed-transition ATS. If the emergency power system is being expanded to include large motor loads, such as chillers, then Set delay to account for chiller motor back current to dissipate. Size the generator set large enough to handle the motor loads’ starting current requirements. The electrical engineer needs to know the starting requirements and maximum allowable voltage drop that the overall electrical system can handle, especially computer and control loads. Most major generator manufacturers can provide sizing software. If a standard ATS is being replaced with a closed-transition or parallel-transfer switch, Verify that the existing switchgear can handle the added potential fault current of the generator set. For instance, if the available fault current from the utility is 65 000 A and the generator fault current is 30 000 A, then the system only has to be braced for 65 000 A with a standard ATS. It has to be braced for 95 000 A with either of the other two switches because fault current is additive with multiple sources connected at the same time.

Fig. 10

Parallel-Transfer Switch

Electrical Considerations

zyxwvuts z 56.5

If the emergency power system is being converted from diesel to natural gas, then

Check the acceptable load steps of the new engine: the diesel likely accepted 100% load, but the natural gas engine may be limited to as low as 20% load. Chillers and other large loads frequently exceed the acceptable load increase. Determine whether large-motor-load starting systems can be changed to reduce starting requirements and meet acceptable load steps. If the emergency system is being modified for peaking or curtailment uses, then Obtain the specific utilities interconnection requirements; these tend to be utility-specific and may exceed normal NEC or local codes. Check the existing system for closed-transition or paralleltransfer switch issues and compatibility. Investigate emissions issues; standby emissions permit requirements are almost always less stringent than peaking requirements.

speed. Soft-start starters also reduce the voltage and limit demand during starting, thereby easing stress on the electric system during motor starting. Variable-frequency drives (VFDs) are also used to soft-start a motor, and are designed to control acceleration during starting as well as optimize motor speed to its load. See the section Motor-Starting Methods for more information. A VFD converts ac to dc and then back to variable-frequency, variable-voltage ac. Motor speed is varied by varying the frequency of the ac output voltage, typically using pulse-width modulation (PWM). This power conversion process results in distorted input current and may contribute to building power system voltage distortion. When motors and other loads are supplied from a distorted voltage source, their operating temperatures may rise. Phase Loss Protection. Phase loss can be detected by sensing either voltage loss or current loss on one of the phases. Motor overloads often are set based on the nameplate data of the motor, but the real motor current draw is less because the motor may not be fully loaded. If one of three phases is lost, the current increases in the other two phases, but not by enough to trip the overloads. However, it will overheat and possibly damage the motor. Some phase loss detectors also check phase current to be sure that it is balanced within 10%. This protects the motor and makes the operator aware of potential motor or line problems. Motor-Starting Effects. The following effects do not occur with all motors. For instance, brushless dc and inverter-driven motors, which are electronically controlled, do not have inrush currents that cause light dimming or sags. Light Dimming or Voltage Sags. Light dimming or voltage sag associated with motor starts can be more than a nuisance. Motors have the undesirable effect of drawing several times their full load current while starting. This large current, by flowing through system impedances, may cause voltage sag that can dim lights, cause contactors to drop out, and disrupt sensitive equipment. The situation is worsened by an extremely poor starting displacement factor, usually in the range of 15 to 30%. If the motor-starting-induced voltage sag deepens, the time required for the motor to accelerate to rated speed increases. Excessive sag may prevent the motor from starting successfully. Motor-starting sags can persist for many seconds. The Illuminating Engineering Society ofNorth America (IESNA) is precise in describing lighting reactions. Dimming is an intentional technique to enhance the ambiance of surroundings by varying the perceived lighting levels. It is also used to reduce the electrical power used by lamps when adequate natural lighting is available; the controller electronically follows the natural variations in a way that will not be optically perceived. Similarly, Jlicker is deliberately selected in some lamps to resemble a candle’s flame. In contrast, this chapter discusses possible causes of undesirable,perceptible reductions of a lamp’s lumen output. Momentary undesirable lighting reduction was quite common when building owners selected incandescent lamps, which compete with motors for available electrical current, to provide the desired lighting levels. More efficient lamps are now the norm for almost every application. For fluorescent lamps, electronic ballasts convert the 60 Hz electrical service to much higher frequencies, which eliminates perception of irritating flicker, and provides greater lumens per watt than the former magnetic ballasts. Similar improvements have occurred for mercury, metal halide, and sodium lamps, typically found in large stores, sports, and industrial applications. Including electronic circuitry in the lamps and lighting systems makes power quality even more important for building owners: electronic components are sensitive to both lower and upper threshold voltages, yet the building’s voltage may experience momentary voltage sag as large motors are started. Specific product literature for lamps, lamp ballasts, and lighting controls should be reviewed to ensure client satisfaction with operation of the HVAC system’s motors and controls. Motor-Starting Methods. The following motor-starting methods can reduce voltage sag from motor starts.

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If the emergency system includes a UPS or flywheel system, then

Size the UPS or flywheel for the maximum required load for a specific time; remember that capacity of these systems is x kW for y min. Avoid motor loads as much as possible.

Motors Motor Control and Protection. Motor control must be effective without damaging the motor or its associated equipment. Control must be designed to prevent inadvertent motor starting caused by a fault in the control device. The control should be able to sense motor conditions to keep the motor windings from getting too warm. Motor protection involves sensing motor current and line voltage, and can include bearing vibration, winding temperature, bearing temperature, etc. Motor temperature increase has two basic sources. Heating occurs when dirt or debris blocks airflow over or through the motor, or it comes from the motor current, commonly referred to as 12R, where I is motor current and R is motor resistance. Because the current is squared, its contribution is exponential. R is the motor winding resistance, and is quite small. Therefore, motor resistance contributes a linear function to heating (and therefore temperature rise) in the motor. Motor windings can withstand temperature rise, depending on the motor winding temperature rating. The second source of motor temperature increase is lack of motor cooling. The primary source of cooling is moving air, usually from a shaft-driven fan. As a motor slows down, the fan runs more slowly; therefore, the less air movement, the less cooling. Because fan loads are also exponential, a small decrease in motor speed greatly reduces airflow on the motor, reducing cooling. To compound the issue, the slower the motor runs, the greater the slip, and the greater the motor current. This then becomes a vicious circle. Motor Starters and Thermal Overloads. Motor starters start, stop, protect, and control the motor. They sense motor current based on a time curve: the shorter the time, the more current they let through. They may also limit the number of motor starts in a given period of time so the motor does not exceed its ANSI rating. Another cause for concern is the starter’s ambient temperature: if it is different from the ambient temperature around the motor controller, the thermal overloads need to be sized accordingly. Several motor starter types are available, and they can function several different ways. The across-the-line starter is the simplest but may disturb electric service because of high motor-starting current requirements. The part-winding, reduced-voltage, and wyedelta starters all act by reducing the starting voltage on the motor. Fan and pump loads can usually be started this way; this reduces starting current draw and demand, but sacrifices motor starting

56.6

z zyxwvutsrqpo 201 1 ASHRAE Handbook-HVAC

Applications (SI)

An across-the-line start, energizing the motor in a single step (full-voltage starting), provides low cost and allows the most rapid acceleration. It is the preferred method unless the resulting voltage sag or mechanical stress is excessive. Autotransformer starters have two autotransformers connected to open delta (similar to a delta connection using three single-phase transformers, but with one transformer removed; carries 57.7% of a full delta load). Taps provide a motor voltage of 80, 65, or 50% of system voltage during start-up. Starting torque varies with the square of the voltage applied to the motor, so the 50% tap delivers only 25% of the full-voltage starting torque. The lowest tap that will supply the required starting torque is selected. Motor current varies as the voltage applied to the motor, but line current varies with the square of the tap used, plus transformer losses of -3%. Resistance and reactance starts initially insert impedance in series with the motor. After a time delay, this impedance is shorted out. Starting resistors may be shorted out over several steps; starting reactors are shorted out in a single step. Line current and starting torque vary directly with the voltage applied to the motor, so for a given starting voltage, these starters draw more current than the line with autotransformer starts, but provide higher starting torque. Reactors are typically provided with 50,45, and 37.5% taps. Part-winding starters are attractive for use with dual-rated motors (2201440 V or 2301460 V). The stator of a dual-rated motor consists of two windings connected in parallel at the lower voltage rating, or in series at the higher voltage rating. When operated with a part-winding starter at the lower voltage rating, only one winding is energized initially, limiting starting current and torque to 50% of the values seen when both windings are energized simultaneously. Delta-wye starters connect the stator in wye for starting, then after a time delay, reconnect the windings in delta. The wye connection reduces the starting voltage to 57% of the system line-line voltage, starting current and starting torque are reduced to 33% of their values for full voltage start.

on the equipment characteristics and the amount of voltage deviation from the nameplate rating. NEMA standards provide tolerance limits within which performance will normally be acceptable. In precise operations, however, closer voltage control may be required. In general, a change in the applied voltage causes a proportional change in the current. Because the effect on the load equipment is proportional to the product of the voltage and the current, and because the current is proportional to the voltage, the total effect is approximately proportional to the square of the voltage. However, the change is only approximately proportional and not exact: the change in the current affects the operation of the equipment, so the current continues to change until a new equilibrium position is established. For example, when the load is a resistance heater, the increase in current increases the heater temperature, which increases its resistance and, in turn, reduces the current. This effect will continue until a new equilibrium current and temperature are established. In the case of an induction motor, a voltage reduction reduces the current flowing to the motor, causing the motor to slow down. This reduces the impedance of the motor, increasing the current until a new equilibrium position is established between the current and motor speed.

Utilization Equipment Voltage Ratings

Voltage Selection

Utilization equipment is electrical equipment that converts electric power into some other form of energy, such as light, heat, or mechanical motion. Every item of utilization equipment should have a nameplate listing, which includes, among other things, the rated voltage for which the equipment is designed. In some cases the nameplate will also indicate the maximum and minimum voltage for proper operation. With one major exception, most utilization equipment carries a nameplate rating that is the same as the voltage system on which it is to be used that is, equipment to be used on 120 V systems is rated 120 V. The major exception is motors and equipment containing motors, where performance peaks in the middle of the tolerance range of the equipment: better performance can be obtained over the tolerance range specified in ANSI Standard (34.1 by selecting a nameplate rating closer to the middle of this tolerance range. The difference between the nameplate rating of utilization equipment and the system nominal voltage is necessary because the performance guarantee for utilization equipment is based on the nameplate rating and not on the system nominal voltage. The voltage tolerance limits in ANSI Standard (34.1 are based on ANSINEMA Standard MG 1, Motors and Generators edition, which establishes voltage tolerance limits of the standard lowvoltage induction motor at *lo% of nameplate voltage ratings of 230 and 460 V. Because motors represent the major component of utilization equipment, they were given primary consideration in the establishment of this voltage standard. Figure 11 compares utilization voltages to nameplate ratings.

Generally, the preferred utilization voltage for large commercial buildings is 480Y1277 V, three-phase. The three-phase power load is connected directly to the system at 480 V, and fluorescent ceiling lighting is connected phase-to-neutral at 277 V. Dry-type transformers rated 480 V1208Y1120 V are used to provide 120 V single-phase for convenience outlets and 208 V three-phase for other building equipment. Single-phase transformers with secondary ratings of 1201240 V may also be used to supply lighting and small office equipment. However, single-phase transformers should be connected in sequence on the primary phases to maintain balanced load on all phases of the primary system. Where the supplying utility furnishes the distribution transformers, the choice of voltages will be limited to those the utility will provide. For tall buildings, space will be required on upper floors for transformer installations and the primary distribution cables supplying the transformers. Apartment buildings generally have the option of using either 208Y1120 V three-phaseifour-wire systems, or 1201 240 V single-phase systems, because the major load in residential occupancies consists of 120 V lighting fixtures and appliances. The 208Y1120 V systems are oftenmore economical for large apartment buildings. Single-phase 1201240 V systems should be satisfactory for small apartment buildings and other small buildings. However, large single-phase appliances, such as electric ranges and water heaters rated for use on 1201240 V single-phase systems, will not perform to the rated wattage on a 208Y1120 V systems, because the line-to-line voltage is appreciably below the rated voltage of the appliance.

Fig. 11 Utilization Voltages Versus Nameplate Ratings

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Voltage Level Variation Effects Whenever voltage at the terminals of utilization equipment varies from its nameplate rating, equipment performance and life expectancy change. The effect may be minor or serious, depending

POWER QUALITY VARIATIONS Power quality refers to varied parameters that characterize the voltage and current for a given time and at a given point on the electric

Electrical Considerations

zyxwvuts z 56.7

system. A power quality problem is usually any variation in the voltage or current that actually results in failure or misoperation of equipment in the facility. Therefore, power quality evaluations are a function of both the power system characteristics and the sensitivity of equipment connected to the power system. This section defmes the different kinds of power quality variations that may affect equipment operation. Important reasons for categorizing power anomalies include the following: Identifying the cause of the power anomalies. Understanding the characteristics of a power quality variation can often help identify the cause. Identifying the possible effects on equipment operation. A transient voltage can cause failure of equipment insulation; a sag in voltage may result in dropout of sensitive controls based on an undervoltage setting. Determining the requirements for measurement. Some power quality variations can be characterized with simple voltmeters, ammeters, or strip chart recorders. Other conditions require special-purpose disturbance monitors or harmonic analyzers. Identifying methods to improve the power quality. Solutions depend on the type of power quality variation. Transient disturbances can be controlled with surge arrestors, whereas momentary interruptions could require an uninterruptible power supply (UPS) system for equipment protection. Harmonic distortion may require special-purpose harmonic filters.

Impulsive Transient. An impulsive transient (spikes or notches) is considered unidirectional; that is, the transient voltage or current wave is primarily of a single polarity (Figures 12 and 13). Impulsive transients are often characterized simply by magnitude and duration. Another important component that strongly influences the effect on many types of electronic equipment is the rate of rise, or rise time of the impulse. This rate of rise can be quite steep, and can be as fast as several nanoseconds. Repetitive subtractive transients (Figure 13), often caused by thyristors such as silicon controlled rectifiers (SCRs), are referred to as voltage notches. The high-frequency components and high rate of rise are important considerations for monitoring impulses. Very fast sampling rates are required to characterize impulses with actual waveforms. In many power quality monitors, simple circuits are used to detect the transient’s peak magnitude and duration (or volt-seconds). If impulse waveshapes are recorded, they usually do not include the fundamental frequency (60 Hz) component. When evaluating these disturbances, it is important to remember that stress on equipment is based on the impulse magnitude plus the magnitude of the fundamental component at the instant of the impulse. The voltage, current available, and pulse width determine the amount of energy available in a transient. Oscillatory Transient. An oscillatory transient (Figure 14) is a voltage or current that changes polarity rapidly. Because the term “rapidly” is nebulous, the frequency content is used to divide

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Power quality can be described in terms of disturbances and steady-state variations. Disturbances. Disturbances are one-time, momentary events. Measurement equipment can characterize these events by using thresholds and triggering when disturbance characteristics exceed specified thresholds. Examples include transients, voltage sags and swells, and interruptions. Steady-State Variations. Changes in the long-term or steadystate conditions can also result in equipment misoperation. High harmonic distortion levels can cause equipment heating and failure, as can long-term overvoltages or unbalanced voltages. These are variations best characterized by monitoring over a longer period of time with periodic sampling of the voltages and currents. Steadystate variations are best analyzed by plotting trends of the important quantities (e.g., RMS voltages, currents, distortion levels). These two types of power quality are further defmed in seven major categories and numerous subcategories. There are three primary attributes used to differentiate among subcategories within a power quality category: frequency components, magnitude, and duration. These attributes are not equally applicable to all categories. For instance, it is difficult to assign a time duration to a voltage flicker, and it is not useful to assign a spectral frequency content to variations in the fundamental frequency magnitude (sags, swells, overvoltages, undervoltages, interruptions). Each category is defined by its most important attributes for that particular power quality condition. These attributes are useful for evaluating measurement equipment requirements, system characteristics affecting power quality variations, and possible measures to correct problems. The terminology has been selected to agree as much as possible with existing terminology used in technical papers and standards. The following descriptions focus on causes of the power quality variations, important parameters describing the variation, and effects on equipment.

Fig. 12 Example of Spike

Fig. 13 Example of Notch

Transients Transients are probably the most common disturbance on distribution systems in buildings and can be the most damaging. Transients can be classified as impulsive or oscillatory. These terms reflect the waveshape of a current or voltage transient.

Fig. 14 Example of Oscillatory Transient

201 1 ASHRAE Handbook-HVAC oscillatory transients into three subcategories: high, medium, and low frequency. Frequency ranges from these classifications are chosen to coincide with common types of power system oscillatory transient phenomena. As with impulsive transients, oscillatory transients can be measured with or without including the fundamental frequency. One way to trigger on transients is to continually test for deviation in the waveform from one cycle to the next. This method will record any deviation exceeding the set threshold. When characterizing the transient, it is important to indicate the magnitude with and without the 60 Hz fundamental component. Transients are generally caused by a switching event or by the response of the system to a lightning strike or fault. The oscillations result from interactions between system capacitances and inductances, and occur at the natural frequencies of the system excited by the switching event or fault. High-frequency transients can occur at locations very close to the initiating switching event. Rise times created by closing a switch can be as fast as a few tens of nanoseconds. Short lengths of circuit have very high natural oscillation frequencies that can be excited by a step change in system conditions (e.g., operating a switch). Power electronic devices such as transistors and thyristorslSCRs can cause high-frequency transients many times during each cycle of the fundamental frequency. The transients can be in the tens or hundreds of kilohertz, and occasionally higher. Because of the high frequencies involved, circuit resistance typically damps transients out; thus, they only occur close (within tens to hundreds of metres) to the site of the switching event that generates them. Characterizing these transients with measurements is often difficult because high sampling rates are required. Medium-frequency transients are associated with switching events with somewhat longer circuit lengths (resulting in lower natural frequencies). Switching events on most 480 V distribution systems in a facility cause transient oscillations within this frequency range, which can propagate over a significant portion of the low-voltage system. Motor interruption (defmite interruption) is a good example of a common switching event that can excite transients in this frequency range. Transients coupled from the primary power system (e.g., coupled through the step down transformer) can also cause mediumfrequency transients. The most common cause of transients on the primary power system is capacitor switching. Capacitor energizing results in an initial step change in the voltage, which gets coupled through stepdown transformers by the transformer capacitance and then excites natural frequencies of the low-voltage system (typically 2 to 10 kHz). Low-frequency transients are usually caused by capacitor switching, either on the primary distribution system or within the customer facility. Lowerfrequency transients result from capacitance of the switched capacitor bank oscillating with the inductance of the power system. The natural frequencies excited by these switching operations are much lower than those of the low-voltage system without the capacitor bank, because of the large capacitance of the capacitor bank itself. Capacitor switching operations are common on most distribution systems and many transmission systems. Energizing a capacitor results in an oscillatory transient with a natural frequency in the range of 300 to 2000 Hz (depending on the capacitor size and the system inductance). The peak magnitude of the transient can approach twice the normal peak voltage (per unit), and lasts between 0.5 and 3 cycles, depending on system damping. Isolation transformers, voltage arresters, and/or filters can reduce transients.

Applications (SI)

ground). Depending on the fault location and system conditions, the fault can cause either momentary voltage rises (swells) or momentary voltage drops (sags). The fault condition can be close to or remote from the point of interest. Sags. Sags (Figure 15) are often associated with system faults but can also be caused by switching heavy loads or starting large motors (usually a longer-duration variation). Figure 15 shows a typical voltage sag that can be associated with a remote fault condition. For instance, a fault on a parallel feeder circuit (on the primary distribution system) results in a voltage drop at the substation bus that affects all of the other feeders until the fault is cleared by opening a fuse or circuit breaker. The percent drop in the RMS voltage magnitude and duration of the low-voltage condition are used to characterize sags. Voltage sags are influenced by system characteristics, system protection practices, fault location, and system grounding. The most common problem caused by voltage sags is tripping sensitive controls (e.g., adjustable-speed drives or process controllers), relays or contactors dropping out, and failure of power supplies to ride through the sag. Many types of voltage regulators are not fast enough to provide voltage support during sags, but ferroresonant transformers and some other line conditioners can provide some ride-through capability or can quickly compensate for deep sags. In practice, sags are the type of power quality variation that most frequently causes problems. Fault conditions remote from a particular customer can still cause voltage sags that can cause equipment problems. Because there are no easy ways to eliminate faults on the power system, it is always necessary for customers to consider the effects of sags. Swells. Swells or surges can also be associated with faults on the primary distribution system (Figure 16). They can occur on nonfaulted phases when there is a single-line-to-ground fault. Swells are characterized by their magnitude (RMS value) and duration. The severity of a voltage swell is a function of fault location, system impedance, and grounding. On a three-phase ungrounded system (delta), the line-to-ground voltages on the ground phases are 1.73 per unit (i.e., 1.73 times the normal line-to-ground voltage) during a single-line-to-ground fault condition. Close to the substation on a grounded system, there is no voltage rise on the ground phases because the substation transformer is usually deltawye, providing a low-impedance path for the fault current.

Fig. 15 Example of Sag

Short-Duration Variations Short-duration voltage variations are momentary changes in the fundamental voltage magnitude. Common causes are faults on the power system (short circuits between phases or from phase to

Fig. 16 Example of Swell (Surge)

z

Electrical Considerations

Fig. 17 Example of Overvoltage

56.9

zyxwvuts Fig. 19 Derating Factor Curve

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Fig. 18 Example of Undervoltage

Long-Duration Variations

to the system strength, these voltage drops can result in a significant system undervoltage. The magnitude of this starting current decreases over a period ranging from 1 s to minutes, depending on the inertia of the motor and the load, until the motor reaches full speed. This type of undervoltage can be mitigated by using various starting techniques to limit the starting current and is largely self-corrected when the starting is completed. For more information, see the section on Motor-Starting Effects. Voltage Unbalance. Ideally, all phase-to-phase voltages to a three-phase motor should be equal or balanced. Unbalance between the individual phase voltages is caused by unbalanced loading on the system and by unbalances in the system impedances. Voltage unbalance is an important parameter for customers with motors because most three-phase motors have fairly stringent limitations on negative-sequence voltage (a measure of voltage unbalance), which is generated in the motor by unbalances in supplied voltages. Negative sequence currents heat the motor significantly. Voltage unbalance limitations (and steady-state voltage requirements in general) are discussed in ANSI Standard C84.1. The National Electrical Manufacturers Association (NEMA) has developed standards and methods for evaluating and calculating voltage unbalance. Unbalance, as defined by NEMA, is calculated by the following equation:

Long-duration RMS voltage deviations generally do not result from system faults. They are caused by load changes on the system and system switching operations. The duration of these voltage variations depends on the operation ofvoltage regulators and other types of voltage control on the power system (e.g., capacitor controls, generator exciter controls). The time required for these voltage controllers to respond to system changes ranges from large fractions of a second to seconds. Long-duration variations can be overvoltages or undervoltages, depending on the cause of the variation. Voltage unbalance should be considered when evaluating steady-state or long-duration voltage variations. Unbalanced voltages can be one of the major causes of motor overheating and failure. With increasing emphasis on energy-efficient motors, requirements for voltage balance (i.e., limitations on negative sequence voltage magnitudes) may become even more important. Overvoltages. Overvoltages (Figure 17) can result from load switching (e.g., switching off a large load), variations in system generation, or variations in reactive compensation on the system (e.g., switching a capacitor bank on). These voltages must be evaluated against the long-duration voltage capability of loads and equipment on the system. For instance, most equipment on the power system is only rated to withstand a voltage 10% above nominal for any length of time. Many sensitive loads can have even more stringent voltage requirements. Long-duration overvoltages must also be evaluated with respect to the long-time overvoltage capability of surge arresters. Metal oxide variation (MOV) arresters in particular can overheat and fail due to high voltages for long durations (e.g., seconds). Overvoltages can be controlled with voltage regulation equipment either on the power system or in a customer’s facility. This can include various tap-changing regulators, ferroresonant regulators, line power conditioners, motor-generator sets, and unintermptible power supplies. Undervoltages. Undervoltages (Figure 18) have the opposite causes of overvoltages. Adding a load or removing a capacitor bank will cause an undervoltage until voltage regulation equipment on the system can bring the voltage back to within tolerances. Motor starting is one of the most common causes of undervoltages. An induction motor draws 6 to 10 times its full load current during starting. This lagging current causes voltage drops in the system impedance. If the started motor is large enough relative

zyxw

% Voltage unbalance

=

Maximum deviation from average voltage 100 x Average voltage

The motor derating factor caused by the unbalanced voltage curve from NEMA Standard MG 1 shows the nonlinear relationship between the percent of voltage unbalance and the associated derating factor for motors (Figure 19). A balanced-voltage three-phase power supply to the motor is essential for efficient system operation. For example, a voltage unbalance of 3.5% can increase motor losses by approximately 15%.

Interruptions and Outages Interruptions can result from power system faults, equipment failures, generation shortages, control malfunctions, or scheduled maintenance. They are measured by their duration (because the voltage magnitude is always zero), which is affected by utility protection system design and the particular event causing the interruption. Interruptions of any significant duration can potentially cause problems with a wide variety of different loads. Computers, controllers, relays, motors, and many other loads are sensitive to interruptions. The only protection for these loads during an interruption is a back-up power supply, a back-up generator (requires time to get started) or a UPS system (can constantly be online).

zyxwvutsrq 201 1 ASHRAE Handbook-HVAC

56.10

Momentary Interruption. A typical momentary interruption (Figure 20) lasts less than 3 s and occurs during a temporary fault, when a circuit breaker successfully recloses after the fault has been cleared. Lightning-induced faults usually fall into this category unless they cause a piece of equipment (e.g., transformer) to fail. Temporary Interruption. Temporary interruptions that last between 3 s and 1 min result from faults that require multiple recloser operations to clear, or require time for back-up switching to reenergize portions of the interrupted circuit (e.g., automatic throwover switches). Power FailureBlackout. Outages lasting at least 1 min (Figure 21) are severe enough to be included in utility companies’ reliability statistics. These failures are caused by fault conditions, maintenance operations that require repair crews, and emergency situations called blackouts. Solutions involve using either UPS systems or back-up generators, depending on the critical nature of the load. UPS systems typically can provide uninterrupted supply for at least 15 min (based on battery capacity). This covers all momentary and temporary interruptions and provides sufficient time for an orderly shutdown. A UPS can be used in conjunction with a switching scheme involving multiple feeds from the utility to provide an even higher level of reliability. If back-up power is required beyond the capability of a UPS system, and multiple feeds are not realistic or adequate, then backup generators are needed. On-site generators are typically used in these applications. Brownout. A brownout is a long-term voltage reduction, usually of 3 to 5%. This is an intentional reduction to reduce load under emergency system conditions.

Harmonic Distortion Harmonic distortion of the voltage waveform occurs because of the nonlinear characteristics of devices and loads on the power system. These nonlinear devices fall into one of three categories: Power electronics Ferromagnetic devices (e.g., transformers) Arcing devices These devices usually generate harmonic currents, and voltage distortion on the system results from these harmonics interacting

with the system impedance characteristics. Harmonic distortion is a growing concern for many customers and for the overall power system because of the increasing applications of power electronic equipment. In many commercial buildings, electronic loads, such as variable-frequency drives, computers, and UPS systems, may be dominant in the facility. With more and more buildings switching to electronic ballasts for fluorescent lighting, an even higher percentage of the facility load falls into this category. Harmonic distortion levels can be characterized by the complete harmonic spectrum with magnitudes and phase angles of each individual harmonic component. However, it is more common to use a single quantity, the total harmonic distortion (THD), to characterize harmonic distortion of a particular waveform. It is important in general to distinguish between voltage distortion and current distortion because these quantities are handled differently in the standards and should be handled differently when performing measurements and interpreting data. Voltage and current distortion is caused by the harmonic currents generated by nonlinear devices interacting with the impedance characteristics of the power system. Harmonic current distortion results in elevated true RMS current, which increases 12R losses and elevated peak current. Because harmonics flow at frequencies higher than the fundamental frequency (e.g., 180 Hz, 300 Hz, 420 Hz), additional losses are experienced because of the reduction of conductor effective cross-sectional area, a phenomenon known as skin effect. These losses are attributed to 12XLat each harmonic frequency. A particular concern is when resonance conditions on the power system magnify harmonic currents and high-voltage distortion levels. The natural resonance of the power system varies based on system inductance and capacitance and should be evaluated when adding nonlinear devices (equipment) or power factor capacitors to the system. Capacitors offer a low-impedance path to harmonic frequencies and can therefore attract harmonics, often resulting in reduced life, fuse blowing, or capacitor failure. Figure 22 illustrates the voltage waveform with harmonic content. Figures 23 and 24 illustrate distorted current waveforms. Harmonic distortion can be reduced by adding an ac line reactor or harmonic filter at the input of individual nonlinear loads (Figure 25). A 5% impedance line reactor typically reduces

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Fig. 22 Fig. 20

Fig. 21

Applications (SI)

Example of Harmonic Voltage Distortion

Example of Momentary Interruption

Example of Blackout or Power Failure Waveform

Fig. 23 Example of Harmonic Current Distortion for Six-Pulse Rectifier with 5% Impedance Reactor

56.11

Electrical Considerations harmonic distortion for three-phase nonlinear loads to about 35% of the fundamental current. Harmonic current distortion can be reduced to levels of 5 to 8% total harmonic current distortion, at the individual load, using a typical low-pass harmonic filter (Figure 26). The benefit of reducing harmonics right at the contributing load is that the entire upstream power system benefits from reduced levels of current and voltage distortion. Voltage Notches. A voltage waveform with notches (see Figure 13) caused by operating power electronics, especially where SCRs are involved [e.g., adjustable-speed drives (ASDs)], can be considered a special case that falls in between transients and harmonic distortion. Because notching occurs continuously (steady state), it can be characterized by the harmonic spectrum of the affected voltage. However, frequency components associated with the notching can be quite high, and it may not be possible to characterize them with measurement equipment normally used for harmonic analysis. It is usually easier to measure with an oscilloscope or transient disturbance monitor. Three-phase SCR rectifiers (those typically in dc drives, UPS systems, ASDs, etc.) with continuous dc current are the most common cause of voltage notching. The notches occur when the current commutates from one phase to another on the ac side ofthe rectifier. During this period, there is a momentary short circuit between two phases. The severity of the notch at any point in the system is determined by the source of inductance and the inductance between the rectifier and the point being monitored. Often, an isolation transformer or 3% impedance ac line reactor (inductor) can be used in the circuit to reduce the effect of notching on the source side. The additional inductance increases the severity

of voltage notches at the rectifier terminals (commutation time, or width of the notch, increases with increased commutation reactance); however, most of the notching voltage appears across the ac inductor and notching is less severe on the source side, where other equipment shares a common voltage source. Steep voltage changes caused by notching can also result in ringing (oscillation) because of capacitances and inductances in the supply circuit. This oscillation can disturb sensitive controls connected to the affected circuit. The high frequencies involved can also cause noise be capacitively coupled to adjacent electrical or communication circuits.

Voltage Flicker

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Loads that vary with time, especially in the reactive component, can cause voltage flicker; the varying voltage magnitudes can affect lighting intensity. Arc furnaces are the most common cause of voltage flicker. The envelope of the 60 Hz variations is defined as the flicker signal V, and its RMS magnitude is expressed as a percentage of the fundamental. Voltage flicker is measured with respect to sensitivity of the human eye. A typical plot of the 60 Hz voltage envelope characterizing voltage flicker is shown in Figure 27. The characteristics of voltage flicker are mainly determined by load characteristics and the system short-circuit capacity. For a critical load, it may be necessary to provide a dedicated feed so that it is not on the same circuit with a major load that causes voltage flicker. Using fast switching compensation, such as a static volt-amperereactive (VAR) system, or dynamic VAR compensation system, can mitigate the problem. Another method is to effectively increase the short-circuit capacity at the point of common coupling with other loads by using a series capacitor. Protecting the series capacitor during fault conditions requires careful design. Voltage flicker appears as a modulation of the fundamental frequency (similar to amplitude modulation of an AM radio signal).

Fig. 24 Example of Harmonic Current Distortion for One-Phase Input Current for Single Personal Computer

Fig. 26

Fig. 25

Example of VFD with ac Line Reactor

z

Example of VFD with Low-Pass Harmonic Filter

Fig. 27 Example of Flicker

201 1 ASHRAE Handbook-HVAC Applications (SI)

56.12

Fig. 28

conductors should always be physically separated from control circuit conductors. Magnetic shielding can also help. Capacitive (Electrostatic) Coupling. Capacitive coupling between conductors results in coupling of transient voltage signals between circuits. Transient voltages with high-frequency components or high rates of rise are the most likely to be capacitively coupled between circuits (the coupling capability of a capacitor increases with frequency). Switch operations, arcing, lightning, or electrostatic discharge can cause these transients. Electric fields capacitively couple voltage between conductors. Strength is measured in volts per metre and may range from very slight to many kilovolts per metre. High magnitudes of capacitively coupled voltages can affect normal operations of various types of electronic devices, or even cause discharges and damage. Possible solutions include applying shielding and coating, and improving design of power equipment to reduce the generation of high-transient-voltage conditions. To minimize interference, power conductors should always be physically separated from control circuit conductors. Electromagnetic Interference (EMI). EM1 refers to interference caused by electromagnetic waves over a wide range of frequencies. Many interference sources start out as either strongly magnetic or strongly electric, but within about half a wavelength the fields convert to a balanced ratio of electric and magnetic fields (an electromagnetic field). Transients such as electrostatic discharge, arcing, contacts, power electronic switching, fluorescent lighting, and lightning cause electromagnetic waves. Steady-state EM1 can occur in the form of radio frequency interference (RFI) from microwave and radar transmissions, radio and TV broadcasts, corona of high-voltage transmission line, arc welding, and other sources that generate radio-frequency electromagnetic waves. Although RFI is not destructive, it can cause a variety of malfunctions of susceptible electronic equipment and can disturb microcomputers and programmable controllers; the level of disturbance depends on the amount of RFI. Solutions include using appropriate shielding or filtering techniques.

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Example of Electrical Noise

Therefore, it is easiest to defme a magnitude for voltage flicker as the RMS magnitude of the modulation signal, which can be found by demodulating the waveform to remove the fundamental frequency and then measuring the magnitude of the modulation. Typically, magnitudes as low as 0.5% can result in perceptible light flicker if frequencies are in the range of 1 to 10 Hz. Flicker limitations are discussed in ANSIiIEEE Standard 146. Light dimming, another type of light flicker, is caused by starting motors. Large single- or three-phase motors, as used in air conditioners, have the undesirable effect of drawing 6 to 10 times their full load current while starting. This large current, by flowing through system impedances, causes voltage sag that may dim lights.

Noise Noise, a continuous, unwanted signal on the power circuits (Figure 28), can have a wide variety of different causes (e.g., switching, arcing, electric fields, magnetic fields, radio waves) and can be coupled onto the power circuit in a number of different ways. The noise source and susceptible circuit can be coupled by electric or magnetic fields or by electromagnetic interference (EMI). The frequency range and magnitude of noise depend on the source that produces the noise. A typical magnitude of noise measured in the voltage is less than l % of the RMS voltage magnitude. Noise having enough amplitude disturbs electronic equipment such as microcomputers and programmable controllers. Some noise can be eliminated by using an isolation transformer with an electrostatic shield; other noise requires EM1 filtering or line conditioners. Wiring and grounding practices also significantly affect the noise levels at particular loads. The appropriate method for controlling noise depends on the methods of coupling, frequency range of the noise, and susceptibility of the equipment being protected. Inductive (Magnetic) Coupling. Magnetic fields induce currents in conductors. The magnetic fields are caused by current flowing in nearby power conductors, parts of circuits, data lines, or even building structure, and can be temporary or steady state. The actual coupled currents in power conductors and equipment conductors depend on exposure (length of conductor in the field), angle between conductor and field, and magnetic field strength. Conductors canying large currents and/or with large spacing between conductors can create strong 60 Hz magnetic fields that do not decay quickly with distance from the source. These fields can cause distortion on CRT or TV screens, and may interfere with sensitive electronic (especially analog) devices such as radio-controlled equipment, energy and building automation systems, photoelectric sensors, test and measurement equipment, and data processing equipment. During building design, steps should be taken to minimize generation of strong magnetic fields, and to keep sensitive equipment well separated from these areas. Current flow in the power system ground can be an important cause of magnetic fields because the loop area between the supply conductor and the return path through the ground can be very large. Therefore, grounding techniques to minimize noise levels can help reduce magnetic field problems. To minimize interference, power

BILLING RATES Equipment specifications state how much electricity is used, but the cost of that electricity is usually the determining factor in HVAC&R system design and equipment selection. Electricity tariffs or rates set prices for How much electricity is used; energy (MJ) Rate at which electricity is used; demand (kW) Quality of electricity used; power factor (VAR or kVAR) Electric rates are contracts defining what the electricity user will pay for the amounts consumed. Rates may be based on cost, policy, market, or a combination of costipolicy and market. Additionally, rates may be based on either kW or kVA demand. Designers should not assume that the types of rates will remain the same over the life of a building.

Cost-Based Rates Cost-based rates are designed to charge each class of consumer based on the utility’s cost to serve. Costs depend on megajoules used, maximum demand, and time of day at which electricity is used. A customer class is a group of electricity consumers whose use characteristics are similar; each customer class has a different rate or tariff. Typical customer classes are residential, multi-family, small commercial, large commercial, small industrial, large industrial, electric water heating, electric space heating, street lighting, etc. Cost-based rates are usually predicated on the following assumptions: The more electricity a customer uses the less it costs, per megajoule, to serve that customer.

Electrical Considerations The higher the demand of a customer, the more it costs to serve that customer. It costs less per megajoule to serve a customer with a higher load factor. Load factor LF is defmed as the customer’s average demand divided by the peak demand, or the energy consumed in the billing period divided by the peak demand times the number of hours in the billing period. [LF = MJ used in the billing period (peak demand x hours in billing period)] It costs less for a utility to deliver electricity at times of low system load than at times of high system load.

Energy Charge. The consumer pays the utility a fixed amount for every megajoule used. Small customers, especially residential, often simply pay for energy used. Certain loads may have usage profiles that allow the utility to provide electricity at times of low production costs (e.g., street lighting) or cost less per megajoule because the customer uses significantly more than a typical customer (e.g., electric space heating). These loads are often metered separately and are charged a lower cost per megajoule than generalservice usage. Fuel Adjustment Clause (FAC). A significant part of the cost of electricity is the fuel needed to generate it. In the 1970s, the price of primary energy sources (especially oil) became extremely volatile, and the fuel adjustment clause was designed to accommodate this without requiring frequent rate adjustments. Energy charges with FACs consist of two parts: a fixed charge per megajoule and a variable charge per megajoule that depends on the average price of fuel purchased by the power generator. During periods of low fossil fuel prices or high hydro runoff, for example, the FAC results in lower prices to the consumer. Demand Charge. “Demand” is the maximum rate of use of electricity. It is expressed in kilowatts (kW) or kilovolt-amps (kVA) and is typically measured over 15, 30, or 60 min periods. For example, 1 k w h used in 15 min is equal to 4 kW demand (1 k W 0 . 2 5 hours). Demand charges are designed to cover the system capacity cost to deliver energy to a customer and/or the marginal generation cost to produce electricity at time of highest usage. To deliver electricity to a consumer, a utility must install wires, transformers, and meters; the higher the customer’s projected demand, the larger the capacity of wires and transformers serving the customer must be. From a systemwide perspective, the utility must also build enough generation and transmission capacity to serve the system load at its highest peak level. A noncoincident demand (NCD) charge is a charge per kilowatt for the customer’s maximum demand for electricity (in any 15, 30, or 60 minperiod) during the billing cycle. Noncoincident demand charges are generally imposed to cover the cost to transform and deliver energy to the consumer. A coincident demand (CD) charge (also known as a peak or on-peak demand charge) is a charge per kilowatt for the customer’s maximum demand for electricity in any 15,30, or 60 min period occurring during times of high system load. For example, in a summer-peaking utility, the demand charge may be applied only to the maximum demand occurring between 11:30 AM and 6:OO PM on weekdays from May to September. CD charges are designed to pay for additional generation and other system reinforcement costs needed to meet peak demands. Ratcheted Demand Charge. Demand charges may be calculated based on the customer’s maximum demand during each billing cycle, or the maximum demand during the 12 mo preceding the electricity bill. A high demand in one month “ratchets” the demand charge up for some or all of the following 11 months. Seasonal Rate. Some utilities’ generation costs vary significantly from one season to another. For example, spring runoff may yield more low-cost hydroelectric energy, or high summer airconditioning loads may result in more power generation by less efficient peaking plants. A seasonally adjusted rate reflects this by setting different kilowatt andor megajoule charges for different seasons.

56.13 Time of Use (TOU) Rate. A utility’s average production cost for electricity usually varies with the total system load. As demand increases, less efficient (i.e., more costly) generators are used. Increasing peak loads also require that a utility invest in greater generation, transmission, and distribution capacity to meet the peak. A TOU rate is designed to recover the increased production or capacity costs during times of system peak. Electricity use is recorded by multiregister meters and priced at different levels, depending on whether the peak/ off-peak or peakishoulderioff-peak model is used. TOU rates are usually designed not only to “recover” time-differentiated production costs, but also to induce consumers to shift their electricity usage from peak periods to times of lower system load. In this way, TOU rates are both “cost-based” and “policy-based.’’Thermal energy storage (TES) systems are one method for consumers to reduce their onpeak demand or energy charges and to consume electricity during lower-cost, off-peak times. With TES, a consumer may use the same or more total electricity but will pay less for it. Declining Block Rate. In designing cost-based rates, the cost to serve is usually inversely proportional to the amount consumed. To reflect this, energy may be priced according to a declining block rate, where the cost per megajoule decreases as usage increases. For example, a residential customer may pay $0.033/MJ for the frst 3000 MJ used in a month, $0.028/MJ for the next 2000 MJ, and $0.022/MJ for all electricity above 5000 MJ. Demand-Dependent Block Rate. For larger customers, the size of the blocks of a block rate may depend on the measured demand. For example, a commercial consumer may pay $0.033/MJ for the first 300 MJ per kilowatt of billing demand, $0.028/MJ for the next 550 MJ per kilowatt of billing demand, and $0.022/MJ for every MJ above 850 MJ per kilowatt of billing demand. Load Factor Penalty. Utilities recover their fixed costs (e.g., capital cost of a transformer) as well as production costs through energy (MJ) charges as well as demand charges. If a consumer’s load factor is less than expected, then the utility’s megajoule revenues may not be sufficient to recover its fixed costs. This may occur for a customer with self-owned on-site generation who relies on the utility mainly when the on-site generator is being maintained. In this case, the utility may impose a load factor penalty or surcharge. Power Factor Penalty. Apower system is more efficient and stable when all three phases are equally loaded (balanced) and serving pure resistive load (100% power factor). Some inductive loads, such as most lighting and motors, require reactive power, which may be more difficult and expensive for the utility to supply. Moreover, reactive power (kVAR) is not always measured, and therefore not billed, by typical megajoule meters. Therefore, ut impose a power factor penalty or surcharge on customers with very reactive or inductive loads (power factor not close to 100%) to pay for the VARs that it must supply. Customer Charge. This is a monthly, usually fixed charge that a consumer must pay, regardless of whether any electricity is used, for being a customer of a utility. This charge typically covers customer services such as the costs of billing, metering, and customer support services, such as call centers. Connection Fee. When electric service is initiated, especially when construction (additional distribution lines, substations, distribution transformers, etc.) is required, the utility may charge a connection fee. For example, a utility may charge a residential customer a fixed cost per metre of distribution line that must be constructed beyond an initial 150 m of line. Some customers may require redundant facilities to ensure reliable service (e.g., a second feeder and load transfer switch for a hospital). The utility would probably include such costs in its connection fee.

Policy-Based Rates Policy-based rates are designed to encourage consumers to modify their energy use to better conform with the objectives of

56.14 the utility or legislative or regulatory body (e.g., using nonpolluting or renewable energy sources, deferring grid expansion or generator construction by shifting electricity demand from peak periods, better using waste heat from industrial processes, etc.). It can be argued that some policy-based rates are in fact cost-based, but they incorporate “externalities,” or external costs that cannot be directly allocated to a consumer’s electricity use. The time of use rate could fall under either category. Inverted Block Rate. The marginal cost to provide an existing customer with additional energy decreases as energy use per kilowatt of connected load increases. However, additional energy use often hastens the need to construct new generation facilities. An inverted block rate motivates the consumer to reduce energy use by charging less for the f r s t megajoule used. For example, a residential consumer may pay $0.022 for the first 3000 MJ per month, $0.028 for the next 1800 MJ, and $0.033 for all usage above 5000 MJ. As with the declining block rate, the break points between “blocks” may be based on demand for that billing cycle. Lifeline Rate. Lifeline rates are designed so poor consumers will still be able to afford necessary electricity (e.g., enough for refrigeration, lights, adequate heat in winter, etc.). For example, a consumer pays a subsidized price per megajoule for a minimal amount of electricity and the market rate for any usage above the minimum (e.g., $O.Ol/MJ for the first 2500 MJ and $0.03/MJ for usage above 2500 MJimonth). Net Metering. This is applicable for consumers who own their own on-site generation, still buy electricity from the grid, but sometimes can generate more electricity than is needed in their facility. Net metering is a contract in which the customer pays the utility for the net electricity purchased (i.e., excess on-site generation is sold to the grid and offsets what the customer owes the utility for purchases from the grid). Green Power Rate. Customers may sign up for blocks of electricity produced by renewable sources, such as wind turbines. Because of electricity from such sources usually costs more than electricity produced by conventional generation, the green energy is sold at a premium. Surcharges. Government agencies may add special surcharges to electric bills to provide funding for specific energy-related or general-purpose programs. For example, in the United States, many state governments collect public benefit funds through electric bills to provide money for energy efficiency, renewable energy, lowincome weatherization, and research programs. Other surcharges may be for power plant upgrades or putting electric distribution lines underground. Surcharges can be fixed or charged on a perkWh basis. Some surcharges may be capped at a specific dollar amount per type of customer. Taxes. Government agencies may collect sales and other specific taxes through utility bills. The taxes may be calculated as a percentage total ofthe entire bill, or on aper-kWh basis (such as $0.001 per kWh). For some customers, taxes and surcharges may comprise a significant portion of the total bill.

Market-Based Rates Electric utilities are restructuring to disaggregate electricity production, transmission, and distribution and open the market to competition. The theory is that a competitive electricity sector, governed by market rules, is more efficient, lower-cost, and more congruent with consumer needs than regulated electric utilities. Market-based rates are not new, but they are becoming more prevalent. Rates tend to be volatile, and are structured as a contract between the consumer and energy supplier, rather than as a traditional tariff. As a result, they tend to be more customer-specific than uniform over a customer class. Real-Time Pricing (RTP). Under this scheme, the cost of electricity varies with each hour. The supplier sets a price for electricity based on its forecasted cost to produce or provide the electricity.

201 1 ASHRAE Handbook-HVAC Applications (SI) Hour-by-hour prices are communicated to the customer from 1 to 24 h in advance, and the consumer decides what, if any, action to take in response to the forecasted prices. The most common RTP programs send prices to consumers each evening, to cover the next day. Some programs send prices 4 h in advance, and several also allow 1 h alerts for “surprise” prices during system emergencies or forced outages. Consumers who were on a demand (kilowatt) and energy (MJ) rate often are billed only for energy use (MJ) on RTP, because the hourly energy cost incorporates the demand charge. The RTP may only apply to the generation portion of the electric bill if transmission and distribution charges are still regulated. Fixed Pricing. Some consumers in a deregulated market may opt for fixed prices for their electric supply. In these situations, the consumer may pay a price that is higher or lower than the RTP or spot prices. With this type of pricing, the burden of price risk goes to the supplier, who may charge a risk premium to the customer. Spot Pricing. Consumers in some regions may purchase some or all of their electricity on the spot market, based on the current marginal cost of electricity. This is done through a power exchange, with the consumer either contracting directly with the exchange or going through a third-party electricity broker. Consumers may also purchase electricity through a combination of long-term contracts and spot market purchases. Interruptible Rates and Responsive Loads. At times of high marginal electricity costs, it may be more cost-effective for a utility to pay its customers to reduce electricity consumption than to contract for additional electricity supplies. With interruptible rates, a consumer agrees to reduce power consumption to or below an agreed-upon level (or go off-line) when requested to do so by the utility, in return for a lower price. The utility’s requests may be limited in number of times per year (or month) the consumer can be asked to reduce load, maximum duration of the load reduction, and minimum notice required (typically 1 to 4 h) before electric load is reduced. In other cases, there is no limit to the number or length of utility requests. Direct Load Control. This is similar to interruptible load, but instead of the consumer’s complying with the utility’s request, the utility can exercise direct control over the consumer’s appliances. Appliances commonly contracted for load control programs are water heaters, swimming pool pumps, air conditioners, heat pumps, resistance space heat, and controllable thermostats for HVAC&R systems. The tariff usually is in the form of a monthly rebate or fixed bill credit for each controllable appliance. Performance-Based Rates. These are designed to ensure that the consumer receives acceptable quality and reliability of electric supply. The utility and consumer agree on a minimum standard for service quality in terms of number and duration of outages, voltage sags and swells, harmonic levels, or other transient phenomena. If these minimum service quality levels are not met, the utility must rebate money to the consumer; the amount rapidly increases as performance or service quality declines. In some cases, the rate, or type of rate charged, may not change, but customers receive bill credits or rebates based on a reduction in the electric company’s rate of return. Performance Contracting. In performance contracting, a consumer contracts with a third party to pay for the end-use applications of electricity. This usually involves an agreement where the performance contractor [often called an energy service company (ESCO)] installs and sometimes operates and maintains improved equipment for HVAC&R systems, lighting, building or process energy management, etc. The consumer’s payments are indexed to successful equipment performance. That performance is often evaluated in terms of the facility’s utility bills and calculated cost savings comparing the actual energy costs with estimates of what the costs would have been without the ESCO’s intervention. A

z

Electrical Considerations

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more detailed explanation of performance contracting is presented in ASHRAE Guideline 14-2002.

CODES AND STANDARDS NEC@ The National Electrical Code@(NEC) is devised and published by the National Fire Protection Association, a consensus standards writing industry group. It is revised every three years. The code exists in several versions: the full text, an abridged edition, and the NEC Handbook (which contains the authorized commentary on the code, as well as the full text). It sets minimum electrical safety standards, and is widely adopted.

UL Listing Underwriters Laboratories (UL), formerly an insurance industry organization, is now independent and nonprofit. It tests electrical components and equipment for potential hazards. When a device is UL-listed, UL has tested the device, and it meets their requirements for safety (i.e., f r e or shock hazard). It does not necessarily mean that the device actually does what it is supposed to do. The UL does not have power of law in the United States; non-UL-listed devices are legal to install. However, insurance policies may have clauses that limit their liability in a claim related to failure of a non-UL-listed device. The NEC requires that a wiring component used for a specific purpose is UL-listed for that purpose. Thus, certain components must be UL-listed before inspector approval andor issuance of occupancy permits.

CSA Approved The Canadian Standards Association (CSA) is made up ofvarious government agencies, power utilities, insurance companies, electrical manufacturers, and other organizations. They update CSA Standard C22.1, the Canadian Electrical Code (CEC), every two or three years. The Canadian Standards Association (or recognized equivalent) must certify every electrical device or component before it can be sold in Canada. Implicit in this is that all wiring must be done with CSAapproved materials. Testing is similar to UL testing (a bit more stringent), except that CSA approval is required by law. Like the UL, if a f r e is caused by non-CSA-approved equipment, the insurance company may not pay the claim.

56.15

ULC

Underwriters Laboratory of Canada (ULC) is an independent organization that undertakes the quarterly inspection of manufacturers to ensure continued compliance of UL listedrecognized products to agency reports and safety standards. This work is done under contract to UL, Inc.; they are not a branch or subsidiary of UL.

NAFTA Wiring Standards Since the North America Free Trade Agreement (NAFTA) came into effect on January 1, 1994, CSA approval of a device is legally considered equivalent to UL approval in the United States, and UL listing is accepted as equivalent to CSA approval in Canada. Devices marked only with UL approval are acceptable in the CEC, and CSA approval by itself of a device is accepted by the NEC. This allows much freer trade in electrical materials between the two countries. This does not affect the electrical codes themselves, so differences in practice between the NEC and CEC remain.

IEEE The Institute of Electrical and Electronic Engineers’ Standard 519 suggests limits for both harmonic current and voltage distortion, based on electrical system conditions.

zyxwvut BIBLIOGRAPHY

ANSI. 2006. Electric power systems and equipment-Voltage ratings (60 Hz). Standard (34.1-2006. American National Standards Institute, Washington, D.C. ASHRAE. 2002. Measurement of energy and demand savings. Guideline 14-2002. CSA. 2006. Canadian electrical code, part I, 20th ed.: Safety standard for electrical installations. Standard C22.1-06. Canadian Standards Association, Toronto. IEEE. 1980. Definitions of fundamental waveguide terms. ANSI/IEEE Standard 146-1980. Institute of Electrical and Electronics Engineers, Piscataway, NJ. IEEE. 1992. Recommended practices and requirements for harmonic control in electrical power systems. ANSI/IEEE Standard 519-1992. Institute of Electrical and Electronics Engineers, Piscataway, NJ. NEMA. 2007. Condensed information guide for general purpose industrial ac small and medium squirrel-cage induction motor standards. ANSI/ NEMA Standard MG 1-2007. National Electrical Manufacturers Association, Rosslyn, VA. NFPA. 201 1. National electrical codea. Standard 70-2011. National Fire Protection Association, Quincy, MA.

zyxw zyx zyxwvut CHAPTER 57

ROOM AIR DISTRIBUTION Indoor Air Quality and Sustainability ..................................... Application Guidelines ............................................................ Mixed Air Distribution ............................................................. Fully Strati$ed Air Distribution

57.1 57.2 57.2 57.6

Partially Mixed Air Distribution .............................................. Terminal Units........................................................................ Fan Selection .......................................................................... Chilled Beams

R

OOM air distribution systems, like other HVAC systems, are intended to achieve required thermal comfort and ventilation for space occupants and processes. Although air terminals (inlets and outlets), terminal units, local ducts, and the rooms themselves may affect room air distribution, this chapter addresses only air terminals and their effect on occupant comfort. This chapter is intended to help HVAC designers apply air distribution systems to occupied spaces, providing information on characteristics of various air distribution strategies, and tools and guidelines for applications and system design. Naturally ventilated spaces are not addressed; see Chapter 16 of the 2009 ASHRAE Handbook-Fundamentals for details. Also see Chapter 20 of the 2009 ASHRAE Handbook-Fundamentals for more information on space air diffusion; Chapter 19 of the 2008 ASHRAE Handbook-HVAC Systems and Equipment for information on room air distribution equipment; and Chapter 48 of this volume for sound and vibration control guidance. Room air distribution systems can be classified by (1) their primary objective and (2) the method by which they attempt to accomplish that objective. The objective of any air distribution system can be classified as one of the following: Conditioning andor ventilation of the space for occupant thermal comfort Conditioning andor ventilation to support processes within the space A combination of these As a general guideline, the occupied zone in a space is any location where occupants normally reside, and may differ from project to project; it is application-specific, and should be carefully defmed by the designer. The occupied zone is generally considered to be the room volume between the floor level and 1.8 m above the floor. Standards and guidelines, such as ANSIiASHRAE Standards 55 and 62.1, further defme the occupied zone (e.g., Standard 55 exempts areas near walls). Occupant comfort is defmed in detail in ANSIiASHRAE Standard 55-2004. Figure 5.2.1.1 ofthe standard shows acceptable ranges of temperature and humidity for spaces. As a general guide, 80% of occupants intypical office spaces can be satisfied with thermal environments over a wide range of temperatures and relative humidities. Designers often target indoor dry-bulb temperatures between 22 and 25”C, relative humidities between 25 and 60%, and occupied zone air velocities below 0.25 mis. ANSIiASHRAE Standard 113 describes a method for evaluating effectiveness of various room air distribution systems in achieving thermal comfort. Room air distribution methods can be classified as one of the following: Mixed systems (e.g., overhead distribution) have little or no thermal stratification of air in the occupied and/or process space. Full thermal stratification systems (e.g., thermal displacement ventilation) have little or no air mixing in the occupied andor process space. The preparation of this chapter is assigned to TC 5.3, Room Air Distnbution.

57.9 57.10 57.15 57.19

Partially mixed systems (e.g., most underfloor air distribution designs) provide limited air mixing in the occupied andor process space. TasWambient air distribution (e.g., personally controlled desk outlets, spot conditioning systems) focuses on conditioning only part of the space for thermal comfort andor process control. Because taskiambient design requires a high degree of individual control, it is not covered in this chapter; see Chapter 20 of the 2009 ASHRAE Handbook-Fundamentals for details. Limited design guidance is also provided by Bauman and Daly (2003). Figure 1 illustrates the spectrum between the two extremes (full mixing and full stratification) of room air distribution strategies.

INDOOR AIR QUALITY AND SUSTAINABILITY Air distribution systems affect not only indoor air quality (IAQ) and thermal comfort, but also energy consumption over the entire life of the project. Choices made early in the design process are important. ANSIiASHRAEiIESNA Standard 90.1 provides energy efficiency requirements that affect supply air characteristics. The U.S. Green Building Council’s (USGBC) Leadership in Energy and Environmental Design (LEEDO) Green Building Rating SystemTMwas originally created in response to indoor air quality concerns, and has evolved to include prerequisites and credits for increasing ventilation effectiveness and improving thermal comfort (USGBC 2009). These requirements and optional points are relatively easy to achieve if good room air distribution design principles, methods, and standards are followed. Environmental tobacco smoke (ETS) control is a LEED prerequisite. Banning indoor smoking is a common approach, but if indoor smoking is to be allowed, ANSIiASHRAE Standard 62.1-2010 requires that more than the base non-ETS ventilation air be provided where ETS is present in all or part of a building. Rock (2006) provides additional advice on dealing with ETS. Ventilation effectiveness is affected directly by the room air distribution system’s design, construction, and operation, but is very difficult to predict. Many attempts have been made to quantify ventilation effectiveness, including ASHRAE Standard 129. However, this standard is only for experimental tests in well-controlled laboratories and should not be applied directly to real buildings. Because of the difficulty in predicting ventilation effectiveness, ASHRAE Standard 62.1 provides a table of typical values that were determined through the experiences of its Standard Project Committee and reviewers or extracted from research literature; for example, well-designed ceiling-based air diffusion systems produce nearperfect air mixing in cooling mode, and yield an air change effectiveness of almost 1.O. More information on ASHRAE Standard 62.1 is available in its user’s manual (ASHRAE 201 1). Displacement and underfloor air distribution (UFAD) systems have the potential for values greater than 1.O. More information on ceiling- and wall-mounted air inlets and outlets can be found in Rock and Zhu (2002). Performance of displacement systems is described by Chen and Glicksman (2003), and UFAD is discussed in detail by Bauman and Daly (2003).

57.1

201 1 ASHRAE Handbook-HVAC

57.2

Fig. 1

Classification of Air Distribution Strategies

Air terminals, such as diffusers or grilles, may become unsightly over time because of accumulation of dirt on their faces (smudging). Instead of replacing air terminals, and thus requiring new materials and energy for manufacturing, they can often be cleaned in place to restore their appearance. Those that cannot be cleaned and must be replaced should be recycled, not discarded, to recover the various metals and other desirable materials of construction.

APPLICATION GUIDELINES Design Constraints Space design constraints affect room air distribution system choices and how air inlets and outlets are used. Space constraints may include the following: Dimensions Heat gain and loss characteristics Use Acoustical requirements Available locations for air inlets and outlets

Applications (SI)

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Table 1 Recommended Return Inlet Face Velocities Inlet Location

Velocity Across Gross Area, m / s

Above occupied zone In occupied zone, not near seats In occupied zone, near seats Door or wall louvers Through undercut area of doors

>4 3 to 4 2 to 3 1 to 1.5 1 to 1.5

to special vertical takeoff ducts that connect the outlet with the horizontal duct. In all these cases, devices for directing and equalizing the airflow may be necessary for proper direction and diffusion of the air.

Return Air Inlets The success of a mixed air distribution system depends primarily on supply diffuser location. Return grille location is far less critical than with outlets. In fact, the return air intake affects room air motion only immediately around the grille. Measurements of velocity near a return air grille show a rapid decrease in magnitude as the measuring device is moved away from the grille face. Table 1 shows recommended maximum return air grille velocities as a function of grille location. Every enclosed space should have returdtransfer inlets of adequate size per this table. For stratified and partially mixed air distribution systems, there are advantageous locations for return air inlets. For example, an intake can be located to return the warmest air in cooling season. If the outlet is selected to provide adequate throw and directed away from returns or exhausts, supply short-circuiting is normally not a problem. The success of this practice is confirmed by the availability and use of combination supply and return diffusers.

zyxwvutsrqpon

Inlet and outlet characteristics are discussed in Chanter 19 of the 2008 ASHRAE Handbook-HVAC Systems and Equipment. This chapter discusses more specific application considerations for air inlets and outlets.

Sound Sound emitted from inlets and outlets is directly related to the airflow quantity and free area velocity. The airflow sound intensity in a space also depends on the room’s acoustical absorption and the observer’s distance from air distribution devices, For more information, see Chapter 48 of this volume and Chapter 8 in the 2009 ASHRAE Handbook-Fundamentals .

Inlet Conditions to Air Outlets The way an airstream approaches an outlet is important. For good air diffusion, the inlet configuration should create a uniform discharge velocity profile from the outlet, or the outlet may not perform as intended. The outlet usually cannot correct effects of improper duct approach. Many sidewall outlets are installed either at the end of vertical ducts or in the side of horizontal ducts, and most ceiling outlets are attached either directly to the bottom of horizontal ducts or

MIXED AIR DISTRIBUTION In mixed air systems, high-velocity supply jets from air outlets maintain comfort by mixing room air with supply air. This air mixing, heat transfer, and resultant velocity reduction should occur outside the occupied zone. Occupant comfort is maintained not directly by motion of air from outlets, but from secondary air motion from mixing in the unoccupied zone. Comfort is maximized when uniform temperature distribution and room air velocities of less than 0.25 d s are maintained in the occupied zone.

Room Air Distribution

z zyxwvutsrq 57.3

Maintaining velocities less than 0.25 d s in the occupied zone is often overlooked by designers, but is critical to maintaining comfort. The outlet’s selection, location, supply air volume, discharge velocity, and air temperature differential determine the resulting air motion in the occupied zone.

Principles of Operation Mixed systems generally provide comfort by entraining room air into discharge jets located outside occupied zones, mixing supply and room air. Ideally, these systems generate low-velocity air motion (less than 0.25 d s ) throughout the occupied zone to provide uniform temperature gradients and velocities. Proper selection of an air outlet is critical for proper air distribution; improper selection can result in room air stagnation, unacceptable temperature gradients, and unacceptable velocities in the occupied zone that may lead to occupant discomfort. The location of a discharge jet relative to surrounding surfaces is important. Discharge jets attach to parallel surfaces, given sufficient velocity and proximity. When a jet is attached, the throw increases by about 40% over a jet discharged in an open area. This difference is important when selecting an air outlet. For detailed discussion of the surface effect on discharge jets, see Chapter 20 of the 2009 ASHRAE Handbook-Fundamentals .

Space Ventilation and Contaminant Removal These systems are intended to maintain acceptable indoor air quality by mixing supply and room air (dilution ventilation). Supply air is typically a conditioned mixture of ventilation and recirculated air. Outlet type and discharge velocity determine the mixing rate of the space and should be a design consideration. The room’s return or exhaust air carries away diluted air contaminants. Space air ventilation rates are mandated under ASHRAE Standard 62.1-2010, but supply airflow rates are often higher because of thermal loads.

Benefits and Limitations Benefits of fully mixed systems include the following: Most office applications can use lower supply dry-bulb temperatures, for smaller ductwork and lower supply air quantities. Air can be supplied at a lower moisture content, possibly eliminating the need for a more complex humidity control system. Vertical temperature gradients are lower for cooling applications with high internal heat gains, which may improve thermal comfort. Mixed systems are the most common design for distribution systems, because designers and installers are familiar with the required system components and installation. Limitations of mixed systems include the following: Partial-load operation in variable-air-volume (VAV) systems may reduce outlet velocities, reducing room air mixing and compromising thermal comfort. Designers should consider this when selecting outlets. Cooling and heating with the same ceiling or high-sidewall diffuser may cause inadequate performance in heating mode andor excessive velocity in cooling mode. Ceilings more than 4 m high may require special design considerations to provide acceptable comfort in the occupied zone. Care should be taken to select the proper outlet for these applications. Because mixed systems typically use high-velocity jets of air, any obstructions in the space (e.g., bookshelves, wall partitions, furniture) can reduce comfort. Lighter-than-air contaminants are uniformly mixed in the space and typically result in higher contaminant concentrations, which may compromise indoor air quality. Mixed air systems typically use either ceiling or sidewall outlets discharging air horizondly, o r floor- or sill-mounted outlets dis-

Fig. 2

Air Supplied at Ceiling Induces Room Air into Supply Jet

charging air vertically. They are the most common method of air distribution in North America.

Horizontal Discharge Cooling with CeilingMounted Outlets Ceiling-mounted outlets typically use the surface effect to transport supply air in the unoccupied zone. The supply air projects across the ceiling and, with sufficient velocity, can continue down wall surfaces and across floors, as shown in Figure 2. In this application, supply air should remain outside the occupied zone until it is adequately mixed and tempered with room air. Air motion in the occupied zone is generated by room air entrainment into the supply air (Nevins 1976). Overhead outlets may also be installed on exposed ducts, in which case the surface effect does not apply. Typically, if the outlet is mounted 300 mm or more below a ceiling surface, discharge air will not attach to the surface. The unattached supply air has a shorter throw and can project downward, resulting in high air velocities in the occupied zone. Some outlets are designed for use in exposed duct applications. Typical outlet performance data presented by manufacturers are for outlets with surface effect; consult manufacturers for information on exposed duct applications.

Vertical-Discharge Cooling or Heating with Ceiling-Mounted Outlets Vertically projected outlets are typically selected for high-ceiling applications that require forcing supply air down to the occupied zone. It is important to keep cooling supply air velocity below 0.25 d s in the occupied zone. For heating, supply air should reach the floor. There are outlets specifically designed for vertical projection and it is important to review the manufacturer’s performance data notes to understand how to apply catalog data. Throws for heating and cooling differ and also vary depending on the difference between supply and room air temperatures.

Cooling with Sidewall Outlets Sidewall outlets are usually selected when access to the ceiling plenum is restricted. Sidewall outlets within 300 mm of a ceiling and set for horizontal or a slightly upward projection the sidewall outlet provide a discharge pattern that attaches to the ceiling and travels in the unoccupied zone. This pattern entrains air from the occupied zone to provide mixing. In some applications, the outlet must be located 0.5 to 1.25 m below the ceiling. When set for horizontal projection, the discharge at some distance from the outlet may drop into the occupied zone. Most devices used for sidewall application can be adjusted to project the air pattern upwards toward the ceiling. This allows the discharge air to attach to the ceiling, increasing throw distance and minimizing drop. This application provides occupant comfort by inducing air from the occupied zone into the supply air.

57.4

z zyxwvutsrqp 201 1 ASHRAE Handbook-HVAC

Some outlets may be more than 1.25 m below the ceiling (e.g., in high-ceiling applications, the outlet may be located closer to the occupied zone to minimize the volume of the conditioned space). Most devices used for sidewall applications can be adjusted to project the air pattern upward or downward, which allows the device’s throw distance to be adjusted to maximize performance. When selecting sidewall outlets, it is important to understand the manufacturer’s data. Most manufacturers offer data for outlets tested with surface effect, so they only apply if the device is set to direct supply air toward the ceiling. When the device is 1.25 m or more below a ceiling, or supply air is directed horizontally or downward, the actual throw distance of the device is typically shorter. Many sidewall outlets can be adjusted to change the spread of supply air, which can significantly change throw distance. Manufacturers usually publish throw distances based on specific spread angles.

Although not typically selected for nonresidential buildings, floor-mounted outlets can be used for mixed system cooling applications. In this configuration, room air from the occupied zone is induced into the supply air, providing mixing. When cooling, the device should be selected to discharge vertically along windows, walls, or other vertical surfaces. Typical nonresidential applications include lobbies, long corridors, and houses of worship. It is important to select a device that is specially designed for floor applications. It must be able to withstand both the required dynamic and static structural loads (e.g., people walking on them, loaded carts rolling across them). Also, many manufacturers offer devices designed to reduce the possibility of objects falling into the device. It is strongly recommended that obstructions are not located above these in-floor air terminals, to avoid restricting their air jets. Long floor-mounted grilles generally have both functioning and nonfunctioning segments. When selecting air outlets for floor mounting, it is important to note that the throw distance and sound generated depend on the length of the active section. Most manufacturers’ catalog data include correction factors for length’s effects on both throw and sound. These corrections can be significant and should be evaluated. Understanding manufacturers’ performance data and corresponding notes is imperative.

Cooling with Sill-Mounted Air Outlets Sill-mounted air outlets are commonly used in applications that include unit ventilators and fan coil units. The outlet should be selected to discharge vertically along windows, walls, or other vertical surfaces, and project supply air above the occupied zone. As with floor-mounted grilles, when selecting and locating sill grilles, consider selecting devices designed to reduce the nuisance of objects falling inside them. It is also recommended that sills be designed to prevent them from being used as shelves.

Heating and Cooling with Perimeter CeilingMounted Outlets

Space Temperature Gradients and Airflow Rates

A fully mixed system creates homogeneous thermal conditions throughout the space. As such, thermal gradients should not be expected to exist in the occupied zone. Improper selection, sizing, or placement may prevent full mixing and can result in stagnant areas, or having high-velocity air entering the occupied zone. Supply airflow requirements to satisfy space sensible heat gains or losses are inversely proportional to the temperature difference between supply and return air. The following equation can be used to calculate space airflow requirements (at standard conditions): 4,

e =1.2(t,-ts) where Q

Cooling with Floor-Mounted Air Outlets

Applications (SI)

=

required supply airflow rate to meet sensible load, L/s

qs = net sensible heat gain in the space, W

tr = return or exhaust air temperature, “C ts = supply air temperature, “C

zy

zy

For fully mixed systems with conventional ceiling heights, the return (or exhaust) and room air temperatures are the same; for example, a room with a set-point temperature of 24°C has, on average, a 24°C return or exhaust air temperature.

Methods for Evaluation The objective of air diffusion is to create the proper combination of room air temperature, humidity, and air motion in the occupied zone to provide thermal comfort and acceptable indoor environmental quality. There are three recommended methods of selecting outlets for mixed air systems using manufacturers’ data: By appearance, flow rate, and sound data By isovels (lines of constant velocity) and mapping By comfort criteria These selection methods are not meant to be independent. It is the designer’s choice as to which to start with, but it is recommended that at least two methods be used for any design. Variation from accepted thermal limits (ASHRAE Standard 55), lack of uniform thermal conditions in the space, or excessive fluctuation of conditions in one part of the space may produce discomfort. Thermal discomfort also can arise from any of the following conditions: Excessive air motion (draft) Excessive room air temperature stratification (horizontal, vertical, or both) Failure to deliver or distribute air according to load requirements at different locations Rapid fluctuation of room temperature

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When air outlets are used at the perimeter with vertical projection for heating andor cooling, they should be located near the perimeter surface, and selected so that the published 0.75 d s isothermal throw extends at least halfway down the surface or 1.5 m above the floor, whichever is lower. In this manner, during heating, warm air mixes with the cool downdraft on the perimeter surface, to reduce or even eliminate drafts in the occupied space. If a ceiling-mounted air outlet is located away from the perimeter wall, in cooling mode, the high-velocity cool air reduces or overcomes the thermal updrafts on the perimeter surface. To accomplish this, the outlet should be selected for horizontal discharge toward the wall. Outlet selection should be such that isothermal throw to the terminal velocity of 0.75 d s should include the distance from the outlet to the perimeter surface. For heating, the supply air temperature should not exceed 8.5 K above the room air temperature.

Selection

By Appearance, Flow Rate, and Sound Data. For a given appearance, flow rate, pressure drop, and sound level criteria, designers can select outlets from manufacturers’ catalogs, using the following steps:

Determine air volumetric flow requirements based on load and room size. For VAV systems, evaluation should include the range of flow rates from minimum occupied to design load. Determine acceptable outlet noise criterion (NC); consult Chapter 48 of this volume, or Chapter 8 in the 2009 ASHRAE Handbook-Fundamentals . Locate a range of products from manufacturers’ catalogs that meet the airflow and NC requirements. Multiple outlets in a space at the same catalogedNC, and other design considerations, may result in actual sound levels greater than cataloged values.

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zyxwvutsrqpon

Room Air Distribution Table 2

Effect of Neck-Mounted Damper on Air Outlet NC

Total Pressure Ratio*

dB Increase

57.5

100%

150%

200%

400%

0

4.5

8

16

*Ratio of air pressure before and after damper.

Manufacturers' data are obtained using ideal inlet conditions, and may vary from field installations. From experience, For identical outlets 3 m or more apart, the cataloged NC rating applies. Identical outlets within 3 m of each other add no more than 3 dB to the sound pressure level. For continuous linear outlets, only the sound produced by the closest 3 m need be considered. A wide-open damper installed in the neck of a diffuser can add 4 to 5 NC to the cataloged NC value. Significantly closed balancing dampers can add more than 10 NC, depending on duct pressure and how far upstream it is installed. Table 2 gives an example. 4. Select air terminals from manufacturers' catalogs that meet aesthetic and physical needs. Although these selections may meet the sound requirements for a project, the results do not fully address occupant comfort. Without evaluating the throw of the outlets or room air mixing, this selection method may result in excessive air velocities in the occupied zone, or limited mixing and resultant stagnation. It is recommended that the designer consider selection by isovel mapping or by comfort criteria in addition to selection by appearance, flow rate, and sound data. Either of these methods addresses resulting air motion in the occupied zone and occupant comfort. By Isovels and Mapping. Using manufacturers' catalog throw data, a designer can predict the path of an outlet's discharge jet. Most manufacturers' catalogs list the distance a jet travels to reach a terminal velocity of 0.75 to 0.25 d s . With this information, the designer can map the path of the discharge jet for a given outlet. This evaluation can prevent problems such as excessively high air velocities in the occupied zone, or stagnation in a given area. Note that most manufacturers' throw data are based on isothermal supply air; the supply jet temperature is equal to the room air temperature. When using this mapping method, consider the positive or negative buoyancy of nonisothermal (heated or cooled) supply air. In both heating and cooling, a discharge jet should travel the distance shown in the catalog to a terminal velocity of 0.75 d s without much influence from buoyancy. When evaluating a jet at lower terminal velocities (e.g., 0.5 to 0.25 d s ) , consider buoyancy's effect on the distance the jet will travel. A cool air jet travels less far along a horizontal surface than an isothermal jet does. If an outlet is selected so that the horizontal jet does not have enough velocity to reach a vertical surface, the jet can separate from the horizontal surface and project down into the occupied zone, causing drafts and discomfort. Manufacturers' tables show the drop of a cool air jet so the designer can predict the resulting path. When evaluating heated air, the designer should consider the positive buoyancy of the discharge jet. A heatedjet projecting along a horizontal surface or in an upward vertical pattern travels farther than an isothermal jet. In downward vertical discharge, a heated jet travels a shorter distance than an isothermal jet. Combining selection by isovels and mapping with acoustical selection allows discharge jet location and intensity in a space to be predicted. Outlet selection should be evaluated at the space's typical operating points (i.e., maximum heating and cooling, and minimum heating and cooling). The following steps may be used:

Select outlet(s) that meet designNC, pressure drop, and flow rate requirements. Identify the supply jet location using cataloged throw data. Evaluate air jet mapping to ensure terminal velocities in the occupied zone do not exceed 0.25 d s . For overhead heating applications, At < 8.5 K (see Chapter 20 of the 2009 ASHRAE Handbook-Fundamentals), evaluate the diagram to ensure that jet velocities l .5 m from the floor are at least 0.75 d s .

Other design considerations include the following: In multiple-outlet applications, jets should not collide to cause a downward projection of air resulting in velocities greater than 0.25 d s in the occupied zone. For VAV applications, consider both minimum and maximum flow conditions.

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Selection by Comfort Criteria To,& Selection by isovels and mapping is effective at predicting the path of the discharge jet from an outlet and evaluating resultant occupant comfort. However, there is an established method to quantify occupant comfort during cooling conditions, based on space dimensions and isothermal catalog throw data. This method can be used to predict a space's resulting air diffusion performance index (ADPI). The comfort criteria T0,,,IL method was developed to predict occupant comfort during cooling conditions, using manufacturers' isothermal catalog throw data ( K usually for 0.25 d s terminal velocity) and the dimensions available for throw (L) on the plan view of a mechanical drawing. By using the ratio of TO,,,lL, the designer can predict the level of comfort with a single rating number: ADPI. ADPI can provide further information about the comfort level in a space for results obtained from the NC and mapping selection methods. Air Distribution Performance Index (ADPI). The air distribution performance index was developed as a way to quantify the comfort level for a space conditioned by amixed air system in cooling. ADPI uses the effective draft temperature collected at an array of points taken within the occupied zone to predict comfort. ADPI is the percentage of points in a space where the effective draft temperature is between -1.5 and +1"C and the air velocity is less than 0.35 d s . A high percentage of people have been found to be comfortable in cooling applications for office-type occupations where these conditions are met. High ADPI values generally correlate to high space thermal comfort levels with the maximum obtainable value of 100. Select outlets to provide a minimum ADPI value of 80. The effective draft temperature provides a quantifiable indication of comfort at a discrete point in a space by combining the physiological effects of air temperature and air motion on a human body. The effective draft temperature ted (the difference in temperature between any point in the occupied zone and the control condition) can be calculated using the following equation proposed by Rydberg and Norback (1 949) and modified by Straub (Straub and Chen 1957; Straub et al. 1956) in discussion of a paper by Koestel and Tuve (1 955):

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1. Identify the occupied zone for the space.

ted= (t, t,) -

-

7.73(VX 0.15) -

(2)

where ted = t, = t, = V, =

effective draft temperature, "C local airstream dry-bulb temperature, "C average (control) room dry-bulb temperature, "C local airstream centerline velocity, d s

T,,,IL Selection Method. This method uses the ratio of cataloged isothermal throw data at 0.25 d s to the characteristic length for a given device (Table 3). Each type of diffuser has different performance characteristics and therefore may provide a different ADPI value for the same

57.6

zyxwvutsrqp zyxwvutsrqp zyxwvutsr 201 1 ASHRAE Handbook-HVAC Applications (SI)

Table 3

Characteristic Room Length for Several Diffusers (Measured from Center of Air Outlet)

Diffuser Type

Characteristic Length L

High sidewall grille Circular ceiling diffuser Sill grille Ceiling slot diffuser Light troffer diffusers

Distance to wall perpendicular to jet Distance to closest wall or intersecting air jet Length of room in direction of jet flow Distance to wall or midplane between outlets Distance to midplane between outlets plus distance from ceiling to top of occupied zone Distance to wall or midplane between outlets

Perforated, louvered ceiling diffusers

Table 4 Air Diffusion Performance Index (ADPI) Selection Guide Terminal Device

Room TO,,/L for ForADPI Range Load, Maximum Maximum Greater of W/m2 ADPI ADPI Than Tn.25/L

250 190 125 60 Circular ceiling 250 diffusers 190 125 60 Sill grille, straight 250 vanes 190 125 60 250 Sill grille, spread vanes 190 125 60 250 Ceiling slot diffusers (for 190 125 T0.50/L) 60 190 Light troffer diffusers 125 60 Perforated, 35 to 160 louvered ceiling diffusers High sidewall grilles

1.8 1.8 1.6 1.5 0.8 0.8 0.8 0.8 1.7 1.7 1.3 0.9 0.7 0.7 0.7 0.7 0.3 0.3 0.3 0.3 2.5 1.o 1.o 2.0

68 72 78 85 76 83 88 93 61 72 86 95 94 94 94 94 85 88 91 92 86 92 95 96

~

70 70 80 70 80 80 90 60 70 80 90 90 80 ~

~

80 80 80 80 80 90 90 90 80

~

1.5 to 2.2 1.2 to 2.3 1.0 to 1.9 0.7 to 1.3 0.7 to 1.2 0.5 to 1.5 0.7 to 1.3 1.5 to 1.7 1.4 to 1.7 1.2 to 1.8 0.8 to 1.3 0.6 to 1.5 0.6 to 1.7 ~

~

0.3 to 0.7 0.3 to 0.8 0.3 to 1.1 0.3 to 1.5 10 pW/cm2

180" 2.44 m 2.1 m > 10 pW/cm2

360" 2.89 m 2.4 m > 10 pW/cm2

360" 2.89 m 2.4 m > 10 pW/cm2

*Appropriately designed W fixtures are available for all locations. Only the most commonly used have been included in the table.

mycobacteria, and is presumably effective against viruses, as well (First et al. 2007a, 2007b; Miller et al. 2002; Xu etal. 2003). Beyond UVC emission strength, effectiveness of upper-air UVGI is related to air mixing, relative humidity, and the inherent characteristics of the pathogenic organisms being addressed (Ka et al. 2004; KO et al. 2000; Rudnick 2007). Effectiveness improves greatly with well-mixed air (First et al. 2007a, 2007b; Miller et al. 2002; Riley et al. 1971a, 1971b). Ventilation systems should maximize air mixing to receive the greatest benefit from upper-room UVGI. Relative humidity should be less than 60%; levels over 80% RH may reduce effectiveness (Kujundzic et al. 2007; Xu et al. 2003). To maintain efficient output from low-pressure UVC lamps in the upper room, room temperature should be within recommended ASHRAE Standard 5 5 guidelines for occupant comfort. For example, in high-risk areas such as corridors of infectious disease wards, a minimum of 0.4 pW/cm2 at eye level is a good engineering guide (Coker et al. 2001). No long-term health effects of UVC exposure at levels found in the lower occupied part of rooms are known. The overall effectiveness of upper-air UVGI systems improves significantly when the air in the space is well mixed. Although convection air currents created by occupants and equipment can provide adequate air circulation in some settings, mechanical ventilation systems that maximize air mixing are preferable. If air mixing with mechanical ventilation is not possible, fans can be placed in the room to enhance mixing. Depending on the disinfection goals, upper-air systems should be operated in a fashion similar to corresponding in-duct systems. Those systems designed to reduce or eliminate the spread of airborne infectious diseases in buildings with continuous occupancy andor with immunocompromised populations, should be operated 24 h per day, 7 days per week. Upper-air systems designed for improved indoor air quality installed in more traditional commercial buildings can be operated intermittently, or powered on during hours of normal building occupancy and powered off when the facility is empty. This may provide acceptable indoor air quality during periods of building occupancy while saving energy and requiring less frequent lamp replacements. However, intermittent operation must be factored into the initial system design because of the effect that cycling UV lamps on and off may have on lamp performance and lamp life.

zyxwvutsrqpo zy

In-Duct Systems: Airstream Disinfection The principal design objective for an in-duct system is to distribute UV energy uniformly in all directions throughout the length of the duct or air-handling unit (AHU) to deliver the dose to air moving through the irradiated zone with the minimum energy system power. Enhancing the overall reflectivity of the inside of the air handler can improve UVGI system performance by reflecting UVC energy back into the irradiated zone, thus increasing the effective UV dose. Using materials such as aluminum or other highly reflective materials can increase reflectivity. Properly designed in-duct UV air disinfection systems also maintain the cleanliness of cooling coil surfaces and condensate pans because of the high power required for this ap-

Fig. 10

Upper-Room UVGI Fixtures with 180° Emission Profile Covering Corridors

Onginally published in Public Health Reports (Bnckner et al. 2003)

Fig. 11 Example Upper-Air UVGI Layout for Meeting Room plication. Systems designed specifically for coil and condensate pan applications are likely not adequate for proper air disinfection. Design dose is a function of the design-basis microbe (i.e., the targeted microorganism with the smallest k-value) and the desired level of disinfection. Generally, a single-pass inactivation efficiency is specified, analogous to the specification of a particulate filter MERV rating. In some cases, the design disinfection level may be a true performance specification based on the exposure in an occupied space. Determining this value requires analysis of the entire system that is used to determine the single-pass performance based. Which approach is selected depends on the type of application. Laboratory/ hospital installations are more likely to have specific, identified targets than, for example, school or office installations. The required

CHAPTER 61

CODES AND STANDARDS

T

zyx

HE Codes and Standards listed here represent practices, methods, or standards published by the organizations indicated. They are useful guides for the practicing engineer in determining test methods, ratings, performance requirements, and limits of HVAC&R equipment. Copies of the standards can be obtained from most of the organizations listed in the Publisher column, from Global Engineering Documents at global.ihs.com, or from CSSINFO at cssinfo.com. Addresses of the organizations are given at the end of the chapter. A comprehensive database with over 250,000 industry, government, and international standards is at www.nssn.org.

Selected Codes and Standards Published by Various Societies and Associations Subject

Title

Air Commercial Application, Systems, and Equipment, 1st ed. conditioners Residential Equipment Selection, 2nd ed. Methods of Testing Air Terminal Units Non-Ducted Air Conditioners and Heat Pumps-Testing and Rating for Performance Ducted Air-Conditioners and Air-to-Air Heat Pumps-Testing and Rating for Performance Guidelines for Roof Mounted Outdoor Air-Conditioner Installations Heating and Cooling Equipment (2005) Central Performance Standard for Single Package Central Air-Conditioners and Heat Pumps Performance Standard for Rating Large and Single Packaged Air Conditioners and Heat Pumps Performance Standard for Split-System and Single-Package Central Air Conditioners and Heat Pumps Heating and Cooling Equipment (2005) Gas-Fired Gas-Fired, Heat Activated Air Conditioning and Heat Pump Appliances

Packaged Terminal Room

Gas-Fired Work Activated Air Conditioning and Heat Pump Appliances (Internal Combustion) Performance Testing and Rating of Gas-Fired Air Conditioning and Heat Pump Appliances Packaged Terminal Air-Conditioners and Heat Pumps

Room Air Conditioners Method of Testing for Rating Room Air Conditioners and Packaged Terminal Air Conditioners Method of Testing for Rating Room Air Conditioner and Packaged Terminal Air Conditioner Heating Capacity Method of Testing for Rating Fan-Coil Conditioners Performance Standard for Room Air Conditioners Room Air Conditioners Room Air Conditioners (2007) Unitary Unitary Air-conditioning and Air-Source Heat Pump Equipment Sound Rating of Outdoor Unitary Equipment Application of Sound Rating Levels of Outdoor Unitary Equipment Commercial and Industrial Unitary Air-conditioning and Heat Pump Equipment Methods of Testing for Rating Electrically Driven Unitary Air-conditioning and Heat Pump Equipment Methods of Testing for Rating Heat-Operated Unitary Air-conditioning and Heat Pump Equipment Methods of Testing for Rating Seasonal Efficiency of Unitary Air Conditioners and Heat Pumps Method of Testing for Rating Computer and Data Processing Room Unitary Air Conditioners Method of Rating Unitary Spot Air Conditioners Ships Specification for Mechanically Refiigerated Shipboard Air Conditioner Accessories Flashing and Stand Combination for Air Conditionine Units (Unit Curb) Air Commercial Application, Systems, and Equipment, 1st ed. Conditioning Heat Pump Systems: Principles and Applications, 2nd ed. Residential Load Calculation, 8th ed. Commercial Load Calculation, 4th ed. Comfort, Air Quality, and Efficiency by Design Environmental Systems Technology, 2nd ed. (1999)

61.1

zyx

Publisher

Reference

ACCA ACCA ASHRAE IS0 IS0 SMACNA UL/CSA CSA CSA

ACCA Manual CS ANSI/ACCA Manual S A N W A S H M E 130-2008 IS0 5151:1994 I S 0 13253:1995 SMACNA 1998 ANSILJL 1995/C22.2 No. 236-05 CAN/CSA-C656-05 CAN/CSA-C746-06

CSA

CAN/CSA-C656-05

UL/CSA CSA

AHRIKSA

ANSVUL 1995/C22.2 No. 236-05 ANSI 2 2 1.40.1-1996 (R2002)/CGA 2.9 1-M96 ANSI 221.40.2-1996 (R2002)/CGA 2.92-M96 ANSI 221.40.4-1996 (R2002)/CGA 2.94-M96 AHRI 310/380-04/CSA C744-04

AHAM ASHRAE

ANSI/AHAM RAC-1-2008 ANWASHME 16-1983 (RA09)

ASHRAE

ANWASHME 58-1986 (RA09)

ASHRAE CSA CSA UL AHRI AHRI AHRI AHRI ASHRAE

ANWASHME 79-2002 (RA06) CAN/CSA-C368.1-M90 (R2007) C22.2 No. 117-1970 (R2007) ANSILJL 484 ANSI/AHRI 210/240-2006 AHRI 270-95 AHRI 275-97 AHRI 340/360-2007 ANWASHME 37-2009

ASHRAE

ANWASHME 40-2002 (RA06)

ASHRAE

ANWASHME 116-2010

ASHRAE

ANWASHME 127-2007

ASHRAE ASTM IAPMO

ANSVASHRAE 128-2001 ASTM F1433-97 (2004) IAPMO PS 120-2004 ACCA Manual CS ACCA Manual H ANSI/ACCA Manual J ACCA Manual N ACCA Manual RS NEBB

CSA CSA

ACCA ACCA ACCA ACCA ACCA NEBB

zyxw zyxw

201 1 ASHRAE Handbook-HVAC Applications (SI)

61.2

Selected Codes and Standards Published by Various Societies and Associations (Continued) Subject

Title

Publisher

Installation of Air Conditioning and Ventilating Systems Standard of Purity for Use in Mobile Air-conditioning Systems HVAC Systems-Applications, 1st ed. HVAC Systems-Duct Design, 4th ed. Heating and Cooling Equipment (2005) Air Conditioning of Aircraft Cargo Aircraft Fuel Weight Penalty Due to Air Conditioning Air Conditioning Systems for Subsonic Airplanes Environmental Control Systems Terminology Testing of Airplane Installed Environmental Control Systems (ECS) Guide for Qualification Testing of Aircraft Air Valves Control of Excess Humidity in Avionics Cooling Engine Bleed Air Systems for Aircraft Aircraft Ground Air Conditioning Service Connection Air Cycle Air Conditioning Systems for Militaly Air Vehicles Refrigerant 12 Automotive Air-conditioning Hose Design Guidelines for Air Conditioning Systems for Off-Road Operator Enclosures Test Method for Measuring Power Consumption of Air Conditioning and Brake Compressors for Trucks and Buses Information Relating to Duty Cycles and Average Power Requirements of Truck and Bus Engine Accessories Rating Air-Conditioner Evaporator Air Delively and Cooling Capacities Recovely and Recycle Equipment for Mobile Automotive Air-conditioning Systems R134a Refrigerant Automotive Air-conditioning Hose Service Hose for Automotive Air Conditioning Mechanical Refrigeration and Air-conditioning Installations Aboard Ship Practice for Mechanical Symbols, Shipboard Heating, Ventilation, and Air Conditioning (HVAC) Laboratoly Methods of Testing Air Curtains for Aerodynamic Performance Air Terminals Standard Methods for Laboratoly Airflow Measurement Method of Testing the Performance of Air Outlets and Inlets Rating the Performance of Residential Mechanical Ventilating Equipment Air Curtains for Entrancewavs in Food and Food Service Establishments

NFPA SAE SMACNA SMACNA UL/CSA SAE SAE SAE SAE SAE SAE SAE SAE SAE SAE SAE SAE SAE

Air Diffusion

Air Filtevs

I

Aircraft

Automotive

Ships

I

_

Reference

NFPA 90A-02 SAE 51991-1999 SMACNA 1987 SMACNA 2006 ANSVUL 1995/C22.2 No. 236-05 SAE AIR806B-1997 SAE AIR1168/8-1989 SAE ARP85E-1991 SAE ARP147E-2001 SAE ARP217D-1999 SAE ARP986C-1997 SAE ARP987A-1997 SAE ARP1796-2007 SAE AS4262A-1997 SAE AS4073-2000 SAE 55 1-2004 SAE 5169-1985 SAE 51340-2003

SAE

SAE 51343-2000

SAE SAE SAE SAE ASHRAE ASTM

SAE 51487-2004 SAE 51990-1999 SAE 52064-2005 SAE 52196-1997 ANWASHRAE 26-2010 ASTM F856-97 (2004)

AMCA AHRI ASHRAE ASHRAE CSA NSF

AMCA 220-05 AHRI 880-98 ANWASHME 41.2-1987 (RA92) ANSVASHRAE 70-2006 CAN/CSA C260-M90 (R2007) NSF/ANSI 37-2007

Air Distribution Basics for Residential and Small Commercial Buildings, 1st ed. Method of Testing the Performance of Air Outlets and Inlets Method of Testing for Room Air Diffusion

ACCA ASHRAE ASHRAE

ACCA Manual T ANSVASHRAE 70-2006 ANWASHME 113-2009

Comfort, Air Quality, and Efficiency by Design Industrial Ventilation: A Manual of Recommended Practice, 26th ed. (2007) Air Cleaners Residential Air Filter Equipment Commercial and Industrial Air Filter Equipment Agricultural Cabs-Engineering Control of Environmental Air Quality-Part 1: Definitions, Test Methods, and Safety Procedures Part 2: Pesticide Vapor Filters-Test Procedure and Performance Criteria Method of Testing General Ventilation Air-Cleaning Devices for Removal Efficiency by Particle Size Code on Nuclear Air and Gas Treatment Nuclear Power Plant Air-Cleaning Units and Components Testing of Nuclear Air-Treatment Systems Specification for Filter Units, Air Conditioning: Viscous-Impingement and Dry Types. Replaceable Test Method for Air Cleaning Performance of a High-Efficiency Particulate Air Filter System Specification for Filters Used in Air or Nitrogen Systems Method for Sodium Flame Test for Air Filters Particulate Air Filters for General Ventilation: Determination of Filtration Performance Electrostatic Air Cleaners (2000) High-Efficiency, Particulate, Air Filter Units (1996) Air Filter Units (2004) Exhaust Hoods for Commercial Cooking Equipment (1995) Grease Filters for Exhaust Ducts (2000)

ACCA ACGIH AHAM AHRI AHRI ASABE

ACCA Manual RS ACGIH ANSI/AHAM AC- 1-2006 AHRI 680-2004 AHRI 850-2004 ANSI/ASAE S525-1.2-2003

ASABE ASHRAE

ANSI/ASAE S525-2-2003 ANWASHRAE 52.2-2007

ASME ASME ASME ASTM

ASME AG-1-2003 ASME N509-2002 ASME N5 10-2007 ASTM F1040-87 (2007)

ASTM

ASTM F1471-93 (2001)

ASTM BSI BSI

ASTM F1791-00 (2006) BS 3928:1969 BS EN 779:2002

UL UL UL UL UL

ANSILJL 867 ANSILJL 586 ANSI/UL 900 UL 710 UL 1046

zyxwvutsrqpo

Air Cuvtains

zyxw zyxwvutsrqponm 61.3

Codes and Standards

Selected Codes and Standards Published by Various Societies and Associations (Continued)

Subject Air-Handling Units

Title

Commercial Application, Systems, and Equipment, 1st ed. Central Station Air-Handling Units Non-Recirculating Direct Gas-Fired Industrial Air Heaters Air Leakage Residential Duct Diagnostics and Repair (2003) Air Leakage Performance for Detached Single-Family Residential Buildings Method of Determining Air Change Rates in Detached Dwellings Test Method for Determining Air Change in a Single Zone by Means of a Tracer Gas Dilution Test Method for Determining Air Leakage Rate by Fan Pressurization Test Method for Field Measurement of Air Leakage Through Installed Exterior Window and Doors Practices for Air Leakage Site Detection in Building Envelopes and Air Retarder Systems Test Method for Determining the Rate of Air Leakage Through Exterior Windows, Curtain Walls, and Doors Under Specified Pressure and Temperature Differences Across the Specimen Test Methods for Determining Airtightness of Buildings Using an Orifice Blower Door Practice for Determining the Effects of Temperature Cycling on Fenestration Products Test Method for Determining Air Flow Through the Face and Sides of Exterior Windows, Curtain Walls, and Doors Under Specified Pressure Differences Across the Specimen Test Method for Determining Air Leakage of Air Bamer Assemblies Boilers Packaged Boiler Engineering Manual (1999) Selected Codes and Standards of the Boiler Industry (2001) Operation and Maintenance Safety Manual (1995) Fluidized Bed Combustion Guidelines (1995) Guide to Clean and Efficient Operation of Coal Stoker-Fired Boilers (2002) Guideline for Performance Evaluation of Heat Recovery Steam Generating Equipment (1995) Guidelines for Industrial Boiler Performance Improvement (1999) Measurement of Sound from Steam Generators (1995) Guideline for Gas and Oil Emission Factors for Industrial, Commercial, and Institutional Boilers (1997) Combustion Control Guidelines for Single Burner Firetube and Watertube Industrial/ Commercial/Institutional Boilers (1999) Combustion Control Guidelines for Multiple-Burner Boilers (2001) Boiler Water Quality Requirements and Associated Steam Quality for Industrial/ Commercial and Institutional Boilers (2005) Commercial Application, Systems, and Equipment, 1st ed. Method of Testing for Annual Fuel Utilization Efficiency of Residential Central Furnaces and Boilers Boiler and Pressure Vessel Code-Section I: Power Boilers; Section I V Heating Boilers Fired Steam Generators Boiler, Pressure Vessel, and Pressure Piping Code Testing Standard for Commercial Boilers, 2nd ed. (2007) Rating Procedure for Heating Boilers, 6th ed. (2005) Prevention of Furnace Explosions/Implosions in Multiple Burner Boilers Heating, Water Supply, and Power Boilers-Electric (2004) Boiler and Combustion Systems Hazards Code Gas-Fired Low-Pressure Steam and Hot Water Boilers Gas or Oil Controls and Safety Devices for Automatically Fired Boilers Industrial and Commercial Gas-Fired Package Boilers Oil-Burning Equipment: Steam and Hot-Water Boilers Single Burner Boiler Operations Prevention of Furnace Explosions/Implosions in Multiple Burner Boilers Oil-Fired Boiler Assemblies (1995) Commercial-Industrial Gas Heating Equipment (2006) Standards and Typical Specifications for Tray Type Deaerators, 7th ed. (2003) Terminology Ultimate Boiler Industry Lexicon: Handbook of Power Utility and Boiler Terms and Phrases, 6th ed. (2001) Building Codes ASTM Standards Used in Building Codes Practice for Conducting Visual Assessments for Lead Hazards in Buildings Standard Practice for Periodic Inspection of Building Facades for Unsafe Conditions Structural Welding Code-Steel BOCA National Building Code, 14th ed. (1999) Uniform Building Code, vol. 1, 2, and 3 (1997)

Publisher

Reference

ACCA AHRI CSA ACCA ASHRAE ASHRAE ASTM

ACCA Manual CS ANSI/AHRI 430-99 ANSI Z83.4-2003/CSA 3.7-2003 ACCA ANWASHRAE 119-1988 (RA04) ANWASHRAE 136-1993 (RA06) ASTM E741-00 (2006)

ASTM ASTM

ASTM E779-03 ASTM E783-02

ASTM ASTM

ASTM E l 186-03 ASTM E1424-91 (2000)

ASTM ASTM ASTM

ASTM E1827-96 (2007) ASTM E2264-05 ASTM E2319-04

ASTM

ASTM E2357-05

ABMA ABMA ABMA ABMA ABMA ABMA

ABMA 100 ABMA 103 ABMA 106 ABMA 200 ABMA 203 ABMA 300

ABMA ABMA ABMA

ABMA 302 ABMA 304 ABMA 305

ABMA

ABMA 307

ABMA ABMA

ABMA 308 ABMA 402

ACCA ASHRAE

ACCA Manual CS ANWASHRAE 103-2007

ASME ASME CSA HYDI HYDI NFPA UL NFPA CSA ASME CSA CSA NFPA NFPA UL UL HE1 ABMA

BPVC-2007 ASME PTC 4-1998 CSA B51-2003 (R2007) HYDI BTS-2007 IBR ANSI NFPA 8502-99 ANSILJL 834 NFPA 85-07 ANSI Z21.13-2004/CSA 4.9-2004 ASME CSD-1-2006 CAN 1-3.1-77 (R2006) B 140.7-2005 ANSINFPA 8501-01 ANSINFPA 8502-99 UL 726 UL 795 HE1 2954 ABMA 101

ASTM ASTM ASTM AWS BOCA ICBO

ASTM ASTM E2255-04 ASTM E2270-05 AWS Dl.lM/Dl. 1:2008 BNBC UBC V1, V2, V3

zyxw zyxw

201 1 ASHRAE Handbook-HVAC Applications (SI)

61.4

Selected Codes and Standards Published by Various Societies and Associations (Continued) Subject

Title

Publisher

International Building Code (2009) ~, International Code Council Performance Code (2009) International Existing Building Code (2009) International Energy Conservation Code (2009) International Property Maintenance Code (2009) International Residential Code (2009) Directory of Building Codes and Regulations, State and City Volumes (annual) Building Construction and Safety Code National Building Code of Canada (2005) Standard Building Code (1999) Safety Code for Elevators and Escalators Natural Gas and Propane Installation Code Propane Storage and Handling Code Uniform Mechanical Code (2006) International Mechanical Code (2009) International Fuel Gas Code (2009) Standard Gas Code (1999) Guidelines for Burner Adjustments of Commercial Oil-Fired Boilers (1996) Domestic Gas Conversion Burners

ICC ICC ICC ICC ICC ICC NCSBCS NFPA NRCC SBCCI ASME CSA CSA IAPMO ICC ICC SBCCI ABMA CSA

Installation of Domestic Gas Conversion Burners Installation Code for Oil Burning Equipment Oil-Burning Equipment: General Requirements Vapourizing-Type Oil Burners Oil Burners: Atomizing-Type Pressure Atomizing Oil Burner Nozzles Oil Burners (2003) Waste Oil-Burning Air-Heating Appliances (1995) Commercial-Industrial Gas Heating Equipment (2006) Commercialhdustnal Gas andor Oil-Burning Assemblies with Emission Reduction Eauioment (2006) Commercial Application, Systems, and Equipment, 1st ed. Absorption Water Chilling and Water Heating Packages Water Chilling Packages Using the Vapor Compression Cycle Method of Testing Liquid-Chilling Packages Performance Standard for Rating Packaged Water Chillers Specification for Clay Flue Liners Specification for Industrial Chimney Lining Brick Practice for Installing Clay Flue Lining Guide for Design and Construction of Brick Liners for Industrial Chimneys Guide for Design, Fabrication, and Erection of Fiberglass Reinforced Plastic Chimney Liners with Coal-Fired Units Chimneys, Fireplaces, Vents, and Solid Fuel-Burning Appliances Medium Heat Appliance Factory-Built Chimneys (200 1) Factory-Built Chimneys for Residential Type and Building Heating Appliance (200 1) Practice for Cleaning and Maintaining Controlled Areas and Clean Rooms Practice for Design and Construction of Aerospace Cleanrooms and Contamination Controlled Areas Practice for Tests of Cleanroom Materials Practice for Aerospace Cleanrooms and Associated Controlled EnvironmentsCleanroom Operations Test Method for Sizing and Counting Airborne Particulate Contamination in Clean Rooms and Other Dust-Controlled Areas Designed for Electronic and Similar Applications Practice for Continuous Sizing and Counting of Airborne Particles in Dust-Controlled Areas and Clean Rooms Using Instruments Capable of Detecting Single SubMicrometre and Larger Particles Procedural Standards for Certified Testing of Cleanrooms. 2nd ed. (1996) Forced-Circulation Air-Cooling and Air-Heating Coils Methods of Testing Forced Circulation Air Cooling and Air Heating Coils Threshold Limit Values for Physical Agents (updated annually) Good HVAC Practices for Residential and Commercial Buildings (2003) Comfort, Air Quality, and Efficiency by Design (1997) Thermal Environmental Conditions for Human Occupancy

CSA CSA CSA CSA CSA CSA UL UL UL UL

IBC ICC PC IEBC IECC IPMC IRC NCSBCS (electronic only) ANSINFPA 5000-2006 NRCC SBC ASME A17.1-2004 CAN/CSA-B149.1-05 CAN/CSA-B149.2-05 IAPMO IMC IFGC SBC ABMA 303 ANSI 221.17-1998 (R2004)/ CSA 2.7-M98 ANSI 221.8-1994 (R2002) CAN/CSA-B139-06 CAN/CSA-B140.0-03 B 140.1- 1966 (R2006) CAN/CSA-B140.2.1-M90 (R2005) B140.2.2-1971 (R2006) ANSI/UL 296 ANSILJL 296A UL 795 UL 2096

ACCA AHRI AHRI ASHRAE CSA ASTM ASTM ASTM ASTM ASTM

ACCA Manual CS AHRI 560-2000 AHRI 550/590-2003 A N W A S H M E 30-1995 CAN/CSA C743-02 (R2007) ASTM C3 15-07 ASTM C980-88 (2007) ASTM C1283-07a ASTM C1298-95 (2007) ASTM D5364-93 (2002)

NFPA UL UL ASTM ASTM

ANSINFPA 2 11-06 ANSI/UL 959 ANSVUL 103 ASTM E2042-04 ASTM E2217-02 (2007)

ASTM ASTM

ASTM E2312-04 ASTM E2352-04

ASTM

ASTM F25-04

ASTM

ASTM F50-07

NEBB AHRI ASHRAE ACGIH ACCA ACCA ASHRAE

NEBB AHRI 410-2001 ANSVASHRAE 33-2000 ACGIH ACCA ACCA Manual RS ANWASHRAE 55-2010

I

Mechanical

Burners

Chillers

Chimneys

Cleanrooms

Coils Comfort Conditions

Reference

zyxwvutsrqpo

zyxw zyxw 61.5

Codes and Standards

Selected Codes and Standards Published by Various Societies and Associations (Continued) Subject

Compressors

Refrigerant

Computers

Condensers

Condensing Units

containers

Controls

Title

Publisher

Classification for Serviceability of an Office Facility for Thermal Environment and Indoor Air Conditions Hot Environments-Estimation of the Heat Stress on Working Man, Based on the WBGT Index (Wet Bulb Globe Temperature) Ergonomics of the Thermal Environment-Analytical Determination and Interpretation of Thermal Comfort Using Calculation of the PMV and PPD Indices and Local Thermal Comfort Criteria Ergonomics of the Thermal Environment-Determination of Metabolic Rate Ergonomics of the Thermal Environment-Estimation of the Thermal Insulation and Water Vauour Resistance of a Clothing Ensemble

ASTM

Reference

ASTM E2320-04

IS0

I S 0 7243:1989

IS0

I S 0 7730:2005

IS0 IS0

I S 0 8996:2004 I S 0 9920:2007

Displacement Compressors, Vacuum Pumps and Blowers Performance Test Code on Compressors and Exhausters Compressed Air and Gas Handbook, 6th ed. (2003) Positive Displacement Condensing Units Positive Displacement Refrigerant Compressors and Compressor Units Safety Standard for Refrigeration Systems Methods of Testing for Rating Positive Displacement Refrigerant Compressors and Condensing Units Testing of Refrigerant Compressors Refrigerant Compressors-Presentation of Performance Data Hermetic Refrigerant Motor-Compressors (1996)

ASME ASME CAGI AHRI AHRI ASHRAE ASHRAE

ASME PTC 9-1970 (RA97) ASME PTC 10-1997 (RA03) CAGI AHRI 520-2004 AHRI 540-2004 ANWASHRAE 15-2010 ANWASHRAE 23.1-2010

IS0 IS0 UL/CSA

I S 0 917:1989 I S 0 9309:1989 UL 9WC22.2 No.140.2-96 (R2001)

Method of Testing for Rating Computer and Data Processing Room Unitary Air Conditioners Method of Test for the Evaluation of Building Energy Analysis Computer Programs Protection of Electronic Comuuter/Data Processing Eauiument Commercial Application, Systems, and Equipment, 1st ed. Water-cooled Refrigerant Condensers, Remote Type Remote Mechanical-Draft Air-Cooled Refrigerant Condensers Remote Mechanical Draft Evaporative Refrigerant Condensers Safety Standard for Refrigeration Systems Method of Testing for Rating Remote Mechanical-Draft Air-Cooled Refrigerant Condensers Methods of Testing for Rating Water-cooled Refrigerant Condensers Methods of Laboratory Testing Remote Mechanical-Draft Evaporative Refrigerant Condensers Steam Surface Condensers Standards for Steam Surface Condensers, 10th ed. Standards for Direct Contact Barometric and Low Level Condensers, 7th ed. (1995) Refrigerant-Containing Comuonents and Accessories. Nonelectrical (200 1) Commercial Application, Systems, and Equipment, 1st ed. Commercial and Industrial Unitary Air-conditioning Condensing Units Methods of Testing for Rating Positive Displacement Refrigerant Compressors and Condensing Units Heating and Cooling Eauiument (2005) Series 1 Freight Containers-Classifications, Dimensions, and Ratings Series 1 Freight Containers-Specifications and Testing; Part 2: Thermal Containers Animal Environment in Cargo Compartments Temperature Control Systems (2002) BACneta-A Data Communication Protocol for Building Automation and Control Networks Method of Test for Conformance to BACneta Temperature-Indicating and Regulating Equipment Performance Requirements for Electric Heating Line-Voltage Wall Thermostats Performance Requirements for Thermostats Used with Individual Room Electric Space Heating Devices Solid-state Controls for Appliances (2003) Limit Controls (1994) Primary Safety Controls for Gas- and Oil-Fired Appliances (1994) Temperature-Indicating and -Regulating Equipment (2007) Tests for Safety-Related Controls Employing Solid-state Devices (2004) Control Centers for Changing Message Type Electric Signals (2003) Automatic Electrical Controls for Household and Similar Use; Part 1: General Requirements (2002) Process Control Eauiument (2002)

ASHRAE

ANWASHRAE 127-2007

ASHRAE NFPA ACCA AHRI AHRI AHRI ASHRAE ASHRAE

ANWASHRAE 140-2007 NFPA 75-03 ACCA Manual CS AHRI 450-2007 AHRI 460-2005 AHRI 490-2003 ANWASHRAE 15-2010 ANWASHRAE 20-1997 (RA06)

ASHRAE ASHRAE

A N W A S H M E 22-2007 ANWASHRAE 64-2005

ASME HE1 HE1 UL ACCA AHRI ASHRAE

ASME PTC 12.2-1998 HE1 2629 HE1 2634 ANSILJL 207 ACCA Manual CS AHRI 365-2002 ANWASHRAE 23.1-2010

UL/CSA IS0 IS0 SAE AABC ASHRAE

ANSILJL 1995/C22.2 No. 236-95 I S 0 668:1995 I S 0 1496-2:1996 SAE AIR1600A-1997 National Standards, Ch. 12 ANWASHRAE 135-2008

ASHRAE CSA CSA CSA

ANWASHRAE 135.1-2009 C22.2 No. 24-93 (R2003) C273.4-M1978 (R2003) CAN/CSA (328-06

UL UL UL UL UL UL UL

UL 244A ANSI/UL 353 ANSILJL 372 UL 873 UL 991 UL 1433 UL 60730-1A

UL

UL 6101OC-1

zyxw zyxw zyx

201 1 ASHRAE Handbook-HVAC Applications (SI)

61.6

Selected Codes and Standards Published by Various Societies and Associations (Continued) Subject Commercial and Industrial

Residential

Title

Publisher

Guidelines for Boiler Control Systems (Gas/Oil Fired Boilers) (1998), Guideline for the Integration of Boilers and Automated Control Systems in Heating Applications (1998) Industrial Control and Systems: General Requirements Preventive Maintenance of Industrial Control and Systems Equipment Industrial Control and Systems, Controllers, Contactors, and Overload Relays Rated Not More than 2000 Volts AC or 750 Volts DC Industrial Control and Systems: Instructions for the Handling, Installation, Operation and Maintenance of Motor Control Centers Rated Not More than 600 Volts Industrial Control Equipment (1999) Manually Operated Gas Valves for Appliances, Appliance Connector Valves and Hose End Valves Gas Appliance Pressure Regulators Automatic Gas Ignition Systems and Components I

_

Gas Appliance Thermostats Manually-Operated Piezo-Electric Spark Gas Ignition Systems and Components Manually Operated Electric Gas Ignition Systems and Components Residential Controls-Electrical Wall-Mounted Room Thermostats Residential Controls-Surface Type Controls for Electric Storage Water Heaters Residential Controls-Temperature Limit Controls for Electric Baseboard Heaters Hot-Water Immersion Controls Line-Voltage Integrally Mounted Thermostats for Electric Heaters Residential Controls-Class 2 Transformers Safety Guidelines for the Application,Installation,and Maintenanceof Solid State Controls Electncal Quick-Connect Terminals (2003) Coolers Refngeration Equipment . . Unit Coolers for Refrigeration Refrigeration Unit Coolers (2004) Air Methods of Testing Forced Convection and Natural ConvectionAir Coolers for Refiigeration Drinking Methods of Testing for Rating Drinking-Water Coolers with Self-contained Water Mechanical Refrigeration Drinking-Water Coolers (1993) Drinking Water System Components-Health Effects Evaporative Method of Testing Direct Evaporative Air Coolers Method of Test for Rating Indirect Evaporative Coolers Food and Terminology for Milking Machines, Milk Cooling, and Bulk Milk Handling Equipment Beverage Methods of Testing for Rating Vending Machines for Bottled, Canned, and Other Sealed Beverages Methods of Testing for Rating Pre-Mix and Post-Mix Beverage Dispensing Equipment Manual Food and Beverage Dispensing Equipment Commercial Bulk Milk Dispensing Equipment Refrigerated Vending Machines (1995) Liquid Refrigerant-Cooled Liquid Coolers, Remote Type Methods of Testing for Rating Liquid Coolers Liauid Cooline Svstems Cooling Towers Cooling Tower Testing (2002) Commercial Application, Systems, and Equipment, 1st ed. Bioaerosols: Assessment and Control (1999) Atmospheric Water Cooling Equipment Water-cooling Towers Acceptance Test Code for Water Cooling Towers Code for Measurement of Sound from Water Cooling Towers (2005) Acceptance Test Code for Spray Cooling Systems (1985) Nomenclature for Industrial Water Cooling Towers (1997) Recommended Practice for Airflow Testing of Cooling Towers (1994) Fiberglass-Reinforced Plastic Panels (2002) Certification of Water Cooling Tower Thermal Performance (R2004) Crop Drying Density, Specific Gravity, and Mass-Moisture Relationships of Grain for Storage Dielectnc Properties of Grain and Seed Thermal Properties of Grain and Grain Products Moisture Relationships of Plant-Based Agncultural Products Construction and Rating of Equipment for Drying Farm Crops

ABMA ABMA

Reference

ABMA301 ABMA 306

NEMA NEMA NEMA

NEMA ICS 1-2000 (R2005) NEMA ICS 1.3-1986 (R2001) NEMA ICS 2-2000 (R2004)

NEMA

NEMA ICS 2.3-1995 (R2002)

UL CSA

NEMA NEMA NEMA NEMA NEMA NEMA NEMA UL CSA AHRI UL ASHRAE ASHRAE

ANSILJL 508 ANSI 221.15-1997 (R03)/CGA 9.11997 ANSI 221.18-2007/CSA 6.3-2007 ANSI 221.20-2007/C22.2 No. 1992007 ANSI 221.23-2000 (R2005) ANSI 221.77-2005/CGA 6.23-2005 ANSI 221.92-2005/CSA 6.29-2005 (R2007) NEMA DC 3-2003 NEMA DC 5-2002 NEMA DC 10-1983 (R2003) NEMA DC 12-1985 (R2002)) NEMA DC 13-1979 (R2002) NEMA DC 20-1992 (R2003) NEMA ICS 1.1-1984 (R2003) ANSI/UL 3 10 CAN/CSA-C22.2No. 120-M91(R2004) AHRI 420-2000 ANSILJL 412 A N W A S H M E 25-2001 (RA06) ANWASHRAE 18-2008

UL NSF ASHRAE ASHRAE ASABE ASHRAE

ANSILJL 399 NSF/ANSI 61-2007a ANWASHRAE 133-2008 AN SI/ASHRAE 143-2007 ASAE S300.3-2003 ANWASHRAE 32.1-20 10

ASHRAE NSF NSF UL AHRI ASHRAE SAE AABC ACCA ACGIH ASME NFPA CTI CTI CTI CTI CTI CTI CTI ASABE ASABE ASABE ASABE ASABE

A N W A S H M E 32.2-2003 (RA07) NSF/ANSI 18-2005 NSF/ANSI 20-2007 ANSI/UL 541 AHRI 480-2007 ANWASHRAE 24-2009 SAE AIR1811A-1997 National Standards, Ch 13 ACCA Manual CS ACGIH ASME PTC 23-2003 NFPA 214-05 CTI ATC-105 (00) CTI ATC-128 (05) CTI ATC-133 (85) CTI NCL-109 (97) CTI PFM-143 (94) CTI STD-131 (02) CTI STD-201(04) ANSI/ASAE D241.4-2003 ASAE D293.2-1989 (R2005) ASAE D243.4-2003 ASAE D245.5-19995 (R2001) ASAE S248.3-1976 (R2005)

CSA CSA CSA CSA CSA

zyxw zyxw 61.7

Codes and Standards

Selected Codes and Standards Published by Various Societies and Associations (Continued) Subject

Title

Cubes, Pellets, and Crumbles-Definitions and Methods for Determining Density, Durability, and Moisture Content Resistance to Airflow of Grains, Seeds, Other Agricultural Products, and Perforated Metal Sheets Shelled Corn Storage Time for 0.5% Dry Matter Loss Moisture Measurement-Unground Grain and Seeds Moisture Measurement-Meat and Meat Products Moisture Measurement-Forages Moisture Measurement-Peanuts Energy Efficiency Test Procedure for Tobacco Curing Structures Thin-Layer Drying of Agricultural Crops Moisture Measurement-Tobacco Thin-Layer Drying of Agricultural Crops Temperature Sensor Locations for Seed-Cotton Drying Systems Dehumidifiers Commercial Application, Systems, and Equipment, 1st ed. Bioaerosols: Assessment and Control (1999) Dehumidifiers Method of Testing for Rating Desiccant Dehumidifiers Utilizing Heat for the Regeneration Process Moisture Separator Reheaters Dehumidifiers Performance of Dehumidifiers Dehumidifiers (2004) Desiccants Method of Testing Desiccants for Refrigerant Drying Documentation Preoaration of Ooeratine and Maintenance Documentation for Building Svstems Driers Liquid-Line Driers Method of Testing Liquid Line Refrigerant Driers Refrigerant-Containing Components and Accessories, Nonelectrical (200 1) Ducts and Hose, Air Duct, Flexible Nonmetallic, Aircraft Fittings Ducted Electric Heat Guide for Air Handling Systems, 2nd ed. Factory-Made Air Ducts and Air Connectors (2005) Construction Industrial Ventilation: A Manual of Recommended Practice, 26th ed. (2007) Preferred Metric Sizes for Flat, Round, Square, Rectangular, and Hexagonal Metal Products Sheet Metal Welding Code Fibrous Glass Duct Construction Standards, 5th ed. Residential Fibrous Glass Duct Construction Standards, 3rd ed. Thermoplastic Duct (PVC) Construction Manual, 2nd ed. Accepted Industry Practices for Sheet Metal Lagging, 1st ed. Fibrous Glass Duct Construction Standards, 7th ed. HVAC Duct Construction Standards, Metal and Flexible, 3rd ed. Rectangular Industrial Duct Construction Standards, 2nd ed. Industrial Round Industrial Duct Construction Standards, 2nd ed. Rectangular Industrial Duct Construction Standards, 2nd ed. Installation Flexible Duct Performance and Installation Standards, 4th ed. Installation of Air Conditioning and Ventilating Systems Installation of Warm Air Heating and Air-conditioning Systems Material Specification for General Requirements for Flat-Rolled Stainless and Heat-Resisting SpecificaSteel Plate, Sheet and Strip tions Specification for General Requirements for Steel, Sheet, Carbon, and High-Strength, Low-Alloy, Hot-Rolled and Cold-Rolled Specification for Steel Sheet, Zinc-Coated (Galvanized) or Zinc-Iron Alloy-Coated (Galvannealed) by the Hot-Dipped Process Specification for General Requirements for Steel Sheet, Metallic-Coated by the Hot-Dip Process Specification for Steel, Sheet and Strip, Cold-Rolled, Carbon, Structural, High-Strength Low-Alloy and High-Strength Low-Alloy with Improved Formability Specification for Steel, Sheet and Strip, Hot-Rolled, Carbon, Structural, High-Strength Low-Alloy and High-Strength Low-Alloy with Improved Formability Practice for Measuring Flatness Characteristics of Coated Sheet Products System Installation Techniques for Perimeter Heating and Cooling, 1lth ed. Design Residential Duct Systems Commercial Low Pressure, Low Velocity Duct System Design, 1st ed. Air Distribution Basics for Residential and Small Commercial Buildings, 1st ed. Method of Test for Determining the Design and Seasonal Efficiencies of Residential Thermal Distribution Systems

Publisher ASABE

Reference

ASAE S269.4-1991

ASABE

ASAE D272.3-1996

ASABE ASABE ASABE ASABE ASABE ASABE ASABE ASABE ASABE ASABE ACCA ACGIH AHAM ASHRAE

ASAE D535-2005 ASAE S352.2-2003 ASAE S353-2003 ASAE S358.2-2003 ASAE S410.1-2003 ASAE S416-2003 ANSI/ASAE S448.1-2001 (R2006) ASAE S487-2003 ASAE S488-1990 (R2005) ASAE 530.1-2007 ACCA Manual CS ACGIH ANSI/AHAM DH-1-2008 ANWASHRAE 139-2007

ASME CSA CSA UL ASHRAE ASHRAE AHRI ASHRAE UL SAE SMACNA UL ACGIH ASME AWS NAIMA NAIMA SMACNA SMACNA SMACNA SMACNA SMACNA SMACNA SMACNA ADC NFPA NFPA ASTM

PTC 12.4-1992 (RA04) C22.2 No. 92-1971 (R2004) CAN/CSA C749-07 ANSILJL 474 ANWASHRAE 35-2010 ASHRAE Guideline 4-2008 ANSI/AHRI 710-2004 ANWASHRAE 63.1-1995 (RAO1) ANSILJL 207 SAE AS1 50 1C-1994 SMACNA 1994 ANSILJL 181 ACGIH ASME B32.100-2005 AWS D9.1M/D9.1:2006 NAIMA AH1 16 NAIMA AH1 19 SMACNA 1995 SMACNA 2002 SMACNA 2003 SMACNA 2005 SMACNA 2004 SMACNA 1999 SMACNA 2004 ADC-9 1 NFPA 90A-06 NFPA 90B-06 ASTM A480/A480M-O6b

ASTM

ASTM A568/A568M-O7a

ASTM

ASTM A653/A653M-07

ASTM

ASTM A924/A924M-07

ASTM

ASTM Al008/A1008M-O7a

ASTM

ASTM A1011/A1011M-07

ASTM ACCA ACCA ACCA ACCA ASHRAE

ASTM A1030/A1030M-05 ACCA Manual 4 ANSI/ACCA Manual D ACCA Manual Q ACCA Manual T ANWASHRAE 152-2004

zyxw

zyxw zyxw

201 1 ASHRAE Handbook-HVAC Applications (SI)

61.8

Selected Codes and Standards Published by Various Societies and Associations (Continued) Subject

Testing

Electrical

Energy

Exhaust Systems

Title

Publisher

Closure Systems for Use with Rigid Air Ducts (2005) Closure Systems for Use with Flexible Air Ducts and Air Connectors (2005) Duct Leakage Testing (2002) Residential Duct Diagnostics and Repair (2003) Flexible Air Duct Test Code Test Method for Measuring Acoustical and Airflow Performance of Duct Liner Materials and Prefabricated Silencers Method of Testing to Determine Flow Resistance of HVAC Ducts and Fittings Method of Testing HVAC Air Ducts and Fittings HVAC Air Duct Leakage Test Manual, 1st ed. HVAC Duct Systems Inspection Guide, 3rd ed. Electrical Power Systems and Equipment-Voltage Ratings . . Test Method for Bond Strength of Electrical Insulating Varnishes by the Helical Coil Test Standard Specification for Shelter, Electrical Equipment, Lightweight Canadian Electrical Code, Part I (20th ed.) Part I I X e n e r a l Requirements ICC Electrical Code, Administrative Provisions (2006) Enclosures for Electrical Equipment (1000 Volts Maximum) Low Voltage Cartridge Fuses Industrial Control and Systems: Terminal Blocks Industrial Control and Systems: Enclosures Application Guide for Ground Fault Protective Devices for Equipment General Color Requirements for Wiring Devices Wiring Devices-Dimensional Requirements National Electrical Code National Fire Alarm Code Compatibility of Electrical Connectors and Wiring Molded-Case Circuit Breakers, Molded-Case Switches, and Circuit-Breaker Enclosures Air-conditioning and Refrigerating Equipment Nameplate Voltages Comfort, Air Quality, and Efficiency by Design Energy Standard for Buildings Except Low-Rise Residential Buildings Energy-Efficient Design of Low-Rise Residential Buildings Energy Conservation in Existing Buildings Methods of Measuring, Expressing, and Comparing Building Energy Performance Method of Test for the Evaluation of Building Energy Analysis Computer Programs Method of Test for Determining the Design and Seasonal Efficiencies of Residential Thermal Distribution Systems Standard for the Design of High-Performance, Green Buildings Except Low-Rise Residential Buildings Fuel Cell Power Systems Performance International Energy Conservation Code (2009) International Green Construction CodeTM Uniform Solar Energy Code (2000) Energy Management Guide for Selection and Use of Fixed Frequency Medium AC Squirrel-Cage Polyphase Induction Motors Energy Management Guide for Selection and Use of Single-Phase Motors HVAC Systems-Commissioning Manual, 1st ed. Building Systems Analysis and Retrofit Manual, 1st ed. Energy Systems Analysis and Management, 1st ed. Energy Management Equipment (2007) Fan Systems: Supply/Return/Relief/Exhaust(2002) Commercial Application, Systems, and Equipment, 1st ed. Industrial Ventilation: A Manual of Recommended Practice, 26th ed. (2007) Fundamentals Governing the Design and Operation of Local Exhaust Ventilation Systems Safety Code for Design, Construction, and Ventilation of Spray Finishing Operations Laboratory Ventilation Recirculation of Air from Industrial Process Exhaust Systems Method of Testing Performance of Laboratory Fume Hoods Ventilation for Commercial Cooking Operations Performance Test Code on Compressors and Exhausters Flue and Exhaust Gas Analyses Mechanical Flue-Gas Exhausters

UL UL AABC ACCA ADC ASTM

Reference

ANSILJL 181A ANSILJL 181B National Standards, Ch 5 ACCA ADC FD-72 (R1979) ASTM E477-06a

ASHRAE ASHRAE SMACNA SMACNA ANSI ASTM

ANWASHRAE 120-2008 ANSI/ASHRAE/SMACNA 126-2008 SMACNA 1985 SMACNA 2006 ANSI (34.1-2006 ASTM D2519-07

ASTM CSA CSA ICC NEMA NEMA NEMA NEMA NEMA NEMA NEMA NFPA NFPA SAE UL

ASTM E2377-04 C22.1-06 CAN/CSA-C22.2 No. 0-M91 (R2006) ICCEC ANSINEMA 250-2003 NEMA FU 1-2002 (R2007) NEMA ICS 4-2005 ANSINEMA ICS 6-1993 (R2006) ANSINEMA PB 2.2-2004 NEMA WD 1-1999 (R2005) ANSI/NEMA WD 6-2002 NFPA 70-08 NFPA 72-07 SAE AIR1329A-1988 ANSILJL489

AHRI ACCA ASHRAE ASHRAE ASHRAE ASHRAE ASHRAE ASHRAE

AHRI 110-2002 ACCA Manual RS ANSI/ASHRAE/IES 90.1-2010 ANWASHRAELES 90.2-2007 ANSI/ASHRAE/IES 100-2006 AN SI/ASHRAE 105-2007 A N W A S H M E 140-2007 ANWASHRAE 152-2004

ASHRAE/ USGBC ASME ICC ICC IAPMO NEMA

ANSI/ASHRAE/USGBC/IES 189.12009 PTC 50-2002 IECC IGCC IAPMO NEMA MG 10-2001 (R2007)

NEMA SMACNA SMACNA SMACNA UL AABC ACCA ACGIH AIHA

NEMA MG 11-1977 (R2007) SMACNA 1994 SMACNA 1995 SMACNA 1997 UL 916 National Standards, Ch 10 ACCA Manual CS ACGIH ANSI/AIHA 29.2-2006

AIHA AIHA AIHA ASHRAE ASHRAE ASME ASME CSA

ANSI/AIHA 29.3-2007 ANSI/AIHA 29.5-2003 ANSI/AIHA 29.7-2007 A N W A S H M E 110-1995 A N W A S H M E 154-2003 PTC 10-1997 (RA03) PTC 19.10-1981 CAN B255-M81 (R2005)

zyxwvutsrq

zyxw zyxw 61.9

Codes and Standards

Selected Codes and Standards Published by Various Societies and Associations (Continued) Subject

Title

Exhaust Systems for Air Conveying of Vapors, Gases, Mists, and Noncombustible Particulate Solids Draft Equipment (2006) Expansion Thermostatic Refrigerant Expansion Valves Valves Method of Testing Capacity of Thermostatic Refrigerant Expansion Valves Fan-Coil Units Industrial Ventilation: A Manual of Recommended Practice, 26th ed. (2007) Room Fan-Coils Methods of Testing for Rating Fan-Coil Conditioners Heating and Cooling Equipment (2005) Fans Residential Duct Systems Commercial Low Pressure, Low Velocity Duct System Design, 1st ed. Industrial Ventilation: A Manual of Recommended Practice, 26th ed. (2007) Standards Handbook Drive Arrangements for Centrifugal Fans Inlet Box Positions for Centrifugal Fans Designation for Rotation and Discharge of Centrifugal Fans Motor Positions for Belt or Chain Drive Centrifugal Fans Operating Limits for Centrifugal Fans Drive Arrangements for Tubular Centrifugal Fans Impeller Diameters and Outlet Areas for Centrifugal Fans Impeller Diameters and Outlet Areas for Industrial Centrifugal Fans Impeller Diameters and Outlet Areas for Tubular Centrifugal Fans Dimensions for Axial Fans Drive Arrangements for Axial Fans Air Systems Fans and Systems Troubleshooting Field Performance Measurement of Fan Systems Balance Quality and Vibration Levels for Fans Laboratoly Methods of Testing Air Circulator Fans for Rating Laboratoly Method of Testing Positive Pressure Ventilators for Rating Reverberant Room Method for Sound Testing of Fans Methods for Calculating Fan Sound Ratings from Laboratoly Test Data Application of Sone Ratings for Non-Ducted Air Moving Devices Application of Sound Power Level Ratings for Fans Recommended Safety Practices for Users and Installers of Industrial and Commercial Fans Industrial Process/Power Generation Fans: Site Performance Test Standard Mechanical Balance of Fans and Blowers Acoustics-Measurement of Noise and Vibration of Small Air-Moving Devices-Part 1: Airborne Noise Emission Part 2: Structure-Borne Vibration Laboratoly Methods of Testing Fans for Certified Aerodynamic Performance Rating Laboratoly Method of Testing to Determine the Sound Power in a Duct

Fenestration

Laboratoly Methods of Testing Fans Used to Exhaust Smoke in Smoke Management Systems Ventilation for Commercial Cooking Operations Fans Fans and Ventilators Rating the Performance of Residential Mechanical Ventilating Equipment Energy Performance of Ceiling Fans Electric Fans (1999) Power Ventilators 12004) Test Method for Accelerated Weathering of Sealed Insulating Glass Units Practice for Calculation of Photometric Transmittance and Reflectance of Materials to Solar Radiation Test Method for Solar Photometric Transmittance of Sheet Materials Using Sunlight Test Method for Solar Transmittance (Terrestrial) of Sheet Materials Using Sunlight Practice for Determining the Load Resistance of Glass in Buildings Practice for Installation of Exterior Windows, Doors and Skylights Test Method for Insulating Glass Unit Performance Test Method for Testing Resistance to Fogging Insulating Glass Units Specification for Insulating Glass Unit Performance and Evaluation

Publisher NFPA UL AHRI ASHRAE ACGIH AHRI ASHRAE UL/CSA ACCA ACCA ACGIH AMCA AMCA AMCA AMCA AMCA AMCA AMCA AMCA AMCA AMCA AMCA AMCA AMCA AMCA AMCA AMCA AMCA AMCA AMCA AMCA AMCA AMCA AMCA AMCA AMCA AHRI ASA

Reference

ANSINFPA 9 1-04

ASA ASHRAE/ AMCA ASHRAE/ AMCA ASHRAE

UL 378 ANSI/AHRI 750-2007 ANWASHRAE 17-2008 ACGIH AHRI 440-2005 ANWASHRAE 79-2002 (RA06) ANSILJL 1995/C22.2 No. 236-95 ANSI/ACCA Manual D ACCA Manual Q ACGIH AMCA 99-03 ANSI/AMCA 99-2404-03 ANSI/AMCA 99-2405-03 ANSI/AMCA 99-2406-03 ANSI/AMCA 99-2407-03 AMCA 99-2408-69 ANSI/AMCA 99-2410-03 ANSI/AMCA 99-2412-03 ANSI/AMCA 99-2413 -03 ANSI/AMCA 99-2414-03 ANSI/AMCA 99-3001-03 ANSI/AMCA 99-3404-03 AMCA 200-95 (R2007) AMCA 201-02 (R2007) AMCA 202-98 (R2007) AMCA 203-90 (R2007) ANSI/AMCA 204-05 ANSI/AMCA 230-07 ANSI/AMCA 240-06 AMCA 300-05 AMCA 301-06 AMCA 302-73 (R2008) AMCA 303-79 (R2008) AMCA 410-96 AMCA 803-02 AHRI Guideline G-2002 ANSI S12.11-2003/Part UISO 10302:1996 (MOD) ANSI S12.11-2003/Part 2 ANWASHRAE 51-2007 ANSI/AMCA 210-07 ANWASHRAE 68-1997 ANSI/AMCA 330-97 ANWASHME 149-2000 (RA09)

ASHRAE ASME CSA CSA CSA UL UL ASTM ASTM

ANWASHRAE 154-2003 ANWASME PTC 11-1984 (RA03) C22.2 No. 113-M1984 (R2004) CAN/CSA C260-M90 (R2007) CAN/CSA (314-96 (R2007) ANSI/UL 507 ANSI/UL 705 ASTM E773-01 ASTM E971-88 (2003)

ASTM ASTM ASTM ASTM ASTM ASTM ASTM

ASTM E972-96 (2007) ASTM E1084-86 (2003) ASTM E1300-07el ASTM E2112-07 ASTM E2188-02 ASTM E2189-02 ASTM E2190-02

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201 1 ASHRAE Handbook-HVAC Applications (SI)

61.10

Selected Codes and Standards Published by Various Societies and Associations (Continued) Subject

Title

Guide for Assessing the Durability of Absorptive Electrochemical Coatings within Sealed Insulating Glass Units Tables for Reference Solar Spectral Irradiance: Direct Normal and Hemispherical on 37" Tilted Surface Windows Energy Performance of Windows and Other Fenestration Systems Window, Door, and Skylight Installation Energy Performance Evaluation of Swinging Doors Filter-Driers Flow-Capacity Rating of Suction-Line Filters and Suction-Line Filter-Driers Method of Testing Liquid Line Filter-Drier Filtration Capability Method of Testing Flow Capacity of Suction Line Filters and Filter-Driers Fireplaces Factory-Built Fireplaces (1996) Fireolace Stoves (2007) Fire Protection Test Method for Surface Burning Characteristics of Building Materials Test Methods for Fire Test of Building Construction and Materials Test Method for Room Fire Test of Wall and Ceiling Materials and Assemblies Test Method for Determining Fire Resistance of Perimeter Fire Bamers Using Intermediate-Scale Multi-Stoly Test Apparatus Guide for Laboratoly Monitors Test Method for Fire Resistance Grease Duct Enclosure Systems Practice for Specimen Preparation and Mounting of Paper or Vinyl Wall Coverings to Assess Surface Burning Characteristics BOCA National Fire Prevention Code, 11th ed. (1999) Uniform Fire Code International Fire Code (2009) International Mechanical Code (2009) International Urban-Wildland Interface Code (2009) Fire-Resistance Tests-Elements of Building Construction; Part 1: Gen. Requirements Fire-Resistance Tests-Door and Shutter Assemblies Reaction to Fire Tests-Ignitability of Building Products Using a Radiant Heat Source Fire-Resistance Tests-Ventilating Ducts Fire Service Annunciator and Interface Fire Protection Handbook (2008) National Fire Codes (issued annually) Fire Protection Guide to Hazardous Materials Uniform Fire Code Installation of Sprinkler Systems Flammable and Combustible Liquids Code Fire Protection for Laboratories Using Chemicals National Fire Alarm Code Fire Doors and Fire Windows Health Care Facilities Life Safety Code Methods of Fire Tests of Door Assemblies Standard Fire Code (1999) Fire, Smoke and Radiation Damper Installation Guide for HVAC Systems, 5th ed. Fire Tests of Door Assemblies (2008) Heat Responsive Links for Fire-Protection Service (2003) Fire Tests of Building Construction and Materials (2003) Fire Dampers (2006) Fire Tests of Through-Penetration Firestops (2003) Smoke Commissioning Smoke Management Systems ManageLaboratoly Methods of Testing Fans Used to Exhaust Smoke in Smoke Management ment Systems Recommended Practice for Smoke-Control Systems Smoke Management Systems in Malls, Atria, and Large Areas Ceiling Dampers (2006) Smoke Dampers (1999) Freezers Energy Performance and Capacity of Household Refngerators, Refngerator-Freezers, and Freezers Energy Performance Standard for Food Service Refngerators and Freezers Refngeration Equipment Commercial Dispensing Freezers Commercial Refngerators and Freezers

Publisher ASTM ASTM

Reference

ASTM E2354-04

ASTM G173-03el

CSA A440-08 CSA A440.3 -04 CSA A440.4-98 CSA A453-95 (R2000) AHRI AHRI 730-2005 ASHRAE ANWASHRAE 63.2-1996 (RA2010) ASHRAE ANWASHRAE 78-1985 (RA07) UL ANSI/UL 127 UL ANSI/UL 737 ASTMNFPA ASTM E84-08 ASTM ASTM E l 19-08 ASTM ASTM E2257-03 ASTM E2307-04el ASTM ASTM ASTM ASTM

ASTM E2335-04 ASTM E2336-04 ASTM E2404-07a

BOCA IFCI ICC ICC ICC IS0 IS0 IS0 IS0 NEMA NFPA NFPA NFPA NFPA NFPA NFPA NFPA NFPA NFPA NFPA NFPA NFPA SBCCI SMACNA UL UL UL UL UL ASHRAE ASHRAE

BNFPC UPC 1997 IFC IMC IUWIC I S 0 834-1:1999 I S 0 3008:2007 I S 0 5657:1997 I S 0 6944:1985 NEMA SB 30-2005 NFPA NFPA NFPA HAZ-0 1 NFPA 1-06 NFPA 13-2007 NFPA 30-08 NFPA 45-04 NFPA 72-07 NFPA 80-07 NFPA 99-05 NFPA 101-06 NFPA 252-08 SFPC SMACNA 2002 ANSILJL 10B ANSILJL 33 ANSI/UL 263 ANSI/UL 555 ANSILJL 1479 ASHRAE Guideline 5-1994 (RAO1) ANWASHME 149-2000 (RA09)

NFPA NFPA UL UL CSA

NFPA 92A-06 NFPA 92B-05 ANSILJL 555C ANSILJL 555s C300-00 (R2005)

CSA CSA NSF NSF

(327-98 (R2003) CAN/CSA-C22.2No. 120-M91(R2004) NSF/ANSI 6-2007 NSF/ANSI 7-2007

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zyxwvutsrqponmlkji 61.11

Codes and Standards

Selected Codes and Standards Published by Various Societies and Associations (Continued) Subject

Household

Fuels

Furnaces

Gas

Title

Publisher

Commercial Refrigerators and Freezers (2006) Ice Makers (1995) Ice Cream Makers (2005) Household Refrigerators, Refrigerator-Freezers and Freezers Household Refrigerators and Freezers (1993) Threshold Limit Values for Chemical Substances (updated annually) International Gas Fuel Code (2006) Reporting of Fuel Properties when Testing Diesel Engines with Alternative Fuels Derived from Biological Materials Coal Pulverizers Classification of Coals by Rank Specification for Fuel Oils Test Method for Determination of Homogeneity and Miscibility in Automotive Engine Oils Specification for Diesel Fuel Oils Specification for Gas Turbine Fuel Oils Specification for Kerosene Practice for Receipt, Storage and Handling of Fuels Test Method for Determination of Yield Stress and Apparent Viscosity of Used Engine Oils at Low Temperature Test Method for Total Sulfur in Naphthas, Distillates, Reformulated Gasolines, Diesels, Biodiesels, and Motor Fuels by Oxidative Combustion and Electrochemical Detection Test Method for Measurement of Hindered Phenolic and Aromatic Amine Antioxidant Content in Non-Zinc Turbine Oils by Linear Sweep Voltammetly Practice for Enumeration of Viable Bacteria and Fungi in Liquid Fuels-Filtration and Culture Procedures Test Method for Evaluation of Aeration Resistance of Engine Oils in Direct-Injected Turbocharged Automotive Diesel Engine Specification for Middle Distillate Fuel Oil-Militaly Marine Applications Test Method for Determination of Ignition Delay and Derived Cetane Number DCN of Diesel Fuel Oils by Combustion in a Constant Volume Chamber Test Method for Determination of Total Sulfur in Light Hydrocarbon, Motor Fuels, and Oils by Online Gas Chromatography with Flame Photometric Detection Test Method for Sulfur in Gasoline and Diesel Fuel by Monochromatic Wavelength Dispersive X-Ray Fluorescence Spectrometly New Draft Standard Test Method for Flash Point by Modified Continuously Closed Cup Flash Point Tester Test Method for Determining the Viscosity-Temperature Relationship of Used and Soot-Containing Engine Oils at Low Temperatures Test Method for Determination of Trace Elements in Middle Distillate Fuels by Inductively Coupled Plasma Atomic Emission Spectrometly (ICPAES) Test Method for Determining Stability and Compatibility of Heavy Fuel Oils and Crude Oils by Heavy Fuel Oil Stability Analyzer (Optical Detection) Test Method for Determination of Intrinsic Stability of Asphaltene-Containing Residues, Heavy Fuel Oils, and Crude Oils Test Method for Hydrogen Content of Middle Distillate Petroleum Products by LowResolution Pulsed Nuclear Magnetic Resonance Spectroscopy Gas-Fired Central Furnaces Gas Unit Heaters and Gas-Fired Duct Furnaces Industrial and Commercial Gas-Fired Package Furnaces Uniform Mechanical Code (2006) Uniform Plumbing Code (2006) International Fuel Gas Code (2009) Standard Gas Code (1999) Commercial-Industrial Gas Heating Equipment (2006) Commercial Application, Systems, and Equipment, 1st ed. Residential Equipment Selection, 2nd ed. Method of Testing for Annual Fuel Utilization Efficiency of Residential Central Furnaces and Boilers Prevention of Furnace Explosions/Implosions in Multiple Burner Boilers Residential Gas Detectors (2000) Heating and Cooling Equipment (2005) Single and Multiple Station Carbon Monoxide Alarms (2008) International Gas Fuel Code (2006) Gas-Fired Central Furnaces

__

_

I

UL UL UL AHAM UL/CSA ACGIH AGNNFPA ASABE

Reference

ANSI/UL 471 ANSI/UL 563 ANSI/UL 621 ANSI/AHAM HRF-1-2007 ANSVUL 250/C22.2 No. 63-93 (R1999) ACGIH ANSI Z223.UNPFA 54-2006 ASAE EP552-1996

ASME ASTM ASTM ASTM

PTC 4.2 1969 (RA03) ASTM D388-05 ASTM D396-08 ASTM D922-00a (2006)

ASTM ASTM ASTM ASTM ASTM

ASTM D975-07b ASTM D2880-03 ASTM D3699-07 ASTM D4418-00 (2006) ASTM D6896-03 (2007)

ASTM

ASTM D6920-07

ASTM

ASTM D6971-04

ASTM

ASTM D6974-04a

ASTM

ASTM D6984-07a

ASTM ASTM

ASTM D6985-04a ASTM D6890-07b

ASTM

ASTM D7041-04

ASTM

ASTM D7044-04a

ASTM

ASTM D7094-04

ASTM

ASTM D7110-05a

ASTM

ASTMD7111-05

ASTM

ASTM D7112-05a

ASTM

ASTM D7157-05

ASTM

ASTM D7171-05

CSA CSA CSA IAPMO IAPMO ICC SBCCI UL ACCA ACCA ASHRAE

ANSI Z21.47-2006/CSA 2.3-2006 ANSI Z83.8-2006/CSA-2.6-2006 CGA 3.2-1976 (R2003) Chapter 13 Chapter 12 IFGC SGC UL 795 ACCA Manual CS ANSI/ACCA Manual S ANWASHRAE 103-2007

NFPA UL UL/CSA UL AGNNFPA CSA

NFPA 8502-99 ANSILJL 1484 ANSILJL 1995/C22.2 No. 236-95 ANSI/UL 2034 ANSI Z223.UNFPA 54-2006 ANSI Z21.47-2006/CSA 2.3-2006

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201 1 ASHRAE Handbook-HVAC Applications (SI)

61.12

Selected Codes and Standards Published by Various Societies and Associations (Continued) Subject

Title

Publisher

Gas Unit Heaters and Gas-Fired Duct Furnaces Industrial and Commercial Gas-Fired Package Furnaces International Fuel Gas Code (2009) Standard Gas Code (1999) Commercial-Industrial Gas Heating Equipment (2006) Specification for Fuel Oils Specification for Diesel Fuel Oils Test Method for Smoke Density in Flue Gases from Burning Distillate Fuels Standard Test Method for Vapor Pressure of Liquefied Petroleum Gases (LPG) (Expansion Method) Oil Burning Stoves and Water Heaters Oil-Fired Warm Air Furnaces Installation of Oil-Burning Equipment Oil-Fired Central Furnaces (2006) Oil-Fired Floor Furnaces (2003) Oil-Fired Wall Furnaces (2003) Installation Code for Solid-Fuel-Burning Appliances and Equipment Solid-Fuel-Fired Central Heating Appliances Solid-Fuel and Combination-Fuel Central and Supplementary Furnaces (2006)

CSA CSA ICC SBCCI UL ASTM ASTM ASTM ASTM CSA CSA NFPA UL UL UL CSA CSA UL

B 140.3-1962 (R2006) B140.4-04 NFPA 3 1-06 UL 727 ANSI/UL 729 ANSILJL 730 B365-01 (R2006) CAN/CSA-B366.1 -M91 (R2007) ANSILJL 391

Green Buildings

Standard for the Design of High-Performance, Green Buildings Except Low-Rise Residential Buildings International Green Construction CodeTM

ASHRAE/ USGBC ICC

ANSI/ASHRAE/USGBC/IES 189.12009 IGCC

Heaters

Gas-Fired High-Intensity Infrared Heaters

CSA

ANSI 283.19-2001/CSA 2.35-2001 (R2005) ANSI 283.20-2008/CSA 2.34-2008 ACGIH ACGIH ANSI/ASAE S423-1991 ASME PTC 4.3-1968 (RA91) ASTM E1602-03 ANSI 283.4-2003/CSA 3.7-2003 C22.2 No. 155-M1986 (R2004) CAN3-B140.9.3 M86 (R2006) HE1 2622 ANSI/UL 499 ANSILJL 574 UL 733 ANSI/UL 875 ANSILJL 896 SAE 51310-1993 SAE 51350-1988

Oil

Solid Fuel

Gas-Fired Low-Intensity Infrared Heaters Threshold Limit Values for Chemical Substances (updated annually) Industrial Ventilation: A Manual of Recommended Practice, 26th ed. (2007) Thermal Performance Testing of Solar Ambient Air Heaters Air Heaters Guide for Construction of Solid Fuel Burning Masonry Heaters Non-Recirculating Direct Gas-Fired Industrial Air Heaters Electric Duct Heaters Portable Kerosene-Fired Heaters Standards for Closed Feedwater Heaters, 7th ed. (2004) Electric Heating Appliances (2005) Electric Oil Heaters (2003) Oil-Fired Air Heaters and Direct-Fired Heaters (1993) Electric Dry Bath Heaters (2004) Oil-Burning Stoves (1993) Engine Electric Engine Preheaters and Battery Warmers for Diesel Engines Selection and Application Guidelines for Diesel, Gasoline, and Propane Fired Liquid Cooled Engine Pre-Heaters Fuel Warmer-Diesel Engines Nonresidential Installation of Electric Infrared Brooding Equipment Gas-Fired Construction Heaters

Pool

Room

Recirculating Direct Gas-Fired Industrial Air Heaters Portable Industrial Oil-Fired Heaters Fuel-Fired Heaters-Air Heating-for Construction and Industrial Machinely Commercial-Industrial Gas Heating Equipment (2006) Electric Heaters for Use in Hazardous (Classified) Locations (2006) Methods of Testing and Rating Pool Heaters Gas-Fired Pool Heaters Oil-Fired Service Water Heaters and Swimming Pool Heaters Specification for Room Heaters, Pellet Fuel Burning Type Gas-Fired Room Heaters, Vol. 11, Unvented Room Heaters Gas-Fired Unvented Catalytic Room Heaters for Use with Liquefied Petroleum (LP) Gases Vented Gas-Fired Space Heating Appliances Vented Gas Fireplace Heaters Unvented Kerosene-Fired Room Heaters and Portable Heaters (1993) Movable and Wall- or Ceiling-Hung Electric Room Heaters (2000) Fixed and Location-Dedicated Electric Room Heaters (1997) Solid Fuel-Tvoe Room Heaters (1996)

CSA ACGIH ACGIH ASABE ASME ASTM CSA CSA CSA HE1 UL UL UL UL UL SAE SAE SAE ASABE CSA CSA CSA SAE UL UL ASHRAE CSA CSA ASTM CSA CSA CSA CSA UL UL UL UL

Reference

ANSI Z83.8-2006/CSA-2.6-2006 CGA 3.2-1976 (R2003) IFGC SGC UL 795 ASTM D396-08 ASTM D975-07b ASTM D2156-94 (2003) ASTM D6897-2003a

SAE 51422-1996 ASAE EP258.3-2004 ANSI 283.7-00 (R2005)/CSA 2.1400 (R2006) ANSI 283.18-2004 B140.8-1967 (R2006) SAE 51024-1989 UL 795 ANSI/UL 823 ANWASHRAE 146-2006 ANSI 221.56-2006/CSA 4.7-2006 B140.12-03 ASTM E1509-04 ANSI 221.11.2-2007 ANSI 221.76-1994 (R2006) ANSI 221.86-2004/CSA 2.32-2004 ANSI 221.88-2005/CSA 2.33-2005 UL 647 UL 1278 UL 202 1 ANSILJL 1482

zyxw zyxw 61.13

Codes and Standards

Selected Codes and Standards Published by Various Societies and Associations (Continued) Subject

Title

Transport

Heater, Airplane, Engine Exhaust Gas to Air Heat Exchanger Type Installation, Heaters, Airplane, Internal Combustion Heater Exchange Type Heater, Aircraft, Internal Combustion Heat Exchanger Type Motor Vehicle Heater Test Procedure Heater, Aircraft, Internal Combustion Heat Exchanger Type Unit Gas Unit Heaters and Gas-Fired Duct Furnaces Oil-Fired Unit Heaters (1995) Heat Remote Mechanical-Draft Evaporative Refrigerant Condensers Exchangers Method of Testing Air-to-Air Heat/Energy Exchangers Boiler and Pressure Vessel Code-Section VIII, Division 1: Pressure Vessels Single Phase Heat Exchangers Air Cooled Heat Exchangers Standard Methods of Test for Rating the Performance of Heat-Recovery Ventilators Standards for Power Plant Heat Exchangers, 4th ed. (2004) Standards of Tubular Exchanger Manufacturers Association, 9th ed. (2007) Refrigerant-Containing Components and Accessories, Nonelectrical (200 1) Heating Commercial Application, Systems, and Equipment, 1st ed. Comfort, Air Quality, and Efficiency by Design Residential Equipment Selection, 2nd ed. Heating, Ventilating and Cooling Greenhouses Heater Elements Determining the Required Capacity of Residential Space Heating and Cooling Appliances Heat Loss Calculation Guide (2001) Residential Hydronic Heating Installation Design Guide Radiant Floor Heating (1995) Advanced Installation Guide (Commercial) for Hot Water Heating Systems (2001) Environmental Systems Technology, 2nd ed. (1999) Pulverized Fuel Systems Aircraft Electrical Heating Systems Heating Value of Fuels Performance Test for Air-conditioned, Heated, and Ventilated Off-Road SelfPropelled Work Machines HVAC Systems-Applications, 1st ed. Electric Baseboard Heating Equipment (1994) Electric Duct Heaters (2004) Heating and Cooling Equipment (2005) Heat Pumps Commercial Application, Systems, and Equipment, 1st ed. Geothermal Heat Pump Training Certification Program Heat Pumps Systems, Principles and Applications, 2nd ed. Residential Equipment Selection, 2nd ed. Industrial Ventilation: A Manual of Recommended Practice, 26th ed. (2007) Water-Source Heat Pumps Ground Water-Source Heat Pumps Ground Source Closed-Loop Heat Pumps Commercial and Industrial Unitary Air-conditioning and Heat Pump Equipment Methods of Testing for Rating Electrically Driven Unitary Air-conditioning and Heat Pump Equipment Methods of Testing for Rating Seasonal Efficiency of Unitary Air-Conditioners and Heat Pumps Performance Standard for Split-System and Single-Package Central Air Conditioners and Heat Pumps Installation Requirements for Air-to-Air Heat Pumps Performance of Direct-Expansion (DX) Ground-Source Heat Pumps Water-Source Heat Pumps-Testing and Rating for Performance, Part 1: Water-to-Air and Brine-to-Air Heat Pumps Part 2: Water-to-Water and Brine-to-Water Heat Pumps Heating and Cooling Equipment (2005) Gas-Fired Gas-Fired, Heat Activated Air Conditioning and Heat Pump Appliances Gas-Fired, Work Activated Air Conditioning and Heat Pump Appliances (Internal Combustion) Performance Testing and Rating of Gas-Fired Air Conditioning and Heat Pump Auuliances

Publisher SAE SAE SAE SAE SAE CSA UL AHRI ASHRAE ASME ASME ASME CSA HE1 TEMA UL ACCA ACCA ACCA ASABE CSA CSA

Reference

SAE ARP86-1996 SAE ARP266-2001 SAE AS8040-1996 SAE 5638-1998 SAE AS8040-1996 ANSI 283.8-2006/CSA-2.6-2006 ANSILJL 73 1 AHRI 490-2003 A N W A S H M E 84-2008 ASME BPVC-2007 ASME PTC 12.5-2000 (RA05) ASME PTC 30-1991 (RA05) C439-00 (R2005) HE1 2623 TEMA ANSILJL 207 ACCA Manual CS ACCA Manual RS ANSI/ACCA Manual S ANSI/ASAE EP406.4-2003 C22.2 No. 72-M1984 (R2004) CAN/CSA-F280-M90 (R2004)

HYDI HYDI HYDI HYDI NEBB NFPA SAE SAE SAE

HYDI H-22 IBR Guide HYDI 004 HYDI 250 NEBB NFPA 8503-97 SAE AIR860-2000 SAE 51498-2005 SAE 51503-2004

SMACNA UL UL UL/CSA ACCA ACCA ACCA ACCA ACGIH AHRI AHRI AHRI AHRI ASHRAE

SMACNA 1987 ANSILJL 1042 ANSILJL 1996 ANSILJL 1995/C22.2 No. 236-95 ACCA Manual CS ACCA Training Manual ACCA Manual H ANSI/ACCA Manual S ACGIH AHRI 320-98 AHRI 325-98 AHRI 330-98 AHRI 340/360-2007 ANWASHRAE 37-2009

ASHRAE

ANWASHRAE 116-2010

CSA

CAN/CSA-C656-05

CSA CSA CSA

C273.5-1980 (R2002) C748-94 (R2005) CAN/CSA C13256-1-01

CSA UL/CSA CSA

CAN/CSA C13256-2-01 (R2005) ANSILJL 1995/C22.2 No. 236-95 ANSI 221.40.1-1996 (R2002)/CGA 2.9 1-M96 ANSI 221.40.2-1996 (R2002)/CGA 2.92-M96 ANSI 221.40.4-1996 (R2002)/CGA 2.94-M96

CSA CSA

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61.14

201 1 ASHRAE Handbook-HVAC Applications (SI)

Selected Codes and Standards Published by Various Societies and Associations (Continued)

Subject

Title

Heat Recovery Gas Turbine Heat Recovely Steam Generators Water Heaters, Hot Water Suuulv Boilers, and Heat Recoverv Eauiument HighStandard for the Design of High-Performance, Green Buildings Except Low-Rise Performance Residential Buildings Buildinxs International Green Construction CodeTM Humidifiers Commercial Application, Systems, and Equipment, 1st ed. Comfort, Air Quality, and Efficiency by Design Bioaerosols: Assessment and Control (1999) Humidifiers Central System Humidifiers for Residential Applications Self-contained Humidifiers for Residential Applications Commercial and Industrial Humidifiers Humidifiers (2001) Ice Makers Performance Rating of Automatic Commercial Ice Makers Ice Storage Bins Methods of Testing Automatic Ice Makers Refrigeration Equipment Performance of Automatic Ice-Makers and Ice Storage Bins Automatic Ice Making Equipment Ice Makers (1995) Incinerators Incinerators and Waste and Linen Handling Systems and Equipment Residential Incinerators (2006) Indoor Air Good HVAC Practices for Residential and Commercial Buildings (2003) Quality Comfort, Air Quality, and Efficiency by Design (Residential) (1997) Bioaerosols: Assessment and Control (1999) Ventilation for Acceptable Indoor Air Quality Ventilation and Acceptable Indoor Air Quality in Low-Rise Residential Buildings Test Method for Determination of Volatile Organic Chemicals in Atmospheres (Canister Sampling Methodology) Guide for Using Probability Sampling Methods in Studies of Indoor Air Quality in Buildings Guide for Using Indoor Carbon Dioxide Concentrations to Evaluate Indoor Air Quality and Ventilation Guide for Placement and Use of Diffusion Controlled Passive Monitors for Gaseous Pollutants in Indoor Air Test Method for Determination of Metals and Metalloids Airborne Particulate Matter by Inductively Coupled Plasma Atomic Emissions Spectrometly (ICP-AES) Test Method for Metal Removal Fluid Aerosol in Workplace Atmospheres Practice for Emission Cells for the Determination of Volatile Organic Emissions from Materials/Products Practice for Collection of Surface Dust by Micro-Vacuum Sampling for Subsequent Metals Determination Test Method for Determination of Beryllium in the Workplace Using Field-Based Extraction and Fluorescence Detection Practice for Referencing Suprathreshold Odor Intensity Guide for Specifying and Evaluating Performance of a Single Family Attached and Detached Dwelling-Indoor Air Quality Classification for Serviceability of an Office Facility for Thermal Environment and Indoor Air Conditions Practice for Continuous Sizing and Counting of Airborne Particles in Dust-Controlled Areas and Clean Rooms Using Instruments Capable of Detecting Single SubMicrometre and Larger Particles Ambient Air-Determination of Mass Concentration of Nitrogen Dioxide-Modified Griess-Saltzman Method Air Quality-Exchange of Data Environmental Tobacco Smoke-Estimation of Its Contribution to Respirable Suspended Particles-Determination of Particulate Matter by Ultraviolet Absorptance and by Fluorescence Indoor Air-Part 3: Determination of Formaldehyde and Other Carbonyl Compounds-Active Sampling Method Workplace Air Quality-Sampling and Analysis of Volatile Organic Compounds by Solvent DesorptiodGas Chromatography-Part 1: Pumped Sampling Method Part 2: Diffusive Sampling Method Workplace Air Quality-Determination of Total Organic Isocyanate Groups in Air Using 1-(2-Methoxyphenyl) Piperazine and Liquid Chromatography

- _

I

Publisher

Reference

ASME NSF ASHRAE/ USGBC ICC ACCA ACCA ACGIH AHAM AHRI AHRI AHRI UL/CSA AHRI AHRI ASHRAE CSA CSA NSF UL NFPA UL ACCA ACCA ACGIH ASHRAE ASHRAE ASTM

ANWASME PTC 4.4-1981 (RA03) NSF/ANSI 5-2007 ANSI/ASHRAE/USGBC/IES 189.12009 IGCC ACCA Manual CS ACCA Manual RS ACGIH ANSI/AHAM HU-1-2006 AHRI 610-2004 AHRI 620-2004 ANSI/AHRI 640-2005 ANSILJL 99WC22.2 No. 104-93 AHRI 810-2007 AHRI 820-2000 A N W A S H M E 29-2009 CAN/CSA-C22.2No. 120-M91(R2004) C742-98 (R2003) NSF/ANSI 12-2007 ANSI/UL 563 NFPA 82-04 UL 791

ASTM

ASTM D5791-95 (2006)

ASTM

ASTM D6245-07

ASTM

ASTM D6306-98 (2003)

ASTM

ASTM D7035-04

ASTM ASTM

ASTM D7049-04 ASTM D7143-05

ASTM

ASTM D7144-05a

ASTM

ASTM D7202-06

ASTM ASTM

ASTM E544-99 (2004) ASTM E2267-04

ASTM

ASTM E2320-04

ASTM

ASTM F50-07

IS0

I S 0 6768:1998

IS0 IS0

I S 0 7168:1999 I S 0 15593:2001

IS0

I S 0 16000-3:2001

IS0

I S 0 16200-1:2001

IS0 IS0

I S 0 16200-2:2000 I S 0 16702:2007

zyxw

~

ACCA ACCA Manual RS ACGIH ANWASHRAE 62.1-2010 ANWASHRAE 62.2-2010 ASTM D5466-01 (2007)

COMPOSITE INDEX

Index Terms

Links

This index covers the current Handbook series published by ASHRAE. The four volumes in the series are identified as follows: S = 2008 HVAC Systems and Equipment F = 2009 Fundamentals R = 2010 Refrigeration A = 2011 HVAC Applications Alphabetization of the index is letter by letter; for example, Heaters precedes Heat exchangers, and Floors precedes Floor slabs. The page reference for an index entry includes the book letter and the chapter number, which may be followed by a decimal point and the beginning page in the chapter. For example, the page number S31.4 means the information may be found in the 2008 HVAC Systems and Equipment volume, Chapter 31, beginning on page 4. Each Handbook volume is revised and updated on a four-year cycle. Because technology and the interests of ASHRAE members change, some topics are not included in the current Handbook series but may be found in the earlier Handbook editions cited in the index.

A Abbreviations

F37

Absorbents liquid

F2.14

refrigerant pairs

F2.15

F32.3

Absorption ammonia/water

F30.1

hydrogen cycle

R18.8

technology

R18.7

chillers

F30.69

S3.4

turbines

S17.4

coefficient of performance (COP)

F2.13

concepts coupling

F2.15

double-effect calculations

F2.17

cascaded

F2.15

cycle characteristics dehumidification

F2.14 S23.10 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Absorption (Cont.) equipment

R18.1

evolving technologies ideal thermal

R18.10 F2.13

industrial exhaust gas cleaning

S29.17

refrigeration cycles

F2.13

ammonia/water

F30.1

F30.69

lithium bromide/water

F30.1

F30.69

types

F2.16

modeling analysis and performance simulation

F2.16

phase constraints

F2.13

representations

F2.15

solar cooling

A35.18

A35.26

water/lithium bromide technology components

R18.1

control

R18.6

double-effect chillers

R18.3

maintenance

R18.7

operation

R18.6

single-effect chillers

R18.2

single-effect heat transformers

R18.3

terminology

R18.1

working fluids

F2.14

Acoustics. See Sound Activated carbon adsorption

A46.6

ADPI. See Air diffusion performance index (ADPI) Adsorbents impregnated

S29.24

solid

A46.6

F32.4

dehumidification

S23.1

S23.10

indoor air cleaning

A46.6

Adsorption

industrial exhaust gas cleaning moisture Aeration, of farm crops Aerosols

S29.24 F32.1 A25 S28.1

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

S36.3

S36.9

Index Terms

Links

Affinity laws for centrifugal pumps

S43.7

AFUE. See Annual fuel utilization efficiency (AFUE) AHU. See Air handlers Air age of, and ventilation

F16.4

changes per hour (ach)

F16.4

drying

S23.11

flux

F25.2

liquefaction

R47.8

permeability

F25.2

permeance

F25.2

separation

R47.17

transfer

F25.2

Air barriers

F26.13

Airborne infectious diseases

F10.6

Air cleaners. (See also Filters, air; Industrial exhaust gas cleaning) gaseous (indoor air) adsorbers

A46.6

chemisorbers

A46.7

economics

A46.14

energy consumption

A46.14

environmental effects on

A46.15

installation

A46.14

media selection

A46.10

operation and maintenance

A46.15

safety

A46.14

sizing

A46.10

terminology

A46.6

testing

A46.16

types

A46.9

industrial exhaust systems

A32.8

particulate contaminants

S28.1

industrial ventilation

S28.2

particle collection mechanisms

S28.2

penetration

S28.3 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Air cleaners (Cont.) residential

S28.9

safety requirements

S28.12

selection

S28.8

standards

S28.3

test methods

S28.2

S28.5

types air washers

S40.8

combination

S28.6

electronic

S9.1

evaporative coolers

S40.8

maintenance

S28.8

media filters

S28.5

S28.5

Air conditioners. (See also Central air conditioning) packaged terminal (PTAC) design

S49.5 S49.5

heavy-duty commercial grade

S49.6

S2.3

sizes and classifications

S49.5

testing

S49.7

residential

A1

split systems

S2.6

through-the-wall room units

A1.6

unitary

A1.4

retail stores

A2.1

rooftop units

S2.8

room codes and standards

S49.4

design

S49.1

features

S49.3

filters

S49.4

installation and service

S49.4

noise

S49.4

performance

S49.2

sizes and classifications

S49.1

split systems

S48.1

coil placement

S48.8

residential and light-commercial

S2.6

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

S28.7

S32.2

Index Terms

Links

Air conditioners (Cont.) unitary air handlers

S48.7

application

S48.1

capacity control

S48.7

certification

S48.6

circuit components

S48.6

codes and standards

S48.5

desuperheaters

S48.4

efficiency

S48.5

electrical design

S48.7

installation

S48.2

maintenance

S48.2

mechanical design

S48.8

multizone

S48.4

piping

S48.7

refrigerant circuit control

S48.6

space conditioning/water heating

S48.4

types

S48.2

unit ventilators

S48.6

S48.4

S27.1

window-mounted

S2.3

Air conditioning. (See also Central air conditioning) airports

A3.6

animal buildings

A24.4

arenas

A5.4

atriums

A5.9

auditoriums

A5.3

automobiles

A10.1

bakeries

R41

buses

A11.2

bus terminals

A3.6

changeover temperature

S5.11

clean spaces

A18

commercial buildings

A3.1

computer rooms

A19

concert halls

A5.4

convention centers

A5.5

S5.13

S2.6

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Air conditioning (Cont.) data processing areas

A19

desiccant dehumidification and

S23.10

dormitories

A6.1

educational facilities

A7.1

engine test facilities

A17.1

A6.8

equipment outdoor

S2.8

refrigeration

S3.3

exhibition centers

A5.5

fairs

A5.8

fixed-guideway vehicles gymnasiums

A11.7 A5.5

health care facilities

A8

hospitals

A8.2

nursing facilities

A8.14

outpatient

A8.14

hotels and motels

A6

houses of worship

A5.3

ice rinks

A5.5

industrial environments

A14

kitchens

A33

laboratories

A16.1

mass transit

A11.2

mines

A29

natatoriums

A5.6

nuclear facilities

A28

office buildings

A3.1

paper products facilities

A26.2

photographic processing and storage areas

A22.1

places of assembly

A5

plant growth chambers

A24.17

power plants

A27.10

printing plants

A20

public buildings

A3.1

rail cars

A11.5

retrofitting, contaminant control solar energy systems

A31

R7.9 A35.15

A35.18

A35.26

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Air conditioning (Cont.) subway stations

A15.14

swimming areas

A5.6

systems decentralized

S2.1

floor-by-floor

S2.6

forced-air, small

S9.1

packaged outdoor equipment

S2.8

rooftop

S2.8

radiant panel

S6.1

selection

S1.1

self-contained

S2.6

space requirements

S1.5

split

S2.6

temporary exhibits

S1.8

A5.8

textile processing plants

A21.4

theaters

A5.3

transportation centers

A3.6

warehouses

A3.8

wood products facilities Air contaminants

A26.1 F11

(See also Contaminants) Aircraft

A12

air conditioning

A12.10

air distribution

A12.12

air filters

A12.9

air quality

A12.13

A12.14

cabin pressurization control performance

A12.11

A12.13

A12.9

A12.15

carbon dioxide concentration

A12.14

environmental control system (ECS)

A12.11

air-conditioning packs air-cycle machine

A12.13

A12.15

A12.11

A12.13

A12.9 A12.10

cabin pressure control

A12.9

design conditions

A12.1

engine bleed air system

A12.10

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

A12.15

Index Terms

Links

Aircraft (Cont.) load determination

A12.1

outside air

A12.9

pneumatic system

A12.10

regulations

A12.14

heating

A12.6

humidity

A12.12

oxygen levels ozone concentration ventilation Air curtains, display cases

A12.1

A12.9

A12.12

A12.14

A12.6

A12.15

A12.15

R15.5

Air diffusers sound control, sound

11.15

testing

A38.2

Air diffusion air jets angle of divergence

F20.3

Archimedes number

F20.6

behavior

F20.3

centerline velocity

F20.3

Coanda effect

F20.6

entrainment ratios

F20.5

fundamentals

F20.3

isothermal, radial flow

F20.6

multiple

F20.7

nonisothermal

F20.6

surface (wall and ceiling)

F20.6

throw

F20.5

ceiling-mounted diffusers

F20.11

equipment

S19

evaluation

F20.12

air velocity

F20.13

exhaust inlets

F20.11

methods displacement ventilation mixed-air systems

F20.16 F20.7

outlets Group A

F20.7

F20.10

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Air diffusion (Cont.) Group B

F20.8

F20.10

Group C

F20.9

F20.11

Group D

F20.9

F20.11

Group E

F20.9

F20.11

performance

F20.10

performance index

F20.12

return inlets

F20.11

space

F20.13

F20.1

standards

F20.12

system design

F20.9

temperature gradient

F20.9

terminology

F20.2

Air diffusion performance index (ADPI)

A57.5

F20.12

F20.13

Air distribution aircraft cabins

A12.12

air terminals

A57.1

animal environments

A24.3

buildings

S4.1

central system

A42.1

control

S4.17

ductwork

S1.7

equipment

S19

fixed-guideway vehicles

A11.9

forced-air systems, small

S9.7

industrial environments

A31.3

in-room terminal systems

S5.10

isovels

A57.5

kitchen makeup air

A16.9

mapping

A57.5

occupied zone

A57.1

rail cars retail stores ships sound control, sound systems

S4.10

A33.23

laboratories

places of assembly

A24.5

A5.2 A11.7 A2.1 A13.2

A13.4

11.8

11.37

A57.1 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Air distribution (Cont.) design considerations

A57.2

fully stratified

A57.6

mixed

A57.2

partially mixed

A57.9

rooms

A57.1

terminal boxes

A47.12

testing, adjusting, balancing

A38.3

textile processing plants

A21.6

zone control

17

Air exchange rate air changes per hour (ach) modeling

F16.4 F16.22

multizone measurement

F16.6

time constants

F16.4

tracer gas measurement method

F16.5

Air filters. See Filters, air Airflow air-to-transmission ratio around buildings

S5.12 F24

air intake contamination estimation minimum dilution

F24.11

coefficients wind pressure

F24.3

computational modeling

F24.9

internal pressure

F24.9

LES model

F24.10

modeling and testing wind tunnels

F24.9 F24.10

patterns

A45.3

RANS model

F24.1

F24.10

wind data

F24.3

F24.6

effects on system operation intakes and exhausts

F24.7

system volume

F24.9

ventilation

F24.7

velocity pressure (Bernoulli equation)

F24.3

through building components

F25.7

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Airflow (Cont.) clean spaces

A18.3

computational fluid dynamics computer-aided modeling condensers, evaporative control

A40.14 A18.5 S38.15 F25

and convection

F25.5

displacement flow

F16.3

entrainment flow

F16.3

exhaust hoods

A32.3

furnaces

S32.3

with heat and moisture flow

F26

F27

A18.13

A18.14

F25.12

laminar

A18.4

measurement of

A38.2

modeling in buildings

F13

hygrothermal

F25.13

nonunidirectional

A18.3

perfect mixing

F16.3

pressure differentials

F25.4

smoke management

A53.5

solar energy systems

A35.25

terminology

F25.2

tracking

A47.9

unidirectional,

A18.4

velocity measurement

F36.14

and water vapor flow

F25.8

Airflow retarders

F25.7

Air flux

F25.2

F25.8

(See also Airflow) Air handlers all-air systems

S4.3

cooling

S4.4

dampers

S4.7

dehumidification

S4.5

distribution systems

S4.9

A42.1

draw-through

S4.3

economizers

S4.7 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Air handlers (Cont.) fans

S4.4

filter

S4.8

heating

S4.5

humidification

S4.5

location

S4.4

mixing plenum

S4.7

psychrometrics

S4.4

reheat

S4.9

sequencing

A42.35

set point reset

A42.36

sound levels

S4.6

S4.9

11.8

strategies

A42.35

unitary, air conditioners

S48.7

vibration isolation

S4.10

Air intakes design

A45.1

hospitals

A8.2

location to avoid contamination outdoor

A45.2 S4.7

vehicular facilities, enclosed

A15.37

Air jets. See Air diffusion Air leakage. (See also Infiltration) area

F16.15

building distribution,

F16.16

commercial buildings

F16.25

controlling, air-vapor retarder

F16.17

leakage function

F16.14

measurement

F16.14

F16.15

Air outlets accessories

S19.4

dampers

S19.4

location

S9.4

selection

S19.2

smudging

S19.3

sound level

S19.2

supply

S19.1

surface effects

S19.2

S19.7

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

S4.9

Index Terms

Links

Air outlets (Cont.) temperature differential

S19.2

types

S19.3

Airports, air conditioning

A3.6

Air quality. (See also Indoor air quality) aircraft cabins

A12.13

animal buildings

A24.2

bus terminals

A15.24

diesel locomotive facilities

A15.28

parking garages

A15.19

road tunnels

A15.9

tollbooths

A15.26

Airtightness

F36.22

Air-to-air energy recovery Air-to-transmission ratio Air transport

S25 S5.12 R27

animals

R27.2

commodity requirements

R27.2

design considerations

R27.2

galley refrigeration

R27.5

ground handling

R27.4

perishable cargo

R27.1

refrigeration

R27.3

shipping containers

R27.3

Air washers air cleaning

S40.8

coolers

S40.6

dehumidification performance factor

S40.8

heat and mass simultaneous transfer

F6.11

high-velocity spray type

S40.7

humidification

S40.7

maintenance

S40.8

spray type

S40.6

textile processing plants

A21.4

water treatment

A49.9

Algae, control

S40.9

A49.5

All-air systems advantages

S4.1 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

All-air systems (Cont.) air distribution

S4.10

air handlers

S4.3

buildings

S4.1

constant-volume

S4.10

control

S4.17

cooling

S4.4

costs

S4.3

dehumidification

S4.5

disadvantages

S4.1

dual-duct

S4.12

S4.8

S4.9

S4.12

economizers

S4.7

heating

S4.2

S4.5

humidification

S4.5

S4.9

multizone

S4.13

primary equipment

S4.4

single-duct

S4.10

variable-air-volume (VAV),

S4.11

zoning

S4.12

S4.2

Ammonia absorption ammonia/water

F2.18

ammonia/water/hydrogen

R18.8

R18.7

in animal environments,

A24.2

A24.9

properties, ammonia/water

F30.1

F30.34

system practices

F30.34

R2

Anchor bolts, seismic restraint

A55.7

Anemometers air devices types

A38.2 F36.16

Animal environments air contaminants ammonia

A24.2

carbon dioxide

A24.2

air distribution

A24.3

air inlets

A24.6

air quality control

A24.2

air transport

R27.2

A24.9

A24.5

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Animal environments (Cont.) cattle, beef and dairy

A24.7

cooling

A24.4

design

A24.1

disease control

A24.3

evaporative cooling

A24.4

fans

A24.6

heating

A24.4

hydrogen sulfide

A24.2

insulation

A24.4

laboratory conditions

A16.14

moisture control

A24.2

particulate matter (PM)

A24.2

poultry

A24.8

shades

A24.3

swine

A24.7

temperature control

A24.1

ventilation

A24.5

Annual fuel utilization efficiency (AFUE)

S32.8

A52.13

A24.9

S33.2

Antifreeze ethylene glycol

F31.4

hydronic systems

S12.23

propylene glycol

F31.4

Antisweat heaters (ASH)

R15.5

Apartment buildings service water heating, ventilation

A50.15

A50.18

A1.6

Aquifers, thermal storage

S50.6

Archimedes number

F20.6

Archives. See Museums, galleries, archives, and libraries Arenas air conditioning

A5.4

smoke management

A53.12

Argon recovery

R47.17

Asbestos

F10.4

ASH. See Antisweat heaters (ASH)

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Atriums air conditioning

A5.9

smoke management

A53.12

Attics, unconditioned

F27.2

Auditoriums

A5.3

Automobiles engine test facilities

A17.1

HVAC

A10

design factors

A10.1

subsystems air-handling

A10.3

heating

A10.7

refrigeration

A10.7

Autopsy rooms

A9.5

Avogadro’s law, and fuel combustion

A9.6

F28.10

B Backflow-prevention devices

S46.13

BACnet®

A40.17

F7.18

Bacteria control

A49.5

food, growth in

R22.1

humidifiers, growth in

S21.1

pathogens

F10.7

Bakery products

R41

air conditioning

R41.1

bread

R41

cooling

R41.4

dough production

R41.2

freezing

R41.5

ingredient storage

R41.1

refrigeration

R16.2

slicing

R41.5

wrapping

R41.5

Balance point, heat pumps

R41.1

S48.9

Balancing. (See also Testing, adjusting, and balancing) air distribution systems

A38.3

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Balancing (Cont.) dual-duct systems

A38.4

HVAC systems

A38.1

hydronic systems

A38.6

induction systems

A38.5

kitchen ventilation systems

A33.3

refrigeration systems

R5.1

steam distribution systems

A38.15

temperature controls

A38.16

variable-air-volume (VAV) systems

A38.4

BAS. See Building automation system (BAS) Baseboard units application

S35.5

design effects

S35.3

finned-tube

S35.1

heating equipment

S35.1

nonstandard condition corrections

S35.3

radiant

S35.1

rating

S35.3

Basements conditioned

A44.11

heat loss

F17.11

heat transfer

F27.2

moisture control

A44.11

unconditioned

A44.11

Beer’s law

F4.16

Bernoulli equation

F21.1

generalized

F3.2

kinetic energy factor

F3.2

steady flow

F3.12

wind velocity pressure

F24.3

Best efficiency point (BEP) Beverages

F3.6

S43.7 R39

beer

R39.1

storage requirements

R21.11

carbonated

R39.10

coolers

R39.11

fruit juice

F18.30

R38.1 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Beverages (Cont.) liquid carbon dioxide storage

R39.12

refrigeration systems

R39.11

refrigerators for

R16.2

thermal properties

R19.1

time calculations cooling

R20.1

freezing

R20.7

wine production

R39.8

storage temperature

R39.10

BIM. See Building information modeling (BIM) Bioaerosols airborne bacteria

F11.2

control

F11.7

fungus spores

F11.2

microbiological particulate

F11.6

mold

F11.6

pollen

F11.2

sampling

F11.7

viruses

F11.2

origins

F11.1

particles

F10.4

Biocides, control

A49.5

Biodiesel

F28.6

Biological safety cabinets

A16.6

Biomanufacturing cleanrooms

A18.7

F11.6

Bioterrorism. See Chemical, biological, radiological, and explosive (CBRE) incidents Boilers

S31

air supply

S34.26

aluminum

S31.3

burners

S30.1

burner types

S31.6

carbonic acid

S10.2

cast iron

S31.2 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Boilers (Cont.) central multifamily

A1.6

plants

S11.3

classifications

S31.1

codes

S31.5

combination

S31.4

condensing

S31.3

construction materials

S31.1

controls

A47.1

flame safeguard

S31.7

copper

S31.3

draft types

S31.3

dry-base

S31.2

efficiency

S31.5

electric

S31.4

equipment gas-fired

S3.5 S30.5

venting

S34.18

integrated

S31.4

modeling

F19.14

noncondensing

S31.3

oil-fired venting

S34.19

piping

S10.3

rating

S31.5

residential

S31.3

selection

S31.5 A50.28

sizing

S31.6

stainless steel

S31.3

standards

S31.5

steam

S31.1

systems steel

S30.11

A1.3

scotch marine

service water heating

S31.6

S10.3 S31.2

stokers

S30.17

storing

A49.11

venting

S34.18

S34.19

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

S31.7

Index Terms

Links

Boilers (Cont.) wall-hung

S31.4

waste heat

S10.3

water

S31.1

water treatment

A49.10

wet-base

S31.2

wet-leg

S31.2

working pressure

S31.1

Boiling critical heat flux

F5.4

evaporators flow mechanics

F5.4

heat transfer

F5.5

film

F5.1

natural convection systems

F5.1

nucleate

F5.1

pool

F5.1

F5.2

Brayton cycle cryogenics

R47.11

gas turbine

S7.18

Bread

R41

Breweries carbon dioxide production

R39.6

refrigeration fermenting cellar

R39.4

Kraeusen cellar

R39.5

stock cellar

R39.5

systems

R39.7

wort cooler

R39.3

storage tanks

R39.6

vinegar production

R39.8

Brines. See Coolants, secondary Building automation systems (BAS) Building energy monitoring

A40.17

F7.14

A41

(See also Energy, monitoring) Building envelopes air barrier requirements

A44.1 A44.5 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Building envelopes (Cont.) air intrusion

A44.2

air leakage control

A44.4

attics

A44.8

bound water

A44.2

building assembly

A44.1

building enclosure

A44.1

component

A44.1

condensation

A44.1

convective loop

A44.2

driving rain load

F25.3

dropped ceiling

A44.7

durability

A44.2

energy conservation

A44.1

exfiltration

A44.2

S21.2

existing buildings changing HVAC equipment in

A44.11

envelope modifications in

A44.12

face-sealed systems

A44.9

fenestration

A44.2

foundations

A44.11

heat transfer through

A44.11

moisture effects

A44.11

historic buildings

A44.11

hygrothermal design analysis

A44.2

infiltration

A44.2

insulation

F26.2

interstitial spaces

A44.7

interzonal environmental loads

A44.7

material properties

F26

moisture content

A44.2

moisture control

A44.5

museums, galleries, archives, and libraries plenum

A23.12 A44.2

return air

A44.7

rain screen designs

A44.9

roofs

A44.8

insulated sloped assemblies

A44.8

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Building envelopes (Cont.) low-slope assemblies

A44.8

steep-roof assemblies

A44.8

vegetated roofing

A44.8

R-value

A44.2

clear-wall

A44.4

material

A44.2

system

A44.2

total

A44.2

sorption

A44.2

structural failure, from moisture

F25.14

surface condensation

A44.7

terminology

A44.1

thermal break

A44.2

thermal bridge

A44.2

thermal bridges

F25.7

thermal insulation

A44.2

thermal mass

A44.4

thermal performance

A44.3

thermal transmittance

A44.2

U-factor (thermal transmittance)

A44.2

U-value

F25.7

vapor barrier continuous

A44.5

vapor diffusion control

A44.2

vapor retarder (vapor barrier)

A44.2

wall/window interface

A44.6

walls

A44.9

curtain

A44.9

precast concrete panels

A44.9

steel-stud

A44.10

water-resistive barrier (WRB)

A44.2

wind washing

A44.2

zone method

A44.4

Building information modeling (BIM), Building materials, properties

A40.15 F26

Building thermal mass charging and discharging

S50.15

effects of

S50.14 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Building thermal mass (Cont.) precooling

A42.37

Burners air supply

S34.26

controls

S30.20

conversion

S30.4

dual-fuel gas/oil

S30.6

S30.14

gas-fired

S30.3

altitude compensation

S30.10

combustion and adjustments

S30.20

commercial

S30.6

industrial

S30.6

residential

S30.5

venting

S34.18

oil-fired

S30.11

commercial

S30.12

fuel handling system

S30.15

preparation system

S30.16

storage

S30.14

industrial

S30.12

residential

S30.11

venting

S34.19

venting

S34.18

S34.19

Buses air conditioning

A11.2

garage ventilation

A15.21

Bus terminals air conditioning

A3.6

physical configuration

A15.23

ventilation equipment

A15.33

operation areas

A15.24

control

A15.26

effects of alternative fuel use

A15.25

platforms

A15.24

Butane, commercial

F28.5

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

C CAD. See Computer-aided design (CAD) Cafeterias, service water heating

A50.14

Calcium chloride brines

F31.1

A50.21

Candy chocolate

R42.1

manufacture chilling

R42.3

coating

R42.4

cooling

R42.4

dipping

R42.2

drying

R42.3

enrobing

R42.2

plants

R42.1

refrigeration plant

R42.4

storage humidity

R42.7

temperature

R42.6

Capillary action and moisture flow

F25.8

Capillary tubes capacity balance

R11.25

characteristic curve

R11.25

pressure-reducing device

R11.24

restrictor orifice

S22.2

selection

R11.26

Carbon dioxide in aircraft cabins

A12.14

in animal environments

A24.2

combustion

F28.1

greenhouse enrichment

A24.14

liquefaction

R39.7

measurement

F36.23

refrigerant storage Carbon emissions

F28.11

R3.1 R39.12 F34.6

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Carbon monoxide analyzers

A15.10

health effects

F10.11

parking garages

A15.19

road tunnels

A15.11

A15.20

A15.9

tollbooths

A15.26

Cargo containers

R25

airborne sound

R25.7

air circulation

R25.3

ambient design factors

R25.6

commodity precooling

R25.10

control

R25.5

controlled atmosphere

R25.5

costs, owning and operating

R25.9

design

R25.1

R25.11

equipment attachment provisions

R25.3

design and selection factors

R25.6

operating economy

R25.7

qualification testing

R25.8

selection

R25.9

system application factors

R25.8

types

R25.3

heating only

R25.5

insulation barrier

R25.1

load calculations

R25.8

maintenance

R25.11

mechanical cooling and heating operations

R25.3 R25.10

qualification testing

R25.8

safety

R25.7

sanitation

R25.3

shock and virbration

R25.6

space considerations

R25.10

storage effect cooling

R25.5

system application

R25.8

temperature-controlled transport

R25.1

temperature settings

R25.8

R25.10 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Cargo containers (Cont.) use

R25.10

vapor barrier

R25.1

ventilation

R25.5

Carnot refrigeration cycle Cattle, beef, and dairy

R25.10

F2.6 A24.7

(See also Animal environments) CAV. See Constant air volume (CAV) Cavitation

F3.13

pumps, centrifugal

S43.9

valves

S46.2

CBRE. See Chemical, biological, radiological, and explosive (CBRE) incidents Ceiling effect. See Coanda effect Ceilings sound correction

11.31

sound transmission

11.38

natural ventilation

F16.13

Central air conditioning

A42

(See also Air conditioning) Central plants boiler

S11.3

chiller

S11.1

distribution design

S11.5

district heating and cooling

S11.3

emission control

S11.4

heating medium

S11.3

hotels and motels

A6.7

thermal storage

S11.4

S11.4

Central systems cooling and heating

S3.1

features

S1.3

furnaces

S32.1

humidifiers

S21.5

residential forced air

S9.1

space requirements

S1.5

in tall buildings

A4.8

acoustical considerations

A4.11

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Central systems (Cont.) economic considerations

A4.10

location

A4.10

ventilation, with in-room terminal systems Cetane number engine fuels

S5.2 F28.8

CFD. See Computational fluid dynamics (CFD) Charging, refrigeration systems

R8.4

Chemical, biological, radiological, and explosive (CBRE) incidents biological events

A59 A59.8

building envelope as protection chemical agent types

F16.11

F16.18

A59.6

gases and vapors

A59.8

incapacitating

A59.6

irritants

A59.6

toxic

A59.6

chemical events

A59.5

explosive events

A59.10

design considerations

A59.11

loading description

A59.10

radiological events

A59.9

Chemical plants automation

R46.3

energy recovery

R46.4

flow sheets

R46.1

instrumentation and controls

R46.8

outdoor construction

R46.4

piping

R46.8

pumps

R46.8

refrigeration compressors

R46.6

condensers

R46.6

cooling towers

R46.8

equipment

R46.3

evaporators

R46.7

load

R46.2

safety requirements

R46.2

spray ponds

R46.8

R46.6

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Chemical plants (Cont.) systems

R46.1

safety requirements

R46.2

specifications

R46.1

tanks

R46.8

Chemisorption

A46.7

R46.5

Chilled water (CW) combined heat and power (CHP) distribution

S7.44

district heating and cooling

S11.4

S11.19

optimal temperature,

A42.26

pumping system,

A42.12

A42.27

A42.25

A42.29

A42.25

A42.27

S12.1

S12.17

pump sequencing reset systems central plant

S11.32

A38.14

heat transfer vs. flow one-pipe

A38.7 S12.19

testing, adjusting, balancing

A38.8

two-pipe

S12.19

thermal storage

S50.4

water treatment

A49.10

Chillers absorption

S3.4

ammonia/water

R18.7

heat-activated

S7.39

water/lithium bromide

R18.2

blast

R16.3

central plants

A47.4

S11.1

centrifugal air-cooled

S42.12

controls

S42.11

equipment

S42.8

fouling

S42.11

free cooling

S42.12

hot-gas bypass

S42.10

maintenance

S42.12

purge units

S42.11

rating

S42.10 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

S11.4

Index Terms

Links

Chillers (Cont.) refrigerant selection

S42.8

transfer units,

S42.12

selection methods

S42.10

temperature lift

S42.10

control

A47.4

capacity

S42.4

considerations

S42.14

S42.11

regulating

S42.4

safety

S42.4

costs

S42.3

direct expansion

R1.26

economizing

S42.1

expansion turbines

S42.1

flash

S42.1

heat recovery

S42.2

injection

S42.1

liquid-chilling systems liquid heads

S42.1

S42 S42.3

load distribution

A42.30

maintenance

S42.5

marine water boxes

S42.3

noise generation

11.15

optimization

A47.5

prerotation vanes

S42.4

S42.12

S42.15

S42.11

S42.9

reciprocating components

S42.5

control

S42.7

equipment

S42.5

performance

S42.6

refrigerant selection

S42.6

selection methods

S42.7

refrigeration cycle

S42.1

screw applications

S42.15

capacity control

S42.14

components

S42.13 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Chillers (Cont.) equipment

S42.13

maintenance

S42.15

performance

S42.14

selection methods

S42.3

S42.7

S42.10

A42.29

A42.29

A42.32

sequencing standards

S42.5

subcooling

S42.1

and turbines

S17.4

vapor compression model

F19.15

variable-flow

S42.2

variable-speed

S42.4

vibration control

S42.10

S42.11

walk-in

R16.3

Chilton-Colburn j-factor analogy

F6.7

Chimneys

S34

accessories

S34.28

capacity calculation examples

S34.12

caps

S34.30

codes

S34.32

design equations

S34.3

draft

S34.1

available

S34.1

S34.3

theoretical

S34.2

S34.3

fireplace

S34.1

S34.20

flue gas

S34.1

functions

S34.2

gas, appliance venting

S34.18

masonry

S34.18

materials

S34.26

standards

S34.27

terminations

S34.30

wind effects

S34.3

Chlorinated polyvinyl chloride (CPVC)

A34.6

Chocolate

R42.1

S34.20

S34.32

S34.30

(See also Candy) Choking

F3.13

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

CHP systems. See Combined heat and power (CHP) Cinemas

A5.3

Claude cycle

R47.8

Cleanrooms. See Clean spaces Clean spaces

A18

aerospace

A18.14

air filters

A18.3

A18.9

A18.13

airflow

A18.3

A18.5

A18.13

applications

A18.2

biomanufacturing cleanrooms

A18.7

construction

A18.19

contaminant control

A18.3

cooling

A18.15

energy conservation

A18.17

fire safety

A18.16

high-bay

A18.14

humidity control

A18.16

makeup air

A18.15

noise control

A18.19

operation

A18.19

particle sources

A18.9

A18.18

A18.3

pharmaceutical aseptic

A18.7

start-up

A18.11

biomanufacturing

A18.7

contaminant control

A18.9

control and monitoring design

A18.10 A18.8

isolators

A18.10

nonaseptic

A18.11

unidirectional hoods

A18.9

pressurization

A18.16

process exhaust,

A18.16

semiconductor

A18.13

system sizing and redundancy

A18.17

temperature control,

A18.16

terminology

A18.18

A18.1 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

A18.14

Index Terms

Links

Clean spaces (Cont.) testing

A18.7

vibration control

A18.19

Clear-sky solar radiation, calculation Climate design information

F14.7 F14

Clothing insulation, clo units

F9.8

moisture permeability

F9.8

CLTD/CLF. See Cooling load temperature differential method with solar cooling load factors (CLTD/CLF) Coal classification

F28.8

handling facilities,

A27.6

heating value

F28.9

stokers

A27.9

S30.17

types

F28.8

Coanda effect

A33.6

Codes

F20.6

A61 (See also Standards)

air conditioners, room

S49.4

air distribution

A57.1

boilers

S31.5

building codes

S18.1

chilled-beam system

A57.18

chimneys, fireplaces, and gas vents

S34.32

condensers

S38

evaporative

S38.18

water-cooled

S38.7

coolers, liquid data processing

S41.4 A19.16

dehumidifiers, room

S24.3

duct construction

S18.1

electrical

A56.15

furnaces

S32.10

makeup air units

S27.9

motors

S44.2

nuclear facilities

A28.12 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

S19.2

Index Terms

Links

Codes (Cont.) piping

S45.6

tall buildings

A4.14

Coefficient of performance (COP) absorption

F2.13

compressors

S37.2

economic (ECOP), combined heat and power (CHP) refrigeration

S7.50 F2.3

room air conditioners

F2.13

S49.2

Cogeneration. See Combined heat and power (CHP) Coils air-cooling

S4.8

airflow resistance

S22.6

applications

S22.1

aqueous glycol coils

S22.2

construction and arrangement

S22.1

control

A47.6

direct-expansion coils

S22.2

fluid flow arrangement

S22.3

heat transfer

S22.6

load determination

S22.14

maintenance

S22.15

S22.4

S22.3

performance cooling and dehumidifying

S22.9

cooling-only

S22.7

rating

S22.6

refrigerant coils

S22.2

selection

S22.5

on ships

A13.4

water coils

S22.2

air-heating

S26.1

aqueous glycol

S26.2

construction

S26.1

design

S26.1

electric

A47.3

installation

S26.4

S26.3

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Coils (Cont.) maintenance

S26.5

rating

S26.3

refrigerant

S26.3

selection

S26.3

shipboard

A13.4

steam

A47.2

S26.1

water

A47.2

S14.8

condensers

S26.2

S38

evaporative

S38.15

dehumidifying

S22.1

desuperheating

S38.17

energy recovery loops

S25.11

halocarbon refrigeration systems

R1.27

heat and mass simultaneous transfer

F6.12

heat reclaim

S26.3

preheat

S4.8

reheat

S4.9

Colburn’s analogy

S26.2

F4.17

Colebrook equation friction factor

F21.6

pressure drop

F22.1

Collectors, solar

A35.6

A35.11

A35.23

S36.3 (See also Solar energy) Colleges and universities

A7.11

Combined heat and power (CHP) economic feasibility

S7 S7.49

estimate

S7.50

load duration curve

S7.50

two-dimensional

S7.52

simulation

S7.53

electrical systems

S7.44

expansion engines/turbines,

S7.31

heat-activated chillers

S7.39

heat recovery engines

S7.33

turbines

S7.37

S7.34

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

A35.25

Index Terms

Links

Combined heat and power (CHP) (Cont.) load profiling

S7.4

maintenance

S7.17

modular systems

S7.3

packaged systems

S7.3

peak shaving

S7.4

prime movers fuel cells

S7.22

selection

S7.4

thermal output

S7.33

turbines combustion

S7.18

S7.46

steam

S7.25

S7.47

thermal energy storage

S7.40

utilization systems air

S7.43

district heating and cooling

S7.43

hydronic

S7.43

service hot water

S7.43

vibration control, foundations Combustion

S7.15 F28

air pollution

F28.14

air required for

F28.10

altitude compensation

F28.3

calculations air required for

F28.10

carbon dioxide, theoretical

F28.11

efficiency

F28.12

flue gas dew point

F28.12

loss

F28.14

quantity produced,

F28.11

water vapor in

F28.12

coals characteristics

F28.9

classification

F28.9

heating value

F28.9

types

F28.8 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Combustion (Cont.) condensation in

F28.16

continuous

F28.2

corrosion in

F28.16

diesel fuel

F28.7

efficiency

F28.12

engine fuels, cetane number excess air

F28.8 F28.10

flammability limits

F28.1

fuel oils

F28.6

gaseous fuels illuminants

F28.10

liquefied petroleum gas

F28.5

natural gas

F28.5

types and properties

F28.5

gas turbine fuel

F28.7

heating value

F28.3

ignition temperature

F28.2

illuminants

F28.10

liquid fuels

F28.6

engines

F28.7

noise

F28.17

oscillation

F28.17

pollution

F28.14

principles

F28.1

pulse

F28.2

reactions

F28.1

resonance

F28.17

solid fuels

F28.8

soot

F28.17

sound

F28.17

stoichiometric

F28.1

types

F28.1

Combustion air systems air required

S34.26

analysis

F36.32

burners gas

S30.20 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Combustion air systems (Cont.) oil

S30.11

control

S30.2

efficiency boilers

S31.5

industrial exhaust gas cleaning venting

S29.27 S34.1

Combustion turbine inlet cooling (CTIC), thermal storage

S7.20

S17.1

S50.17

Comfort. (See also Physiological principles, humans) environmental indices

F9.20

environmental parameters air velocity

F36.29

asymmetric thermal radiation

F9.14

draft

F9.14

floor temperature

F9.15

radiant temperature

F9.11

vertical air temperature difference

F9.15

humidity

F25.14

local discomfort

F9.14

nonuniform conditions

F9.14

predicted mean vote (PMV)

F9.17

predicted percent dissatisfied (PPD)

F9.17

productivity

F9.13

radiant heating

A54.3

F36.29

F36.30

special environments extreme cold

F9.25

hot and humid environments

F9.24

infrared heating

F9.23

radiant heating, comfort equations

F9.24

steady-state energy balance two-node model

F9.16 F9.18

task performance

F9.13

thermal sensation scale

F9.11

zones

F9.19

Commercial and public buildings air leakage airports

F10.12

A3.1 F16.25 A3.6

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

S21.1

Index Terms

Links

Commercial and public buildings (Cont.) burners gas

S30.3

oil

S30.12

bus terminals

S30.6

A3.6

central cooling systems

A42.1

cruise terminals

A3.6

design concepts

A3.3

ducts construction

S18.2

design, small applications

S9.10

furnaces

S32.5

general design considerations humidifiers

A3.1 S21.6

ice rinks

R44

kitchen ventilation

A33.1

load characteristics

A3.2

malls

A2.6

office buildings

A3.1

retail facilities

A2.1

service water heating

A50.13

transportation centers

A3.6

warehouses

A3.8

Commissioning

A43

acceptance

A43.7

basis of design (BOD)

A43.2

certification

A43.12

checklist

A43.2

construction

A43.6

control systems

F7.18

costs

A43.8

A43.11

desiccant dehumidifiers

S23.7

design

A43.5

design review

A43.7

existing buildings

A43.1

in integrated building design

A58.8

issues log

A43.8

laboratories

A43.5

A47.21

A43.11

A16.20 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Commissioning (Cont.) makeup air units

S27.9

new construction

A43.1

objectives

A43.2

occupancy and operations

A43.10

owner’s project and requirements (OPR)

A43.2

predesign

A43.4

pumps, centrifugal

S43.13

recommissioning

A43.1

A43.11

retrocommissioning

A43.1

A43.11

systems manual

A43.2

A43.6

team

A43.3

test procedures

A43.8

Compressors

A43.10

S37

air conditioners, room ammonia refrigeration systems

S49.2 R2.2

bearings centrifugal

S37.36

reciprocating

S37.7

rotary

S37.13

scroll

S37.23

single-screw

S37.14

twin-screw

S37.20

centrifugal

S37.10

S7.45

angular momentum

S37.29

bearings

S37.36

capacity control

S37.33

critical speed

S37.34

design

S37.35

drivers

S37.35

efficiency

S37.32

isentropic analysis

S37.30

lubrication

S37.36

Mach number

S37.31

noise

S37.5

paralleling

S37.35

polytropic analysis

S37.30

refrigeration cycle

S37.28

S37.36

S37.23

S37.34

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Compressors (Cont.) surging

S37.33

testing

S37.32

turbocompressors

S37.28

variable-speed

S37.33

vibration

S37.34

chemical industry refrigeration drives

R46.6 R2.2

dynamic

S37.1

engine-driven

S7.45

halocarbon refrigeration systems

R1.24

heat pump systems

S8.6

motors

S37.6

noise generation

11.15

operation and maintenance,

S37.36

orbital

S37.23

positive-displacement performance

S44.4

S37.6 S37.2

reciprocating

S7.45

application

S37.7

S37.11

bearings

S37.7

capacity control

S37.10

S37.11

crankcase

R1.33

features

S37.9

lubrication

S37.10

parallel

R2.11

performance

S37.8

special devices

S37.11

types

S37.7

valves

S37.10

rotary

R2.12

bearings

S37.11

S37.14

S37.13

screw

S7.46

lubricant cooling

R2.14

single

S37.14

bearings

S37.14

capacity control, project S37.17 requirements compression process,

S37.14

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Compressors (Cont.) economizers

S37.16

lubrication

S37.15

noise and vibration,

S37.18

oil-injected

S37.15

performance

S37.18

volume ratio

S37.16

twin

S37.19

bearings

S37.20

capacity control

S37.20

compression process,

S37.19

hermetic

S37.23

lubrication

S37.22

volume ratio

S37.21

scroll

S37.23

bearings

S37.25

capacity control

S37.25

efficiency

S37.26

variable-speed

S37.26

trochoidal (Wankel)

S37.27

Computational fluid dynamics (CFD) assessing predictions

F13.1 F13.11

boundary conditions for inlet

F13.6

outlet

F13.7

reporting

F13.13

sources/sinks

F13.8

surfaces

F13.7

symmetry

F13.8

walls

F13.7

considerations

F13.9

grids

F13.4

mathematical approaches

F13.1

meshing

F13.4

reporting

F13.9

steps

F13.9

turbulence modeling

F13.3

validation

F13.9

F13.13

F13.10

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Computational fluid dynamics (CFD) (Cont.) verification

F13.9

viscosity modeling

F13.10

Computer-aided design (CAD) Computers

A18.5

A40.14

A40

abbreviations for programming

F37.1

BACnet®

A40.18

building automation systems (BAS)

A40.17

F7.18

computational fluid dynamics

A15.3

A40.14

computer-aided design (CAD)

A18.5

A40.14

F7.4

F7.10

for control

A53.14

design tools acoustic calculations

A40.11

building information modeling (BIM)

A40.15

combined heat and power (CHP)

S7.53

computational fluid dynamics

A40.14

computer-aided design (CAD)

A40.14

duct design

A40.10

equipment selection and simulation

A40.12

load calculations

A40.9

piping design

A40.11

refrigerant properties

A40.16

smoke control analysis

A53.12

ventilation

A40.17

road tunnel

A15.3

equipment

A40.12

graphics

A53.13

A43.2

A40.14

hardware

A40.1

HVAC simulation

A40.13

Internet

A40.7

modeling

F7.20

monitoring and control

A40.17

networking components

A40.5

peripherals

A40.5

smoke control analysis software

A53.12

A53.13

A40.2

antispyware

A40.2

custom programming

A40.4

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

F7.20

Index Terms

Links

Computers (Cont.) development tools

A40.4

energy analysis

F19.3

firewall

A40.2

graphics

A40.3

HVAC

A40.9

readymade

A40.4

road tunnel

A15.3

terminology

A40.2

utilities

A40.2

supervisory control

A40.16

A40.17

World Wide Web

A40.8

Concert halls

A5.4

Concrete cooling

R45.1

pozzolanic admixtures

R45.1

selection

R45.1

thermal design

R45.4

water heating for

A50.24

Condensate steam systems

F22.13

water treatment

A49.11

S10.6

Condensation in building components

F25.14

in combustion systems

F28.16

concealed

S21.3

control, with insulation

F23.3

dew-point analysis

F25.13

dropwise

F5.8

energy recovery equipment

S25.7

film

F5.8

heat transfer coefficients

F5.9

interstitial, and drying

F25.13

noncondensable gases

F5.10

with oil

F5.11

oil-fired appliances

S34.19

prevention, dehumidification for

S23.10

surface

F25.2

F25.12

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

S11.7

S11.19

Index Terms

Links

Condensation (Cont.) in tubes

F5.8

visible

S21.2

Condensers

S38

air conditioners, room

S49.2

air-cooled

R15.16

control

S38

air-side

S38.12

low-pressure-drop

S38.11

refrigerant-side,

S38.11

installation

S38.13

machine room

R15.17

maintenance

S38.13

noise

R15.18

rating

S38.11

remote from compressor

R15.17

types

S38.8

S38.11

S42.8

S42.13

S38.8

ammonia refrigeration systems

R2.2

horizontal shell-and-tube

R2.16

parallel horizontal shell-and-tube

R2.16

piping

R2.15

cascade

R5.1

chemical industry refrigeration

R46.6

in chillers

S42.6

circuiting

S38.5

evaporative

R15.17

airflow

S38.15

capacity control

S38.18

codes

S38.18

coils

S38.15

desuperheating

S38.17

wetting method,

S38.15

freeze prevention

S38.16

heat transfer

S38.14

liquid subcoolers

S38.17

location

R2.17

maintenance

S38.18

multicircuiting with liquid coolers

S38.17

S38.14

S38.16

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Condensers (Cont.) multiple-condenser installations

S38.16

purging

S38.18

rating

S38.16

standards

S38.18

water

S38.18

halocarbon refrigeration systems air-cooled

R1.33

evaporative

R1.32

piping

R1.23

pressure control

R1.32

water

R1.32

retail food store refrigeration

R15.16

water-cooled

S38.1

circuiting

S38.5

codes

S38.7

Darcy-Weisbach equation

S38.4

fouling factor

S38.4

heat removal

S38.1

cooling tower

S13.1

once-through

S13.1

heat transfer

S38.2

liquid subcooling

S38.5

maintenance

S38.7

noncondensable gases

S38.6

pressure drop

S38.4

standards

S38.7

types

S38.5

Conductance, thermal

F4.3

F25.1

Conduction display cases

R15.4

steady-state

F4.3

thermal

F4.1

F4.3

F25.1

F26.4

F25.1

F26.4

Conductivity, thermal apparent of thermal insulation

F26.4

foods

R19.9

soils

F26.12 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Constant air volume (CAV) control

A42.1

supply air temperature reset

A42.36

versus variable-air-volume (VAV)

A16.12

Constant-volume, all-air systems dual-duct

S4.12

single-duct

S4.10

terminal units

S4.16

Construction. (See also Building envelopes) curtain wall

F15.5

glass block wall

F15.19

in integrated building design

A58.7

A58.8

Containers. (See also Cargo containers) air transport

R27.3

marine transport

R26.2

Contaminants clean spaces

A18.3

food

R22.1

A18.9

gaseous combustion

F28.14

S29.27

concentration, indoor, measurement

A46.4

control

A46.6

F11.14

adsorption,

A46.6

S29.24

catalysis

A46.8

chemisorption,

A46.7

desiccant dehumidification,

S23.10

dilution ventilation,

A46.6

hoods and local exhaust

A46.6

incineration

S29.27

source elimination wet-packed scrubbers environmental tobacco smoke (ETS)

A46.6 S29.18 F11.2

flammable

F11.18

indoor air

F11.16

industrial

F11.16

inorganic

F11.14

measurement

A46.4

F11.10

F36.31

nuclear facilities

A28.3

A28.5

A28.8

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Contaminants (Cont.) outdoor air

F11.15

ozone

A46.13

polycyclic aromatic compounds (PAC)

F10.5

radioactive

F11.19

radon

A46.13

soil gases

F11.20

vapors, flammable

F11.18

volatile organic compounds (VOC)

F11.11

health effects

F10.9

total (TVOC),

F11.13

indoor, concentration prediction organism destruction

F10.17

F13.16 R22.4

particulate aerosols

S28.1

asbestos

F10.4

classification

F11.1

coarse

F11.2

collection mechanisms

S28.2

combustion

S29.15

F28.14

dusts

S28.1

combustible

F11.18

environmental tobacco smoke (ETS)

F11.2

fine

F11.3

fogs

F11.1

fumes

F11.1

measurement

F11.3

F36.32

mists

F11.1

pollen

F11.6

polycyclic aromatic compounds (PAC)

F10.5

radioactive

F11.3

F11.19

size distribution

F11.4

smogs

F11.1

smokes

F11.1

suspended particles, counters

F11.6

synthetic vitreous fibers

F10.5

ultrafine

F11.3

refrigerant systems

S29.10

F11.3

R7.1 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Contaminants (Cont.) dirt

R7.6

field assembly

R7.8

filter-driers

R7.6

generation by high temperature

R6.9

lubricants

R7.7

metallic

R7.6

moisture

R7.1

motor burnout

R7.8

noncondensable gases

R7.7

residual cleaning agents

R7.7

sludge, tars, and wax

R7.7

solvents

R7.7

special system characteristics

R7.9

textile processing

R7.8

A21.7

Continuity fluid dynamics

F3.2

Control. (See also Controls, automatic; Supervisory control) absorption units

R18.6

R18.9

air-cooled condensers,

S38.11

aircraft cabin pressure

A12.11

A12.13

air-handling systems

A42.35

A47.9

all-air systems

S4.17

authority

F7.7

automobile air conditioning

A10.8

biological growth

A49.5

boilers

A47.1

building pressurization

A47.8

burners

S30.19

bus terminal ventilation

A15.26

central air conditioning

A42.1

chemical plants

R46.3

chilled-water pumps

A42.12

chillers

A42.29

combustion turbines

A42.25

A42.27

S7.22

components

F7.4

condensers

S38

evaporative

S31.6

S38.18 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Control (Cont.) cooling

S6.20

coils

A47.6

S22.3

A42.21

A42.25

tower fans towers

A47.5

corrosion

A49.2

dehumidifying coils

S22.3

A49.9

design principles controlled area size

A47.20

energy conservation

A47.19

load matching

A47.20

sensor location

A47.21

system selection

A47.20

economizers

A47.2

electric heating slabs

S6.20

energy recovery equipment

S25.7

engines

S7.15

fans

A47.7

air volume

S44.8

fire

A53.1

fixed-guideway vehicle air conditioning, forced-air systems, small fundamentals

A47.10

S25.11

S20.9

A11.8 S9.3 F7

furnaces

S32.2

gaseous contaminants

A46.1

heaters infrared

S15.4

heating coils

A47.2

heat pumps

S48.10

heat recovery systems

S32.5

S33.2

S33.4

S23.1

S8.18

heat timers

S10.13

humidifiers

S21.7

humidity

A47.12

S21.1

hydronic heating systems

S12.13

S14.8

justice facilities laboratory systems liquid chillers low-temperature

A9.3 A16.12 S42.4

S42.7

S42.11

R2.7 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

S42.14

Index Terms

Links

Control (Cont.) makeup air units motors protection

A47.16

S27.9

S44.5

S44.6

S44.6

nuclear facilities

A28.5

optimization

A42.1

outdoor air quantity

A47.9

paper moisture content

A20.2

parking garage ventilation photographic materials processing

A15.20 A22.3

pipe-tracing systems

A51.20

plant growth chambers

A24.17

processes

A46.6

radiant panels

A47.4

radioactivity

A28.8

rail car air conditioning

A11.7

refrigerant flow

R11.1

residential heating and cooling road tunnel ventilation

S6.19

A1.6 A15.11

scale

A49.4

ship air conditioning merchant

A13.3

naval surface

A13.4

smoke

A53.1

snow-melting systems

A51.10

solar energy

A35.12

differential temperature controller

S36.16

hot-water dump

S36.17

overtemperature protection

S36.17

sound

11.1

A35.24

A35.26

11.49

F8.15

static pressure variable flow rates

A47.8

steam systems

S10.13

thermal storage systems unit heaters

A42.38

S50.23

S27.7

unit ventilators

A47.15

S27.3

variable-air-volume (VAV) systems

A42.1

A47.7

vibration

11.41 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

S36.16

Index Terms

Links

Control (Cont.) zone systems

A47.17

zone valves

S10.13

Controlled-atmosphere (CA) storage apples

R35.3

apricots

R35.13

berries

R35.13

cherries, sweet,

R35.12

figs

R35.13

grapes

R35.8

nectarines

R35.12

peaches

R35.12

pears

R35.6

plums

R35.11

refrigerated facilities

R35.7

R23.3

strawberries,

R35.13

vegetables

R37.6

Controlled-environment rooms (CERs), and plant growth

A24.16

Controls, automatic

F7

(See also Control) authority

F7.7

classification

F7.4

closed loop (feedback)

F7.1

commissioning

F7.18

components controlled devices actuator,

F7.4

dampers,

F7.4

operator

F7.4

positive positioners

F7.8

valves

F7.4

F7.6

controllers direct digital (DDC)

A38.16

static pressure

A47.8

thermostats

F7.11

sensors flow rate,

F7.10

F7.8 F7.10 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

F7.19

Index Terms

Links

Controls, automatic (Cont.) humidity (hygrometers)

F7.9

indoor air quality

F7.10

lighting level

F7.10

location,

A47.21

power sensing and transmission

F7.10

pressure

F7.9

temperature

F7.9

transducers, electronic-to-pneumatic (E/P)

F7.13

computers

A40.17

F7.4

control action types

F7.2

F7.4

F7.18

dampers

F7.6

F7.4

F7.10

F7.10

R11.4

actuator mounting

F7.8

actuators

F7.8

types

F7.6

direct digital (DDC)

A38.16

explosive atmospheres

A47.18

extraordinary incidents

A47.19

feedback (closed loop)

F7.1

fuzzy logic

F7.3

mobile applications

A47.18

modeling

F19.23

modulating

F7.2

open loop

F7.1

positive positioners

F7.8

proportional/integral (PI)

F7.3

proportional-integral-derivative (PID)

F7.3

proportional-only (P)

F7.3

refrigerant flow safety sensors

R11.1 A47.18 F7.8

static pressure

A47.8

switches

R11.1

systems

F7.1

terminology

F7.1

testing transducers, pressure

A38.16 R11.4 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

F7.19

Index Terms

Links

Controls, automatic (Cont.) tuning

F7.3

two-position

F7.2

valves

F7.4

actuators

F7.6

flow characteristics

F7.5

selection and sizing

F7.5

F7.18

F7.6

Convection flow, fully developed turbulent

F4.17

forced

F4.16

condensation in tubes

F5.8

evaporation in tubes

F5.4

equations

F5.6

laminar

F4.17

transition region

F4.17

turbulent

F4.17

free

F4.18

mass

F6.5

natural

F4.18

steam heating systems thermal

F5.9

F5.1

S10.11 F4.1

Convectors application

S35.5

design effects

S35.3

heat-distributing unit

S35.1

nonstandard condition corrections

S35.3

rating

S35.2

Convention centers

A5.5

Conversion factors

F38

Coolants, secondary brines corrosion inhibition properties

F31.4

F31.1

calcium chloride solutions d-limonene

F31.1 F31.12

ethyl alcohol solutions halocarbons

A49.10

F31.1 F31.12

inhibited glycols This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

F7.19

Index Terms

Links

Coolants, secondary (Cont.) corrosion inhibition

F31.11

ethylene glycol

F31.4

propylene glycol

F31.4

service considerations

F31.11

low-temperature refrigeration

R48.10

nonhalocarbon nonaqueous fluids

F31.12

polydimethylsiloxane

F31.12

potassium formate solutions

F31.1

refrigeration systems

R13.1

sodium chloride solutions

F31.1

Coolers. (See also Refrigerators) beverage

R39.11

cryocoolers

R47.11

forced-circulation air

R14.1

installation and operation

R14.6

liquid (See also Evaporators) Baudelot

S41.2

brazed (semiwelded) plate

S41.2

in chillers

S42.6

evaporative, with evaporative condensers

S41.2

freeze prevention

S41.5 S41

coefficients

S41.3

fouling factor

S41.4

maintenance

S41.6

oil return

S41.6

piping

R1.25

pressure drop

S41.4

refrigerant flow control

S41.5

residential

R1.26

A1.5

shell-and-tube

S41.1

tube-in-tube

S41.1

vessel design requirements

S41.4

retail food store

S42.13

S38.17

flooded

heat transfer

S42.8

R15.1

walk-in

R15.12

water

R39.11

R16.3

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Cooling. (See also Air conditioning) absorption equipment

R18.1

animal environments

A24.4

bakery products

R41.4

concrete active systems

R45.5

air blast

R45.2

chilled water

R45.1

embedded coils

R45.1

inundation

R45.2

passive

R45.4

controls

S6.20

foods and beverages, time calculations

R20.1

fruits and vegetables evaporative

R28.8

forced-air

R28.6

hydrocooling

R28.3

load calculation

R28.1

package icing

R28.8

vacuum cooling

R28.9

geothermal energy systems greenhouses

A34.9 A24.12

radiant panel systems

S6.1

radiative

A35.17

solar energy systems

A35.15

A35.18

A35.26

S12.1

S12.17

S12.18

water systems dynamometers

A17.4

Cooling load calculations

F17

central plant

S3.2

coil

F18

F18.2

nonresidential

F18

heat balance

F18.2

conduction transfer functions

F18.19

heat gain fenestration

F18.14

sol-air temperature

F18.22

heat sources

F18.3 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Cooling load (Cont.) radiant time series (RTS) method sol-air temperature refrigeration

F18.2 F18.22 S5.11

residential

F17

heat balance (RHB) method

F17.2

load factor (RLF) method

F17.2

space

F18.2

Cooling load temperature differential method with solar cooling load factors (CLTD/CLF), Cooling towers

F18.49 S39

approach to wet bulb

S39.1

capacity control

S39.2

airflow

A42.22

fan cycling

S39.8

fan sequencing

A42.21

flow modulation

A42.14

two-speed fans

S39.8

variable-frequency fan drives

S39.8

variable- vs. fixed-speed fans

A42.14

construction materials

S39.7

design conditions

S39.2

drift

S39.11

eliminators

S39.11

economics

S39.7

fill

S39.3

fogging

S39.11

free cooling

S39.10

freeze protection

S13.3

heat and mass simultaneous transfer

F6.12

indirect evaporative coolers

S13.3

inspections

S39.11

Legionella pneumophila

S39.12

maintenance

S39.11

model

F19.16

number of transfer units (NTU)

S39.16

S39.12

S39.10

S40.5

S39.13

performance curves

S39.13 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Cooling towers (Cont.) monitoring

S39.11

thermal

S39.15

tower coefficients

S39.17

piping

S13.2

plumes

S39.11

principle of operation

S39.1

recommissioning

A49.8

selection

S39.7

shutdown

A49.9

siting

S39.7

sound, attenuators

S39.8

S39.10

start-up

A49.8

testing

A38.15

theory

S39.15

counterflow integration

S39.16

cross-flow integration

S39.17

heat and mass transfer

S39.15

types

S39.15

S3.5

direct contact

S39.5

indirect contact

S39.2

open systems

S13.1

water treatment

A49.4

S39.6

A49.8

A49.9

A49.3

A49.9

S39.13 winter operation

S39.10

inspections

S39.13

Cool storage

S50.1

COP. See Coefficient of performance (COP) Corn, drying

A25.1

Correctional facilities. See Justice facilities Corrosion brines

F31.4

in combustion systems

F28.16

concentration cell corrosion

A49.2

contributing factors

A49.2

control

A49.2

in boilers

A49.10

cathodic protection

A49.4

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

S13.2

Index Terms

Links

Corrosion (Cont.) buried pipe

S11.24

in cooling towers

A49.4

cycles of concentration

A49.3

in geothermal energy systems

A34.6

inhibitors

A49.3

materials selection

A49.3

passivation

A49.4

protective coatings

A49.3

in steam and condensate systems energy recovery equipment

A49.11 S25.7

galvanized metals

F31.11

glycol degradation

F31.11

inhibited glycols

F31.11

microorganism influence oil-fired appliances

A49.2

A49.5

S34.20

oxygen corrosion

A49.2

secondary coolant systems

R13.5

service water systems

A50.9

types

A49.2

under insulation

F23.6

white rust

A49.4

under insulation

R10.2

A49.11

Costs. (See also Economics) all-air systems

S4.3

analysis period

A37.2

economic analysis techniques computer analysis

A37.13

inflation

A37.10

internal rate of return

A37.11

life-cycle cost analyses

A37.9

payback

A37.9

present value (worth)

A37.10

savings-to-investment ratio (SIR)

A37.11

energy

A37.4

financing alternatives

A37.8

inflation

A37.9

A37.10

interest and discount rate

A37.4

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Costs (Cont.) laboratory systems

A16.20

life-cycle

A37.12

energy recovery equipment

S25.11

operation and maintenance

A39.1

piping insulation

S25.15

S25.22

S11.17

maintenance

A37.7

operating actual

A37.4

electrical energy

A37.5

natural gas

A37.6

other fuels

A37.6

snow-melting systems

A51.8

A51.10

owning initial cost

A37.1

insurance

A37.4

taxes

A37.4

periodic

A37.4

refrigerant phaseout

A37.8

Cotton, drying

A25.8

Courthouses

A9.4

Courtrooms

A9.5

CPVC. See Chlorinated polyvinyl chloride (CPVC) Crawlspaces heat loss

F17.11

insulation

A44.11

vented vs. unvented

A44.11

wall insulation

A44.11

Critical spaces forensic labs

A9.7

justice facilities

A9.4

Crops. See Farm crops Cruise terminals

A3.6

Cryogenics

R47

biomedical applications cryomicroscopy

R49.6

cryopreservation

R49.1 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Cryogenics (Cont.) cryoprotective agents

R49.2

cryosurgery

R49.7

induced hypothermia

R49.7

refrigeration

R49.1

specimen preparation

R49.6

Brayton cycle

R47.11

cascade cycle

R47.8

Claude cycle

R47.8

cryobiological

R49.8

cryocoolers recuperative

R47.11

Brayton

R47.11

Joule-Thomson

R47.11

Kleemenko

R47.13

regenerative

R47.14

Gifford-McMahon

R47.15

orifice pulse tube

R47.14

Stirling

R47.14

cryopumping

R47.1

equipment coiled-tube exchanger

R47.21

compressors

R47.20

expansion devices

R47.20

heat exchangers

R47.21

regenerators

R47.22

systems

R47.20

turboalternators

R47.21

turboexpanders

R47.21

fluids cold burns

R47.28

flammability

R47.29

storage vessels

R47.26

transfer

R47.27

freezers, industrial hazards

R29.5 R47.28

Heylandt cycle

R47.8

instrumentation

R47.27 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Cryogenics (Cont.) insulation low-temperature

R47.23

selection (table)

R47.26

thermal conductivity (table)

R47.24

isenthalpic expansion

R47.6

isentropic expansion

R47.7

Joule-Thomson cycle

R47.6

Kleemenko cycle

R47.13

Linde cycle

R47.6

liquefaction balanced flow condition

R47.6

of gases

R47.6

liquid-level sensors

R47.27

mixed refrigerant cycle

R47.8

natural gas processing

R47.19

properties electrical

R47.5

magnetic

R47.5

mechanical

R47.6

thermal

R47.3

purification of gases

R47.19

recovery of gases

R47.17

separation of gases, Gibbs phase rule

R47.16

staging

R47.15

Stirling cycle

R47.14

storage systems

R47.26

transfer systems

R47.27

R47.18

CTIC. See Combustion turbine inlet cooling (CTIC) Curtain walls

F15.5

Cycloparaffins

R12.3

D Dairy products aseptic packaging,

R33 R33.20

butter manufacture

R33.6 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Dairy products (Cont.) refrigeration load

R33.9

buttermilk

R33.5

cheese cheese room refrigeration

R33.12

manufacture

R33.10

cream

R33.5

display refrigerators

R15.6

ice cream freezing

R33.16

hardening

R33.17

milkfat content

R33.13

mix preparation

R33.14

refrigeration equipment,

R33.19

requirements

R33.16

milk dry

R33.22

evaporated

R33.21

fresh processing

R33.2

production

R33.1

storage

R33.4

sweetened condensed

R33.22

thermal properties

R19.1

UHT sterilization,

R33.19

yogurt

R33.5

Dampers air outlet controls, automatic

S19.4

S19.7

F7.6

F7.7

fire and smoke control

A53.8

furnaces

S32.2

S32.9

S4.7

S19.4

S19.7

S19.4

S19.7

opposed-blade outdoor air

A47.9

parallel-blade

S4.8

return air

S4.7

sound control

11.13

splitter

S19.7 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Dampers (Cont.) vehicular facilities, enclosed

A15.34

vent

S34.28

Dams, concrete cooling

R45.1

Darcy equation

F21.6

Darcy-Weisbach equation ductwork sectional losses pressure drop

F21.11 F3.6

water-cooled condensers

S38.4

water systems

S43.4

F22.1

Data-driven modeling black-box

F19.24

calibrated simulation

F19.24

empirical

F19.24

examples

F19.30

gray-box

F19.25

neural network

F19.30

steady-state

F19.25

Data processing areas air-conditioning systems humidification

A19.1 S21.1

design criteria

A19.1

codes, standards, and guidelines

A19.16

Daylighting interior building illumination,

F15.51

light transmittance

F15.52

solar radiation

F15.1

Defrosting air coolers, forced-circulation air-source heat pump coils

R14.4 S8.7

ammonia liquid recirculation systems

R2.22

household refrigerators and freezers

R17.5

meat coolers

R30.2

retail food store refrigerators,

S8.8

R15.19

Degree-days

F14.11

F19.19

Dehumidification

A47.12

S23

absorption

S23.10

adsorption

S23.10 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

S48.9

Index Terms

Links

Dehumidification (Cont.) air washers

S40.8

all-air systems

S4.5

desiccant

S23.1

applications

S23.1

air-conditioning systems,

S23.10

condensation prevention,

S23.10

gaseous contaminant control

S23.10

industrial processes

S23.8

materials storage

S23.8

testing

S23.10

ventilation air preconditioning

S23.11

S23.8

capacity

S23.2

equipment

S23.3

high-pressure

S23.8

S23.10

liquid

F32.3

solid

F32.4

evaporative cooling

A52.2

performance factor

S40.8

residential

S40.8

A1.5

Dehumidifiers desiccant

S23

capacity

S23.2

commissioning

S23.8

high-pressure

S23.10

liquid

S23.3

operation

S23.7

rotary solid

S23.4

solid

S23.4

ice rinks

S24.6

indoor swimming pool

S24.4

makeup air treatment

S24.3

mechanical

S24.1

components

S24.2

psychrometrics

S24.1

types

S24.2

wraparound heat exchangers

S24.7

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Dehydration of eggs

R34.11

farm crops

A25.1

industrial systems for

A30.1

refrigeration systems

R8.1

Density fluids

F3.1

modeling

R19.6

Dental facilities

A8.15

Desiccants

F32.1

adsorption

S23.1

S23.1

cosorption of water vapor and air contaminants

F32.5

dehumidification

S23.1

glycols

S23.2

isotherms

F32.5

life

F32.5

liquid

S23.2

lithium chloride

S23.2

materials

F32.1

refrigerant systems

S23.3

R7.5

equilibrium curves

R7.4

moisture

R7.3

types liquid absorbents

F32.3

solid adsorbents

F32.4

wheel

S23.4

Desuperheaters air conditioners, unitary

S48.4

in ammonia refrigeration

R2.3

condensers, evaporative,

S38.17

heat pumps, unitary

S48.4

Dew-point analysis

F27.8

method

F25.13

Diamagnetism, and superconductivity

R47.5

Diesel fuel

F28.8

Diffusers, air sound control

11.12

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Diffusion coefficient

F6.2

eddy

F6.7

moisture flow

F25.10

molecular

F6.1

space air

F20.1

Diffusivity thermal, of foods

R19.17

water vapor

F25.2

Dilution exhaust

F24.11

smoke

A53.4

ventilation

A31.2

Dining halls, in justice facilities

A46.6

A9.4

DIR. See Dispersive infrared (DIR) Direct digital control (DDC)

F7.4

F7.10

F13.4

F24.10

Direct numerical simulation (DNS), turbulence modeling Dirty bombs. See Chemical, biological, radiological, and explosive (CBRE) incidents Discharge coefficients, in fluid flow

F3.9

Dispersive infrared (DIR)

F7.9

Display cases

R15.1

District heating and cooling applicability

R15.4

S11 S11.1

central plants boiler

S11.3

chiller

A47.4

distribution design

S11.5

emission control

S11.4

equipment

S11.3

heating medium

S11.3

thermal storage

S11.4

combined heat and power (CHP)

S7.43

components

S11.1

S11.1

S11.4

S11.19

S11.32

consumer interconnections chilled water

S11.4

components

S11.28 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

District heating and cooling (Cont.) direct connection

S11.27

flow control

S11.29

hot water

S11.31

indirect, with heat exchangers

S11.28

steam

S11.19

temperature differential control

S11.33

costs

S11.30

A37.9

distribution system aboveground systems condensate drainage and return conduits

S11.18

S11.19

S11.7

S11.19

S11.22

S11.24

constant-flow

S11.5

construction

S11.18

entry pits

S11.25

hydraulic design

S11.6

insulation economical thickness

S11.17

pipe

S11.8

pipe

S11.7

thermal design conditions

S11.8

underground systems

S11.20

valve vaults

S11.25

variable-flow

S11.5

water hammer

S11.7

economics

S11.2

geothermal heating systems

A34.8

heating conversion to

S11.32

heat transfer analysis

S11.9

ground to air

S11.17

S11.21

S11.11

pipes in air

S11.17

buried trenches or tunnels

S11.15

shallow trenches

S11.16

single buried pipe

S11.11

soil temperature calculation

S11.10

two pipes buried

S11.13

metering

S11.33 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

District heating and cooling (Cont.) pressure losses

S11.7

thermal storage

S11.4

water systems

S11.1

S50.7

S50.16

A50.14

A50.18

A50.20

burners

S30.1

S30.14

chimney

S34.1

d-limonene

F31.12

DNS. See Direct numerical simulation (DNS) Doors air exchange

F16.26

U-factors

F27.8

Dormitories air conditioning

A6.8

design criteria

A6.1

energy systems

A6.1

load characteristics

A6.1

service water heating Draft

available

S34.1

S34.3

theoretical

S34.2

S34.3

comfort affected by

F9.14

cooling towers

S39.3

Drag, in fluid flow

F3.5

Driers

R7.6

S39.5

(See also Dryers) Drip station, steam systems

S11.7

Dryers. (See also Driers) commercial and industrial adsorption

S23.10

agitated-bed

A30.6

calculations

A30.2

conduction

A30.3

constant-moisture solvent

A30.7

convection

A30.4

dielectric

A30.4

drying time determination

A30.2

flash

A30.6

fluidized-bed

A30.6

freeze drying

A30.6

S23.11

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Dryers (Cont.) mechanism

A30.1

microwave

A30.4

psychrometrics

A30.1

radiant infrared

A30.3

selection

A30.3

superheated vapor

A30.6

tunnel

A30.5

ultraviolet (UV)

A30.3

vacuum drying

A30.6

desiccant, high-pressure farm crops

S23.10 A25.1

Drying air

S23.11

desiccant, high-pressure

S23.10

dew-point control

S23.11

farm crops

S23.11

A25.1

gases

S23.11

DTW. See Dual-temperature water (DTW) system Dual-duct systems all-air systems

S4.12

control

A47.17

terminal boxes,

A47.15

testing, adjusting, balancing Dual-temperature water (DTW) system DuBois equation

A38.4 S12.1 F9.3

Duct design all-air systems

S4.10

Bernoulli equation

F21.1

commercial, small applications

S9.10

computer analysis

A40.10

Darcy equation

F21.6

Darcy-Weisbach equation

F21.11

design considerations space pressure relationships duct fitting database

F21.13 F21.9

dynamic losses This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Duct design (Cont.) duct fitting database

F21.9

local loss coefficients

F21.9

fan-system interface

F21.11

fitting loss coefficients duct fitting database

F21.9

flexible ducts

F21.9

tables

F21.26

friction losses

F21.6

head

F21.2

industrial exhaust systems

S29.28

methods

F21.16

noise

F21.16

pressure

F21.2

residential

S9.8

roughness factors

F21.6

stack effect

F21.2

testing, adjusting, and balancing

F21.16

Ducts acoustical lining

11.21

in hospitals

A8.13

airflow measurement in

A38.2

antimicrobial

S18.5

classifications

S18.1

cleaning

S18.2

S18.4

construction codes

S18.1

commercial

S18.2

acoustical treatment

S18.4

hangers

S18.4

materials,

S18.2

plenums and apparatus casings

S18.4

industrial

S18.4

hangers

S18.5

materials,

S18.4

kitchen exhaust

S18.5

master specifications

S18.6

outdoor ducts

S18.6 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Ducts (Cont.) residential

S18.2

seismic qualification

S18.6

sheet metal welding

S18.6

standards

S18.1

commercial,

S18.2

industrial

S18.4

residential

S18.2

thermal insulation

S18.6

underground

S18.6

desiccant dehumidifiers

S23.7

efficiency testing

S9.11

fabric

S18.6

fibrous glass

S18.3

flat oval

F21.7

flexible

S18.3

fluid flow

F3.1

forced-air systems, small

S9.2

friction chart

F21.7

industrial exhaust systems

A32.6

insulation

S18.3

S9.8

F23.12

leakage

S18.2

noise in

11.12

noncircular

F21.7

plastic

S18.5

rectangular

F21.7

road tunnels

S18.2

A15.10

roughness factors

F21.6

round

S18.2

ships

A13.3

S18.5

sound attenuation

11.18

control

F8.12

velocity measurement in vibration control security concerns, Dust mites

F36.17 11.51 A59.11 F25.14

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

S18.5

Index Terms

Links

Dusts

S28.1

synthetic

S28.2

Dynamometers

A17.1

E Earth, stabilization

R45.3

Earthquakes, seismic-resistant design

A55.1

Economic analysis

R45.4

A37

computer analysis

A37.13

inflation

A37.10

internal rate of return

A37.11

life-cycle cost analyses

A37.9

payback

A37.9

improved

A37.10

simple

A37.9

present value (worth)

A37.10

savings-to-investment ratio (SIR)

A37.11

Economic coefficient of performance (ECOP),

S7.50

Economics. (See also Costs) district heating and cooling

S11.2

energy management planning

A36.1

energy recovery equipment

S25.22

evaporative cooling

A52.16

indoor gaseous contaminant control

A46.14

insulation thickness, pipe

S11.17

laboratory systems

A16.20

owning and operating costs

A52.18

A37.1

Economizers air-side

F16.18

compressors, single-screw

S37.16

control

A42.35

humidification load calculation

S21.3

kitchen ventilation

A33.3

water-side

S2.3

ECOP. See Economic coefficient of performance (ECOP) ECS. See Environmental control system (ECS) Eddy diffusivity

F6.7 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Educational facilities

A7

air conditioning

A7.1

service water heating

A50.22

EER. See Energy efficiency ratio (EER) Effectiveness, heat transfer

F4.21

Effective radiant flux (ERF)

A54.2

Efficiency air conditioners room

S49.2

unitary

S48.5

boilers

S31.5

combustion

F28.12

compressors centrifugal

S37.32

positive-displacement

S37.3

reciprocating

S37.8

rotary

S37.12

scroll

S37.26

single-screw

S37.18

fins

S37.9

F4.4

forced-air systems, small

S9.11

furnaces

S9.12

heat pumps, unitary

S48.5

industrial exhaust gas cleaning

S29.3

infrared heaters

S15.3

motors

S44.2

pumps, centrifugal

S43.6

refrigerating

S9.9

F2.3

Eggs

R34

composition

R34.1

dehydration,

R34.11

processing plant sanitation

R34.13

products

R34.9

shell eggs packaging

R34.8

processing

R34.5

refrigeration

R34.5

spoilage prevention

R34.4

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Eggs (Cont.) storage

R34.8

structure

R34.1

transportation

R34.8

storage

R34.1

thermal properties

R19.1

EIFS. See Exterior insulation finishing system (EIFS) Electricity billing rates,

A56.12

codes

A56.15

costs

A37.5

generation, on-site

A37.9

imbalance

S44.1

motor starting

A56.5

performance

A56.1

power quality variations

A56.6

principles

A56.2

safety

A56.1

voltage

A56.1

measurement

A37.9

S44.7

F36.26

Electric thermal storage (ETS) Electrostatic precipitators

S50.12 S28.7

S29.7

Elevators smoke control

A53.11

in tall buildings

A4.2

Emissions, pollution

F28.7

Emissivity

F4.2

Emittance, thermal

F25.2

Enclosed vehicular facilities

A15

Energy audit

A36.6

balance comfort

F9.2

refrigeration systems

R5.3

F9.16

conservation air conditioners, room

S49.3

building envelopes

A44.1

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Energy (Cont.) building supervisory control clean spaces

A42.1 A18.17

educational facilities farm crop drying

A7.1 A25.3

greenhouses

A24.15

hospitals

A8.13

industrial environments

A31.6

infrared heaters

S15.1

kitchen ventilation

A33.1

pumps, centrifugal

S43.13

temperature and ventilation control

A47.19

textile processing

A21.7

thermal insulation

F23.1

consumption benchmarking

A36.6

building HVAC, control effect on

A42.13

emergency reduction

A36.15

gaseous contaminant control

A46.14

humidifiers

S21.3

United States

F34.6

world

F34.5

costs

A37.4

efficiency in commercial and food service refrigerators

R16.7

energy efficiency ratio (EER)

S49.2

and humidity

F25.15

emergency use reduction

A36.15

estimating

F19

analysis

F19.3

application to cooling and dehumidifying coils

F19.11

degree-day and bin methods

F19.17

annual degree-day

F19.18

variable base

F19.19

balance point temperature

F19.18

correlation

F19.22 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Energy (Cont.) degree-day

F19.21

forecasting

A42.40

general considerations

F19.1

integration of systems

F19.23

models

F19.1

monthly degree-day

F19.20

seasonal efficiency of furnaces

F19.19

simulating

F19.22

software selection

F19.3

field survey audit

A38.17

forecasting building needs

A42.40

management

A36

cost control

A36.10

emergency energy use reduction

A36.15

energy audits

A36.11

A36.6

energy-efficiency measures (EEM) comparing

A36.11

implementation

A36.15

improving discretionary operations

A36.10

resource evaluation modeling

A36.1 F19

calculating

F19.7

classical approach

F19.1

data-driven approach

F19.1

data-driven models

F19.2

forward models

F19.1

general considerations

F19.1

in integrated building design

A58.4

system controls

F19.24

F19.23

monitoring

A41

applications

A41.1

data

A41.6

design and implementation methodology

A41.6

documentation

A41.7

A41.15

planning

A41.6

A41.15

quality assurance

A41.6

A41.15

production, world

F34.4

recovery (See also Heat recovery) This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Energy (Cont.) air-to-air

S25

in chemical industry

R46.4

industrial environments

A31.6

renewable

S40.3

F35.2

resources

F34

demand-side management (DSM)

F34.3

electricity

F34.1

fossil fuel

F34.1

integrated resource planning (IRP)

F34.3

nonrenewable

F34.1

renewable

F34.1

United States

F34.6

world

F34.4

savings verification

A41.2

self-imposed budgets

F35.5

wheels

F35.2

S25.10

Energy efficiency ratio (EER)

S49.2

Energy savings performance contracting (ESPC)

A37.8

Engines

S7

air systems, compressed

S7.13

applications centrifugal compressors

S7.45

heat pumps

S7.46

reciprocating compressors

S7.45

screw compressors

S7.46

continuous-duty standby

S7.4

controls and instruments

S7.15

exhaust systems

S7.14

expansion engines

S7.31

fuels

F28.7

cetane number

F28.8

heating values

S7.11

selection

S7.10

heat recovery exhaust gas

S7.35

jacket water

S7.34 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Engines (Cont.) lubricant

S7.34

reciprocating

S7.34

turbocharger

S7.35

heat release

A17.1

jacket water system

S7.13

lubrication

S7.12

noise control

S7.15

performance

S7.10

reciprocating

S7.9

vibration control

S7.15

water-cooled

S7.13

Engine test facilities

A17

air conditioning

A17.1

dynamometers

A17.1

exhaust

A17.2

noise levels

A17.4

ventilation

A17.1

A17.4

Enhanced tubes. See Finned-tube heat transfer coils Enthalpy calculation

F2.4

definition

F2.2

foods

R19.7

recovery loop, twin-tower water vapor

S25.14 F6.9

wheels

S25.10

Entropy

F2.1

calculation

F2.4

Environmental control animals. See Animal environments humans. See Comfort plants. See Plant environments retail food stores equipment and control store ambient effect Environmental control system (ECS)

R15.21 R15.3 A12

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Environmental health

F10

biostatistics

F10.2

epidemiology

F10.2

exposure

F10.5

industrial hygiene

F10.3

microbiology/mycology

F10.3

physical hazards electrical hazards

F10.14

electromagnetic radiation

F10.16

noise

F10.16

thermal comfort

F10.12

diseases affected by

F10.14

vibrations

F10.14

standards

F10.10

Environmental tobacco smoke (ETS) contaminants

A46.2

secondhand smoke

F11.17

sidestream smoke

F10.6

superheated vapors

F11.2

Equipment vibration

11.42

F8.18

ERF. See Effective radiant flux (ERF) ESPC. See Energy savings performance contracting (ESPC) Ethylene glycol, in hydronic systems

S12.23

ETS. See Environmental tobacco smoke (ETS) Electric thermal storage (ETS) Evaluation. See Testing Evaporation, in tubes forced convection

F5.4

equations

F5.6

natural convection

F5.1

Evaporative coolers. (See also Refrigerators) liquid (See also Evaporators) in chillers

A1.5

S38.17

S42.13 Evaporative cooling

A52

applications air cleaning

A52.2

S40.8

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

S42.5

S42.8

Index Terms

Links

Evaporative cooling (Cont.) animal environments

A24.4

combustion turbines

S7.21

commercial

A52.9

dehumidification

A52.2

A52.13

S40.8

gas turbines

A52.13

greenhouses

A24.13

A52.15

A52.2

S40.7

humidification industrial air conditioning

A14.7

area cooling

A52.11

process cooling

A52.13

spot cooling

A52.12

laundries

A52.13

makeup air pretreatment

S40.6

motors

A52.12

power generation facilities

A52.13

precooling

S40.6

produce storage

A52.14

residential

A52.9

wood and paper products facilities

A52.13

cooling towers

S39.1

direct

A52.1

economics

A52.16

entering air condition

A52.18

A52.2

S40.1

equipment direct

S40.1

indirect

S40.2

maintenance

S40.8

two-stage

S40.5

exhaust requirement

A52.10

heat recovery and

A52.7

S25.20

S40.4

indirect

A52.1

A52.2

S25.20

S40.2

psychrometrics

A52.1

A52.10

A52.17

A52.18

A52.8

A52.17

A52.10

A52.17

A49.9

S40.9

staged booster refrigeration two-stage (indirect/direct) water treatment

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

S40.5

Index Terms

Links

Evaporative cooling (Cont.) Legionella pneumophila

S40.9

Evaporators. (See also Coolers, liquid) air conditioners, room

S49.2

ammonia refrigeration systems equipment

R2.2

piping

R2.18

automobile air conditioning

A10.5

chemical industry refrigeration

R46.7

flooded

A10.11

F5.4

halocarbon refrigeration systems, piping liquid overfeed systems Exfiltration

R1.28 R4.6 F16.1

Exhaust animal buildings

A24.6

clean spaces

A18.16

A18.18

engines heat recovery

S7.35

installation recommendations

S7.14

engine test facilities

A17.2

industrial environments

A14.8

A32.1

A33.10

A33.31

A16.3

A16.9

kitchens laboratories stack height

A16.13

photographic processing areas

A22.3

stacks buildings

A45.1

design strategies

A45.1

exhaust dilution prediction equations

A45.11

exhaust velocity

A45.1

industrial exhaust systems

A32.8

location relative to air intake

A45.2

wake downwash

A45.2

vehicular facilities, enclosed Exhibit buildings, temporary Exhibit cases Exhibition centers smoke management

A15.37 A5.8 A23.5

A23.16

A5.5 A53.12 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Expansion joints and devices bends

S45.10 S45.10

joints district heating and cooling

S11.18

packed

S45.13

packless

S45.13

loops

S45.11

Expansion tanks

S11.4

hydronic systems

S14.4

closed

S12.4

diaphragm

S12.4

expansion chamber

S12.4

functions of

S12.4

open

S12.4

sizing equations

S12.5

secondary coolant systems solar energy systems

S12.10

R13.3 A35.12

Explosions. See Chemical, biological, radiological, and explosive (CBRE) incidents

F Fairs

A5.8

Family courts

A9.3

(See also Juvenile facilities) Fan-coil units

S5.4

capacity control

S5.6

maintenance

S5.6

performance under varying load

S5.10

types

S5.5

ventilation

S5.5

wiring

S5.5

Fans

S20

air conditioners, room all-air systems

S49.2 S4.4

S4.6

animal environments

A24.6

control

A47.7

S20.9

cooling tower capacity control

A42.21

S39.8

draft

S34.29 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

S4.9

Index Terms

Links

Fans (Cont.) fixed- vs. variable-speed

A42.14

flow control

S20.9

furnaces

S32.2

industrial exhaust systems

A32.8

isolation

S20.9

kitchen exhaust

S44.8

A33.18

laws

S20.4

operating principles

S20.1

parallel operation

S20.7

plenum

S20.1

plug

S20.1

pressure relationships

S20.5

effect of duct system on

S20.6

rating

S20.4

selection

11.10

ships, naval surface

A13.3

sound level

11.8

system effects

S20.7

testing

S20.4

types

S20.1

unstable operation

A47.9

variable- vs. fixed-speed

A42.14

vehicular facilities, enclosed

A15.33

S20.7

S20.8

Farm crops aeration

A25.3

dryeration

A25.3

A25.9

drying combination

A25.4

corn

A25.1

cotton

A25.8

deep-bed

A25.4

energy conservation

A25.3

equipment

A25.2

full-bin

A25.4

hay

A25.7

layer

A25.5

peanuts

A25.8 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Farm crops (Cont.) rice

A25.9

shallow-layer

A25.3

soybeans

A25.6

specific

A25.6

microbial growth

A25.1

recirculation

A25.3

storing

A25

grain aeration

A25.9

moisture migration

A25.9

Faults, system reasons for detecting

A39.6

f-Chart method sizing heating and cooling systems

A35.20

Fenestration. (See also Windows) air leakage

F15.50

area

A44.2

attachments

F15.30

building envelopes

A44.2

codes

F15.59

components

F15.1

condensation resistance

F15.54

control of rain entry

A44.10

cooling load

F18.14

draperies

F15.32

durability

F15.58

energy flow

F15.2

energy performance, annual

F15.54

exterior shading

F15.1

glazing (glass)

F15.1

occupant comfort

F15.56

opaque elements

F15.29

shading devices

F15.30

solar gain

A44.10

solar heat gain

F15.13

standards

F15.59

thermal radiation

F15.16

U-factors Fick’s law and moisture flow

F15.1

F15.4

F15.17

F15.6

F6.1 F25.10 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Filters, air

S28

(See also Air cleaners) air conditioners, room

S49.4

aircraft

A12.9

A12.14

clean spaces

A18.3

A18.9

demisters

A28.8

desiccant dehumidifiers

S23.7

dry, extended surface

S28.6

electronic

S28.5

furnaces

S32.2

high-efficiency particulate air (HEPA) filters

A28.3

A18.13

S28.7

S28.3

S28.5

S29.2 tests

S28.3

hospitals

A8.2

industrial air-conditioning

A14.7

industrial exhaust gas fabric

S29.10

granular bed

S29.14

installation

S28.9

kitchens

A33.6

laboratories

A16.9

maintenance

S28.8

nuclear facilities

A28.3

panel

S28.6

places of assembly

A33.10

A28.8

A5.1

printing plants

A20.4

renewable media, moving-curtain

S28.7

residential

A1.5

safety requirements

S28.12

selection

S28.8

ships

A13.4

standards

S28.3

test methods

S28.2

types

S28.6

ultralow-penetration air (ULPA) filters

S28.5

S28.7

viscous impingement

S28.6

S28.7

Filters, water

S28.5

A49.7

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

S29.2

S28.7

Index Terms

Links

Finned-tube heat-distributing units

S35.1

design

S35.3

nonstandard condition corrections

S35.3

rating

S35.3

Finned-tube heat transfer coils

F4.24

energy recovery loops

S25.11

two-phase flow in

S35.5

F5.14

Fins

F4.4

Fire/smoke management. See Smoke management Firearm laboratories

A9.6

Fireplaces

S33.4

chimney design

S34.20

Fire safety clean space exhaust systems fire and smoke dampers

A18.16 A53.8

industrial exhaust gas cleaning

S29.29

insulation fire resistance ratings

F23.6

justice facilities

A9.3

kitchens

A33.19

laboratories

A16.11

nuclear facilities

A28.2

penetration fire stopping

A53.1

smoke management

A53.1

thermal insulation

F23.5

Fish

A9.6

R19

R32

fresh

R19.2

R32.1

frozen

R19.4

R32.4

thermal properties

R19.1

Fitness facilities. (See also Gymnasiums) in justice facilities

A9.5

Fittings duct fitting database

F21.9

effective length

F3.8

halocarbon refrigeration systems loss coefficients local

R1.10 F3.8 F21.9

pipe This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Fittings (Cont.) sizing

F22.1

standards

S45.2

tees

F22.8

F22.8

Fixed-guideway vehicles

A11.7

(See also Mass-transit systems) Fixture units

A50.1

pipe sizing

A50.26

F22.9

Flammability limits, gaseous fuels Flash tank, steam systems

F28.1 S10.14

Floors coverings panel systems

S6.7

temperature comfort slabs, heat loss

F9.15 F17.11

F18.32

R27.1

R27.3

Flowers, cut air transport cooling

R28.11

refigerators

R16.3

storage, temperatures

R21.12

Flowmeters

A38.13

bypass spring impact meters in conduits

A38.13 F3.13

devices

A38.13

district heating and cooling systems

S11.33

flow nozzles

F36.19

hoods

F36.18

orifice plates

A38.13

positive-displacement meters

F36.21

rotameters

F36.20

turbine meters

A38.13

ultrasonic

A38.13

velocity impact meters

A38.13

venturi meters

A38.13

Fluid dynamics computations Fluid flow

F36.17

F36.19

F36.22

F36.19

F13.1 F3

analysis

F3.6

Bernoulli equation

F3.6 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Fluid flow (Cont.) kinetic energy factor

F3.2

pressure variation

F3.2

boundary layer

F3.4

cavitation

F3.13

choking

F3.13

compressible

F3.13

expansion factor

F3.12

pressure

F3.12

continuity

F3.2

Darcy-Weisbach equation

F3.6

devices

F3.5

discharge coefficients

F3.9

drag

F3.5

friction factors

F3.6

incompressible

F3.9

laminar

F3.2

measurement

A38.11

noise

F36.19

F3.13

nonisothermal effects

F3.5

parabolic velocity profile, Poiseuille

F3.3

patterns

F3.4

pipe friction

F3.6

Poiseuille

F3.3

properties

F3.1

Reynolds number, Re

F3.3

section change losses

F3.8

sensors

F3.10

F3.8

F7.10

separation

F3.4

turbulent

F3.3

two-phase boiling

F5.1

condensation

F5.8

evaporation

F5.2

pressure drop unsteady

F5.4

F5.11 F3.11

valve losses

F3.8

vena contracta

F3.4

F3.9

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Fluid flow (Cont.) wall friction

F3.3

Food. (See also specific foods) codes

R15.2

cooling and freezing times cooling

R20.1 R20.1

equivalent heat transfer dimensionality

R20.4

estimating algorithms

R20.5

irregular shapes

R20.3

slabs, cylinders, and spheres

R20.2

freezing estimating algorithms

R20.12

geometric considerations equivalent heat transfer dimensionality

R20.9

equivalent sphere diameter

R20.12

mean conducting path

R20.10

phase change

R20.8

precooling

R20.8

subcooling

R20.8

industrial freezing methods

R29.1

long-term storage

R40.7

R20.7

microbial growth control

R22.3

generalized

R22.1

requirements

R22.2

plants

R40.3

processing facilities contamination prevention

R22.3

dairy

R33.1

fruits

R40.5

main dishes

R40.1

meat

R30.1

organism destruction

R22.4

potato products

R40.5

poultry

R31.1

precooked foods

R40.1

refrigeration systems

R40.3

R40.4

R40.6

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Food (Cont.) regulations and standards

R22.5

sanitation

R22.4

vegetables

R40.3

refrigeration dairy products

R33

eggs and egg products

R34.1

fishery products

R32

fruits, fresh

R35

meat products

R30

poultry products

R31

vegetables

R37

R36

refrigerators commercial

R16

retail food store

R15.1

walk-in

R15.12

storage requirements canned foods

R21.11

citrus fruit

R36.3

commodities

R21.1

dried foods

R21.11

fruit

R35

thermal properties

R19

enthalpy

R19.7

heat of respiration

R19.17

ice fraction

R19.19

R19.20

R19.12

R19.16

R19.2

surface heat transfer coefficient thermal conductivity

R19.24 R19.9

thermal diffusivity

R19.17

transpiration coefficient water content, initial freezing point

R19.19

R19.24

R19.2

Food service refrigerators for

R16.1

service water heating

A50.14

vending machines

R16.5

Forced-air systems, residential multifamily

A50.21

A1.1 A1.6

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Forensic labs

A9.5

autopsy rooms

A9.5

A9.6

critical spaces

A9.4

A9.7

firearm labs

A9.5

A9.6

A9.7

intake air quality

A9.6

A35.24

S36.2

S36.17

A51.17

A51.19

blast

R16.3

R23.10

household

R17.1

Fouling factor condensers, water-cooled

S38.4

coolers, liquid

S41.4

Foundations moisture control

A44.11

Fountains, Legionella pneumophila control, equation and heat transfer Four-pipe systems

A49.7 F25.5 S5.3

load

S12.19

room control

S5.15

zoning

S5.15

Framing materials

F15.2

solar gain

F15.18

Freeze drying

A30.6

biological materials

R49.4

Freeze prevention. (See also Freeze protection systems) condensers, evaporative coolers, liquid

S38.16 S41.5

cooling tower piping

S13.3

sump water

S39.10

energy recovery equipment hydronic systems

S25.7 S12.23

insulation for

F23.3

solar energy systems Freeze protection systems Freezers

cabinets

R17.2

defrosting

R17.5

R29.1

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

R30.15

Index Terms

Links

Freezers (Cont.) durability

R17.12

performance evaluation

R17.9

refrigerating systems

R17.4

safety

R17.11

testing

R17.9

industrial

R29.1

walk-in

R16.3

Freezing beverages

R20.7

biomedical applications

R49.1

foods bakery products

R41.5

egg products

R34.9

fish

R32.5

freezing time calculations

R20.7

ice cream

R33.15

meat products

R30.16

poultry products

R31.5

processed and prepared food

R40.1

industrial

R29.1

soil

R45.3

R45.4

Friction, in fluid flow conduit

F3.6

wall

F3.3

Friction losses

F21.7

duct design

F21.6

fittings

F22.1

roughness factors

F21.6

valves

F22.1

Fruit juice

R38

F22.8

F22.8

Fruits dried storage

R42.7

thermal properties

R19.1

fresh air transport apples, storage

R27.1 A52.14

R35.1

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Fruits (Cont.) apricots

R35.13

avocados

R36.8

bananas

R36.5

berries

R35.13

cherries, sweet

R35.12

citrus

A52.14

cooling

R28.1

deciduous tree

R35

desiccation

R21.1

deterioration rate

R21.1

display refrigerators

R15.8

figs

R35.13

grapes

R35.8

mangoes

R36.8

nectarines

R35.12

peaches

R35.12

pears

R35.6

pineapples

R36.8

plums

R35.11

storage diseases

R35.1

strawberries

R35.13

thermal properties

R19.1

vine fruits

R35.1

frozen

R40.5

Fuel cells, combined heat and power (CHP) Fuels

R36.1

S7.22 F28

classification combustion

F28.5 F28

engines

S7.10

flammability limits

F28.1

gaseous

F28.5

heating value

F28.3

ignition temperature

F28.2

liquid

F28.6

S7.11

oil. See Oil, fuel systems solid

S7.11 F28.8 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Fuels (Cont.) turbines

S7.20

Fume hoods, laboratory exhaust

A16.3

Fungal pathogens

F10.7

Furnaces

S32

air cleaners and filters

S32.2

airflow configurations

S32.3

air supply

S34.26

burners

S30.1

casings

S32.1

codes

S32.2

S32.10

commercial

S32.5

efficiency

S32.10

components

S32.1

controls

S32.2

derating

S30.10

duct

S32.5

duct furnaces

S30.6

electric

S32.4

fans and motors

S32.2

floor furnaces

S33.2

gas-fired

S32.1

codes

S32.10

commercial

S32.5

installation

S32.10

residential

S32.1

standards

S32.11

upflow

S32.5

S32.9

S32.10

S32.9

S32.5

humidifiers

S32.2

installation

S32.10

location

S32.6

natural gas

S30.11

draft hoods

S32.2

residential

S32.1

capacity ratings,

S32.9

combustion system

S32.4

efficiency

S32.9

heat exchangers,

S32.1

S32.1

S32.9

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

S32.4

S32.9

Index Terms

Links

Furnaces (Cont.) vent dampers

S32.2

S32.9

venting

S32.2

S34.18

S32.4

S32.10

oil venting

S34.19

performance criteria

S32.8

propane

S32.4

regulating agencies

S32.10

S32.11

residential

A1.3

annual fuel utilization efficiency (AFUE)

S32.8

efficiency

S9.12

floor furnaces

S33.2

indoor or outdoor

S32.4

performance criteria

S32.8

selection

S32.6

selection

S32.6

standards

S32.11

stokers

S30.17

thermal storage

S50.13

unducted

S32.5

upflow

S32.5

venting

S34.18

wall furnaces

S32.1

S34.19

S33.1

G Galleries. See Museums, galleries, archives, and libraries Garages automotive repair

A15.21

bus

A15.21

contaminant criteria

A15.19

parking

A3.7

A15.18

ventilation airflow rate

A15.19

control

A15.20

equipment

A15.33

residential

F16.20

system configuration

A15.20

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Gases compressed, storage

A16.8

drying

S23.11

liquefaction

R47.6

purification

R47.16

R47.19

separation gaseous oxygen

R47.18

Gibbs phase rule

R47.16

Gas-fired equipment

S34

(See also Natural gas) noise

F28.17

Gas vents

S34.1

GCHP. See Ground-coupled heat pumps (GCHP) Generators absorption units

R18.1

combined heat and power (CHP)

S7.40

Geothermal energy

R18.10

A34

corrosion control

A34.6

direct-use systems

A34.3

cooling

A34.9

equipment

A34.5

heating

A34.8

service water heating

A34.9

district heating

A34.8

geothermal fluids

A34.1

disposal

A34.4

temperature

A34.1

A34.3

A34.10

A34.30

heat exchangers

A34.6

A34.29

materials performance

A34.5

resources

A34.1

valves

A34.7

ground-source heat pump (GSHP) systems

water wells flow rate

A34.3

pumps

A34.6

terminology

A34.28

A34.26

water quality testing

A34.4

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

S8.4

Index Terms

Links

Geothermal heat pumps (GHP) Glaser method

A34.10 F25.13

Glazing angular averaging

F15.15

glass

F15.1

plastic

F15.28

solar-optical properties

F15.13

spectral averaging

F15.15

spectral range

F15.16

systems

F15.15

Global warming potential (GWP)

R6.1

Glycols, desiccant solution

S23.2

Green design, and sustainability

F35.1

Greenhouses. (See also Plant environments) evaporative cooling,

A52.15

plant environments

A24.10

Grids, for computational fluid dynamics

F13.4

Ground-coupled heat pumps (GCHP) closed-loop ground-source,

A34.10

heat exchanger

S48.12

Ground-source heat pumps (GSHP)

A34.1

Groundwater heat pumps (GWHP)

A34.25

A34.9

GSHP. See Ground-source heat pumps (GSHP) Guard stations in justice facilities

A9.4

GWHP. See Groundwater heat pumps (GWHP) GWP. See Global warming potential (GWP) Gymnasiums

A5.5

A7.3

H HACCP. See Hazard analysis and critical control point (HACCP) Halocarbon coolants, secondary, refrigerant systems

F31.12 R1.1

Hartford loop

S10.3

Hay, drying

A25.7 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Hazard analysis and control

F10.3

Hazard analysis and critical control point (HACCP)

R22.4

in meat processing facilities Hazen-Williams equation

R30.1 F22.1

HB. See Heat balance (HB) Health airborne pathogens

F10.7

asbestosis

F10.4

carbon monoxide

F10.11

coalworker’s pneumoconiosis in justice facilities

F10.4 A9.3

Legionella pneumophila and moisture problems

F10.6 F25.14

silicosis

F10.4

synthetic vitreous fibers (SVFs)

F10.5

Health care facilities

A8.

(See also specific types) Heat flow rates

F18.1

latent respiratory loss

F9.4

skin loss

F9.3

F9.10

sensible respiratory

F9.4

skin

F9.3

space extraction rate

F18.2

timers

S10.13

Heat and moisture control

F27.1

Heat balance

S8.19

air

F18.18

conduction transfer function

F18.19

cooling load calculation methods

F18.2

equations

F18.19

input procedure

F18.20

model

F18.15

studies

S8.19

surface

F18.15

F18.15

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Heat capacity

F25.1

Heat control

F27

Heaters

S33

automobiles

A10.5

catalytic

S33.1

control

S33.2

direct-contact

S14.6

electric

S15.2

fireplaces

S33.4

gas

S15.1

control valves

S33.2

efficiency requirements

S33.2

infrared

S15.1

room

S33.1

thermostats

S33.2

wall furnaces

S33.1

hot-water

S33.3

S30.6

A51.12 S15.1

indirect

S30.7

oil-fired

S15.3

radiant

A54.1

S30.6

A54.4

in-space

S33.1

kerosene

S33.3

oil

S15.3

S33.3

S30

S33

radiant

S33.1

S27.4

hydronic snow melting infrared

S33.4

electric

S15.2

gas-fired

S15.1

infrared

S30.6

oil-fired infrared

S15.3

panels

S33.4

quartz

S33.4

residential

S33.1

room

S33.1

solid fuel

S33.4

standards

S33.6

steam

S27.4

stoves

S33.5

A54.8

S30.6

S33.7

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

S30.7

S33.1

Index Terms

Links

Heaters (Cont.) testing

S33.7

unit

S27.4

control

S27.7

pneumoconiosis location

S27.6

maintenance

S27.8

piping

S27.7

ratings

S27.6

selection

S27.4

sound level

S27.6

types

S27.4

ventilators

S27.1

water

S30.6

A50

Heat exchangers

S47

air-to-air energy recovery

S25.1

heat pipes

S25.12

rotary enthalpy wheels

S25.10

thermosiphon

S25.14

animal environments

A24.4

antifreeze effect on

S12.23

chimneys

S34.29

counterflow

F4.21

district heating and cooling

S47.1

S11.28

double-wall construction

S47.3

effectiveness, capacity rate ratio

F4.21

enhanced surfaces

F5.14

fouling

S47.5

furnaces

S32.1

geothermal energy systems

A34.6

halocarbon refrigeration systems

R1.28

heat transfer

S47.1

installation

S47.6

liquid suction

R1.28

number of transfer units (NTU)

F4.21

parallel flow

F4.21

plate

F4.23

R1.29

S11.29

S47.3

brazed components

A34.29

S47.4 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

S41.2

Index Terms

Links

Heat exchangers (Cont.) gasketed

S11.28

plate-and-frame

S11.28

pressure drop in

F5.13

welded

S11.29

S47.3

S47.3

selection

S47.5

shell-and-coil

R1.29

S11.29

S47.2

shell-and-tube

R1.29

S11.29

S41.1

components

S47.4

converters

S47.2

straight-tube

S47.2

tube-in-tube

R1.29

U-tube

S47.2

solar energy

S36.14

S41.1

systems solar energy

A35.12

steam

S10.3

water, medium- and high-temperature

S14.8

wraparound

S24.7

Heat flow

F25

(See also Heat transfer) and airflow

F25.12

through flat building component hygrothermal modeling and moisture

F25.6 F25.13 12

paths, series and parallel Heat flux

F25.7 F25.1

radiant panels

S6.2

Heat gain. (See also Load calculations) appliances

F18.6

calculation solar heat gain coefficient (SHGC)

F18.17

standard air values

F18.13

control

F25

electric motors

F18.6

engine test facilities, dynamometers

A17.1

fenestration

F18.14

floors

F18.25

F26

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

F27

S41.2

Index Terms

Links

Heat gain (Cont.) hospital and laboratory equipment

F18.8

humans

F18.3

laboratories

A16.2

latent, permeable building materials

F18.14

lighting

F18.3

office equipment

F18.8

radiant panels

S6.7

space

F18.1

Heating absorption equipment

R18.1

animal environments

A24.4

equipment

S3.1

baseboard units

S35.1

boilers

S31.1

convectors

S35.1

finned-tube units

S35.1

furnaces

S32.1

radiators

S35.1

geothermal energy systems greenhouses

S26-S33

A34.8 A24.11

industrial environments

A14.6

infrared

S15.1

radiant

A54.1

nonresidential

S12.16

places of assembly

A54.8

A5.1

plant growth chambers

A24.17

power plants

A27.10

residential

A1.1

solar energy

S36.1

systems all-air

S4.2

S4.5

selection

S1.1

S1.8

small forced-air

S9.1

dynamic simulation model (HOUSE) solar energy steam thermal storage

S9.12 A35.15

A35.26

S10.1 S50.11 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

S48

Index Terms

Links

Heating load calculations,

F18.28

central plant

S3.2

residential calculations crawlspace heat loss Heating values of fuels

F17.11 F28.3

F28.7

F28.9

Heat loss. (See also Load calculations) basement

F18.31

crawlspaces,

F17.11

floor slabs

F18.32

latent heat loss

F17.12

radiant panels

F18.32

S6.7

Heat pipes, air-to-air energy recovery

S25.12

Heat pumps absorption

R18.3

air-source

S48.1

add-on

S48.9

S48.8

air-to-air

S8.4

S8.9

air-to-water

S8.6

S8.9

balance point

S48.9

compressor selection

S48.10

control

S48.10

defrost cycle

S48.9

installation

S48.10

refrigerant circuits

S48.10

selection

S48.9

boosters

S50.13

cascade systems

S8.6

components

S8.6

compression cycles

S8.2

control efficiency

S48.5

engine-driven

S7.46

S8.7

S8.8

A34.13

S8.14

ground-source ground-coupled

A34.10

heat transfer analysis

A34.14

horizontal systems

A34.11

A34.22

vertical systems

A34.10

A34.13

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

S48.12

Index Terms

Links

Heat pumps (Cont.) water loop

S8.14

groundwater

A34.11

A34.25

S48.12

surface water

A34.12

A34.30

S48.12

terminology

A34.10

heat recovery heat pumps

S8.9

design principles

S8.12

waste heat recovery

S8.13

heat sources and sinks

S8.2

ice-source

S8.4

R43.7

industrial process

S8.8

closed-cycle systems

S8.9

design

S8.12

heat recovery

S8.8

open-cycle systems

S8.11

semi-open-cycle systems

S8.11

packaged terminal heat pumps (PTHPs) testing

S8.9

S49.5 S49.7

room

S49.1

split systems

S48.1

supplemental heating

S8.8

through-the-wall

S2.3

types

S8.4

unitary

S48.1

application

S48.1

certification

S48.6

codes

S48.5

desuperheaters

S48.4

installation

S48.2

space conditioning/water heating

S48.4

standards

S48.5

types

S48.2

water heaters

A50.3

A50.27

water-source certification

S48.12

design

S48.12

entering water temperature

S48.12

groundwater

A34.11

A34.25

S48.12

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Heat pumps (Cont.) indirect systems

A34.29

surface water

A34.12

A34.30

closed-loop heat pumps

A34.31

A34.32

lake heat transfer

A34.30

open-loop heat pumps

A34.30

testing

S48.12

S48.12

water loop

S8.14

water-to-air

S8.4

water-to-water

S8.6

window-mounted

S2.3

S48.12

Heat recovery. (See also Energy, recovery) balanced heat recovery

S8.18

cascade systems

S8.13

coils

S26.3

combined heat and power (CHP)

S7.33

combustion turbines

S7.37

evaporative cooling

A52.7

heat-activated chillers

S7.39

heat balance

S8.19

heat pumps

S8.9

industrial exhaust systems

A32.8

kitchen ventilation

A33.2

laboratories

S25.20

A16.19

liquid chillers

S42.2

multiple buildings

S8.21

reciprocating engines

S7.34

retail food store refrigeration service water heating

S42.12

R15.18 A50.4

steam systems

S10.3

turbines

S7.37

supermarkets

A2.4

terminology

S8.1

waste heat

S8.13

water loop heat pump systems

S8.14

S10.14

Heat storage. See Thermal storage

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

S40.4

Index Terms

Links

Heat stress index (HSI)

A31.5

industrial environments

A31.5

thermal standards

A31.5

Heat transfer

F4

F9.21

F26.

(See also Heat flow) across air space

F25.6

antifreeze effect on water apparent transfer coefficient

S12.23 F25.6

augmentation active

F4.27

passive

F4.24

coefficients

F15.5

condensation

F5.9

convective

F9.7

convective evaporation

F5.6

evaporative

F9.8

foods

R19.24

Lewis relation

F9.4

low-temperature

R48.9

overall

F4.25

coils air-cooling and dehumidifying

S22.6

air-heating

S26.4

condensers

S38.2

water-cooled

S38.2

conductance

F4.3

conduction

F4.1

shape factors

F4.3

F4.4

control

F25

F26

convection buffer layer

F4.1

coefficient

F4.1

external

F4.17

flow, fully developed laminar

F4.17

forced, boundary layer

F4.16

free internal

F4.1

F4.18

F4.17 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

F27

Index Terms

Links

Heat transfer (Cont.) laminar sublayer

F4.1

natural

F4.1

turbulent region

F4.1

definition

F25.1

diffuse radiators

F4.15

district heating and cooling pipes

S11.9

effectiveness

F4.21

extended surfaces

F4.18

F4.4

factor, friction

F4.17

film coefficient

F25.1

resistance

F25.1

F25.5

F4.4

F4.7

fins forced convection, air coolers

F4.16

Fourier’s law

F25.5

ground

F19.7

ground loops

A34.14

heat exchangers

S47.1

insulation

F36.31

lakes

A34.30

mass transfer convection

F6.5

molecular diffusion

F6.3

simultaneous with

F6.9

cooling coils

F6.12

number of transfer units (NTU)

F4.22

radiant balance

F4.15

radiation actual, gray

F4.2

angle factor

F4.13

Beer’s law

F4.12

F4.16

blackbody

F4.11

spectral emissive power

F4.12

black surface

F4.2

energy transfer

F4.11

exchange between surfaces

F4.14

in gases

F4.16 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Heat transfer (Cont.) gray surface

F4.12

hemispherical emissivity

F4.12

Krichoff’s law

F4.12

monochromatic emissive power

F4.12

Stefan-Boltzmann law

F4.11

relation

F4.2

thermal

F4.2

Wien’s displacement law simultaneous

F4.12 F6.9

snow-melting systems fluids

A51.1 A51.10

solar energy systems

A35.11

steady-state

F25.5

terminology

F25.1

transient cooling time estimation

F4.8

cylinder

F4.9

radiation

F4.8

slab

F4.9

sphere

F4.9

transmission data

F26

water

S12.3

Heat transmission doors

F27.8

floor slabs

F18.32

properties

F26.1

windows

F27.8

Heat traps

A50.2

Helium in air

F1.1

recovery

R47.18

and thermal radiation

F4.16

High-efficiency particulate air (HEPA) filters

A28.3

S28.7

High-rise buildings. See Tall Buildings High-temperature short-time (HTST) pasteurization

R33.2 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

S29.2

Index Terms

Links

High-temperature water (HTW) system

S12.1

Homeland security. See Chemical, biological, radiological, and explosive (CBRE) incidents Hoods draft

S32.2

gaseous contaminant control

A46.6

S34.28

industrial exhaust systems capture velocities

A32.2

compound hoods

A32.5

design principles

A32.3

entry loss

A32.4

overhead hoods

A32.5

sidedraft hoods

A32.6

volumetric flow rate

A32.2

kitchen exhaust

A33.30

ductless

A33.17

recirculating systems

A33.17

residential

A33.30

type I

A33.10

type II

A33.10

laboratory fume

A33.19

A33.17

A16.3

sound control

11.34

unidirectional

A18.9

Hospitals

A8.2

air conditioning

A8.2

air movement

A8.3

air quality

A8.2

cooling

A8.13

design criteria administration

A8.11

ancillary spaces

A8.9

autopsy rooms

A8.10

diagnostic and treatment

A8.11

infectious isolation

A8.8

intensive care units

A8.8

laboratories

A8.9

nursery suites

A8.8

nursing areas

A8.8 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Hospitals (Cont.) operating rooms

A8.5

humidity

S21.2

patient rooms

A8.8

pharmacies

A8.10

protective isolation

A8.8

recovery rooms

A8.8

service areas

A8.12

sterilizing and supply

A8.12

surgery and critical care

A8.5

energy conservation

A8.13

heating and hot-water standby

A8.13

indoor air quality (IAQ)

A8.2

infection sources and control

A8.2

insulation

A8.13

Legionella pneumophila

A8.2

pressure relationships and ventilation

A8.4

smoke control

A8.5

zoning

A8.13

Hot-box method, of thermal modeling Hotels and motels

F25.7 A6

accommodations

A6.3

back-of-the-house (BOTH) areas

A6.6

central plant

A6.7

design criteria

A6.1

guest rooms

A6.4

indoor air quality (IAQ)

A6.6

load characteristics

A6.1

makeup air units

A6.7

public areas

A6.6

service water heating, showers

A50.14

sound control

A6.8

systems

A6.3

Hot-gas bypass

R1.34

HOUSE dynamic simulation model

S9.12

Houses of worship

A50.20

A5.3

HSI. See Heat stress index (HSI)

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

HTST. See High-temperature short-time (HTST) pasteurization Humidification

S21

air washers

S40.7

all-air systems

S4.5

S4.9

control

A47.12

A47.13

design

S21.3

direct evaporative cooling

A52.2

evaporative coolers

S40.7

load calculations

S21.4

Humidifiers

S21.1

S21

all-air systems

S4.9

bacterial growth

S21.1

central air systems industrial and commercial

S21.6

residential

S21.5

commercial

S21.6

controls

S21.7

energy considerations

S21.3

equipment

S21.4

evaporative cooling

S21.7

furnaces

S32.2

industrial

S21.6

Legionella pneumophila control

A49.7

load calculations

S21.3

nonducted

S21.5

portable

S21.5

residential

A1.5

scaling

S21.4

supply water

S21.4

terminal

S4.17

S21.7

S9.1

S21.5

F32.1

S21.1

Humidity building envelope affected by control

S21.2 A47.12

disease prevention and treatment

S21.1

human comfort conditions

S21.1

measurement odors affected by

F36.10 F12.2 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

S23.1

Index Terms

Links

Humidity (Cont.) sound transmission affected by

S21.2

static electricity affected by

S21.2

HVAC Security

A59

owner’s project requirements (OPR)

A59.1

risk evaluation

A59.2

system design

A59.3

design measures

A59.3

maintenance management

A59.5

modes of operation

A59.3

Hydrogen, liquid

R47.2

Hydronic systems

S35.

(See also Water systems) central multifamily

A1.6

combined heat and power (CHP)

S7.43

heating and cooling design

S12.1

heat transfer vs. flow

A38.6

pipe sizing

F22.6

residential

A1.3

snow melting

A38.7

A51.10

testing, adjusting, balancing

A38.6

A38.8

baseboard

S35.1

S35.3

S35.5

convectors

S35.1

S35.2

S35.5

finned-tube

S35.1

S35.3

S35.5

heaters

S27.4

makeup air

S27.9

pipe coils

S35.1

radiant panels

S6.11

ceiling

S6.13

design

S6.11

floor

S6.15

wall

S6.15

radiators

S35.1

ventilators

S27.1

units

water treatment

S35.2

S35.5

F7.9

F36.10

A49.10

Hygrometers Hygrothermal loads

S35.5

F25.2 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

F36.11

Index Terms

Links

Hygrothermal modeling

F25.13

criteria

F25.14

dew-point method

F25.13

transient analysis

F25.13

F27.11

F27.11

I IAQ. See Indoor air quality (IAQ) Ice commercial

R43.6

delivery systems

R43.5

manufacture

R43.1

storage

R43.4

thermal storage

R43.3

S50.7

Ice makers commercial

R16.6

heat pumps

R43.7

household refrigerator,

R17.2

large commercial

R43.1

storage

R43.4

thermal storage

R43.3

types

R43.1

water treatment

A49.7

A49.9

A5.5

R44

conditions

R44.4

R44.5

dehumidifiers

S24.6

energy conservation

R44.5

floor design

R44.8

heat loads

R44.2

pebbling

R44.11

surface building and maintenance

R44.10

water quality

R44.11

Ice rinks

ID50 mean infectious dose

A59.8

Ignition temperatures of fuels

F28.2

IGUs. See Insulating glazing units (IGUs) Indoor air quality (IAQ). (See also Air quality) bioaerosols health effects

F10.7

project requirements (OPR) particles

F10.4

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Indoor air quality (IAQ) (Cont.) sources

F10.7

environmental tobacco smoke (ETS)

F10.6

gaseous contaminant control

A46.1

hospitals

A8.2

hotels and motels

A6.6

humidity

F25.14

kitchens

A33.22

modeling

F13.1

particulate matter

F10.4

polycyclic aromatic compounds (PAC)

F10.5

polycyclic aromatic hydrocarbons (PAH)

F10.5

radon action levels

F10.17

sensors

F7.10

standards

F10.10

synthetic vitreous fibers

F10.5

volatile organic compounds (VOC)

F10.9

Indoor environmental modeling computational fluid dynamic (CFD)

F13 F13.1

contaminant transport

F13.16

multizone network

F13.14

verification and validation

F13.17

Induction air-and-water systems systems

A38.5 S5.8

units under varying load

S5.10

Industrial applications burners gas

S30.6

oil

S30.12

gas drying

S23.11

heat pumps

S8.8

humidifiers

S21.6

process drying

S23.11

process refrigeration

R46.1

thermal storage

S50.17

service water heating

A50.24

steam generators

A27.4 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Industrial environments

A14

air conditioning

A14

cooling load

A14.6

design

A14.5

evaporative systems

A14.7

maintenance

A14.8

refrigerant systems

A14.7

spot cooling

A31.3

ventilation

A31.1

A31

A52.12

air distribution

A31.3

air filtration systems

A14.7

S28.2

contaminant control

A14.5

A14.8

energy conservation

A31.6

energy recovery

A31.6

energy sustainability

A31.6

evaporative cooling

A52.12

heat control

A31.4

heat exposure control

A31.6

heating systems

A14.6

heat stress

A31.5

local exhaust systems

A31.6

air cleaners

A32.8

airflow near hood

A32.3

air-moving devices

A32.8

ducts

A32.6

energy recovery

A32.8

exhaust stacks

A32.8

fans

A32.8

hoods

A32.2

operation and maintenance

A32.9

system testing

A32.9

process and product requirements

A14.1

spot cooling

A31.3

thermal control

A14.4

ventilation systems

A31.2

Industrial exhaust gas cleaning

A32.1

S29.28

A31.6

S29

(See also Air cleaners) auxiliary equipment

A32

S29.28 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

S29.1

Index Terms

Links

Industrial exhaust gas cleaning (Cont.) equipment selection

S29.1

gaseous contaminant control

S29.17

absorption

S29.17

adsorption

S29.24

incineration

S29.27

spray dry scrubbing

S29.18

wet-packed scrubbers

S29.18

gas stream

S29.2

monitoring

S29.1

operation and maintenance particulate contaminant control

S29.24

S29.29 S29

collector performance

S29.3

electrostatic precipitators

S29.8

fabric filters

S29.26

S29.10

inertial collectors

S29.4

scrubbers (wet collectors) settling chambers

S29.15 S29.3

regulations

S29.1

safety

S29.29

scrubbers (wet collectors)

S29.15

Industrial hygiene

F10.3

Infiltration. (See also Air leakage) air exchange

R24.4

rate

F16.3

F16.12

air leakage air-vapor retarder

F16.17

building data

F16.15

controlling

F16.17

calculation, residential,

F16.22

climatic zones

F16.19

commercial buildings

F16.25

direct flow through doorways

R24.6

driving mechanisms

F16.12

examples

F16.23

fenestration

F15.50

indoor air quality (IAQ)

F16.10

infiltration degree-days

F16.12

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Infiltration (Cont.) latent heat load

F16.11

leakage function

F16.14

measurement,

F36.22

refrigerated facilities

R24.4

residential buildings

F16.14

sensible heat load

F16.11

terminology

F16.1

thermal loads,

F16.11

ventilation

R15.4

Infrared applications comfort

F9.23

drying

A30.3

energy generators

S15.1

greenhouse heating

F9.24

A24.12

heaters

A54.1

electric

S15.2

gas-fired

S15.1

industrial environments

A14.7

oil-fired

S15.3

system efficiency

S15.3

snow-melting systems,

A54.4

A54.8

S30.6

A51.16

In-room terminal systems changeover temperature,

S5.11

performance under varying load

S5.10

primary air

S5.10

refrigeration load

S5.11

Instruments

F14

(See also specific instruments or applications) Insulating glazing units (IGUs)

F15.1

Insulation, thermal airflow retarders

F25.8

animal environments

A24.4

below-ambient system

R10.1

clothing

R10.2

F9.8

compressive resistance

F23.7

condensation control

F23.3 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

S15.1

Index Terms

Links

Insulation, thermal (Cont.) corrosion under

F23.6

cryogenic

R47.23

ducts

F23.12

flexible

F23.10

process

F23.12

economic thickness, in mechanical systems electrical

S18.6

F23.1 R6.9

motor, breakdown of

S44.11

energy conservation

F23.1

fire resistance ratings

F23.6

fire safety

F23.5

flame spread index

F23.5

foundations

A44.3

freeze protection

F23.3

green buildings

F23.1

heat gain

F23.15

heat loss

F23.15

heat transfer

F36.31

hospitals

A8.13

insertion loss

F23.5

limited combustible

F23.6

materials

F23.7

cellular

F23.7

fibrous

F23.7

foil, scrim, and kraft paper (FSK)

F23.10

foil-reinforced kraft (FRK)

F23.11

granular

F23.7

reflective

F23.7

moisture control

F26.1

noise control

F23.4

noncombustible

F23.6

operating temperature

F23.7

performance

F26.4

personnel protection

F23.2

pipes

F26.2

F23.10

economic thickness

S11.17

hangers

F23.10 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Insulation, thermal (Cont.) underground

F23.12

properties

F25.1

refrigerant piping

R10.1

design

R10.1

installation

R10.8

jacketing

R10.7

joint sealant

R10.7

maintenance

R10.9

thickness tables

R10.4

vapor retarders

R10.7

refrigerated facilities

R23.12

smoke developed index

F23.5

solar energy systems

S36.4

tanks, vessels, and equipment

F23.7

thermal storage systems, water

S50.6

water absorption

F23.7

water vapor permeability

F23.7

water vapor permeance

F23.7

water vapor retarders

F23.9

weather barriers

F23.8

weather protection

F23.8

budgeting

R10.4

R24.1

S36.12

F23.12

thermal conductivity

Integrated building design (IBD)

S11.8

A58.1 A58.5

commissioning construction phase

A58.8

QA/QC procedures

A58.8

communication

A58.5

construction contract administration

A58.7

document phase

A58.8

post-construction activities

A58.9

design basis

A58.6

criteria

A58.6

development

A58.8

intent

A58.8 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Integrated building design (IBD) (Cont.) team

A58.5

design-phase contract

A58.1

documentation

A58.8

A58.8

drawings preliminary

A58.7

working

A58.7

energy modeling

A58.4

building optimization

A58.4

equipment selection

A58.4

system optimization

A58.4

objectives

A58.1

organization

A58.5

programming

A58.4

project closeout

A58.8

delivery

A58.9

design

A58.6

manual

A58.7

predesign

A58.9

quality assurance/quality control (QA/QC)

A58.5

schematic design

A58.1

specifications outline

A58.7

project manual

A58.7

training

A58.5

Integrated design process (IDP) Intercoolers, ammonia refrigeration systems

A58.1 R2.3

J Jails

A9.3

Joule-Thomson cycle Judges’ chambers Juice Jury facilities Justice facilities

R47.6 A9.5 R38.1 A9.5 A9

control rooms

A9.3

courthouses

A9.4

A9.4

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Justice facilities (Cont.) courtrooms

A9.4

dining halls

A9.4

energy considerations

A9.2

fire/smoke management

A9.3

fitness facilities

A9.5

forensic labs

A9.1

A9.5

guard stations

A9.3

A9.4

health issues

A9.3

heating and cooling plants

A9.2

jail cells

A9.5

jails

A9.3

judges’ chambers

A9.4

jury rooms

A9.5

juvenile

A9.1

kitchens

A9.4

laundries

A9.4

libraries

A9.3

police stations

A9.1

prisons

A9.3

system controls

A9.3

system requirements

A9.1

terminology

A9.1

types of

A9.1

U.S. Marshals

A9.5

Juvenile facilities

A9.5

A9.5

A9.5

A9.1

(See also Family courts)

K K-12 schools

A7.2

Kelvin’s equation

F25.9

Krichoff’s law

F4.12

Kitchens

A33

air balancing

A33.3

multiple-hood systems air filtration

A33.4 A33.6

A33.10

cooking effluent control of

A33.6 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Kitchens (Cont.) generation of

A33.1

thermal plume behavior

A33.5

dishwashers, piping

A50.8

energy conservation economizers

A33.3

reduced airflow

A33.3

residential hoods

A33.31

restaurants

A33.1

exhaust hoods

A33

ductless

A33.17

recirculating systems

A33.17

residential

A33.30

systems

A33.10

type I

A33.10

type II

A33.10

A33.17

A33.10

A33.31

A33.18

S18.5

exhaust systems ducts effluent control

A33.6

fans

A33.18

fire safety

A33.10

hoods

A33.10

maintenance

A33.29

multiple-hood systems

A33.4

residential

A33.31

terminations

A33.19

fire safety

A33.19

fire suppression

A33.19

multiple-hood systems

A33.21

prevention of fire spread

A33.21

residential

A33.31

grease removal

A33.6

heat recovery

A33.2

indoor air quality (IAQ) in justice facilities

A33.21

A33.21

A33.10

A33.22 A9.4

integration and design maintenance

A33.19

A33.3 A33.29

makeup air systems This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Kitchens (Cont.) air distribution

A33.23

maintenance

A33.29

replacement

A33.22

residential

A33.31

operation

A33.28

residential

A33.29

service water heating

A50.8

ventilation

A33

chambers

A9.4

Kleemenko cycle

R47.13

Krypton, recovery

R47.18

Kyoto protocol

A9.5

F35.4

L Laboratories

A16

air distribution

A16.9

air filtration

A16.9

air intakes

A16.13

animal labs

A16.14

cage environment

A24.9

ventilation performance

A24.9

biological safety cabinets biosafety levels

A16.6 A16.17

clean benches

A16.8

cleanrooms

A18.1

clinical labs

A16.18

commissioning

A16.20

compressed gas storage

A16.8

containment labs

A16.17

controls

A16.12

design parameters

A16.2

duct leakage rates

A16.10

economics

A16.20

exhaust devices

A16.8

exhaust systems

A16.10

fire safety

A16.11

fume hoods

A16.3 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Laboratories (Cont.) controls

A16.13

performance

A16.4

hazard assessment

A16.2

heat recovery,

A16.19

hospitals

A8.9

loads

A16.2

nuclear facilities

A28.11

paper testing labs

A26.4

radiochemistry labs,

A16.18

safety

A16.2

scale-up labs,

A16.18

stack heights,

A16.13

supply air systems

A16.11

A16.9

system maintenance

A16.18

system operation

A16.18

teaching labs,

A16.18

types

A16.1

ventilation

A16.8

Laboratory information management systems (LIMS) Lakes, heat transfer

A9.7 A34.30

Laminar flow air

A18.4

fluids

F3.2

Large eddy simulation (LES), turbulence modeling

F13.3

Laser Doppler anemometers (LDA)

F36.16

Laser Doppler velocimeters (LDV)

F36.16

Latent energy change materials Laundries evaporative cooling, in justice facilities service water heating

F24.10

S50.2 A52.13 A9.4

F25.9

A50.22

A50.23

LCR. See Load collector ratio (LCR) LD50, mean lethal dose

A59.8

LDA. See Laser Doppler anemometers (LDA) LDV. See Laser Doppler velocimeters (LDV) LE. See Life expectancy (LE) rating Leakage, ducts

S18.2 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Leakage function, relationship

F16.14

Leak detection of refrigerants

F29.8

methods

R8.4

Legionella pneumophila

A49.6

air washers

S40.9

control

A49.7

cooling towers

S39.12

decorative fountains

A49.7

evaporative coolers

S40.9

hospitals

S39.13

A8.2

Legionnaires’ disease

A49.6

service water systems

A50.10

Legionnaires’ disease. See Legionella pneumophila LES. See Large eddy simulation (LES) Lewis relation

F6.9

F9.4

Libraries. See Museums, galleries, archives and libraries Life expectancy (LE) rating film

A22.3

Lighting cooling load

F18.3

greenhouses

A24.14

heat gain

F18.3

plant environments

A24.17

sensors

F7.10

Light measurement

F36.28

LIMS. See Laboratory information management systems (LIMS) Linde cycle

R47.6

Liquefied natural gas (LNG)

S17.4

vaporization systems

S17.4

Liquefied petroleum gas (LPG) Liquid overfeed (recirculation) systems ammonia refrigeration systems

F28.5 R4 R2.22

circulating rate

R4.3

evaporators

R4.6

line sizing

R4.7

liquid separators

R4.7

overfeed rate

R4.3

pump selection

R4.5 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

F10.6

Index Terms

Links

Liquid overfeed (recirculation) systems (Cont.) receiver sizing

R4.7

recirculation

R4.1

refrigerant distribution

R4.2

terminology

R4.1

Lithium bromide/water

F30.1

Lithium chloride

S23.2

F30.69

Load calculations cargo containers

R25.8

coils, air-cooling and dehumidifying

S22.14

computer calculation

A40.9

humidification

S21.3

hydronic systems

S12.2

internal heat load

R24.3

nonresidential

F18.1

precooling fruits and vegetables

R28.1

F18.18

refrigerated facilities air exchange

R24.4

direct flow through doorways

R24.6

equipment

R24.6

infiltration

R24.4

internal

R24.3

product

R24.3

transmission

R24.1

residential cooling residential heat balance (RHB) method

F17.2

residential load factor (RLF) method

F17.2

residential heating crawlspace

F17.11

procedure

F17.11

snow-melting systems Load collector ratio (LCR)

A51.1 A35.21

Local exhaust. See Exhaust Loss coefficients control valves duct fitting database fittings flexible ducts Louvers

F3.9 F21.9 F3.8 F21.9 F15.29 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Low-temperature water (LTW) system

S12.1

LPG. See Liquefied petroleum gas (LPG) LTW. See Low-temperature water (LTW) system Lubricants

R12

(See also Lubrication; Oil) additives

R12.4

ammonia refrigeration component characteristics

R2.7 R12.3

effects

R12.28

evaporator return

R12.15

foaming

R12.27

halocarbon refrigeration compressor floodback protection

R1.31

liquid indicators

R1.32

lubricant management

R1.10

moisture indicators

R1.31

purge units

R1.32

receivers

R1.32

refrigerant driers

R1.31

separators

R1.30

strainers

R1.31

surge drums or accumulators

R1.30

mineral oil aromatics

R12.3

naphthenes (cycloparaffins)

R12.3

nonhydrocarbons

R12.3

paraffins

R12.3

miscibility moisture content

R12.13 R8.1

oxidation

R12.27

properties

R12.4

floc point

R12.20

viscosity

R12.5

refrigerant contamination

R7.7

reactions with

R6.5

solutions

R12.8

density

R12.9 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Lubricants (Cont.) solubility

R12.10

viscosity

R12.14

requirements

R12.12

R12.14

R12.12

R12.14

R12.2

separators

R11.23

solubility air

R12.27

hydrocarbon gases

R12.22

refrigerant solutions

R12.10

water

R12.25

stability

R12.28

synthetic lubricants

R12.3

testing

R12.1

wax separation

R12.20

Lubrication combustion turbines

S7.22

compressors centrifugal

S37.36

reciprocating

S37.10

rotary

S37.13

single-screw

S37.15

twin-screw

S37.22

engines

S7.12

M Mach number

S37.31

Maintenance. (See also Operation and maintenance) absorption units

R18.7

air cleaners

S28.8

air conditioners, retail store

A2.1

air washers

S40.8

chillers

S42.5

S42.12

coils air-cooling and dehumidifying air-heating

S26.5

combined heat and power (CHP) systems condensers

S22.15

S7.17 S38

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Maintenance (Cont.) air-cooled

S38.13

evaporative

S38.18

water-cooled

S38.7

cooking equipment

A33.29

coolers, liquid

S41.6

cooling towers

S39.11

costs

A37.7

documentation

A39.7

energy recovery equipment

S25.7

evaporative coolers

S40.8

filters, air

S28.8

gaseous air cleaners

A46.15

heat pumps, unitary

S48.2

industrial air-conditioning systems

A14.8

infrared heaters

S15.5

kitchen ventilation systems,

A33.28

laboratory HVAC equipment

A16.18

liquid chillers

S42.15

makeup air units

S27.10

manual

S25.11

A33.31

A39.8

solar energy systems

A35.24

turbines combustion

S7.22

steam

S7.31

unit heaters

S27.8

Makeup air units

S27.8

applications

S27.8

codes

S27.9

commissioning

S27.9

controls

A47.16

design

S27.9

S27.8

maintenance

S27.10

selection

S27.8

standards

S27.9

types

S27.9

Malls

A2.6

Manometers differential pressure readout

A38.12

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Manufactured homes

A1.7

airflow modeling example Masonry, insulation

F13.18 F26.7

(See also Building envelopes) Mass transfer

F6

convection

F6.5

eddy diffusion

F6.9

Lewis relation energy recovery, air-to-air heat transfer simultaneous with

F6.9

F9.4

S25.5

S25.7

F6.9

air washers

F6.11

cooling coils

F6.12

cooling towers

F6.12

dehumidifying coils

F6.12

direct-contact equipment

F6.10

enthalpy potential

F6.9

molecular diffusion

F6.1

in liquids and solids two-film theory

F6.4 S29.21

simultaneous

F6.9

Mass-transit systems buses

A11.1

A11.2

bus garages

A15.21

bus terminals

A15.23

diesel locomotive facilities

A15.27

enclosed vehicular facilities

A15.1

environmental control

A11.1

fixed-guideway vehicles

A11.1

rail cars

A11.1

A11.5

rapid transit

A11.5

A15.11

stations

A15.14

thermal comfort

A11.1

A15.15

thermal load analysis

A11.2

A15.15

tunnels railroad

A15.16

rapid transit

A15.11

subway

A15.11

ventilation

A11.1

A15.5

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

McLeod gages

F36.13

Mean infectious dose (ID50)

A59.8

Mean lethal dose (LD50)

A59.8

Mean radiant temperature (MRT)

A54.1

Mean temperature difference

F4.21

Measurement

F36

(See also Instruments) air exchange rates

F16.12

airflow

A38.2

air infiltration

F36.22

air leakage

F16.15

airtightness

F36.22

carbon dioxide

F36.23

combustion analysis

F36.32

contaminants

F36.32

data acquisition

F36.32

electricity

F36.26

fluid flow

A38.11

gaseous contaminants

F36.31

humidity

F36.10

light levels

F36.28

moisture content

F36.30

moisture transfer odors

F36.30 F12.5 F36.13

rotative speed

F36.26

sound

F36.27 F36.4

thermal comfort

F36.29

uncertainty analysis

A41.13

velocity

F36.14

vibration

F36.26

Meat

F36.3

R30

display refrigerators

R15.7

food processing

R30.1

frozen

R7.3

R8.3

pressure

temperature

F36.19

A46.5

heat transfer in insulation

in refrigeration systems

F3.10

R30.16 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Meat (Cont.) packaged fresh cuts

R30.11

processing facilities boxed beef

R30.7

carcass coolers beef

R30.2

calves

R30.10

hogs

R30.8

lamb

R30.10

energy conservation

R30.17

pork trimmings

R30.10

processed meats bacon slicing rooms

R30.13

freezing

R30.15

lard chilling

R30.14

sausage dry rooms,

R30.13

smokehouses

R30.12

sanitation

R30.1

shipping docks

R30.17

variety meats

R30.10

retail storage

R15.12

thermal properties

R19.1

Mechanical equipment room, central central fan room

A4.6

floor-by-floor fan rooms

A4.6

floor-by-floor units

A4.6

multiple floors

A4.5

Mechanical traps steam systems

S10.8

Medium-temperature water (MTW) system

S12.1

Meshes, for computational fluid dynamics

F13.4

refining

F13.11

Metabolic rate

F9.6

Metals and alloys, low-temperature

R48.6

Microbial growth

R22.4

Microbiology of foods

R22.1

Mines

A29

heat sources

A29.2

mechanical refrigeration plants

A29.9

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Mines (Cont.) spot coolers

A29.10

ventilation

A29.1

wall rock heat flow

A29.3

Modeling. (See also Data-driven modeling; Energy, modeling) airflow

A18.5

around buildings

F24.9

in buildings

F13.1

contaminant transport,

F13.16

multizone

F13.1

F13.14

pollutant transport

F13.1

F13.18

turbulence

F13.3

wind tunnels

F24.10

boilers

F19.14

compressor

F19.15

condenser and evaporator

F19.15

controls

F19.23

cooling tower

F19.16

moisture in buildings

F25.13

small forced-air heating systems systems

S9.12 F19.17

thermal (hot-box method) validation

F25.7 F19.31

Moist air psychrometrics

F1.1

thermodynamic properties standard pressure

F1.10

temperature scale

F1.2

transport properties

F1.15

viscosity

F1.15

Moisture in animal facilities

A24.2

in building materials

F25.8

capacity

F25.2

combustion

F28.12

condensation

S21.2

content

F25.2 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Moisture (Cont.) control

F25

terminology

F26

F25.1

diffusivity

F36.31

farm crops content

A25.1

flow and air- and heat flow

F25.12

isothermal

F25.12

mechanisms

F25.10

modeling

F25.13

flux

F25.2

hygrothermal modeling in insulation

F25.13 F26.1

for refrigeration piping

R10

measurement

F36.30

paint, effects on

F25.14

permeability

F36.30

permeance

F36.30

problems, in buildings

F25.8

ratio

F25.2

in refrigerant systems control

R7.1

desiccants

R7.3

driers

R7.6

drying methods

R7.2

effects

R7.1

factory dehydration

R8.1

hydrocarbon gases’ solubility indicators

R12.22 R7.3

lubricant solubility

R12.25

measurement

R7.3

solubility

R7.1

sources

R7.1

solar vapor drive

F36.30

storage in building materials

F26.15

examples

R8.1

F25.3

sorption isotherms

transfer

R8.3

F25.2 F27.8 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

F27

Index Terms

Links

Moisture (Cont.) transient

F25.12

transmission data

F26.1

water vapor retarders

F16.17

Mold

F26.15

F25.14

Montreal Protocol

F29.1

Motors

S44

air volume control

S44.8

codes

S44.2

compressors

S37.6

controls

S44.6

current imbalance

S44.2

efficiency

S44.2

evaporative cooling

A52.12

field assembly and refrigerant contamination

R7.8

furnaces, residential

S32.2

general purpose

S44.4

harmonics

S44.12

hermetic

S44.4

burnout

R7.8

impedance

S44.10

induction

S44.4

integral thermal protection

S44.5

inverter duty

S44.10

noise

S44.11

power factor correction capacitors

S44.13

power supply (ac)

S44.1

protection

S44.5

pumps, centrifugal

S43.8

service factor

S44.4

standards

S44.2

starting, and electricity

S44.7

switching times

S43.11

S43.12

S44.10

torque

S44.4

in variable-speed drives voltage imbalance

S44.10 S44.1

Movie theaters

A5.3

MRT. See Mean radiant temperature (MRT) This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Multifamily residences

A1.6

Multiple-use complexes air conditioning

A6.8

design criteria

A6.1

load characteristics

A6.1

systems

A6.1

energy inefficient

A6.2

total energy

A6.3

Multisplit unitary equipment Multizone airflow modeling

A6.2

S48.1 F13.14

applications example

F13.18

approaches

F13.16

verification and validation

F13.17

Museums, galleries, archives, and libraries air distribution,

A23.18

air filtration

A23.17

artifact deterioration

A23.5

building construction

A23.12

dehumidification

A23.17

exhibit cases

A23.19

A23.5

humidification,

A23.17

mold growth

A23.5

outside air

A23.17

relative humidity, effect on artifacts system selection

A23.5 A23.16

temperature, effect on artifacts

A23.3

N Natatoriums. (See also Swimming pools) air conditioning

A5.6

dehumidifiers

S24.4

duct design

A5.7

envelope design

A5.7

load estimation

A5.6

pool water chemistry

A5.7

ventilation requirements

A5.6

Natural gas liquefaction

F28.5 R47.8 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Natural gas (Cont.) liquefied

R47.3

pipe sizing

F22.18

processing

R47.19

separation

R47.18

Navier-Stokes equations

F13.1

Reynolds-averaged

F13.3

NC curves. See Noise criterion (NC) curves Net positive suction head (NPSH) Net positive suction pressure (NPSP)

A34.27 R2.3

S43.9

S9.15

S9.16

Night setback furnaces, residential recovery

A42.36

Nitrogen liquid

R47.3

recovery

R47.17

Noise

F8.13 (See also Sound)

air conditioners, room combustion

S49.4 F28.17

compressors centrifugal

S37.5

scroll

S37.26

single-screw

S37.18

condensing units

S37.23

S37.34

R15.18

control, with insulation controls

F23.4 A18.19

engine test facilities

A17.4

fans

S20.8

fluid flow

F3.13

health effects

F10.16

valves

S46.2

water pipes

F22.5

Noise criterion (NC) curves

F8.16

Noncondensable gases condensers, water-cooled,

S38.6

refrigerant contamination

R7.7

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

NPSP. See Net positive suction pressure (NPSP) NTU. See Number of transfer units (NTU) Nuclear facilities

A28

air filtration

A28.3

basic technology

A28.1

codes

A28.8

A28.12

criticality

A28.1

decommissioning

A28.11

Department of Energy facilities requirements confinement systems

A28.4

ventilation

A28.4

fire protection

A28.2

HVAC design considerations

A28.1

Nuclear Regulatory Commission requirements boiling water reactors

A28.9

laboratories

A28.11

medical and research reactors

A28.11

other buildings and rooms

A28.9

power plants

A28.6

pressurized water reactors

A28.8

radioactive waste facilities safety design

A28.11 A28.1

standards

A28.12

tornado and wind protection

A28.2

Number of transfer units (NTU) cooling towers,

S39.16

heat transfer

F4.22

Nursing facilities

A8.14

service water heating

A50.14

Nuts, storage

R42.7

O Odors

F12

analytical measurement control of, in industrial exhaust gas cleaning

F12.5 S29.26

S29.27

factors affecting

F12.2

F12.5

odor units

F12.5 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Odors (Cont.) olf unit

F12.6

sense of smell

F12.1

sensory measurement

F12.2

acceptability

F12.5

sources

F12.1

suprathreshold intensity

F12.3

threshold

F12.1

ODP. See Ozone depletion potential (ODP) Office buildings air conditioning

A3.2

space requirements service water heating

A3.5 A50.14

tall

A3.3

A50.18

A4

Oil, fuel

F28.6

characteristics

F28.6

distillate oils

F28.6

handling

S30.15

heating value

F28.7

pipe sizing

F22.19

preparation

S30.16

residual oils

F28.6

storage buildings

A27.9

storage tanks

S30.14

sulfur content

F28.7

viscosity

F28.6

Oil. (See also Lubricants) in refrigerant systems

R12.3

in two-phase flow

F5.11

Olf unit

F12.6

One-pipe systems chilled-water

S12.19

steam convection heating

S10.11

1993 Fundamentals, Chapter 33, pp. 18-19 (See explanation on first page of index.) Operating costs

A37.4

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Operation and maintenance

A39

(See also Maintenance) compressors,

S37.36

desciccant dehumidifiers

S23.7

documentation

A39.8

industrial exhaust systems

A32.9

exhaust gas cleaning equipment laboratory HVAC equipment

S29.29 A16.18

manuals

A39.8

new technology

A39.9

responsibilities

A39.8

Optimization

A42.4

applications dynamic

A42.15

static

A42.9

dynamic

A42.7

static

A42.4

Outlets, air diffusion, performance Outpatient health care facilities

F20.10 A8.14

Outside air, free cooling cooling towers

S39.9

liquid chillers

S42.12

Owning costs

A37.1

Oxygen in aircraft cabins

A12.9

liquid

R47.3

recovery

R47.17

Ozone activated carbon air cleaner

A46.13

in aircraft cabins catalytic converters

A12.14

limits

A12.15

electronic air filters

S28.8

health effects

F10.11

Ozone depletion potential (ODP)

R6.1

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

P PAC. See Polycyclic aromatic compounds (PAC) Packaged terminal air conditioners (PTACs) residential

S49.5 A1.6

Packaged terminal heat pumps (PTHPs) residential

S49.5 A1.6

PAH. See Polycyclic aromatic hydrocarbons (PAH) Paint, and moisture problems Panel heating and cooling

F25.14 S6

(See also Radiant heating and cooling) advantages

S6.1

air-heated/cooled panels capillary tube mats

S6.19 S6.7

control

S6.19

cooling

S6.1

design

S6.6

calculations

S6.8

disadvantages

S6.2

electric heating systems

S6.16

ceiling

S6.16

floor

S6.18

wall

S6.18

heat flux combined

S6.5

natural convection

S6.3

thermal radiation

S6.2

heating

S6.1

hybrid HVAC

S6.1

hydronic systems

S6.11

ceiling

S6.13

design considerations

S6.11

distribution and layout

S6.14

floor

S6.15

wall

S6.15

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Paper moisture content

A20.2

photographic

A22.1

storage

A22.3

Paper products facilities

A26

air conditioning

A26.2

conduction drying

A30.3

control rooms

A26.3

evaporative cooling

A52.13

finishing area

A26.3

machine area

A26.2

system selection

A26.4

testing laboratories

A26.4

Paraffins

R12.3

Parallel compressor systems

R15.14

Particulate matter indoor air quality (IAQ)

F10.4

F10.5

Pasteurization

R33.2

beverages

R39.6

dairy products

R33.2

eggs

R34.4

R34.10

juices

R38.4

R38.7

Peanuts, drying

A25.8

PEL. See Permissible exposure limits (PEL) Performance contracting

A41.2

Permafrost stabilization

R45.4

Permeability clothing

F9.8

vapor

F36.30

water vapor

F25.2

Permeance air

F25.2

thickness

F36.30

water vapor

F25.2

Permissible exposure limits (PEL)

F10.5

Pharmaceutical manufacturing cleanrooms,

A18.7

Phase-change materials thermal storage of Photographic materials

S50.11

S50.21

A22

processing and printing requirements

A22.1

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Photographic materials (Cont.) storage

A22.1

unprocessed materials Photovoltaic (PV) systems

A22.3

A22.1 S36.18

(See also Solar energy) Physical properties of materials boiling points

F33 F33.1

F33.2

density liquids

F33.2

solids

F33.3

vapors

F33.1

emissivity of solids

F33.3

freezing points

F33.2

heat of fusion

F33.2

heat of vaporization

F33.2

solids

F33.3

specific heat liquids

F33.2

solids

F33.3

vapors

F33.1

F33.2

thermal conductivity solids

F33.3

vapors

F33.1

viscosity liquids

F33.2

vapors

F33.1

Physiological principles, humans. (See also Comfort) adaptation

F9.16

age

F9.16

body surface area (DuBois)

F9.3

clothing

F9.8

cooling load

F18.3

DuBois equation

F9.3

energy balance

F9.2

heat stress

F9.21

F9.24

heat transfer coefficients convective

F9.7 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Physiological principles, humans (Cont.) evaporative

F9.8

Lewis relation

F9.4

radiative

F9.7

hypothalamus

F9.1

hypothermia

F9.1

latent heat loss

F9.3

mechanical efficiency

F9.6

metabolic rate

F9.6

respiratory heat loss

F9.4

seasonal rhythms

F9.16

sensible heat loss

F9.3

sex

F9.10

F9.16

skin heat loss

F9.3

skin wettedness

F9.5

F9.21

thermal exchanges

F9.2

thermoregulation

F9.1

vasodilation

F9.1

Pigs. See Swine Pipes

S45 (See also Piping)

buried, heat transfer analysis codes

S11.11 S45.6

cold springing

S11.18

computer analysis

A40.11

copper tube

S45.1

expansion

S11.18

expansion bends

S45.10

expansion joints

S45.12

expansion loops

S45.10

fluid flow heat transfer analysis insulation

S45.11

S45.11

F3.1 S11.9 F23.10

hangers

F23.10

installation

F23.10

underground

F23.12

iron

S45.2

joining methods

S45.2

S45.2

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Pipes (Cont.) plastic

F22.11

selection

S45.7

S45.8

S45.6

sizing

F22

ammonia systems capacity tables

R2.9

R2.10

fittings

F22.1

F22.8

fuel oil

F22.19

gas

F22.18

hydronic systems

F22.6

air separation

F22.6

insulation and vapor retarders

R2.11

isolated line sections

R2.11

pressure drop equations

F22.1

S12.22

refrigerant retail food store refrigeration service water

R15.13 F22.8

cold water sizing procedure

F22.11

steam

F22.12

condensate return

F22.13

high-pressure

F22.13

low-pressure

F22.13

two-pipe systems

F22.13

valves

F22.1

F22.8

water fixture units

F22.9

flow rate limitations

F22.5

aging allowances

F22.5

erosion

F22.5

noise

F22.5

water hammer

F22.6

standards, fittings

S45.2

steel

S45.1

stress calculations

S45.7

supporting elements

S11.18

S45.8

Piping. (See also Pipes) boilers capacity tables codes

S10.3 R1.5 S45.6 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

R2.8

Index Terms

Links

Piping (Cont.) cooling towers

S13.2

S39.8

district heating and cooling distribution system

S11.6

heat transfer

S11.9

insulation thickness

S11.17

geothermal energy systems

A34.7

heat carrying capacity

S12.3

hydronic snow melting

A51.11

insulation

R10.1

radiant panels, hydronic

S6.14

refrigerant ammonia systems

R2.1

below-ambient

R3.6

R10.1

halocarbon systems

R1.1

heat gain limits

R10.1

insulation

R10.1

jacketing

R10.7

pipe preparation

R10.2

supports and hangers

R10.8

vapor retarders

R10.7

service hot water

A50.5

solar energy

A35.12

S36.3

sound control, sound

11.49

transmission

A38.24

standards

S11.19

system identification

F37.10

S45.6

systems ammonia refrigeration

R2.8

compressor piping

R2.11

condenser and receiver piping

R2.15

evaporator piping

R2.18

R2.12

halocarbon refrigeration capacity tables,

R1.3-9

compressor

R1.24

defrost gas supply lines,

R1.20

discharge lines

R1.18

R1.11

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Piping (Cont.) double hot-gas risers

R1.19

draining prevention

R1.19

evaporator

R1.28

gas velocity

R1.1

hot-gas (discharge) mufflers

R1.20

bypass

R1.34

insulation

R1.5

liquid cooler, flooded location and arrangement,

R1.25 R1.5

minimum gas velocities,

R1.19

oil transport up risers

R1.19

refrigerant feed devices

R1.26

single riser and oil separator

R1.19

vibration and noise solar energy

R1.26

R1.5 A35.12

S36.5

steam

S10.3

S10.5

water

S14.7

circuits

S12.11

distribution

S12.6

unit heaters

S27.7

vibration control

11.49

vibration transmission Pitot tube Places of assembly

A38.24 A38.2

F36.17

A5

air conditioning

A5.2

air distribution

A5.2

air filtration

A5.1

air stratification

A5.2

arenas

A5.4

atriums

A5.9

auditoriums

A5.3

concert halls

A5.4

convention centers

A5.5

exhibition centers

A5.5

fairs

A5.8

gymnasiums

A5.5 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

S36.7

Index Terms

Links

Places of assembly (Cont.) houses of worship

A5.3

lighting loads

A5.1

mechanical equipment rooms

A5.3

movie theaters

A5.3

natatoriums

A5.6

playhouses

A5.3

precooling

A5.2

sound control

A5.1

space conditions

A5.1

stadiums

A5.4

temporary exhibit buildings

A5.8

vibration control

A5.1

Planes. See Aircraft Plank’s equation

R20.7

Plant environments

A24.10

controlled-environment rooms,

A24.16

design

A24.10

greenhouses

A24.10

carbon dioxide enrichment

A24.14

cooling

A24.12

energy conservation

A24.15

evaporative cooling

A24.13

heating

A24.11

heat loss calculation

A24.11

humidity control

A24.14

photoperiod control

A24.14

shading

A24.13

site selection

A24.10

supplemental irradiance

A24.14

ventilation

A24.12

other facilities

A24.21

photoperiod control

A24.14

phytotrons

A24.18

plant growth chambers

A24.16

supplemental irradiance

A24.14

Plate heat exchangers (PHEs)

S11.28

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Plenums construction

S18.4

mixing

S4.7

sound attenuation

11.18

stratification in

A38.2

PMV. See Predicted mean vote (PMV) Police stations

A9.1

Pollutant transport modeling. See Contaminants indoor, concentration prediction Pollution air, and combustion

F28.7

Polycyclic aromatic hydrocarbons (PAH),

F10.5

Polydimethylsiloxane

F28.14

F31.12

Ponds, spray

S39.5

Pope cell

F36.12

Positive positioners

F7.8

Potatoes processed

R40.5

storage

A52.14

Poultry. (See also Animal environments) chilling

R31.1

decontamination

R31.4

freezing

R31.5

packaging

R31.7

processing

R31.1

processing plant sanitation

R31.9

recommended environment,

A24.8

refrigeration, retail

R31.10

storage

R31.10

tenderness control,

R31.10

thawing

R31.11

Power-law airflow model Power plants

R31.4

F13.14 A27

buildings oil pump

A27.9

oil storage

A27.9

steam generator

A27.4

turbine generator

A27.7

coal-handling facilities

A27.6

A27.9

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Power plants (Cont.) combined heat and power (CHP)

S7.1

combustion turbine areas

A27.8

control center

A27.9

cooling

A27.10

design criteria

A27.1

evaporative cooling

A52.13

fuel cells

S7.22

heating

A27.10

turbines combustion

S7.18

steam

S7.25

ventilation

A27.4

rates

A27.3

PPD. See Predicted percent dissatisfied (PPD) Prandtl number

F4.17

Precooling buildings

A42.37

flowers, cut

R28.11

fruits and vegetables, load calculation

R28.1

indirect evaporative

A52.2

places of assembly

A5.2

Predicted mean vote (PMV) comfort

F36.30 F9.17

Predicted percent dissatisfied (PPD) Preschools

F9.17 A7.1

Pressure absolute

F36.13

aircraft cabins

A12.9

clean spaces

A18.16

differential

F36.13

conversion to head hospitals readout

A8.3

A8.4

A38.12 F36.13

gage

F36.13

sensors

A12.13

A38.12

dynamic

measurement

A12.11

A38.2

F36.13

F7.9 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

A12.15

Index Terms

Links

Pressure (Cont.) smoke control

A53.5

A53.9

stairwells

A53.9

A53.10

static control

A47.8

F36.13

steam systems

S10.4

units

F36.13

vacuum

F36.13

Pressure drop. (See also Darcy-Weisbach equation) correlations

F5.11

pipe sizing

F22.1

in plate heat exchangers

F5.13

two-phase fluid flow

F5.11

Pressure losses, district heating and cooling,

S11.7

Primary-air systems

S5.10

Printing plants

A20

air conditioning

A20.1

air filtration

A20.4

binding areas

A20.5

collotype printing rooms

A20.4

letterpress areas

A20.2

lithographic pressrooms

A20.3

paper moisture content control

A20.2

platemaking rooms

A20.2

relief printing areas

A20.2

rotogravure pressrooms

A20.4

salvage systems

A20.4

shipping areas

A20.5

ink drying

A30.3

Prisons

A9.3

Produce desiccation

R21.1

deterioration rate

R21.1

display refrigerators

R15.8

Propane commercial

F28.5

furnaces, residential

S32.10

Propylene glycol, hydronic systems

S12.23

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Psychrometers

F1.9

Psychrometrics

F1

air handlers

S4.4

chart

F1.11

adiabatic mixing

F1.13

of water

F1.13

heat absorption and moisture gain

F1.14

moist air, cooling and heating

F1.12

thermodynamic properties

F1.10

evaporative cooling systems humidity parameters

A52.1

A52.10

A52.17

F1.2

industrial drying

A30.1

moist air standard atmosphere, U.S. thermal conductivity thermodynamic properties

F1.1 F1.15 F1.2

transport properties

F1.15

viscosity

F1.15

perfect gas equations

F1.8

water at saturation, thermodynamic properties

F1.2

F1.10

PTACs. See Packaged terminal air conditioners (PTACs) PTHPs. See Packaged terminal heat pumps (PTHPs) Public buildings. See Commercial and public buildings; Places of assembly Pulldown load

R15.5

Pumps centrifugal

S43

affinity laws

S43.7

antifreeze effect on arrangement

S12.24 S43.9

compound,

S12.8

pumping distributed

S43.12

parallel

S12.7

S43.10

primary-secondary

S12.8

S43.12

series

S12.7

S43.11

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

A52.18

Index Terms

Links

Pumps (Cont.) variable-speed standby pump, two-speed motors

S43.12 S12.8 S43.11

casing

S43.2

cavitation

S43.9

commissioning

S43.11

S43.13

construction

S43.1

efficiency, best efficiency point (BEP)

S43.7

energy conservation

S43.13

impellers operation

S43.2

trimming

S43.6

installation

S43.7

S43.8

S43.13

mixing

S12.8

motors

S43.12

operation

S43.2

S43.13

performance net positive suction

S43.9

operating point

S43.5

pump curves,

S12.6

power

S43.6

radial thrust

S43.8

selection

S43.9

types

S43.2

variable-speed

S12.8

S43.3

S43.5

A42.12

A42.25

A42.27

sequencing

A42.25

A42.29

condenser water,

A42.12

as fluid flow indicators

A38.13

geothermal wells

A34.28

chilled-water

lineshaft

A34.6

submersible

A34.6

hydronic snow melting

A51.12

liquid overfeed systems

R4.5

solar energy systems

A35.12

systems, water

S12.6

S14.6

variable-speed

A42.14

A42.27

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Purge units, centrifugal chillers

S42.11

R Radiant heating and cooling

A55

S6.1

S15

S33.4

(See also Panel heating and cooling) applications

A54.8

asymmetry

A54.5

beam heating design

A54.4

control

A47.4

design

A54.2

A54.3

direct infrared

A54.1

A54.4

A54.8

equations

A54.2

floor reradiation

A54.5

infrared

A54.1

A54.4

A54.8

S15

A54.8

S33.4

S35.5

beam heater design

S15.5

control

S15.4

efficiency

S15.3

electric

S15.2

energy conservation

S15.1

gas-fired

S15.1

indirect

S15.2

maintenance

S15.5

oil-fired

S15.3

precautions

S15.4

reflectors

S15.4

installation

A54.7

intensity

S15.1

panels

A54.1

applications

A54.8

control

A47.4

heating

S33.4

hydronic systems

S35.5

radiation patterns

S15.5

A54.5

snow-melting systems

A51.16

terminology adjusted dry-bulb temperature

A54.1

ambient temperature

A54.1

angle factor

S15.5 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Radiant heating and cooling (Cont.) effective radiant flux (ERF)

A54.2

fixture efficiency

S15.4

mean radiant temperature (MRT)

A54.1

operative temperature

A54.1

pattern efficiency

S15.4

radiant flux distribution

S15.6

radiation-generating ratio

S15.4

test instruments

A54.7

total space heating

A54.6

Radiant time series (RTS) method factors

F18.2

S15.5

S6.1

F18.21

F18.21

load calculations, nonresidential

F18.1

Radiation atmospheric

A35.5

diffuse

F15.15

electromagnetic

F10.16

ground-reflected

F15.15

optical waves

F10.18

radiant balance

F4.15

radio waves

F15.18

F10.18

solar

A35.3

thermal

F4.2

angle factors

F4.13

blackbody

F4.11

spectral emissive power

F4.12

black surface

F4.2

display cases

R15.4

energy transfer

F4.11

exchange between surfaces

F4.14

in gases

F4.16

gray

F4.2

heat transfer

F4.2

infrared

F4.11

F4.12

F15.16

Krichoff’s law

F4.12

monochromatic emissive power

F4.12

nonblack

F4.12

transient

F4.8 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

S6.1

Index Terms

Links

Radiators

S35.1

design

S35.3

nonstandard condition corrections

S35.3

types

S35.1

Radioactive gases, contaminants Radiometers

S35.5

F11.19 A54.7

Radon

F10.10

F10.12

control

A46.13

F16.20

indoor concentrations

F11.17

F10.17

Rail cars air conditioning

A11.5

air distribution

A11.7

heaters

A11.7

vehicle types

A11.5

Railroad tunnels, ventilation design

A15.17

diesel locomotive facilities

A15.27

equipment

A15.33

locomotive cooling requirements

A15.17

tunnel aerodynamics,

A15.17

tunnel purge

A15.18

Rain, and building envelopes

F25.3

RANS. See Reynolds-Averaged Navier-Stokes (RANS) equation Rapid-transit systems. See Mass-transit systems Rayleigh number

F4.18

RC curves. See Room criterion (RC) curves Receivers ammonia refrigeration systems high-pressure

R2.3

piping

R2.15

through-type

R2.16

halocarbon refrigerant

R1.21

liquid overfeed systems

R4.7

Recycling refrigerants

R9.3

Refrigerant/absorbent pairs

F2.15

Refrigerant-control devices

R11

air conditioners

S48.6

automobile air conditioning

A10.8

S49.2

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Refrigerant-control devices (Cont.) capillary tubes

R11.24

coolers, liquid

S41.5

heat pumps system

S8.7

unitary

S48.10

lubricant separators

R11.23

pressure transducers

R11.4

sensors

R11.4

short-tube restrictors,

R11.31

switches differential control

R11.2

float

R11.3

pressure control

R11.1

valves, control check

R11.21

condenser pressure regulators

R11.15

condensing water regulators

R11.20

expansion constant pressure

R11.11

electric

R11.10

thermostatic

R11.14

R11.5

float

R11.17

pressure relief devices

R11.22

law

F4.12

solenoid

R11.17

suction pressure regulators

R11.14

Refrigerants

F29.1

absorption solutions

F30.1

F30.69

ammonia

F30.1

F30.34

chemical reactions

R6.5

refrigeration system practices

R2.1

refrigeration systems

R3.1

ammonia/water,

F30.1

analysis

R6.4

automobile air conditioning azeotropic

F30.69

A10.11 F2.6

bakeries

R41.7

carbon dioxide

F30.1

F30.38

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

R6.4

Index Terms

Links

Refrigerants (Cont.) refrigeration systems

R3.1

cascade refrigeration systems CFC conversion

R48.3 R12.28

compatibility with other materials elastomers

R6.9 R6.11

electrical insulation

R6.9

plastics

R6.11

compositional groups

R6.1

ammonia

R6.4

chlorofluorocarbons

R6.1

fluoroethanes

R6.3

fluoroethers

R6.3

fluoromethanes

R6.3

fluoropropanes

R6.3

hydrocarbons

R6.4

hydrochlorofluorocarbons

R6.1

hydrofluorocarbons

R6.3

computer analysis

A40.16

contaminants in

R7

generation by high temperature

R6.9

cryogenic fluids

F30.1

effect on materials

F29.9

emissions

R9.1

environmental acceptability

R6.1

halocarbons

F30.54

F30.1

R6.4

azeotropic blends

F30.1

F30.33

ethane series

F30.1

F30.10

flow rate

R1.1

hydrolysis

R6.5

methane series

F30.1

F30.2-3

propane series

F30.1

F30.25

refrigeration system practices

R1.1

thermal stability

R6.4

zeotropic blends

F30.1

F30.26

F30.1

R6.4

F30.1

F30.42

hydrocarbons ethane ethylene

F30.50 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Refrigerants (Cont.) isobutane

F30.48

methane

F30.1

F30.40

n-butane

F30.1

F30.46

propane

F30.1

F30.44

propylene

F30.1

F30.52

leak detection

F29.8

R8.4

R9.2

lines oil management

R1.10

sizing

R1.2

lithium bromide/water

F30.1

lubricant solutions

R12.8

moisture in

R7.1

performance

F29.6

phaseout, costs

A37.8

piping

F30.69

R1.1

design

R10.1

insulation

R10.1

pressure drop discharge lines

R1.5

suction lines

R1.4

properties

F29.1

electrical

F29.5

global environmental

F29.1

physical

F29.4

rail car air conditioning

R6.1

A11.5

reclamation

R9.4

removing contaminants

R9.2

recovery

R9.3

recycling

R9.3

safety

F29.8

safety classifications

F29.2

sound velocity

F29.5

systems chemistry

R6.1

lubricants

R12.1

thermodynamic properties pressure-enthalpy diagrams

F30.1

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

R6.4

Index Terms

Links

Refrigerants (Cont.) saturated liquid and vapor data

F30.1

tabular data

F30.1

thermophysical properties transport properties

R3.2 F30

water/steam zeotropic

F30.1

F30.36

F2.6

F2.9

Refrigerant transfer units (RTU), liquid chillers

S42.12

Refrigerated facilities

R23

air circulation

R21.10

purification

R21.10

automated

R23.4

construction

R23.4

controlled-atmosphere storage

R23.3

controls

R23.15

R21.10

design building configuration

R23.1

initial building considerations

R23.1

location

R23.1

shipping and receiving docks

R23.3

single-story structures

R23.2

specialized storage facilities

R23.3

stacking arrangement

R23.2

utility space

R23.3

freezers

R23.10

insulation

R23.12

load calculations

R24.1

refrigerated rooms

R23.4

refrigeration systems condensate drains

R23.9

defrosting

R23.9

fan-coil units

R23.8

multiple installations

R23.10

unitary

R23.7

valves

R23.9

sanitation

R21.10 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Refrigerated facilities (Cont.) temperature pulldown vapor retarders

R23.15 R23.5

Refrigeration

R23.12

F1.1

(See also Absorption) absorption cycle

F2.13

air coolers, forced-circulation

R14.1

air transport

R27.3

ammonia systems

R27.5

R2

compressors cooling

R2.12

R2.13

piping

R2.11

R2.12

types

R2.2

controls

R2.7

converting systems equipment

R2.14

R2.21 R2.2

evaporative condensers

R2.17

liquid recirculation (overfeed)

R2.22

lubricant management multistage systems

R2.7 R2.21

piping

R2.8

safety

R2.27

system selection

R2.1

two-stage screw compressor

R2.21

valves

R2.9

vessels

R2.3

autocascade systems

R48.1

azeotropic mixture

F2.6

beverage plants

R39.11

biomedical applications

R49.1

breweries

R39.3

carbon dioxide systems

R3.1

cascade systems compressors

R48.5

refrigerants

R48.5

chemical industry

R46.1

R46.2

F2.3

F2.13

coefficient of performance (COP)

R46.5

compression cycles This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Refrigeration (Cont.) Carnot cycle

F2.6

Lorenz cycle

F2.8

multistage

F2.7

F2.10

zeotropic mixture

F2.9

concrete

R45.1

condensers, cascade

R5.1

food eggs and egg products

R34.1

fish

R32.1

vegetables

R37.1

food processing facilities

R40.1

banana ripening rooms

R36.5

control of microorganisms

R22.3

meat plants

R30.1

food service equipment

R16

fruits, fresh

R35.1

halocarbon systems

R36

R1

accessories

R1.28

heat exchangers

R1.28

lubricant management

R1.10

refrigerant receivers

R1.23

subcoolers

R1.29

valves

R1.10

heat reclaim, service water heating

A50.4

ice rinks

R44.1

insulation

R10.1

liquid overfeed systems

A50.27

R4.1

loads

R24.1

R40.3

low-temperature autocascade systems

R48.1

cascade systems

R48.3

heat transfer

R48.9

material selection

R48.6

secondary coolants

R48.10

single-refrigerant systems lubricant coolers marine

R48.2 R5.2 R26

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Refrigeration (Cont.) fishing vessels

R26.7

ships’ stores

R26.4

refrigerated-facility design

R23.1

retail food store systems secondary coolant systems

R15.12 R13.1

applications

R13.5

coolant selection

R13.1

design control valves

R13.2

expansion tanks

R13.3

piping

R13.2

pulldown time

R13.4

storage tanks

R13.2

system costs

R13.5

soils, subsurface

R45.3

R13.5

R45.4

systems charging, factory

R8.4

chemical reactions

R6.4

component balancing

R5.1

contaminant control

R7

of moisture

R7.1

retrofitting, during

R7.9

copper plating

R6.7

dehydration, factory

R8.1

design balance points

R5.2

energy and mass balance

R5.3

evaluating system chemistry

R6.11

moisture in

R8.1

performance

R5.4

reactions

R6.7

testing, factory

R8.4

ultralow-temperature

R48.1

wineries

R39.8

Refrigeration load

R24

(See also Load calculations) calculations, air-and-water systems

S5.11

safety factor

R24.7 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Refrigeration oils

R12

(See also Lubricants) Refrigerators commercial blast

R16.3

energy efficiency

R16.7

freezers

R16.3

temperatures

R16.2

types

R16.1

cryocoolers

R47.11

food service

R16.1

household

R17.1

absorption cycle

R18.8

cabinets

R17.2

defrosting

R17.5

durability

R17.12

ice makers

R17.2

performance evaluation

R17.9

refrigerating systems

R17.4

safety

R17.11

mortuary

R16.3

retail food store display

A2.3

storage

R15.11

walk-in

R15.1

R16.3

Regulators. (See also Valves) condenser pressure

R11.15

condensing water

R11.20

draft

S34.28

pressure, steam

S10.9

suction pressure

R11.14

Residential systems

A1

air cleaners

S28.9

air leakage

F16.15

calculation

F16.23

climatic infiltration zones dehumidifiers

F16.19 A1.5

duct construction

S18.2

equipment sizing

A1.2 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Residential systems (Cont.) forced-air systems air outlets and returns

S9.3

selection

S9.10

controls

S9.3

design

S9.1

distribution design

S9.7

ducts

S9.6

efficiency testing

S9.11

furnace

S32.1

S9.3

heating performance climate effect

S9.15

dynamic simulation model (HOUSE)

S9.12

factors,

S9.12

night setback effect,

S9.15

zone control

S9.16

S9.9

furnaces

S32.1

gas burners

S30.5

heating and cooling systems

A1.1

humidifiers

S9.1

kitchen ventilation

A33.29

oil burners

S30.11

ventilation

F16.17

water heating

A50.12

Resistance, thermal

F4

S21.5

F25

(See also R-values) calculation

F4.1

contact

F4.8

of flat assembly

F25.5

of flat building components

F25.5

overall

F4.3

radiant panels

S6.6

surface film

F25.1

Resistance temperature devices (RTDs)

F7.9

Resistivity, thermal

F25.1

Resource utilization factor (RUF)

F34.2

Respiration of fruits and vegetables

F36.6

R19.17

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

F26

Index Terms

Links

Restaurants energy conservation

A33.1

kitchen ventilation

A33.1

service water heating, Retail facilities

A50.14

A50.15

A50.21

A2

air conditioning

A2.1

convenience centers

A2.6

department stores

A2.5

design considerations

A2.1

discount and big-box stores

A2.2

load determination

A2.1

malls

A2.6

multiple-use complexes

A2.7

refrigeration

R15.1

shopping centers

A2.6

small stores

A2.1

supermarkets

A2.3

refrigerators

R15.1

service water heating Retrofit performance monitoring

A50.15 A41.4

Retrofitting refrigerant systems, contaminant control

R7.9

Reynolds-averaged Navier-Stokes (RANS) equation

F13.3

airflow around buildings simulation Reynolds number

F24.10

F24.10 F3.3

Rice, drying

A25.9

RMS. See Root mean square (RMS) Road tunnels

A15.3

carbon monoxide allowable concentrations

A15.9

analyzers and recorders

A15.10

computer analysis

A15.3

vehicle emissions

A15.8

A15.11

ventilation air quantities

A15.8

computer analysis

A15.3

controls

A15.9

A15.11 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Road tunnels (Cont.) ducts

A15.10

emergency

A15.1

air quantities

A15.9

enclosed facility

A15.3

enhancements

A15.8

equipment

A15.33

hybrid

A15.8

mechanical

A15.5

natural

A15.5

normal air quantities

A15.8

normal conditions

A15.1

pressure evaluation

A15.9

temporary

A15.1

Roof ponds, Legionella pneumophila control,

A49.7

Roofs insulation

F27.8

U-factors

F27.2

Room air distribution

A57

air terminals

A57.1

chilled beams

A57.18

classification

A57.1

fully stratified

A57.6

mixed

A57.2

occupant comfort

A57.1

occupied zone

A57.1

partially mixed

A57.9

Room criterion (RC) curves

F8.17

Root mean square (RMS)

F36.1

Rotary vane compressors

S37.13

Rotative speed

F36.26

Roughness factors, ducts

F21.6

RTDs. See Resistance temperature devices (RTDs) RTS. See Radiant time series (RTS) RTU. See Refrigerant transfer units (RTU) RUF. See Resource utilization factor (RUF) Rusting, of building components

F25.15

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

R-values

F23

F25

F27.5

F27.6

air cleaners

A46.14

S28.12

automatic controls

A47.18

F26

(See also Resistance, thermal) zone method of calculation

S Safety

burners

S30.1

chemical plants

R46.2

cryogenic equipment

S30.2

S30.20

R47.28

electrical

A56.1

filters, air

S28.12

industrial exhaust gas cleaning

S29.29

nuclear facilities

A28.1

refrigerants

F29.2

service water heating

A50.10

solar energy systems

A35.24

thermal insulation and fires

F23.5

thermal insulation for

F23.2

water systems

S14.9

wood stoves

S33.6

UVGI systems

A60.11

Safety showers, Legionella pneumophila control, Sanitation food production facilities control of microorganisms egg processing

F29.8

S16.8

A49.7 R22 R22.4 R34.13

HACCP

R22.4

meat processing

R30.1

poultry processing

R31.9

regulations and standards

R22.5

refrigerated storage facilities

R21.10

Savings-to-investment-ratio (SIR)

A37.11

Scale control

A49.4

humidifiers

S21.4

service water systems

A50.9

water treatment

A49.4 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Schematic design

A58.9

Schneider system

R23.7

Schools air conditioning

A7.3

service water heating

A50.22

elementary

A50.15

high schools

A50.15

A50.20

Security. See Chemical, biological, radiological, and explosive (CBRE) incidents Seeds, storage

A25.11

Seismic restraint

11.51

anchor bolts

A55.7

design

A55.1

A55.1

design calculations examples

A55.8

static analysis

A55.2

duct construction

S18.6

dynamic analysis

A55.2

installation problems

A55.3

A55.14

snubbers

A55.8

terminology

A55.2

weld capacities

A55.8

Sensible heat psychrometrics

F1.14

ratio

S49.2

Sensors automatic controls

F7.8

location

F7.10

A47.21

Separators, lubricant

R11.23

Service water heating

A50

combined heat and power (CHP) commercial and institutional

S7.43 A50.13

corrosion

A50.9

design considerations

A50.4

distribution system for commercial kitchens

A50.8

manifolding

A50.9

piping

A50.5 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Service water heating (Cont.) pressure differential

A50.5

return pump sizing

A50.7

two-temperature service

A50.8

geothermal energy

A34.9

indirect

A50.3

industrial

A50.24

Legionella pneumophila

A50.10

pipe sizing

A50.28

F22.8

requirements

A50.11

residential

A50.12

safety

A50.10

scale

A50.9

sizing water heaters instantaneous and semi-instantaneous

A50.26

refrigerant-based

A50.27

storage heaters

A50.11

A50.16

A35.13

A35.18

A35.25

A50.26

A50.27

solar energy steam

S10.1

system planning

A50.2

terminology

A50.1

thermal storage

S50.11

water heating equipment placement

A50.11

sizing

A50.11

types

A50.2

water quality

A50.9

SES. See Subway environment simulation (SES) program Shading coefficient

F15.28

devices, indoor

F15.49

fenestration Ships

F15.2 A13

air conditioning air distribution

A13.2

A13.4

controls

A13.3

A13.4

design criteria

A13.1

A13.3

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

A50.4

Index Terms

Links

Ships (Cont.) equipment selection

A13.2

A13.3

systems

A13.2

A13.4

cargo holds

R26.2

cargo refrigeration

R26.1

coils

A13.4

ducts

A13.3

fish freezing

R26.8

fish refrigeration icing

R26.7

R32.1

refrigerated seawater

R26.8

R32.2

merchant

A13.1

naval surface

A13.3

refrigerated stores

R26.4

refrigeration systems

R26.1

regulatory agencies

A13.3

Short-tube restrictors

R11.31

Single-duct systems, all-air

S4.10

SIR. See Savings-to-investment ratio (SIR) Skating rinks

R44.1

Skylights, and solar heat gain Slab heating

F15.19 A51

Slab-on-grade foundations

A44.11

SLR. See Solar-load ratio (SLR) Smoke management

A53

acceptance testing

A53.18

atriums

A53.12

computer analysis,

A53.12

A53.13

design door-opening forces

A53.6

flow areas airflow paths

A53.6

effective

A53.6

open doors

A53.8

pressure differences

A53.8

weather data

A53.8

elevators

A53.11

hospitals

A8.5 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Smoke management (Cont.) large open spaces plugholing

A53.16

plume

A53.13

prestratification layer

A53.16

smoke filling

A53.13

A53.14

steady clear height and upper layer exhaust

A53.14

steady fire

A53.13

unsteady fire

A53.13

zone fire models

A53.13

A53.14

methods airflow

A53.5

buoyancy

A53.6

compartmentation

A53.4

dilution near fire

A53.5

pressurization

A53.5

remote dilution

A53.4

rapid-transit systems

A15.13

road tunnels

A15.9

smoke dampers

A53.8

A53.9

A53.9

A53.10

smoke movement buoyancy

A53.3

expansion

A53.3

HVAC systems

A53.4

stack effect

A53.2

wind

A53.3

stairwells analysis

A53.9

compartmentation

A53.9

open doors

A53.10

pressurization

A53.10

pressurized

A53.9

zones

A53.11

Smudging air outlets

S19.3

Snow-melting systems

A51

back and edge heat losses control

A53.11

A51.7

A51.8

A51.10 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Snow-melting systems (Cont.) electric system design constant wattage systems

A51.15

electrical equipment

A51.13

gutters and downspouts

A51.17

heat flux

A51.13

idling

A51.18

heating elements

A51.13

infrared systems

A51.16

installation

A51.16

mineral insulated cable

A51.13

free area ratio

A51.1

freeze protection systems heat balance

A51.10

A51.17

A51.1

heating requirement annual operating data

A51.8

heat flux equations

A51.2

hydronic and electric

A51.1

load frequencies

A51.3

surface size

A51.7

transient heat flux

A51.7

weather data

A51.3

wind speed

A51.7

hydronic system design components

A51.10

controls

A51.13

fluid heater

A51.12

heat transfer fluid

A51.10

piping

A51.11

pump selection

A51.12

thermal stress

A51.13

operating costs

A51.10

slab design, hydronic and electric snow detectors

A51.8 A51.10

Snubbers, seismic

A55.8

Sodium chloride brines

F31.1

Soft drinks

R39.10

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Soils. (See also Earth) stabilization

R45.3

R45.4

temperature calculation

S11.10

thermal conductivity

F26.12

S11.9

A35

S36.1

active systems

A35.16

A35.17

A35.19

airflow

A35.25 A35.6

A35.11

A35.25

A35.24

A35.26

S36.16

A35.18

A35.26

Solar energy

collectors

A35.5 S36.3

array design piping

S36.7

shading factor

S36.8

concentrating

A35.8

construction glazing

S36.4

insulation,

S36.4

manifolds,

S36.5

design and installation

A35.25

efficiency

A35.10

flat plate

A35.5

glazing materials

A35.7

plates

A35.7

A35.6

module design piping

S36.5

thermal expansion

S36.6

velocity limits

S36.6

mounting

A35.23

performance

A35.9

steady-state conditions

S36.8

selection

S36.9

testing

S36.9

types

S36.3

constant

A35.1

control automatic temperature

S36.16

differential temperature controller

S36.16

hot-water dump

S36.17

overtemperature protection

S36.17

cooling systems

S36.8

A35.15

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Solar energy (Cont.) absorption refrigeration

A35.18

sizing

A35.19

types

A35.15

design, installation, operation checklist, design values, solar irradiation domestic hot water

9

A35.25 A35.4 A35.13

equipment

S36.3

A35.25

S36.1

freeze protection

A35.24

S36.2

heat exchangers,

A35.12

S36.14

external

S36.15

freeze protection

S36.17

internal

S36.14

performance

S36.15

requirements

S36.14

heating systems

A35.16

S50.2

A35.16

A35.17

S36.1

S36.7

active air components

A35.11

control

A35.12

design

S36.1

direct circulation

S36.2

drain-down

S36.17

S36.10

A35.14

hybrid

A35.16

indirect circulation

S36.2

drainback,

A35.14

nonfreezing fluid

S36.2

water heating

A35.14

integral collector storage systems liquid freezing protection

A35.15

S36.3

S36.7

S36.10

S36.2

passive

A35.16

pool heating

A35.15

recirculation

A35.15

residential

S36.2

A1.4

sizing

A35.19

thermosiphon

A35.13 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Solar energy (Cont.) heat pump systems

S8.4

hybrid systems,

A35.16

hydraulics

A35.25

installation

A35.23

irradiation

A35.4

maintenance

A35.24

overheat protection,

A35.24

passive systems,

A35.16

A35.21

photovoltaic (PV) systems

A35.26

S36.18

quality and quantity

A35.1

radiation at earth’s surface

A35.3

safety

A35.24

service water heating systems

A35.13

A35.4

A35.18

A35.25

S50.2 combined with space heating

A35.18

sizing heating and cooling systems

A35.19

spectrum

A35.3

start-up procedure

A35.24

thermal storage systems

A35.11

short circuiting

S36.13

sizing

S36.14

time

A35.1

types

S36.13

uses

A35.25

A35.25

A35.3

Solar heat gain calculation,

F15.17

coefficient

F15.17

roof overhangs,

F15.29

skylights

F15.19

Solar-load ratio (SLR)

A35.21

Solar-optical glazing

F15.13

F15.28

Solar radiation daylighting

F15.1

flux

F15.28

optical properties

F15.15

Solid fuel burners

S30.17 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

A50.4

Index Terms

Links

Solid fuel (Cont.) coal

F28.8

coke

F28.11

Solvent drying, constant-moisture Soot

A30.7 F28.17

Sorbents

F32.1

Sorption isotherm

F25.8

Sound

F8 (See also Noise)

air outlets

S19.2

attenuators

11.18

bandwidths

F8.4

combustion

F28.17

compressors

11.15

computerized analysis

A40.11

cooling towers,

S39.10

ducts

11.12

loudness

F8.14

measurement

F36.27

basics

F8.5

instrumentation

A38.18

level meter

F8.4

F8.4

power

F8.2

pressure

F8.1

speed

F8.2

terminology bandwidths

F8.8

controlling

F8.10

decibel

F8.1

frequency

F8.2

frequency spectrum

F8.15

intensity

F8.2

level

F8.1

loudness

F8.14

pressure

F8.1

quality

F8.14

wavelength testing

F8.2 A38.18 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Sound (Cont.) time averaging

F8.4

transmission

A38.19

humidity affecting paths

S21.2 F8.9

troubleshooting

A38.20

typical sources

F8.10

surface

A35.3

unit heaters

S27.6

Sound control

A48

F8

(See also Noise) acoustical design of HVAC systems

11.1

air handlers

S4.10

A-weighted sound level (dBA)

F8.15

barriers

11.33

ceiling sound transmission

11.38

chillers

11.15

clean spaces

F8.11

A18.19

combustion turbines

S7.22

cooling towers

S39.10

data reliability

11.1

design

11.8

38

ducts

11.12

S18.4

11.18

F8.12

sound attenuation branch division

11

insulated flexible

11.23

plenums

11.18

sheet metal

11.21

silencers

11.23

enclosures

F8.12

engines

S7.15

engine test facilities

A17.4

equipment sound levels

11.8

fans

11.10

fume hood duct design

11.34

hotels and motels

A6.8

insertion loss

11.21

justice facilities

A9.5

10

A9.6

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

F8.15

Index Terms

Links

Sound control (Cont.) mechanical equipment rooms

11.35

noise criterion (NC) curves

F8.16

outdoor, equipment

11.33

piping

11.49

places of assembly

A5.1

return air system sound transmission

11.37

rooftop air handlers

11.11

room criterion (RC) curves

F8.17

room sound correction

11.31

standards

11.54

terminology

F8.10

troubleshooting

A38.19

variable-air-volume (VAV) systems Soybeans, drying

11.50

11.52

11.10 A25.6

Specific heat equation

F2.4

foods

R19.7

liquids

F33.2

materials

F33.1

Spot cooling evaporative

A52.12

industrial environments

A31.3

makeup air units

S27.8

mines

A31.6

A52.12

A29.10

Spot heating

A54.4

Stack effect duct design

F21.2

multizone airflow modeling smoke movement

F13.14 A53.2

Stadiums

A5.4

Stainless steel boilers

S31.3

Stairwells, smoke control

A53.9

Standard atmosphere, U.S.

F1.1

Standards

A61

(See also Codes) air cleaners air conditioners

S28.3

S28.5

S48 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Standards (Cont.) packaged terminal

S49.7

room

S49.4

unitary

S48.5

air distribution

A57.1

boilers

S31.5

chilled-beam system

A57.18

chimneys, fireplaces, and gas vents

S34.27

condensers

S48.6

S34.32

S38

evaporative

S38.18

water-cooled

S38.7

coolers, liquid

S41.4

data processing

A19.16

dehumidifiers, room

S24.3

duct construction

S18.1

commercial

S18.2

industrial

S18.4

residential

S18.2

electrical

A56.15

filters, air

S28.3

furnaces

S32.11

heaters

S33.6

heat pumps

S28.5

S33.7

S48

packaged terminal

S49.7

unitary

S48.5

water-source

S48.6

S48.12

indoor air quality (IAQ)

F10.10

liquid chillers

S42.5

makeup air units

S27.9

motors

S44.2

nuclear facilities

S44.10

A28.12

pipe fittings

S45.2

piping

S11.19

sound control

11.54

tall buildings

A4.14

ventilation

S45.6

F16.18

vibration control

11.54

Static electricity and humidity

S21.2

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Steam quality

S10.2

sources

S10.2

testing, adjusting, balancing thermophysical properties Steam systems

A38.15 F30.1 S10

air, effects of

S10.2

boilers

S10.3

classification

S10.2

coils, air-heating

S26.1

combined heat and power (CHP) distribution,

S7.44

combined steam and water condensate removal

S10.6 S11.7

drip stations

S11.7

return pipes

S11.19

convection heating

S10.11

design

S10.2

piping

S10.5

pressure

S10.4

distribution

S10.12

district heating and cooling district heating and cooling

percentage flash tank

S35.3

S11.18 S11.3

S11.19

S11.30

S10.14 S10.2 S10.14

gas, effects of

S10.2

generator buildings

A27.4

heat exchangers

S10.3

heating

S31.1

S10.15

drainage and return

flash steam

F30.36

A49.11

heat recovery direct recovery

S10.15

flash steam

S10.14

waste heat boilers

S10.3

makeup air units

S27.9

one-pipe systems

S10.11

1993

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Steam systems (Cont.) Fundamentals, Chapter 33, pp. 18-19 (See explanation on first page of index.) piping distribution

S10.5

Hartford loop

S10.3

inlet orifices

S10.12

return

S10.3

sizing

F22.12

supply

S10.3

terminal equipment

S10.6

temperature control

S10.6

S10.5

S10.12

S10.13

terminal equipment forced-convection

S10.11

natural convection

S10.11

units

S35.1

piping design

S10.6

radiant panel

S10.11

traps

S10.7

turbines

S7.25

two-pipe systems

S10.12

unit heaters

S27.4

ventilators

S27.1

valves pressure-reducing

S10.9

safety

S10.9

temperature control water, effects of

S10.13 S10.2

Steam traps

S10.7

Stefan-Boltzmann equation

F4.2

Steven’s law

F12.3

Stirling cycle

R47.14

Stokers

S30.17

F4.11

Storage apples controlled atmosphere bakery ingredients

A52.14

R35.1

R35.1

R35.3

R35.3

R41.1 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Storage (Cont.) candy

R42.5

carbon dioxide

R39.12

citrus

A52.14

cold, facility design

R23.1

compressed gases

A16.8

controlled-atmosphere (CA),

R23.3

cryogenic fluids

R36.3

R47.26

desiccant dehumidification high-pressure

S23.8 S23.11

design, refrigerated-facility

R23.1

eggs

R34.5

farm crops

A25.9

fish fresh

R32.3

frozen

R32.7

flowers, cut

R21.12

food, canned or dried

R21.11

fruit dried

R42.7

fresh

R35.1

furs and fabrics

R21.11

ice

R43.4

meat products, frozen milk

R30.16 R33.4

nursery stock

R21.12

nuts

R42.7

photographic materials

A22.3

unprocessed

A22.1

potatoes

A52.14

poultry products

R31.10

refrigerated-facility design seeds

R23.1 A25.11

tanks, secondary coolant systems

R13.2

vegetables

R37.3

dried

R42.7

wine wood products

A22.4

R21.13

R39.10 A26.2 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Stoves, heating

S33.5

Stratification of air in places of assembly in plenums

A5.2 A38.2

of water, in thermal storage tanks

S50.4

Stroboscopes

F36.26

Subcoolers condensers

S38

evaporative

S38.17

water-cooled

S38.5

two-stage

R1.29

Subway environment simulation (SES) program

A15.3

Subway systems. (See also Mass-transit systems) car air conditioning

A11.5

station air conditioning

A15.14

ventilation

A15.11

Suction risers

R2.26

Sulfur content, fuel oils

F28.7

Superconductivity, diamagnetism

R47.5

Supervisory control

A42

air-handling systems air distribution

A42.1

sequencing

A42.35

set point reset

A42.36

building temperature set point night setback recovery

A42.36

precooling

A42.37

chilled-water pumps

A42.12

A42.25

A42.27

A42.29

A42.32

chillers load distribution

A42.30

sequencing

A42.29

computerized

A40.17

cooling tower fans

A42.14

cool thermal storage systems

A42.38

ice storage control optimization

A42.21

A42.8

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Supervisory control (Cont.) forecasting energy requirements

A42.40

optimization methods dynamic

A42.7

static

A42.4

system based

A42.5

Supply air outlets

S19.1

(See also Air outlets) Surface effect. See Coanda effect Surface transportation automobiles

A10.1

buses

A11.2

fixed-guideway vehicles

A11.7

rail cars

A11.5

Surface water heat pump (SWHP) heat exchanger

S48.12

Surface water heat pump (SWHP) Sustainability

A34.12 F16.1

and air, noise, and water pollution

F35.3

chimney

S34.1

climate change

F35.3

design process

F35.5

energy resources

F35.2

and green design

F35.1

infiltration

F16.1

in integrated building design

A58.3

material resources

F35.3

renewable energy

F35.2

and solid and liquid waste disposal

F35.3

unitary systems

S48.2

ventilation

F16.1

water use

F35.2

F35.1

SVFs. See Synthetic vitreous fibers (SVFs) SWHP. See Surface water heat pump (SWHP) Swimming pools. (See also Natatoriums) dehumidifiers solar heating water chemistry

S24.4 A35.15 A5.7 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

S48.2

Index Terms

Links

Swimming pools (Cont.) water heating for

A50.23

Swine, recommended environment Symbols

A24.7 F37

Synthetic vitreous fibers (SVFs)

F10.5

T Tachometers

F36.26

Tall buildings

A4

codes

A4.14

HVAC design process

A4.3

hydrostatic considerations

A4.11

life safety

A4.14

low-temperature air VAV systems refrigeration machine location

A4.5 A4.11

reverse stack effect

A4.1

stack effect

A4.1

elevator doors

A4.2

heating problems

A4.2

manual doors

A4.2

minimizing

A4.2

smoke and odor propagation

A4.2

standards

A4.14

system selection

A4.4

underfloor air distribution (UFAD) systems

A4.5

vertical transportation

A4.13

water distribution systems

A4.11

Tanks, secondary coolant systems

R13.2

Temperature ambient

A54.1

changeover

S5.11

S5.13

dew-point

F1.8

F1.9

dry-bulb, adjusted effective

A54.1 A52.10

humid operative

F9.20

mean radiant

A54.1

measurement

F36.4

odors affected by

F12.2

F9.20

F9.10

F36.29

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

S6.1

Index Terms

Links

Temperature (Cont.) operative

A54.1

plane radiant

F9.10

radiant asymmetry

F9.11

sensors

F36.29

F7.9

sol-air

F18.22

and task performance

F9.13

vertical differences

F9.15

wet-bulb

F1.8

globe

F9.21

wet-globe

F9.22

wind chill index

F9.22

Temperature-controlled transport Temperature index

F1.9

R25.1 S21.2

Terminal units

A47.12

air distribution

S19.8

S4.15

boxes reheat

A47.13

variable-air-volume (VAV)

11.11

bypass

S19.10

ceiling

S19.9

chilled beams

S5.7

constant volume

S4.16

dual-duct

S19.8

fan-coil

S5.4

fan-powered

A47.12

humidifiers

S4.16

S4.17

induction

A47.14

induction units

S5.8

radiant floor heat

S5.8

radiant panels

S5.8

reheat

S4.16

S19.8

steam systems

S10.11

throttling

S4.16

unit ventilators

S5.6

variable-air-volume (VAV) Terminology

S4.16

S4.16 R50

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

S19.9

Index Terms

Links

Terrorism. See Chemical, biological, radiological, and explosive (CBRE) incidents TES. See Thermal energy storage (TES) Testing air cleaners

A46.16

air conditioners, packaged terminal air leakage, fan pressurization clean spaces

S28.3

S49.7 F16.14 A18.7

compressors centrifugal

S37.32

positive-displacement condensers

S37.5 S38

evaporative

S38.18

water-cooled

S38.7

cooling towers

A38.15

S39.15

desiccant dehumidification for

S23.10

S23.11

duct efficiency

S9.11

fans

S20.4

filters, air

S28.3

heaters

S33.7

heat pumps packaged terminal air conditioners (PTACs)

S49.7

water-source

S48.12

industrial exhaust systems

A32.9

radiant heating system

A54.7

refrigeration systems compressor

R8.5

leak detection

R8.4

performance testing

R8.5

refrigerators, household

R17.9

smoke control systems

A53.18

solar collectors

S36.9

sound instrumentation

A38.18

procedure

A38.19

transmission problems

A38.19

A38.24

vibration This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Testing (Cont.) equipment

A38.22

instrumentation

A38.21

isolators

A38.21

piping transmission

A38.24

procedure

A38.21

11.52

Testing, adjusting, and balancing. (See also Balancing) air diffusers

A38.2

air distribution systems

A38.3

reporting results

A38.6

airflow measurement

A38.2

balancing procedure

A38.5

central plant chilled-water systems

A38.14

cooling towers

A38.15

design considerations

A38.1

dual-duct systems

A38.4

duct design

F21.16

energy audit field survey

A38.17

fluid flow measurement

A38.11

HVAC systems

A38.1

hydronic systems

A38.6

heat transfer vs. flow

A38.6

A38.7

water-side balancing instrumentation

A38.8

proportional method

A38.9

rated differential method

A38.10

sizing balancing valves

A38.8

temperature difference method

A38.9

total heat transfer method,

A38.10

induction systems

A38.5

instruments

A38.3

sound transmission problems,

A38.19

steam distribution systems

A38.15

temperature controls

A38.16

terminology

A38.24

A38.1

variable-air-volume (VAV) systems,

R A38.6

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

TETD/TA. See Total equivalent temperature differential method with time averaging (TETD/TA) TEWI. See Total equivalent warming impact (TEWI) Textile processing plants

A21

air conditioning design air cleaning

A21.5

air distribution

A21.6

collector systems

A21.5

health considerations

A21.7

energy conservation

A21.7

fabric making

A21.3

fiber making

A21.1

yarn making

A21.2

A21.7

TFM. See Transfer function method (TFM) Theaters

A5.3

Thermal bridges

F25.7

Thermal comfort. See Comfort Thermal emittance

F25.2

Thermal energy storage (TES)

S17.4

Thermal properties

F26.1

acoustics

F26.12

air spaces

F26.1

health

F26.12

insulation materials

F26.2

mechanical properties

F26.11

safety

F26.12

Thermal properties of food Thermal resistivity

R19 F25.1

Thermal storage

S50

applications

S50.16

benefits

S50.3

building mass

S50.14

combined heat and power (CHP)

S7.40

controls

S50.1

sequence

S50.23

strategies

A42.38 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Thermal storage (Cont.) precooling

A42.37

cool storage

A42.38

district cooling

S50.16

district heating

S50.7

district heating and cooling

S11.4

electrically charged storage

S50.11

brick storage heaters

S50.12

central furnace

S50.13

heat pump boosters

S50.1

S50.17

S50

room units

S50.12

underfloor heat

S50.14

water heaters

S50.11

S50.13

equipment cooling

S50.4

heating

S50.11

heat storage

S50.1

ice

R43.3

ice storage

S50.1

charging and discharging

S50.11

S50.2

A42.38

control optimization

A42.8

encapsulated ice

S50.2

S50.9

S50.11

harvesting system

S50.2

S50.6

S50.9

ice on coil

S50.1

S50.7

S50.8

piping

S50.21

slurries

S50.10

industrial refrigeration,

S50.17

insulation

S50.6

latent energy change

S50.2

media

S50.2

mission-critical operations

S50.17

off-peak, heating

S50.11

operation

S50.23

phase-change materials

S50.2

piping, ice storage

S50.21

process cooling

S50.17

retrofits

S50.12

S50.4

S50.11

S50.21

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Thermal storage (Cont.) solar energy systems

A35.11

A35.16

S36.10

S50.2

system sizing

S50.17

terminology

S50.1

water storage

S50.4

aquifers

S50.6

performance

S50.5

tank insulation

S36.12

S50.27

S50.6

temperature range

S50.4

thermal stratification

S50.4

S50.5

S50.11

S50.13

water heaters water systems, medium and high temperature

S14.9

water treatment

S50.6

Thermal transmission data Thermistors

A35.25

F26 R11.4

Thermodynamics

F2.1

absorption refrigeration cycles

F2.13

bubble point

F2.5

compressed liquid

F2.2

compression refrigeration cycles

F2.6

cooling and freezing of foods

R20.1

cycle

F2.2

dew point

F2.6

dry saturated vapor

F2.2

enthalpy

F2.4

entropy

F2.4

equations of state

F2.3

laws

F2.2

liquid

F2.2

multicomponent systems

F2.5

principles

F2.1

process

F2.2

properties

F2.1

calculation

F2.4

zeotropic mixture

F2.9

pure substance

F2.2

of refrigerants

F30 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

S36.3

Index Terms

Links

Thermodynamics (Cont.) refrigeration cycle analysis

F2.3

saturated liquid or vapor

F2.2

subcooled liquid

F2.2

superheated vapor

F2.2

terminology

F2.1

vapor

F2.2

Thermometers

F36.5

black globe

A54.7

error sources

F36.5

infrared radiometers

A54.7

thermography

F36.9

liquid-in-glass

F36.9

F36.5

resistance semiconductors

F36.7

temperature devices (RTDs)

F36.6

thermistors

F36.7

thermocouples

F36.7

Thermopile

F7.4

F36.8

R45.4

Thermosiphons heat exchangers

S25.14

solar energy systems

A35.13

Thermostats heater control

S33.2

heating/cooling

F7.11

location

S33.4

A47.21

types

F7.11

Three-pipe distribution

S5.4

Tobacco smoke contaminants

A46.2

A46.8

A46.10

F11.17 environmental (ETS)

F10.6

Tollbooths air quality criteria

A15.26

ventilation

A15.27

A15.33

Total equivalent temperature differential method with time averaging (TETD/TA),

F18.49

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

F11.2

Index Terms

Links

Total equivalent warming impact (TEWI),

R6.1

Trailers and trucks, refrigerated

R25

R15.16

(See also Cargo containers) Transducers, pneumatic pressure

F7.9

Transfer function method (TFM)

A40.9

Transmittance, thermal

F25.1

of flat building component

F25.6

thermal bridging

F25.7

hot-box method

F18.49

F25.7

Transmitters, pneumatic pressure Transpiration

F7.9 R19.19

Transportation centers commercial and public buildings ventilation

A3.6 A15.11

Transport properties of refrigerants

A15.23

F30

Traps ammonia refrigeration systems liquid

R2.18

liquid level indicators

R2.5

purge units

R2.6

suction accumulator

R2.4

vertical suction

R2.4

steam systems

S10.7

thermostatic

S10.7

Trucks, refrigerated

R25

(See also Cargo containers) Tuning automatic control systems

F7.18

Tunnels, vehicular

A15.1

fires

A15.3

railroad

A15.16

rapid transit

A15.11

road

A15.3

Turbines

S7

benefits economic

S17.2

environmental

S17.2

chiller systems absorption

S17.4 S17.4 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Turbines (Cont.) mechanical

S17.4

thermal energy storage (TES)

S17.4

combustion

S7.18

Brayton cycle

S7.18

components

S7.18

controls

S7.22

dual-shaft

S7.18

emissions

S7.22

evaporative cooling applications

S7.21

exhaust gas systems

S7.22

fuels

S7.20

heat recovery

S7.37

instruments

S7.22

lubrication

S7.22

maintenance

S7.22

noise control

S7.22

performance

S7.19

single-shaft

S7.18

split-shaft

S7.18

starting systems

S7.22

thermal output

S7.34

engine test facilities, gas

A17.3

expansion

S7.31

fogging

S17.3

gas

S7.18

evaporative cooling microturbines

S7.46

S17.3

S42.1

A52.13 S7.18

steam applications

S7.47

axial flow

S7.25

heat recovery extraction turbines

S7.38

noncondensing turbines

S7.37

maintenance

S7.31

wetted media

S17.3

Turbochargers, heat recovery

S7.35

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

S17.1

Index Terms

Links

Turbulence modeling

F13.3

identification

F13.10

Turbulent flow, fluids

F3.3

Turndown ratio, design capacity Two-pipe systems

S12.4 S5.4

air-to-transmission ratio

S5.12

central ventilation

S5.12

changeover temperature

S5.13

chilled-water

S12.19

electric heat

S5.14

nonchangeover design

S5.13

steam convection heating zoning

S12.19

S10.12 S5.14

U U.S. Marshal spaces

A9.5

U-factor center-of-glass

F15.4

doors

F15.12

edge-of-glass

F15.4

fenestration products

F15.6

of flat building assembly

F25.7

frame

F15.4

thermal transmittance

F15.4

windows

F27.8

Ultralow-penetration air (ULPA) filters Ultraviolet (UV) lamp systems

S28.7

F27.8

S29.2

S16

fixture configurations

S16.5

in-duct airstream disinfection

A60.7

S16.6

lamps

A60.1

S16.1

germicidal

A60.4

S16.3

aging

S16.5

ballasts

A60.5

S16.4

cooling and heating effects,

A60.6

S16.5

irradiance

A60.5

S16.5

A60.12

S16.8

maintenance photodegradation

S16.8 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

S16.3

Index Terms

Links

Ultraviolet (UV) lamp systems (Cont.) safety

A60.11

S16.8

surface disinfection

A60.10

S16.6

terminology

S16.1

upper-air

A60.10

Ultraviolet air and surface treatment

S16.7 A60

Ultraviolet germicidal irradiation (UVGI)

S16.1

[See also Ultraviolet (UV) lamp systems] in-duct airstream disinfection

A60.7

systems

A60.7

terminology

A60.3

S16.6

Uncertainty analysis measurement

A41.13

precision uncertainty

F36.4

sources

F36.3

systematic uncertainty

F36.4

statistical regression

A41.14

A41.14

Underfloor air distribution (UFAD) systems Unitary systems

A4.5 S48

floor-by-floor systems

S2.6

heat pumps

S2.3

outdoor equipment

S2.8

self-contained

S2.6

split systems

S2.6

through-the-wall

S2.3

window-mounted

S2.3

S48.1

S48.8

S48.1

Unit heaters. See Heaters Units and conversions

F38.1

Unit ventilators

S27.1

Utility interfacing, electric

S7.44

UV. See Ultraviolet (UV) lamp systems UVGI. See Ultraviolet germicidal irradiation (UVGI)

V Vacuum cooling, of fruits and vegetables

R28.9

Validation, of airflow modeling

F13.9

F13.10

F13.17

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

S48.10

Index Terms

Links

Valves

S46 (See also Regulators)

actuators

S46.5

ammonia refrigeration systems control

R2.9

float control

R2.20

relief

R2.10

solenoid

R2.10

stop

R2.9

authority

S46.8

automatic

S46.4

actuators

S46.4

applications

S46.9

control

F7.4

computerized

S46.6

expansion

S22.2

flow characteristics

S46.7

sizing

S46.9

types

S46.6

backflow-prevention devices,

S46.13

balancing

S46.9

sizing

A38.8

body styles

S46.3

cavitation

S46.2

check

R11.21

compressors, reciprocating

S37.10

condensing-pressure-regulating

R11.15

constant-pressure expansion,

R11.14

control valves

F3.8

coefficient

F3.9

discharge bypass

S46.12

R11.16

expansion constant-pressure

R11.11

electric

R11.10

thermostatic float control

R11.14

R11.5 R11.17

flow coefficient

S46.2

geothermal energy

A34.7

S46.9

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Valves (Cont.) halocarbon refrigeration systems equivalent lengths

R1.10

float control

R1.26

hydronic systems control

S12.15

safety relief

S12.20

manual

S46.3

selection

S46.3

materials

S46.1

multiple-purpose

S46.10

noise

S46.2

pressure drop

F22.1

pressure-reducing makeup water

S46.12

pressure relief

S46.11

safety

F22.8

R11.22

ratings

S46.1

refrigerant control

R11.4

regulating and throttling

R11.11

safety

S46.11

solar energy systems

A35.12

solenoid

R11.17

S46.6

S10.9

S10.13

steam system stop-check

S46.13

suction pressure regulating

R11.14

thermostatic

S10.13

water hammer

S46.11

S46.2

zone control

S10.13

Vaporization systems

S17.4

liquefied natural gas (LNG)

S17.4

Vapor pressure

F27.8

Vapor retarders, jackets

F23.9

F33.2

Variable-air-volume (VAV) systems all-air dual-duct

S4.12

single-duct

S4.11

control

A42.1

diversity

A38.5

dual-duct systems

S4.12

A42.3

A42.36

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Variable-air-volume (VAV) systems all-air (Cont.) duct static pressure control

A47.8

fan selection

11.10

sequencing

A47.9

unstable operation

A47.9

humidity control

S21.8

museums, galleries, archives, and libraries

A23.19

pressure-dependent systems

A38.4

pressure-independent systems

A38.4

single-duct

S4.11

sound control

11.10

static pressure control

A38.4

static pressure reset

A42.36

system types

A38.5

terminal boxes

A47.13

testing, adjusting, balancing

A38.4

variable-speed drives

S44.9

versus constant air volume (CAV)

11.11

A16.12

Variable refrigerant flow (VRF)

S48.1

Variable-speed drives

S44.9

S48.13

carrier frequencies effect on drive ratings

S44.12

effect on motor noise

S44.11

conductor impedance

S44.10

control

S44.9

harmonic disturbances load side

S44.12 S44.13

motors

S44.10

impedance

S44.10

pulse width modulation transistors

S44.10 S44.9

voltage waveform distortion

S44.12

VAV. See Variable-air-volume (VAV) systems Vegetables

R37

air transport

R27.1

cooling

R28.1 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

VAV. See Variable-air-volume (VAV) systems (Cont.) deterioration rate

R21.1

display refrigerators

R15.8

dried, storage

R42.7

frozen

R40.3

misters and Legionella pneumophila control

A49.7

refrigeration

R37.1

storage

R37.3

thermal properties

R19.1

transport

R37.2

Vehicles ac- or dc-powered, transit

A11.5

design

R25.1

equipment attachment provisions

R25.3

sanitation

R25.3

temperature-controlled

R25.1

use

R25.10

Vena contracta

F3.4

Vending machines

R16.5

Ventilation

F16

age of air

F16.4

air change effectiveness

F16.5

aircraft

A12.6

A12.15

air exchange rate

F16.3

F16.12

airflow

F16.3

animal environments

A24.5

bus garages

A15.21

bus terminals

A15.23

cargo containers

R25.5

climatic infiltration zones dilution

F16.19 A31.2

A46.6

displacement,

F20.16

S4.14

design

F20.16

driving mechanisms

F16.12

effectiveness

F16.5

engine test facilities

A17.1

forced

F16.1 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Ventilation (Cont.) garages, residential

F16.20

gaseous contaminant control greenhouses

A46.6 A24.12

health care facilities

A8.1

hospitals

A8.2

nursing facilities

A8.14

outpatient

A8.14

hybrid

F16.14

indoor air quality (IAQ)

F16.10

industrial environments

A31

exhaust systems kitchens laboratories

A32.1 A33 A16.8

latent heat load

F16.11

leakage function

F16.14

mechanical

F16.1

mines

A29

natatoriums

A5.6

F24.7

natural airflow

F16.1

guidelines

F16.14

stack effect

F16.13

wind

F16.13

nuclear facilities

A28.4

odor dilution

F12.5

power plants

A27.4

railroad tunnels

A15.16

rapid-transit systems,

A15.11

residential

F16.17

road tunnels

A15.3

roof ventilators

A31.4

security concerns

A59.7

sensible heat load

F16.11

ships standards

F16.12

F24.7

A15.5

A13.1 F16.18

terminology

F16.1

thermal loads

F16.11 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Ventilation (Cont.) tollbooths

A15.26

wind effect on

F24.7

Ventilators roof

A31.4

unit capacity

S27.3

control

A47.15

location

S27.1

selection

S27.3

types

S27.1

S27.3

Venting furnaces

S32.2

gas appliances

S34.18

oil-fired appliances

S34.19

Verification of airflow modeling Vessels, ammonia refrigeration systems Vibration

F13.9

F13.10

F13.17

R2.3 F8.18

compressors centrifugal

S37.34

positive-displacement

S37.5

scroll

S37.26

single-screw

S37.18

critical speeds

S20.8

health effects

F10.14

measurement

F36.28

instrumentation testing Vibration control

A38.21 A38.20 11

air handlers

S4.10

clean spaces

A18.19

criteria data reliability

11.43 11.1

ducts

11.51

engines

S7.15

equipment vibration analysis fans

A38.22 A38.22 S20.9 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Vibration control (Cont.) floor flexibility

11.53

isolators noise

11.41

resonance

11.53

specifications

11.44

testing

A38.21

11.52

piping connectors expansion joint or arched

11.51

flexible

11.50

hose

11.50

noise

11.49

resilient hangers and supports

11.49

places of assembly

A5.1

resonance

11.53

seismic restraint

11.51

standards

11.54

troubleshooting

A38.22

Viral pathogens

A55.1

11.52

F10.7

Virgin rock temperature (VRT), and heat release rate

A29.3

Viscosity

F3.1

fuel oils

F28.6

lubricants

R12.5

modeling

F13.10

moist air

F1.15

Volatile organic compounds (VOC) contaminants

F10.9 A46.2

Voltage

A56.1

imbalance

S44.1

utilization

S44.1

Volume ratio, compressors rotary vane

S37.14

single-screw

S37.16

twin-screw

S37.21

VRF. See Variable refrigerant flow (VRF) VRT. See Virgin rock temperature (VRT) This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

W Walls glass block

F15.19

masonry construction

F27.4

steel frame construction

F27.4

wood-frame construction

F27.3

Warehouses

A3.8

Water boiler thermal models coils

F19.14 S22.2

air-heating

S26.2

coolers

R39.11

distribution

S3.6

central plants

S12.10

S14.7

S11.5

district heating and cooling

S11.18

filtration

A49.7

hammer

F22.6

pipe stress

S11.7

heating geothermal energy systems

A34.9

solar energy systems

A35.13

water treatment for

A49.10

humidifier supply

S21.4

properties

A49.1

S14.2

F30.1

F30.36

refrigerant in refrigerant systems. See Moisture, in refrigerant systems systems, pipe sizing

F22.5

thermal storage systems

S50.4

use and sustainability

F35.2

S50.11

S50.27

vapor (See also Moisture) control

F25.2

flow

F25.10

resistance

F25.2

retarders

F26.13

condensation,

S21.2

refrigerant piping insulation

R10.7

refrigerated facilities

R23.5

R23.12

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Water (Cont.) terminology

F25.2

transmission

F26.15

Water heaters blending injection

A50.4

boilers (indirect)

A50.28

circulating tank

A50.4

combination

A50.4

electric

A50.3

gas-fired

A50.2

heat pump

S48.4

indirect

A50.3

A50.28

instantaneous

A50.3

A50.26

oil-fired

A50.2

placement

A50.11

refrigeration heat reclaim

A50.4

A50.27

semi-instantaneous

A50.4

A50.26

A50.11

A50.26

A50.27

A50.3

A50.11

sizing solar energy

A50.4

storage

A50.2

terminology

A50.1

usable hot-water storage waste heat recovery

A50.10 A50.4

Water/lithium bromide absorption components

R18.1

control

R18.6

double-effect chillers

R18.3

maintenance

R18.7

operation

R18.6

single-effect chillers,

R18.2

single-effect heat transformers

R18.3

terminology

R18.1

Water-source heat pump (WSHP) Water systems

S48.10 S12

air elimination

S12.21

antifreeze

S12.23

precautions capacity control

S12.24 S12.13 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Water systems (Cont.) chilled-water

S12.1

S12.17

combined heat and power (CHP) distribution

S7.44

district heating and cooling closed

S11.19

S11.32

S12.1

S12.2

components

S12.2

condenser water

S13.1

closed

S13.3

once-through

S13.1

open cooling tower

S13.1

air and vapor precautions

S13.2

freeze protection,

S13.3

piping,

S13.2

water treatment

S13.2

overpressure precautions

S13.3

systems

S13.1

water economizer

S13.3

control valve sizing

S12.15

Darcy-Weisbach equation

S43.4

district heating and cooling

S11.3

dual-temperature (DTW)

S12.1

equipment layout,

S12.19

S12.22

expansion tanks functions of

S12.4

sizing equations

S12.5

fill water

S12.20

four-pipe

S12.19

freeze prevention,

S12.23

S12.10

hot-water boilers

S31.1

combined heat and power (CHP) distribution

S7.45

district heating and cooling high-temperature (HTW) loads,

S11.31 S12.1 S12.2

low-temperature (LTW)

S12.1

design considerations

S35.3

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

S14.1

Index Terms

Links

Water systems (Cont.) heating systems

S12.16

loads,

S12.2

nonresidential

S12.16

terminal equipment medium- and high-temperature

S35.1 S12.1

air-heating coils

S14.8

boilers,

S14.2

cascade systems

S14.6

circulating pumps

S14.6

control

S14.8

design,

S14.2

direct-contact heaters

S14.6

direct-fired generators

S14.2

distribution,

S14.7

expansion tanks

S14.4

heat exchangers

S14.8

piping design

S14.7

pressurization

S14.4

safety,

S14.9

space heating

S14.8

thermal storage

S14.9

water treatment

S14.9

medium-temperature (MTW) loads

S14

S12.2 S12.2

loads

S12.2

makeup

S12.20

medium- and high-temperature

S14.1

open

S12.2

pipe sizing

S12.22

piping

S12.11

water distributuion pressure drop determination pumps

S13.1

S12.6 S12.22

S43.4

S43.1 pump curves

S12.6

S43.3

pumping compound

S12.8

distributed

S43.12 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Water systems pumps (Cont.) parallel

S12.7

S43.10

primary-secondary

S12.8

S43.12

series

S12.7

S43.11

variable-speed

S12.8

S43.12

S12.8

S43.11

standby pump two-speed motors

S43.11

safety relief valves

S12.20

steam and, combined

S10.15

temperature classifications

S12.1

turndown ratio

S12.4

two-pipe

S12.19

in tall buildings

A4.11

Water treatment

A49

air washers

A49.9

biological control

A49.5

Legionella pneumophila

S40.9

A49.6

boilers

A49.10

brine systems

A49.10

closed recirculating systems

A49.10

condensers, evaporative

S38.18

condenser water

S13.2

cooling towers

A49.4

A49.8

corrosion control

A49.2

A49.9

evaporative coolers

S40.9

filtration

A49.7

fundamentals

A49.1

heating systems

S39.13

A49.10

ice makers

A49.7

medium- and high-temperature systems

S14.9

nonchemical (physical)

A49.5

once-through systems

A49.9

open recirculating systems

A49.9

scale control

A49.4

sprayed-coil units

A49.9

steam and condensate systems

A49.11

terminology

A49.11

A49.9

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Water treatment (Cont.) thermal storage

S50.6

Water vapor control

A44.6

through air movement

A44.6

through diffusion

A44.6

Water vapor retarders

F26.13

Water wells

A34.26

Weather data climate change’s effect on

F14.13

design conditions

F14.1

calculation

F14.4

clear-sky solar radiation

F14.7

cooling

F14.6

dehumidification

F14.6

heating

F14.5

relationships

F14.5

return period

F14.6

design-day data

F14.11

residential infiltration zones

F16.19

sources

F14.4

Welding sheet metal

S18.6

Wet-bulb globe temperature (WBGT), heat Stress

A31.5

Wheels, rotary enthalpy

S25.10

Whirlpools and spas Legionella pneumophila control

A49.7

service water heating

A50.24

Wien’s displacement law

F4.12

Wind. (See also Climate design information; Weather data) data sources

F24.6

effect on chimneys

S34.3

smoke movement

A53.3

system operation

F24.7

pressure

F24.3

Wind chill index

F9.22

S34.30

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Windows. (See also Fenestration) air leakage

F15.50

solar gain

F15.13

F15.17

U-factors

F15.4

F15.6

Wind restraint design

A55.15

minimum design wind load

A55.15

Wineries refrigeration

R39.8

temperature control fermentation

R39.9

storage

R39.10

wine production

R39.8

Wood construction and moisture

F25.8

dimensional changes

F25.8

Wood products facilities

A26.1

evaporative cooling

A52.13

process area

A26.2

storage

A26.2

Wood pulp

A26.2

Wood stoves

S33.5

World Wide Web (WWW)

A40.8

WSHP. See Water-source heat pump (WSHP) WWW. See World Wide Web (WWW)

X Xenon

R47.18

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

F27.8