2011 ASHRAE Handbook - Heating, Ventilating, and Air-Conditioning Applications (I-P Edition)

869 Pages·2011·82.48 MB·English

2011 ASHRAE HANDBOOK
Heating, Ventilating,
and
Air-Conditioning
APPLICATIONS
Inch-Pound Edition
0 201 1 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-electronic, photocopying, recording,
or other-without permission in writing from ASHRAE.
Volunteer members of ASHRAE Technical Committees and others compiled the infor-
mation in this handbook, and it is generally reviewed and updated every four years. Com-
ments, 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 correc-
tions 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 978-1-936504-06-0
ISSN 1078-6074
The paper for this book was manufactured in an acid- and
elemental-chlorine-free 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 Air- annually, enabling ASHRAE to report new data about material
Conditioning Engineers is the world’s foremost technical society in properties and building physics and to promote the application of
the fields of heating, ventilation, air conditioning, and refrigeration. innovative technologies.
Its members worldwide are individuals who share ideas, identify Chapters in the ASHRAE Handbook are updated through the
needs, support research, and write the industry’s standards for test- experience of members of ASHRAE Technical Committees and
ing and practice. The result is that engineers are better able to keep through results of ASHRAE Research reported at ASHRAE confer-
indoor environments safe and productive while protecting and pre- ences and published in ASHRAE special publications and in
serving the outdoors for generations to come. ASHRAE Transactions.
One ofthe ways that ASHRAE supports its members’ and indus- For information about ASHRAE Research or to become a mem-
try’s need for information is through ASHRAE Research. Thou- ber, contact ASHRAE, 1791 Tullie Circle, Atlanta, GA 30329; tele-
sands of individuals and companies support ASHRAE Research phone: [phone]; www.ashrae.org.
Preface
The 20 1 1 ASHRAE Handbook-HVAC Applications comprises Chapter 40, Computer Applications, updated throughout, has new
over 60 chapters covering a broad range of facilities and topics, and content on building information modeling (BIM) and wireless
is written to help engineers design and use equipment and systems applications.
described in other Handbook volumes. ASHRAE Technical Com- Chapter 41, Building Energy Monitoring, has a new section on
mittees have revised nearly every chapter to cover current require- simplifying methodology for small projects.
ments, technology, and design practice. An accompanying CD- * Chapter 42, Supervisory Control Strategies and Optimization, has
- -
ROM contains all the volume’s chaDters in both I-P and SI units. been reorganized. with new content on thermal storage and ther-
This edition includes two new chapters: mally active building systems (TABS), hybrid cooling plants, and
predictive control.
Chapter 4, Tall Buildings, focuses on HVAC issues unique to tall
Chapter 43, HVAC Commissioning, has been updated throughout
buildings, including stack effect, system selection, mechanical
to reflect ASHRAE Guideline 1. l-2007.
room location, water distribution, vertical transportation, and life
Chapter 44, Building Envelopes, has reorganized and expanded
safety.
content on nonresidential and existing buildings, durability, and
Chapter 60, Ultraviolet Air and Surface Treatment, covers ultra-
common building envelope assemblies.
violet germicidal irradiation (UVGI) systems and relevant guide-
Chapter 48, Noise and Vibration Control, has a new title plus reor-
lines, standards, and practices, as well as energy use and
ganized and new content on noise criteria, chiller noise, and
economic considerations.
vibration measurement.
Here are selected highlights of the other revisions and additions: Chapter 50, Service Water Heating, has expanded content on siz-
ing tankless water heaters plus new data on piping heat loss.
Chapter 3, Commercial and Public Buildings, now covers office
Chapter 55, Seismic- and Wind-Resistant Design, has a new title
buildings, transportation centers, and warehouses and distribution
and reflects changes to building codes, standards for anchor bolt
centers, with new sections on commissioning, sustainability,
design, and other new requirements.
energy efficiency, energy benchmarking, renewable energy, value
Chapter 57, Room Air Distribution, has extensive new application
engineering, and life-cycle cost analysis.
guidelines plus new content on indoor air quality (IAQ), sustain-
Chapter 7, Educational Facilities, has added content on higher
ability, and chilled beams.
education facilities, commissioning, dedicated outdoor air sys-
Chapter 59, HVAC Security, has a new title, with updates from
tems (DOAS), combined heat and power (CHP), and sustainabil-
ASHRAE Guideline 29-2009 and new sections on risk evalua-
ity and energy efficiency.
tion, requirements analysis, and system design.
Chapter 8, Health-Care Facilities, has been updated to reflect
ASHRAE Standard 170-2008 and has revised discussion on This volume is published, both as a bound print volume and in
design criteria for pharmacies. electronic format on a CD-ROM, in two editions: one using inch-
Chapter 18, Clean Spaces, has updated content on standards, fil- pound (I-P) units of measurement, the other using the International
ters, barrier technology, and sustainability plus a new section on System of Units (SI).
installation and test procedures. Corrections to the 2008,2009, and 201 0 Handbook volumes can
Chapter 19, Data Processing and Telecommunication Facilities, be found on the ASHRAE Web site at http:llwww.ashrae.org and in
has a new title and revised andor new content on design temper- the Additions and Corrections section of this volume. Corrections
atures, change rate, humidity, power usage effectiveness (PUE), for this volume will be listed in subsequent volumes and on the
aisle containment, economizer cycles, and computer room air- ASHRAE Web site.
handling (CRAH) units. Reader comments are enthusiastically invited. To suggest
Chapter 33, Kitchen Ventilation, largely rewritten, covers key sus- improvements for a chapter, please comment using the form on
tainability impacts and recent research results. the ASHRAE Web site or, using the cutout pages at the end of this
Chapter 34, Geothermal Energy, has updated tables and graphs, volume’s index, write to Handbook Editor, ASHRAE, 1791 Tullie
with new, step-by-step design guidance on vertical systems, and Circle, Atlanta, GA 30329, or fax [phone], or e-mail
expanded content on hybrid systems, IS0 rating, and system effi- mo wenaashrae. org .
ciency.
Chapter 36, Energy Use and Management, has updates on Mark S. Owen
ASHRAE’s Building Energy Quotient (eQ) labeling program. Editor
CONTENTS
Contributors
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 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. Energy Use and Management (TC 7.6, Building Energy Performance)
37. Owning and Operating Costs (TC 7.8, Owning and Operating Costs)
38. Testing, Adjusting, and Balancing (TC 7.7, Testing and Balancing)
39. Operation and Maintenance Management (TC 7.3, Operation and Maintenance Management)
40. Computer Applications (TC 1.5, Computer Applications)
41. Building Energy Monitoring (TC 7.6)
42. Supervisory Control Strategies and Optimization (TC 7.5, Smart Building Systems)
43. 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 andEquipment, 2009 Fundamentals, 20 10 Refrig-
eration, and 201 1 HVAC Applications volumes
Comment Pages
CHAPTER 1
RESIDENCES
Systems ............................................................................................................................................ 1.1
Equipment Sizing ............................................................................................................................. 1.2
Single-Family Residences ............................................................................................................... 1.3
Multifamily Residences 1.6
Manufactured Homes ...................................................................................................................... 1.7
S
PACE-CONDITIONING systems for residential use vary with systems usually dehumidify air as well as lowering its temperature.
both local and application factors. Local factors include energy Typical forced-air residential installations are shown in Figures 1
source availability (present and projected) and price; climate; and 2.
socioeconomic circumstances; and availability of installation and Figure 1 shows a gas furnace, split-system air conditioner,
maintenance skills. Application factors include housing type, con- humidifier, and air filter. Air from the space enters the equipment
struction characteristics, and building codes. As a result, many dif- through a return air duct. It passes initially through the air filter. The
ferent systems are selected to provide combinations of heating, circulating blower is an integral part of the furnace, which supplies
cooling, humidification, dehumidification, ventilation, and air filter- heat during winter. An optional humidifier adds moisture to the
ing. This chapter emphasizes the more common systems for space heated air, which is distributed throughout the home via the supply
conditioning of both single-family (i.e., traditional site-built and duct. When cooling is required, heat and moisture are removed from
modular or manufactured homes) and multifamily residences. Low- the circulating air as it passes across the evaporator coil. Refrigerant
rise multifamily buildings generally follow single-family practice lines connect the evaporator coil to aremote condensing unit located
because constraints favor compact designs; HVAC systems in high- outdoors. Condensate from the evaporator is removed through a
rise apartment, condominium, and dormitory buildings are often of drainline with a trap.
commercial types similar to those used in hotels. Retrofit and remod- Figure 2 shows a split-system heat pump, supplemental electric
eling construction also adopt the same systems as those for new con- resistance heaters, humidifier, and air filter. The system functions as
struction, but site-specific circumstances may call for unique follows: Air from the space enters the equipment through the return
designs. air duct, and passes through a filter. The circulating blower is an
integral part of the indoor air-handling portion of the heat pump sys-
SYSTEMS tem, which supplies heat through the indoor coil during the heating
season. Optional electric heaters supplement heat from the heat
Common residential systems are listed in Table 1. Three gener-
pump during periods of low outdoor temperature and counteract
ally recognized groups are central forced air, central hydronic, and indoor airstream cooling during periodic defrost cycles. An optional
zoned systems. System selection and design involve such key deci-
sions as (1) source(s) of energy, (2) means of distribution and deliv-
ery, 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 com-
monly added to all but the most basic systems, is provided in heat-
ing systems for thermal comfort (as defined in ASHRAE Standard
55), health, and reduction of static electricity discharges. Cooling
Table 1 Residential Heating and Cooling Systems
Central Central
Forced Air Hvdronic Zoned
Most common Gas Gas Gas
energy Oil Oil Electricity
sources Electricity Electricity
Distribution Air Water Air
medium Steam Water
Refrigerant
Distribution Ducting Piping Ducting
system Piping or
Free delively
Terminal Diffusers Radiators Included with
devices Registers Radiant panels product or same
Grilles Fan-coil units as forced-air or
hydronic systems
Fig. 1 Typical Residential Installation of
The preparation of this chapter is assigned to TC 8.1 1, Unitary and Room Heating, Cooling, Humidifying, and
Air Conditioners and Heat Pumps. Air Filtering System
1.1
1.2 2011 ASHRAE Handbook-HVAC Applications
and in areas such as the southwestern United States, where rooftop-
mounted 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 resi-
dences.
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 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 ofASHRAE Standard 90.2 or sim-
ilar 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 elec-
tric 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 tempera-
Fig. 3 Example of Two-Zone, Ductless Minisplit System in tures. Some oversizing may be desirable to enable recovery from
Typical Residential Installation 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 on-
humidifier adds moisture to the heated air, which is distributed times, wide indoor temperature swings, and inadequate dehumidi-
throughout the home through the supply duct. When cooling is fication when cooling. Gross oversizing may also contribute to
required, heat and moisture are removed from the circulating air as higher energy use by increasing cyclic thermal losses and off-cycle
it passes across the evaporator coil. Refrigerant lines connect the losses. Variable-capacity equipment (heat pumps, air conditioners,
indoor coil to the outdoor unit. Condensate from the indoor coil is and furnaces) can more closely match building loads over broad
removed through a drainline with a trap. ambient temperature ranges, usually reducing these losses and
improving comfort levels; in the case of heat pumps, supplemental
Minisplit systems, which are similar to split systems but are
heat needs may also be reduced.
typically ductless, are increasingly popular worldwide. A typical
Residences of tight construction may have high indoor humidity
two-zone, ductless minisplit system is shown in Figure 3. In this
and a build-up of indoor air contaminants at times. Air-to-air heat
example, the minisplit system consists mainly of two parts: an out-
recovery equipment may be used to provide tempered ventilation air
door condensing unit, which is installed outside, and two indoor air-
to tightly constructed houses. Outdoor air intakes connected to the
handling units that are usually installed on perimeter walls of the
return duct of central systems may also be used when reducing
house. Each indoor air handler serves one zone and is controlled
installed costs is the most important task. Simple exhaust systems
independently from the other indoor unit.
with or without passive air intakes are also popular. Natural ventila-
Unitary systems, such as window-mounted, through-the-wall, or tion by operable windows is also popular iIn sIom e climates. Exces-
rooftop units where all equipment is contained in one cabinet, are sive accumulation of radon is of concern in all buildings; lower-level
also popular. Ducted versions are used extensively in regions where spaces should not be depressurized, which causes increased migra-
residences have duct systems in crawlspaces beneath the main floor tion of soil gases into buildings. All ventilation schemes increase
Residences 1.3
heating and cooling loads and thus the required system capacity, combustion device are grouped in a common chassis and cabinets to
thereby resulting in greater energy consumption. In all cases, mini- provide similar benefits at lower installation costs.
mum ventilation rates, as described in ASHRAE Standards 62.1 and Fuel-Fired Heat Pumps. Extensive research and development
62.2. should be maintained. has been conducted to develop fuel-fred heat pumps. They have
been marketed in North America. More information may be found
SINGLE-FAMILY RESIDENCES in Chapter 48 of the 2008 ASHRAE Handbook-HVACSystems and
Equipment.
Heat Pumps Water-Heating Options. Heat pumps may be equipped with
Heat pumps for single-family houses are normally unitary or desuperheaters (either integral or field-installed) to reclaim heat for
split systems, as illustrated in Figures 2 and 3. domestic water heating when operated in cooling mode. Integrated
Most commercially available heat pumps, particularly in North space-conditioning and water-heating heat pumps with an addi-
America, are electrically powered, air-source systems. Supplemen- tional full-size condenser for water heating are also available.
tal heat is generally required at low outdoor temperatures or during
Furnaces
defrost. In most cases, supplemental or back-up heat is provided by
electric resistance heating elements. Furnaces are fueled by gas (natural or propane), electricity, oil,
Heat pumps may be classified by thermal source and distribution wood, or other combustibles. Gas, oil, and wood furnaces may draw
medium in the heating mode as well as the type of fuel used. The combustion air from the house or from outdoors. If the furnace
most commonly used classes of heat pump equipment are air-to-air space is located such that combustion air is drawn from the out-
and water-to-air. Air-to-water and water-to-water types are also doors, the arrangement is called an isolated combustion system
used. (ICS). Furnaces are generally rated on an ICS basis. Outdoor air is
Heat pump systems are generally described as air-source or ducted to the combustion chamber (a direct-vent system) for man-
ground-source. The thermal sit& for cooling is generally assumed to ufactured home applications and some mid- and high-efficiency
be the same as the thermal source for heating. Air-source systems equipment designs. Using outside air for combustion eliminates
using ambient air as the heat sourceisink are generally the least both infiltration losses associated with using indoor air for combus-
costly to install and thus the most commonly used. Ground-source tion and stack losses associated with atmospherically induced draft-
systems usually use water-to-air heat pumps to extract heat from the hood-equipped furnaces.
ground using groundwater or a buried heat exchanger. Two available types of high-efficiency gas furnaces are noncon-
Ground-Source (Geothermal) Systems. As a heat sourceisink, densing and condensing. Both increase efficiency by adding or
groundwater (from individual wells or supplied as a utility from improving heat exchanger surface area and reducing heat loss dur-
community wells) offers the following advantages over ambient ing furnace off-times. The higher-efficiency condensing type also
air: (1) heat pump capacity is independent of ambient air tempera- recovers more energy by condensing water vapor from combustion
ture, reducing supplementary heating requirements; (2) no defrost products. Condensate is formed in a corrosion resistant heat
cycle is required; (3) although operating conditions for establishing exchanger and is disposed of through a drain line. Care must be
rated efficiency are not the same as for air-source systems, seasonal taken to prevent freezing the condensate when the furnace is
efficiency is usually higher for heating and for cooling; and (4) installed in an unheated space such as an attic. Condensing furnaces
peak heating energy consumption is usually lower. Two other sys- generally use PVC for vent pipes and condensate drains.
tem types are ground-coupled and surface-water-coupled systems. Wood-, corn-, and coal-fueled furnaces are used in some areas as
Ground-coupled systems offer the same advantages, but because either the primary or supplemental heating unit. These furnaces may
surface water temperatures track fluctuations in air temperature, have catalytic converters to enhance the combustion process,
surface-water-coupled systems may not offer the same benefits as increasing furnace efficiency and producing cleaner exhaust.
other ground-source systems. Both system types circulate brine or Chapters 30 and 32 of the 2008 ASHRAE Handbook-HVAC
water in a buried or submerged heat exchanger to transfer heat from Systems and Equipment include more detailed information on fur-
the ground or water. Direct-expansion, ground-source systems, naces and furnace efficiency.
with evaporators buried in the ground, also are available but are sel-
dom used. Water-source systems that extract heat from surface Hydronic Heating Systems
water (e.g., lakes or rivers) or city (tap) water are sometimes used With the growth of demand for central cooling systems, hydronic
where local conditions allow. Further information may be found in systems have declined in popularity in new construction, but still
Chapter 48 of the 2008 ASHRAE Handbook-HVAC Systems and account for a significant portion of existing systems in colder cli-
Equipment. mates. The fluid is heated in a central boiler and distributed by pip-
Water supply, quality, and disposal must be considered for ing to terminal units in each room. Terminal units are typically
groundwater systems. Caneta Research (1 995) and Kavanaugh and either radiators or baseboard convectors. Other terminal units
Rafferty (1997) provide detailed information on these subjects. include fan-coils and radiant panels. Most recently installed resi-
Secondary coolants for ground-coupled systems are discussed in dential systems use a forced-circulation, multiple-zone hot-water
Caneta Research (1995) and in Chapter 31 of the 2009 ASHRAE system with a series-loop piping arrangement. Chapters 12 and 35
Handbook-Fundamentals. Buried heat exchanger configurations of the 2008 ASHRAE Handbook-HVAC Systems and Equipment
may be horizontal or vertical, with the vertical including both have more information on hydronics.
multiple-shallow- and single-deep-well configurations. Ground- Design water temperature is based on economic and comfort
coupled systems avoid water quality, quantity, and disposal con- considerations. Generally, higher temperatures result in lower frst
cerns but are sometimes more expensive than groundwater systems. costs because smaller terminal units are needed. However, losses
However, ground-coupled systems are usually more efficient, espe- tend to be greater, resulting in higher operating costs and reduced
cially when pumping power for the groundwater system is consid- comfort because of the concentrated heat source. Typical design
ered. Proper installation of the ground coil(s) is critical to success. temperatures range from 180 to 200°F. For radiant panel systems,
Add-on Heat Pumps. In add-on systems, a heat pump is added design temperatures range from 110 to 170°F. The preferred control
(often as a retrofit) to an existing furnace or boilerifan-coil system. method allows the water temperature to decrease as outdoor temper-
The heat pump and combustion device are operated in one of two atures rise. Provisions for expansion and contraction of piping and
ways: (1) alternately, depending on which is most cost-effective, or heat distributing units and for eliminating air from the hydronic sys-
(2) in parallel. In unitary bivalent heat pumps, the heat pump and tem are essential for quiet, leak-tight operation.
1.4 2011 ASHRAE Handbook-HVAC Applications
Fossil fuel systems that condense water vapor from the flue gases Some form of back-up heating is generally needed with solar
must be designed for return water temperatures in the range of 120 thermal energy systems. Solar electric systems are not normally
to 130°F for most of the heating season. Noncondensing systems used for space heating because of the high energy densities required
must maintain high enough water temperatures in the boiler to pre- and the economics of photovoltaics. However, hybrid collectors,
vent this condensation. If rapid heating is required, both terminal which combine electric and thermal capabilities, are available.
unit and boiler size must be increased, although gross oversizing Chapter 35 has information on sizing solar heating equipment.
should be avoided.
Unitary Air Conditioners
Another concept for multi- or single-family dwellings is a com-
bined water-heatingispace-heatings ystem that uses water from the In forced-air systems, the same air distribution duct system can
domestic hot-water storage tank to provide space heating. Water cir- be used for both heating and cooling. Split-system central cooling,
culates from the storage tank to a hydronic coil in the system air as illustrated in Figure 1, is the most widely used forced-air system.
handler. Space heating is provided by circulating indoor air across Up flow, downflow, and horizontal-airflow indoor units are avail-
the coil. A split-system central air conditioner with the evaporator able. Condensing units are installed on a noncombustible pad out-
located in the system air handler can be included to provide space side and contain a motor- or engine-driven compressor, condenser,
cooling. condenser fan and fan motor, and controls. The condensing unit and
evaporator coil are connected by refrigerant tubing that is normally
Zoned Heating Systems
field-supplied. However, precharged, factory-supplied tubing with
Most moderate-cost residences in North America have single- quick-connect couplings is also common where the distance be-
thermal-zone HVAC systems with one thermostat. Multizoned sys- tween components is not excessive.
tems, however, offer the potential for improved thermal comfort. A distinct advantage of split-system central cooling is that it can
Lower operating costs are possible with zoned systems because readily be added to existing forced-air heating systems. Airflow
unoccupied areas (e.g., common areas at night, sleeping areas dur- rates are generally set by the cooling requirements to achieve good
ing the day) can be kept at lower temperatures in the winter. performance, but most existing heating duct systems are adaptable
One form of this system consists of individual heaters located in to cooling. Airflow rates of 350 to 450 cfm per nominal ton of
each room. These heaters are usually electric or gas-fred. Electric refrigeration are normally recommended for good cooling perfor-
heaters are available in the following types: baseboard free-convec- mance. As with heat pumps, these systems may be fitted with desu-
tion, wall insert (free-convection or forced-fan), radiant panels for perheaters for domestic water heating.
walls and ceilings, and radiant cables for walls, ceilings, and floors. Some cooling equipment includes forced-air heating as an inte-
Matching equipment capacity to heating requirements is critical for gral part of the product. Year-round heating and cooling packages
individual room systems. Heating delivery cannot be adjusted by with a gas, oil, or electric furnace for heating and a vapor-compres-
adjusting air or water flow, so greater precision in room-by-room sion system for cooling are available. Air-to-air and water-source
sizing is needed. Most individual heaters have integral thermostats heat pumps provide cooling and heating by reversing the flow of
that limit the ability to optimize unit control without continuous fan refrigerant.
operation. Distribution. Duct systems for cooling (and heating) should be
Individual heat pumps for each room or group of rooms (zone) designed and installed in accordance with accepted practice. Use-
are another form of zoned electric heating. For example, two or ful information is found in ACCA Manuals Da and Sa.C hapter 9
more small unitary heat pumps can be installed in two-story or large of the 2008 ASHRAE Handbook-HVAC Systems and Equipment
one-story homes. also discusses air distribution design for small heating and cooling
The multisplit heat pump consists of a central compressor and an systems.
outdoor heat exchanger to service multiple indoor zones. Each zone Because weather is the primary influence on the load, the cooling
uses one or more fan-coils, with separate thermostatic controls for and heating load in each room changes from hour to hour. There-
each zone. Such systems are used in both new and retrofit construc- fore, the owner or occupant should be able to make seasonal or more
tion. frequent adjustments to the air distribution system to improve com-
A method for zoned heating in central ducted systems is the fort. Adjustments may involve opening additional outlets in second-
zone-damper system. This consists of individual zone dampers and floor rooms during summer and throttling or closing heating outlets
thermostats combined with a zone control system. Both variable- in some rooms during winter. Manually adjustable balancing damp-
air-volume (damper position proportional to zone demand) and od ers may be provided to facilitate these adjustments. Other possible
off (damper fully open or fully closed in response to thermostat) refinements are installing a heating and cooling system sized to
types are available. These systems sometimes include a provision to meet heating requirements, with additional self-contained cooling
modulate to lower capacities when only a few zones require heating. units serving rooms with high summer loads, or separate central
systems for the upper and lower floors of a house. On deluxe appli-
Solar Heating cations, zone-damper systems can be used. Another way of balanc-
Both active and passive solar thermal energy systems are some- ing cooling and heating loads is to use variable-capacity
times used to heat residences. In typical active systems, flat-plate compressors in heat pump systems.
collectors heat air or water. Air systems distribute heated air either Operating characteristics of both heating and cooling equipment
to the living space for immediate use or to a thermal storage medium must be considered when zoning is used. For example, a reduction
(e.g., a rock pile). Water systems pass heated water from the collec- in air quantity to one or more rooms may reduce airflow across the
tors through a heat exchanger and store heat in a water tank. evaporator to such a degree that frost forms on the fms. Reduced air-
Because of low delivered-water temperatures, radiant floor panels flow on heat pumps during the heating season can cause overloading
requiring moderate temperatures are often used. A water-source if airflow across the indoor coil is not maintained above 350 cfm per
heat pump between the water storage tank and the load can be used ton. Reduced air volume to a given room reduces the air velocity
to increase temperature differentials. from the supply outlet and might cause unsatisfactory air distribu-
Trombe walls, direct-gain, and greenhouse-like sunspaces are tion in the room. Manufacturers of zoned systems normally provide
common passive solar thermal systems. Glazing facing south (in the guidelines for avoiding such situations.
northern hemisphere), with overhangs to reduce solar gains in the Special Considerations. In residences with more than one story,
summer, and movable night insulation panels reduce heating cooling and heating are complicated by air buoyancy, also known as
requirements. the stack effect. In many such houses, especially with single-zone
Residences 1.5
systems, the upper level tends to overheat in winter and undercool in and return duct systems. When applying supply-to-return duct
summer. Multiple air outlets, some near the floor and others near the humidifiers on heat pump systems, care should be taken to maintain
ceiling, have been used with some success on all levels. To control proper airflow across the indoor coil. Self-contained portable or
airflow, the homeowner opens some outlets and closes others from tabletop humidifiers can be used in any residence. Even though this
season to season. Free air circulation between floors can be reduced type of humidifier introduces all the moisture to one area of the
by locating returns high in each room and keeping doors closed. home, moisture migrates and raises humidity levels in other rooms.
In existing homes, the cooling that can be added is limited by the Overhumidification should be avoided: it can cause condensate
air-handling capacity of the existing duct system. Although the to form on the coldest surfaces in the living space (usually win-
existing duct system is usually satisfactory for normal occupancy, it dows). Also, because moisture migrates through all structural mate-
may be inadequate during large gatherings. In all cases where new rials, vapor retarders should be installed near the wanner inside
cooling (or heating) equipment is installed in existing homes, surface of insulated walls, ceilings, and floors in most temperature
supply air ducts and outlets must be checked for acceptable air- climates. Lack of attention to this construction detail allows mois-
handling capacity and air distribution. Maintaining upward airflow ture to migrate from inside to outside, causing damp insulation,
at an effective velocity is important when converting existing heat- mold, possible structural damage, and exterior paint blistering.
ing systems with floor or baseboard outlets to both heat and cool. It Central humidifiers may be rated in accordance with AHRI Stan-
is not necessary to change the deflection from summer to winter for dard 610. This rating is expressed in the number of gallons per day
registers located at the perimeter of a residence. Registers located evaporated by 140°F entering air. Some manufacturers certify the
near the floor on the inside walls of rooms may operate unsatisfac- performance of their product to the AHRI standard. Selecting the
torily if the deflection is not changed from summer to winter. proper size humidifier is important and is outlined in AHRI Guide-
Occupants of air-conditioned spaces usually prefer minimum line F.
perceptible air motion. Perimeter baseboard outlets with multiple Humidifier cleaning and maintenance schedules must be fol-
slots or orifices directing air upwards effectively meet this require- lowed to maintain efficient operation and prevent bacteria build-up.
ment. Ceiling outlets with multidirectional vanes are also satisfac- Chapter 21 ofthe 2008 ASHRAEHandbook-HVACSystems and
tory. Equipment contains more information on residential humidifiers.
A residence without a forced-air heating system may be cooled
Dehumidifiers
by one or more central systems with separate duct systems, by indi-
vidual room air conditioners (window-mounted or through-the- Many homes also use dehumidifiers to remove moisture and con-
wall), or by minisplit room air conditioners. trol indoor humidity levels. In cold climates, dehumidification is
Cooling equipment must be located carefully. Because cooling sometimes required during the summer in basement areas to control
systems require higher indoor airflow rates than most heating sys- mold and mildew growth and to reduce zone humidity levels. Tra-
tems, sound levels generated indoors are usually higher. Thus, ditionally, portable dehumidifiers have been used to control humid-
indoor air-handling units located near sleeping areas may require ity in this application. Although these portable units are not always
sound attenuation. Outdoor noise levels should also be considered as efficient as central systems, their low frst cost and ability to serve
when locating the equipment. Many communities have ordinances a single zone make them appropriate in many circumstances.
regulating the sound level of mechanical devices, including cooling In hot, humid climates, providing sufficient dehumidification
equipment. Manufacturers of unitary air conditioners often rate the with sensible cooling is important. Although conventional air-
sound level of their products according to an industry standard conditioning units provide some dehumidification as a consequence
(AHRI Standard 270). AHRI Standard 275 gives information on of sensible cooling, in some cases space humidity levels can still
how to predict the dBA sound level when the AHRI sound rating exceed comfortable levels.
number, the equipment location relative to reflective surfaces, and Several dehumidification enhancements to conventional air-
the distance to the property line are known. conditioning systems are possible to improve moisture removal
An effective and inexpensive way to reduce noise is to put dis- characteristics and lower the space humidity level. Some simple
tance and natural barriers between sound source and listener. How- improvements include lowering the supply airflow rate and elimi-
ever, airflow to and from air-cooled condensing units must not be nating off-cycle fan operation. Additional equipment options such
obstructed; for example, plantings and screens must be porous and as condenserireheat coils, sensible-heat-exchanger-assisted evapo-
placed away from units so as not to restrict intake or discharge of air. rators (e.g., heat pipes), and subcoolingireheat coils can further
Most manufacturers provide recommendations regarding accept- improve dehumidification performance. Desiccants, applied as
able distances between condensing units and natural barriers. Out- either thermally activated units or heat recovery systems (e.g.,
door units should be placed as far as is practical from porches and enthalpy wheels), can also increase dehumidification capacity and
patios, which may be used while the house is being cooled. Loca- lower the indoor humidity level. Some dehumidification options
tions near bedroom windows and neighboring homes should also be add heat to the conditioned zone that, in some cases, increases the
avoided. In high-crime areas, consider placing units on roofs or load on the sensible cooling equipment.
other semisecure areas.
Air Filters
Evaporative Coolers
Most comfort conditioning systems that circulate air incorporate
In climates that are dry throughout the entire cooling season, some form of air filter. Usually, they are disposable or cleanable fil-
evaporative coolers can be used to cool residences. They must be ters that have relatively low air-cleaning efficiency. Higher-
installed and maintained carefully to reduce the potential for water efficiency alternatives include pleated media filters and electronic
and thus air quality problems. Further details on evaporative coolers air filters. These high-efficiency filters may have high static pres-
canbe foundinchapter 40 ofthe2008ASHRAEHandbook-HVAC sure drops. The air distribution system should be carefully evaluated
Systems and Equipment and in Chapter 52 of this volume. before installing such filters so that airflow rates are not overly
reduced with their use. Airflow must be evaluated both when the fil-
Humidifiers
ter is new and when it is in need of replacement or cleaning.
For improved winter comfort, equipment that increases indoor Air filters are mounted in the return air duct or plenum and oper-
relative humidity may be needed. In a ducted heating system, a cen- ate whenever air circulates through the duct system. Air filters are
tral whole-house humidifier can be attached to or installed within a rated in accordance with AHRI Standard 680, which was based on
supply plenum or main supply duct, or installed between the supply ASHRAE Standard 52.1. Atmospheric dust spot efficiency levels are