1999 ASHRAE Handbook Preface

777 Pages·1999·36.28 MB·English

1999 ASHRAE Handbook Preface
This handbook describes heating, ventilating, and air condition- • Chapter 39, Building Energy Monitoring, reflects the new direc-
ing for a broad range of applications. Most of the chapters from the tion in this field and focuses on monitoring designed to answer
1995 ASHRAE Handbook have been revised for this volume to specific questions rather than broad-based research-oriented pro-
reflect current requirements and design approaches. New chapters grams. The section on accuracy and uncertainty is rewritten.
on HVAC for museums and power plants, information on air quality
• Chapter 40, Supervisory Control Strategies and Optimization, has
in aircraft, additional information on maintaining a proper environ-
a new title to reflect its reorganization and the significant amount
ment for indoor swimming pools and new information on sound
of new material. The first section defines systems and control
control and building operation make this a particularly useful refer-
variables. The second section, which is intended for practitioners,
ence. Because this book focuses on specific applications for HVAC,
presents computerized control strategies. The third section pre-
it provides background information to designers new to the applica-
sents basic optimization methods and is for researchers and devel-
tion as well as to those needing a refresher on the topic. In addition,
opers of advanced control strategies.
many chapters include valuable data for design. Some of the revi-
sions that have been made are as follows. • Chapter 41, Building Commissioning, has expanded the informa-
tion on the various phases of commissioning.
• Chapter 4, Places of Assembly, provides more comprehensive
• Chapter 42, Building Envelopes, is moved from the 1997
design information on natatoriums.
ASHRAE Handbook—Fundamentals with minor editing.
• Chapter 5, Hotels, Motels, and Dormitories, includes more infor-
mation on hotels and motels, which is reflected in a change in the • Chapter 43, Building Air Intake and Exhaust Design, is a revision
title of the chapter. of the last half of Chapter 15 in the 1997 ASHRAE Handbook.
• Chapter 8, Surface Transportation, has been substantially revised. • Chapter 44, Control of Gaseous Indoor Air Contaminants, has
It now includes information about European bus air conditioning a greatly expanded section on air cleaning. It includes more
and the state of the art in railcar air conditioning. information on the equipment used and on its design, energy
• Chapter 9, Aircraft, has been completely rewritten. It describes use, startup procedures, operation, maintenance, and testing
the environmental control systems used in commercial aircraft procedures.
today and their operation during a typical flight. Applicable reg-
• Chapter 45, Design and Application of Controls, is slightly reor-
ulations are summarized and the section on air quality has been
ganized because the information on control fundamentals was
expanded. Information on air-cycle equipment has been deleted.
moved to the 1997 ASHRAE Handbook.
• Chapter 12, Enclosed Vehicular Facilities, includes more ventila-
• Chapter 46, Sound and Vibration Control, describes all currently
tion design information. Research from a tunnel fire test has pro-
recognized criteria methods—dBA, NC, RC, RC Mark II, and
vided new ventilation design criteria for tunnel ventilation. The
NCB. New sections include information on: (1) uncertainties that
chapter now covers ventilation for toll booths, railroad tunnels,
can reasonably be expected from the data in the chapter, (2)
and areas with vehicles that use alternative fuels.
chiller and air-cooled condenser noise, and (3) data for estimating
• Chapter 13, Laboratories, has additional information on scale-up
ceiling plenum insertion loss.
laboratories and compressed gas storage. The sections on internal
heat load and Biosafety Level 3 have been expanded. • Chapter 47, Water Treatment, is reorganized and has added infor-
• Chapter 15, Clean Spaces, greatly expands on pharmaceutical and mation on biological growth control. A new section covers start-
biomanufacturing cleanrooms. A new section covers high bay up and shutdown procedures.
cleanrooms. • Chapter 49, Snow Melting, includes expanded equations for
• Chapter 20, Museums, Libraries, and Archives, is a new chapter. heating requirements and new load data including maps. Infor-
It discusses in detail the importance of relative humidity on col- mation on piping materials for hydronic systems has been
lections and suggests the degree of environmental control for var- updated.
ious types of collections and historic buildings.
• Chapter 51, Fire and Smoke Management, includes new sections
• Chapter 21, Environmental Control for Animals and Plants, pro-
on fire management (i.e., through-penetration fire stopping) and
vides new information on levels of contaminants in livestock
on smoke management in large spaces.
buildings and suggests several methods of control. It includes
new findings on ventilation for laboratory animals. • Chapter 53, Seismic and Wind Restraint Design, introduces the
proposed International Building Code seismic design equations
• Chapter 24, Power Plants, is a new chapter that introduces HVAC
and describes several new seismic snubbers. The chapter also
design criteria for the various facilities in electrical generating
includes a new section on wind restraint design.
stations and in facilities that produce process heat and power.
• Chapter 29, Industrial Local Exhaust Systems, has been greatly
Each Handbook is published in two editions. One edition con-
expanded with much more information about specific types of
tains inch-pound (I-P) units of measurement, and the other contains
hoods and their design and application.
the International System of Units (SI).
• Chapter 30, Kitchen Ventilation, is updated to reflect code
Look for corrections to the 1996, 1997, and 1998 volumes of the
changes including changed terminology for nonlisted hoods and
new information on exhaust system effluent control. Handbook on the Internet at http://www.ashrae.org. Any changes to
this volume will be reported in the 2000 ASHRAE Handbook and on
• Chapter 33, Thermal Storage, has an expanded discussion of con-
the Internet.
trol strategies.
• Chapter 34, Energy Management, has new and more comprehen- If you have suggestions for improving a chapter or you would
sive energy consumption data for commercial and residential like more information on how you can help revise a chapter, e-mail
buildings in the United States. [email protected]; write to Handbook Editor, ASHRAE, 1791
• Chapter 35, Owning and Operating Costs, has updated informa- Tullie Circle, Atlanta, GA 30329; or fax [phone].
tion of the impact of refrigerant phaseouts. New information is
included on financing alternatives, on district energy service and
on-site electric generation in view of deregulation, and on com- Robert A. Parsons
puter analysis. ASHRAE Handbook Editor
CHAPTER 1
RESIDENCES
Single-Family Residences .............................................................................................................. 1.2
Multifamily Residences .................................................................................................................. 1.5
Manufactured Homes ..................................................................................................................... 1.6
S
PACE-CONDITIONING systems for residential use vary with An optional humidifier (10) adds moisture to the heated air, which
both local and application factors. Local factors include energy is distributed throughout the home from the supply duct (9). When
source availability (both present and projected) and price; climate; cooling is required, the circulating air passes across the evaporator
socioeconomic circumstances; and the availability of installation coil (5), which removes heat and moisture from the air. Refrigerant
and maintenance skills. Application factors include housing type, lines (6) connect the evaporator coil to a remote condensing unit (7)
construction characteristics, and building codes. As a result, many located outdoors. Condensate from the evaporator is removed
different systems are selected to provide combinations of heating, through a drainline with a trap (8).
cooling, humidification, dehumidification, and air filtering. This Figure 2 shows a split-system heat pump, supplemental electric
chapter emphasizes the more common systems for space condition- resistance heaters, a humidifier, and an air filter. The system func-
ing of both single-family (i.e., traditional site-built and modular or tions as follows: Air returns to the equipment through the return air
manufactured homes) and multifamily residences. Low-rise multi- duct (1) and passes through the air filter (2). The circulating blower
family buildings generally follow single-family practice because (3) is an integral part of the indoor unit (or air handler) of the heat
constraints favor compact designs. Retrofit and remodeling con- pump (4), which supplies heat via the indoor coil (6) during the
struction also adopt the same systems as those for new construction, heating season. Optional electric heaters (5) supplement heat from
but site-specific circumstances may call for unique designs. the heat pump during periods of low ambient temperature and coun-
teract airstream cooling during the defrost cycle. An optional
Systems humidifier (10) adds moisture to the heated air, which is distributed
throughout the home from the supply duct (9). When cooling is
The common residential heating systems are listed in Table 1.
required, the circulating air passes across the indoor coil (6), which
Three generally recognized groups are central forced air, central
removes heat and moisture from the air. Refrigerant lines (11) con-
hydronic, and zoned systems. System selection and design involve
nect the indoor coil to the outdoor unit (7). Condensate from the
such key decisions as (1) source(s) of energy, (2) means of distribu-
indoor coil drains away through a drainline with a trap (8).
tion 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) can be added to most systems. Humidification, which can
also be added to most systems, is generally provided in heating sys-
tems only when psychrometric conditions make it necessary for
comfort and health (as defined in ASHRAE Standard 55). Cooling
systems dehumidify as well. Typical residential installations are
shown in Figures 1 and 2.
Figure 1 shows a gas furnace, a split-system air conditioner, a
humidifier, and an air filter. The system functions as follows: Air
returns to the equipment through a return air duct (1). It passes
initially through the air filter (2). The circulating blower (3) is an
integral part of the furnace (4), which supplies heat during winter.
Table 1 Residential Heating and Cooling Systems
Forced Air Hydronic Zoned
Most common Gas Gas Gas
energy sources Oil Oil Electricity
Electricity Electricity Resistance
Resistance Resistance Heat pump
Heat pump Heat pump
Heat distribution Air Water Air
medium Steam Water
Refrigerant
Heat distribution Ducting Piping Ducting
system Piping or
None
Terminal devices Diffusers Radiators Included
Registers Radiant panels with
Grilles Fan-coil units product
Fig. 1 Typical Residential Installation of Heating, Cooling,
The preparation of this chapter is assigned to TC 7.6, Unitary Air Condi-
Humidifying, and Air Filtering System
tioners and Heat Pumps
1.2 1999 ASHRAE Applications Handbook (SI)
designed to meet or exceed the requirements of ASHRAE Standard
90.2, Energy-Efficient Design of New Low-Rise Residential Build-
ings, or similar requirements.
Proper matching of equipment capacity to the design 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.
The use of undersized equipment results in an inability to main-
tain indoor design temperatures at outdoor design conditions and
slow recovery from setback or set-up conditions. Grossly oversized
equipment can cause discomfort due to short on-times, wide indoor
temperature swings, and inadequate dehumidification when cool-
ing. Gross oversizing may also contribute to higher energy use due
to an increase in cyclic thermal losses and off-cycle losses. Variable
capacity equipment (heat pumps, air conditioners, and furnaces) can
more closely match building loads over specific ambient tempera-
ture ranges, usually reducing these losses and improving comfort
levels; in the case of heat pumps, supplemental heat needs may also
be reduced.
Recent trends toward tightly constructed buildings with
improved vapor retarders and low infiltration may cause high
indoor humidity conditions and the buildup of indoor air contami-
nants in the space. 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 lower installed costs are the most important
factor. Simple exhaust systems with passive air intakes are also
Fig. 2 Typical Residential Installation of Heat Pump
becoming popular. In all cases, minimum ventilation rates, as out-
lined in ASHRAE Standard 62 should be maintained.
Single-package systems, where all equipment is contained in one
cabinet, are also popular in the United States. They are used exten-
SINGLE-FAMILY RESIDENCES
sively in areas where residences have duct systems in crawlspaces
beneath the main floor and in areas such as the Southwest, where
Heat Pumps
they are typically rooftop-mounted and connected to an attic duct
system. Heat pumps for single-family houses are normally unitary sys-
tems; i.e., they consist of single-package units or two or more fac-
Central hydronic heating systems are popular both in Europe and
tory-built modules as illustrated in Figure 2. These differ from
in parts of North America where central cooling is not normally pro-
applied or built-up heat pumps, which require field engineering to
vided. If desired, central cooling is often added through a separate
select compatible components for complete systems.
cooling-only system with attic ducting.
Most commercially available heat pumps (particularly in North
Zoned systems are designed to condition only part of a home at
America) are electrically powered air-source systems. Supplemen-
any one time. They may consist of individual room units or central
tal heat is generally required at low outdoor temperatures or during
systems with zoned distribution networks. Multiple central systems
defrost. In most cases, supplemental or backup heat is provided by
that serve individual floors or serve sleeping and common portions
electric resistance heaters.
of a home separately are also widely used in large single-family
Heat pumps may be classified by thermal source and distribution
houses.
medium in the heating mode as well as the type of fuel used. The
The source of energy is a major consideration in heating system
most commonly used classes of heat pump equipment are air-to-air
selection. For heating, gas and electricity are most widely used, fol-
and water-to-air. Air-to-water and water-to-water types are also
lowed by oil, wood, solar energy, geothermal energy, waste heat,
used.
coal, district thermal energy, and others. Relative prices, safety, and
Heat pump systems, as contrasted to the actual heat pump equip-
environmental concerns (both indoor and outdoor) are further fac-
ment, are generally described as air-source or ground-source. The
tors in heating energy source selection. Where various sources are
thermal sink for cooling is generally assumed to be the same as the
available, economics strongly influence the selection. Electricity is
thermal source for heating. Air-source systems using ambient air as
the dominant energy source for cooling.
the heat source/sink are generally the least costly to install and thus
the most commonly used. Ground-source systems usually employ
Equipment Sizing
water-to-air heat pumps to extract heat from the ground via ground-
The heat loss and gain of each conditioned room and of ductwork water or a buried heat exchanger.
or piping run through unconditioned spaces in the structure must be Ground-Source (Geothermal) Systems. As a heat source/sink,
accurately calculated in order to select equipment with the proper groundwater (from individual wells or supplied as a utility from
output and design. To determine heat loss and gain accurately, the community wells) offers the following advantages over ambient
floor plan and construction details must be known. The plan should air: (1) heat pump capacity is independent of ambient air tempera-
include information on wall, ceiling, and floor construction as well ture, reducing supplementary heating requirements; (2) no defrost
as the type and thickness of insulation. Window design and exterior cycle is required; (3) for equal equipment rating point efficiency,
door details are also needed. With this information, heat loss and the seasonal efficiency is usually higher for heating and for cooling;
gain can be calculated using the Air-Conditioning Contractors of and (4) peak heating energy consumption is usually lower. Ground-
America (ACCA) Manual J or similar calculation procedures. To coupled or surface-water-coupled systems offer the same advan-
conserve energy, many jurisdictions require that the building be tages. However, they circulate brine or water in a buried or sub-
Residences 1.3
merged heat exchanger to transfer heat from the ground. Direct Hydronic Heating Systems—Boilers
expansion ground-source systems, with evaporators buried in the
With the growth of demand for central cooling systems, hydronic
ground, are occasionally used. The number of ground-source sys-
systems have declined in popularity in new construction, but still
tems is growing rapidly, particularly of the ground-coupled type.
account for a significant portion of existing systems in northern cli-
Water-source systems that extract heat from surface water (e.g.,
mates. The fluid is heated in a central boiler and distributed by pip-
lakes or rivers) or city (tap) water are also used where local condi-
ing to terminal units (fan coils, radiators, radiant panels, or
tions permit.
baseboard convectors) in each room. Most recently installed resi-
Water supply, quality, and disposal must be considered for dential systems use a forced circulation, multiple zone hot water
groundwater systems. Bose et al. (1985) provides detailed informa- system with a series-loop piping arrangement. Chapters 12, 27, and
tion on these subjects. Secondary coolants for ground-coupled sys- 32 of the 2000 ASHRAE Handbook—Systems and Equipment have
tems are discussed in this manual and in Chapter 20 of the 1997 more information on hydronics and hydronic.
ASHRAE Handbook—Fundamentals. Buried heat exchanger con- Design water temperature is based on economic and comfort
figurations may be horizontal or vertical, with the vertical includ- considerations. Generally, higher temperatures result in lower first
ing both multiple-shallow- and single-deep-well configurations. costs because smaller terminal units are needed. However, losses
Ground-coupled systems avoid water quality, quantity, and disposal tend to be greater, resulting in higher operating costs and reduced
concerns but are sometimes more expensive than groundwater comfort due to the concentrated heat source. Typical design temper-
systems. However, ground-coupled systems are usually more effi- atures range from 80 to 95°C. For radiant panel systems, design
cient, especially when pumping power for the groundwater system temperatures range from 45 to 75°C. The preferred control method
is considered. allows the water temperature to decrease as outdoor temperatures
Add-On Heat Pumps. In add-on systems, a heat pump is rise. Provisions for the expansion and contraction of the piping and
added—often as a retrofit—to an existing furnace or boiler system. heat distributing units and for the elimination of air from the
The heat pump and combustion device are operated in one of two hydronic system are essential for quiet, leaktight operation.
ways: (1) alternately, depending on which is most cost-effective, or Fossil fuel systems that condense water vapor from the flue gases
(2) in parallel. In unitary bivalent heat pumps, the heat pump and must be designed for return water temperatures in the range of 50 to
combustion device are grouped in a common chassis and cabinets to 55°C for most of the heating season. Noncondensing systems must
provide similar benefits at lower installation costs. maintain high enough water temperatures in the boiler to prevent
Fuel-Fired Heat Pumps. Extensive research and development this condensation. If rapid heating is required, both terminal unit
has been conducted to develop fuel-fired heat pumps. They are and boiler size must be increased, although gross oversizing should
beginning to be marketed in North America. be avoided.
Water-Heating Options. Heat pumps may be equipped with
Zoned Heating Systems
desuperheaters (either integral or field-installed) to reclaim heat for
domestic water heating. Integrated space-conditioning and water- Zoned systems offer the potential for lower operating costs,
heating heat pumps with an additional full-size condenser for water because unoccupied areas can be kept at lower temperatures in the
heating are also available. winter and at higher temperatures in the summer. Common areas
can be maintained at lower temperatures at night and sleeping areas
Furnaces at lower temperatures during the day.
One form of this system consists of individual heaters located in
Furnaces are fueled by gas (natural or propane), electricity, oil, each room. These heaters are usually electric or gas-fired. Electric
wood, or other combustibles. Gas, oil, and wood furnaces may draw heaters are available in the following types: baseboard free-convec-
combustion air from the house or from outdoors. If the furnace tion, wall insert (free-convection or forced-fan), radiant panels for
space is located such that combustion air is drawn from the out- walls and ceilings, and radiant cables for walls, ceilings, and floors.
doors, the arrangement is called an isolated combustion system Matching equipment capacity to heating requirements is critical for
(ICS). Furnaces are generally rated on an ICS basis. When outdoor individual room systems. Heating delivery cannot be adjusted by
air is ducted to the combustion chamber, the arrangement is called adjusting air or water flow, so greater precision in room-by-room
a direct vent system. This latter method is used for manufactured sizing is needed.
home applications and some mid- and high-efficiency equipment
Individual heat pumps for each room or group of rooms (zone)
designs. Using outside air for combustion eliminates both the infil-
are another form of zoned electric heating. For example, two or
tration losses associated with the use of indoor air for combustion
more small unitary heat pumps can be installed in two-story or large
and the stack losses associated with atmospherically induced draft
one-story homes.
hood-equipped furnaces.
The multisplit heat pump consists of a central compressor and
Two available types of high-efficiency gas furnaces are noncon- an outdoor heat exchanger to service up to eight indoor zones.
densing and condensing. Both increase efficiency by adding or Each zone uses one or more fan coils, with separate thermostatic
improving heat exchanger surface area and reducing heat loss dur- control for each zone. Such systems are used in both new and ret-
ing furnace off-times. The higher efficiency condensing type also rofit construction.
recovers more energy by condensing water vapor from the combus- A method for zoned heating in central ducted systems is the
tion products. The condensate is developed in a high-grade stain- zone-damper system. This consists of individual zone dampers
less steel heat exchanger and is disposed of through a drain line. and thermostats combined with a zone control system. Both vari-
Condensing furnaces generally use PVC for vent pipes and conden- able-air-volume (damper position proportional to zone demand)
sate drains. and on-off (damper fully open or fully closed in response to ther-
Wood-fueled furnaces are used in some areas. A recent advance mostat) types are available. Such systems sometimes include a
in wood furnaces is the addition of catalytic converters to enhance provision to modulate to lower capacities when only a few zones
the combustion process, increasing furnace efficiency and produc- require heating.
ing cleaner exhaust.
Solar Heating
Chapters 28 and 29 of the 2000 ASHRAE Handbook—Systems
and Equipment include more detailed information on furnaces and Both active and passive solar energy systems are sometimes used
furnace efficiency. to heat residences. In typical active systems, flat plate collectors
1.4 1999 ASHRAE Applications Handbook (SI)
heat air or water. Air systems distribute heated air either to the living unsatisfactory air distribution in the room. Manufacturers of zoned
space for immediate use or to a thermal storage medium (i.e., a rock systems normally provide guidelines for avoiding such situations.
pile). Water systems pass heated water through a secondary heat Special Considerations. In split-level houses, cooling and heat-
exchanger and store extra heat in a water tank. Due to low delivered ing are complicated by air circulation between various levels. In
water temperatures, radiant floor panels requiring moderate temper- many such houses, the upper level tends to overheat in winter and
atures are generally used. undercool in summer. Multiple outlets, some near the floor and oth-
Trombe walls and sunspaces are two common passive sys- ers near the ceiling, have been used with some success on all levels.
tems. Glazing facing south (with overhangs to reduce solar gains To control airflow, the homeowner opens some outlets and closes
in the summer) and movable insulated panels can reduce heating others from season to season. Free circulation between floors can be
requirements. reduced by locating returns high in each room and keeping doors
Backup heating ability is generally needed with solar energy sys- closed.
tems. Chapter 32 has information on sizing solar heating equipment. In existing homes, the cooling that can be added is limited by the
air-handling capacity of the existing duct system. While the existing
Unitary Air Conditioners duct system is usually satisfactory for normal occupancy, it may be
inadequate during large gatherings. In all cases where new cooling
In forced-air systems, the same air distribution duct system can
(or heating) equipment is installed in existing homes, supply-air
be used for both heating and cooling. Split-system central cooling,
ducts and outlets must be checked for acceptable air-handling
as illustrated in Figure 1, is the most widely used forced-air system.
capacity and air distribution. Maintaining upward airflow at an
Upflow, downflow, and horizontal airflow units are available. Con-
effective velocity is important when converting existing heating
densing units are installed on a noncombustible pad outside and
systems with floor or baseboard outlets to both heat and cool. It is
contain a motor- or engine-driven compressor, condenser, con-
not necessary to change the deflection from summer to winter for
denser fan and fan motor, and controls. The condensing unit and
registers located at the perimeter of a residence. Registers located
evaporator coil are connected by refrigerant tubing that is normally
near the floor on the inside walls of rooms may operate unsatisfac-
field-supplied. However, precharged, factory-supplied tubing with
torily if the deflection is not changed from summer to winter.
quick-connect couplings is also common where the distance
Occupants of air-conditioned spaces usually prefer minimum
between components is not excessive.
perceptible air motion. Perimeter baseboard outlets with multiple
A distinct advantage of split-system central cooling is that it can
slots or orifices directing air upwards effectively meet this
readily be added to existing forced-air heating systems. Airflow
requirement. Ceiling outlets with multidirectional vanes are also
rates are generally set by the cooling requirements to achieve good
satisfactory.
performance, but most existing heating duct systems are adaptable
A residence without a forced-air heating system may be cooled
to cooling. Airflow rates of 45 to 60 L/s per kilowatt of refrigeration
by one or more central systems with separate duct systems, by indi-
are normally recommended for good cooling performance. As with
vidual room air conditioners (window-mounted or through-the-
heat pumps, these systems may be fitted with desuperheaters for
wall), or by mini-split-room air conditioners.
domestic water heating.
Cooling equipment must be located carefully. Because cooling
Some cooling equipment includes forced-air heating as an inte-
systems require higher indoor airflow rates than most heating sys-
gral part of the product. Year-round heating and cooling packages
tems, the sound levels generated indoors are usually higher. Thus,
with a gas, oil, or electric furnace for heating and a vapor-compres-
indoor air-handling units located near sleeping areas may require
sion system for cooling are available. Air-to-air and water-source
sound attenuation. Outdoor noise levels should also be considered
heat pumps provide cooling and heating by reversing the flow of
when locating the equipment. Many communities have ordinances
refrigerant.
regulating the sound level of mechanical devices, including cooling
Distribution. Duct systems for cooling (and heating) should be
equipment. Manufacturers of unitary air conditioners often certify
designed and installed in accordance with accepted practice. Useful
the sound level of their products in an ARI program (ARI Standard
information is found in ACCA Manuals D and G. Chapter 9 of the
270). ARI Standard 275 gives information on how to predict the
2000 ASHRAE Handbook—Systems and Equipment also discusses
dBA sound level when the ARI sound rating number, the equipment
air distribution design for small heating and cooling systems.
location relative to reflective surfaces, and the distance to the prop-
Because weather is the primary influence on the load, the cool- erty line are known.
ing load in each room changes from hour to hour. Therefore, the
An effective and inexpensive way to reduce noise is to put dis-
owner or occupant should be able to make seasonal or more fre-
tance and natural barriers between sound source and listener. How-
quent adjustments to the air distribution system to obtain improved
ever, airflow to and from air-cooled condensing units must not be
comfort. Such adjustments may involve opening additional outlets
obstructed. Most manufacturers provide recommendations regard-
in second-floor rooms during the summer and throttling or closing
ing acceptable distances between condensing units and natural bar-
heating outlets in some rooms during the winter. Manually adjust-
riers. Outdoor units should be placed as far as is practical from
able balancing dampers may be provided to facilitate these adjust-
porches and patios, which may be used while the house is being
ments. Other possible refinements are the installation of a heating
cooled. Locations near bedroom windows and neighboring homes
and cooling system sized to meet heating requirements, with addi-
should also be avoided.
tional self-contained cooling units serving rooms with high sum-
mer loads, or of separate central systems for the upper and lower Evaporative Coolers
floors of a house. On deluxe applications, zone-damper systems
can be used. In dry climates, evaporative coolers can be used to cool resi-
dences. Further details on evaporative coolers can be found in
Operating characteristics of both heating and cooling equipment
Chapter 19 of the 2000 ASHRAE Handbook—Systems and Equip-
must be considered when zoning is used. For example, a reduction
ment and in Chapter 50 of this volume.
in the air quantity to one or more rooms may reduce the airflow
across the evaporator to such a degree that frost forms on the fins.
Humidifiers
Reduced airflow on heat pumps during the heating season can cause
overloading if airflow across the indoor coil is not maintained at For improved winter comfort, equipment that increases indoor
above 45 L/s per kilowatt. Reduced air volume to a given room relative humidity may be needed. In a ducted heating system, a
would reduce the air velocity from the supply outlet and could cause central humidifier can be attached to or installed within a supply
Residences 1.5
plenum or main supply duct, or installed between the supply and ASHRAE Standard 52.1. Atmospheric dust spot efficiency levels
return duct systems. When applying supply-to-return duct humidi- are generally less than 20% for disposable filters and vary from 60
fiers on heat pump systems, care should be taken to maintain to 90% for electronic air filters.
proper airflow across the indoor coil. Self-contained humidifiers To maintain optimum performance, the collector cells of elec-
can be used in any residence. Even though this type of humidifier tronic air filters must be cleaned periodically. Automatic indicators
introduces all the moisture to one area of the home, moisture will are often used to signal the need for cleaning. Electronic air filters
migrate and raise humidity levels in other rooms. Overhumidifica- have higher initial costs than disposable or pleated filters, but gen-
tion, which can cause condensate to form on the coldest surfaces in erally last the life of the air-conditioning system. Chapter 24 of the
the living space (usually the windows), should be avoided. 2000 ASHRAE Handbook—Systems and Equipment covers the
Central humidifiers may be rated in accordance with ARI design of residential air filters in more detail.
Standard 610. This rating is expressed in the number of litres per
day evaporated by 60°C entering air. Some manufacturers certify Controls
the performance of their product to the ARI standard. Selecting Historically, residential heating and cooling equipment has been
the proper size humidifier is important and is outlined in ARI controlled by a wall thermostat. Today, simple wall thermostats
Guideline F. with bimetallic strips are often replaced by microelectronic models
Since moisture migrates through all structural materials, vapor that can set heating and cooling equipment at different temperature
retarders should be installed near the warmer inside surface of insu- levels, depending on the time of day. This has led to night setback
lated walls, ceilings, and floors in most temperature climates. control to reduce energy demand and operating costs. For heat pump
Improper attention to this construction detail allows moisture to equipment, electronic thermostats can incorporate night setback
migrate from inside to outside, causing damp insulation, possible with an appropriate scheme to limit use of resistance heat during
structural damage, and exterior paint blistering. Humidifier clean- recovery. Chapter 45 contains more details about automatic control
ing and maintenance schedules should be followed to maintain effi- systems.
cient operation and prevent bacteria buildup. Chapter 20 of the 2000
ASHRAE Handbook—Systems and Equipment contains more infor- MULTIFAMILY RESIDENCES
mation on residential humidifiers.
Attached homes and low-rise multifamily apartments generally
use heating and cooling equipment comparable to that used in sin-
Dehumidifiers
gle-family dwellings. Separate systems for each unit allow individ-
Many homes also use dehumidifiers to remove moisture and ual control to suit the occupant and facilitate individual metering of
control indoor humidity levels. In cold climates, dehumidification is energy use.
sometimes required during the summer in basement areas to control
mold and mildew growth and to reduce zone humidity levels. Tra- Central Forced-Air Systems
ditionally, portable dehumidifiers have been used to control humid-
High-rise multifamily structures may also use unitary heating
ity in this application. While these portable units are not always as
and cooling equipment comparable to that used in single-family
efficient as central systems, their low first cost and the ability to
dwellings. Equipment may be installed in a separate mechanical
serve a single zone make them appropriate in many circumstances.
equipment room in the apartment, or it may be placed in a soffit or
In hot and humid climates, the importance of providing sufficient
above a drop ceiling over a hallway or closet.
dehumidification with sensible cooling is increasingly recognized.
Small residential warm-air furnaces may also be used, but a
While conventional air conditioning units provide some dehumidi-
means of providing combustion air and venting combustion prod-
fication as a consequence of sensible cooling, in some cases space
ucts from gas- or oil-fired furnaces is required. It may be necessary
humidity levels can still exceed the upper limit of 60% relative
to use a multiple-vent chimney or a manifold-type vent system.
humidity specified in ASHRAE Standard 55.
Local codes should be consulted. Direct vent furnaces that are
Several dehumidification enhancements to conventional air placed near or on an outside wall are also available for apartments.
conditioning systems are possible to improve moisture removal Another concept for multifamily residences (also applicable to
characteristics and lower the space humidity level. Some simple single-family dwellings) is a combined water heating/space heating
improvements include lowering the supply air flow rate and elimi- system that uses water from the domestic hot water storage tank to
nating off-cycle fan operation. Additional equipment options such provide space heating. Water circulates from the storage tank to a
as condenser/reheat coils, sensible-heat-exchanger-assisted evapo- hydronic coil in the system air handler. Space heating is provided by
rators (e.g., heat pipes), and subcooling/reheat coils can further circulating indoor air across the coil. A split-system central air con-
improve dehumidification performance. Desiccants—applied as ditioner with the evaporator located in the system air handler can be
either thermally-activated units or heat recovery systems (i.e., included to provide space cooling.
enthalpy wheels)—can also increase dehumidification capacity and
lower the indoor humidity level. Some dehumidification options Hydronic Central Systems
add heat to the conditioned zone that, in some cases, increases the
Individual heating and cooling units are not always possible or
load on the sensible cooling equipment.
practical in high-rise structures. In this case, applied central sys-
tems are used. Two- or four-pipe hydronic central systems are
Air Filters
widely used in high-rise apartments. Each dwelling unit has either
Most comfort conditioning systems that circulate air incorporate individual room units located at the perimeter or interior, or ducted
some form of air filter. Usually they are disposable or cleanable fan-coil units.
filters that have relatively low air-cleaning efficiency. Higher effi- The most flexible hydronic system with the lowest operating
ciency alternatives include pleated media filters and electronic air costs is the four-pipe type, which provides heating or cooling for
filters. These high-efficiency filters may have high static pressure each apartment dweller. The two-pipe system is less flexible in that
drops. The air distribution system should be carefully evaluated it cannot provide heating and cooling simultaneously. This limita-
before the installation of such filters. tion causes problems during the spring and fall when some apart-
Air filters are mounted in the return air duct or plenum and oper- ments in a complex require heating while others require cooling due
ate whenever air circulates through the duct system. Air filters are to solar or internal loads. This spring/fall problem may be overcome
rated in accordance with ARI Standard 680, which is based on by operating the two-pipe system in a cooling mode and providing
1.6 1999 ASHRAE Applications Handbook (SI)
the relatively low amount of heating that may be required by means Air-conditioning equipment must be isolated to reduce noise
of individual electric resistance heaters. Chapter 12 of the 2000 generation or transmission. The design and location of cooling
ASHRAE Handbook—Systems and Equipment discusses hydronic towers must be chosen to avoid disturbing occupants within the
design in more detail. building and neighbors in adjacent buildings. An important load,
frequently overlooked, is heat gain from piping for hot water
Through-the-Wall Units services.
Through-the-wall room air conditioners, packaged terminal air In large apartment houses, a central panel may allow individual
apartment air-conditioning systems or units to be monitored for
conditioners (PTACs), and packaged terminal heat pumps (PTHPs)
maintenance and operating purposes.
give the highest flexibility for conditioning single rooms. Each
room with an outside wall may have such a unit. These units are
MANUFACTURED HOMES
used extensively in the renovation of old buildings because they
are self-contained and do not require complex piping or ductwork Manufactured homes are constructed at a factory and constitute
renovation. over 7% of all housing units and about 25% of all new single-family
Room air conditioners have integral controls and may include homes sold each year. In the United States, heating and cooling sys-
resistance or heat pump heating. PTACs and PTHPs have special tems in manufactured homes, as well as other facets of construction
indoor and outdoor appearance treatments, making them adaptable such as insulation levels, are regulated by HUD Manufactured
to a wider range of architectural needs. PTACs can include gas, elec- Home Construction and Safety Standards. Each complete home or
tric resistance, hot water, or steam heat. Integral or remote wall- home section is assembled on a transportation frame—a chassis
mounted controls are used for both PTACs and PTHPs. Further with wheels and axles—for transport. Manufactured homes vary in
information may be found in Chapter 46 of the 2000 ASHRAE size from small, single-floor section units starting at 37 m2 to large,
Handbook—Systems and Equipment and in ARI Standard 310/380. multiple sections, which when joined together provide over 230 m2
and have the same appearance as site-constructed homes.
Water-Loop Heat Pumps
Heating systems are factory-installed and are primarily forced
Any mid- or high-rise structure having interior zones with high air downflow units feeding main supply ducts built into the sub-
internal heat gains that require year-round cooling can efficiently floor, with floor registers located throughout the home. A small per-
use a water-loop heat pump. Such systems have the flexibility and centage of homes in the far South and in the Southwest use upflow
control of a four-pipe system while using only two pipes. Water- units feeding overhead ducts in the attic space. Typically there is no
source heat pumps allow for the individual metering of each return duct system. Air returns to the air handler from each room
apartment. The building owner pays only the utility cost for the cir- through hallways. The complete heating system is a reduced clear-
culating pump, cooling tower, and supplemental boiler heat. Exist- ance type with the air-handling unit installed in a small closet or
ing buildings can be retrofitted with heat flow meters and timers on alcove usually located in a hallway. Sound control measures may be
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 sink, which in some
cases can eliminate the cooling tower.
Special Concerns for Apartment Buildings
Many ventilation systems are used in apartment buildings.
Local building codes generally govern air quantities. ASHRAE
Standard 62 requires minimum outdoor air values of 25 L/s inter-
mittent or 10 L/s continuous or operable windows for baths and toi-
lets, and 50 L/s intermittent or 12 L/s 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 consid-
ered when estimating heating load.
Buildings using exhaust and supply air systems 24 h a day may
benefit from air-to-air heat recovery devices (see Chapter 44 of the
2000 ASHRAE Handbook—Systems and Equipment). Such recov-
ery devices can reduce energy consumption by transferring 40 to
80% of the sensible and latent heat between the exhaust air and sup-
ply air streams.
Infiltration loads in high-rise buildings without ventilation open-
ings for perimeter units are not controllable on a year-round basis by
general building pressurization. When outer walls are pierced 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 positive
ventilation with at least two air exchanges per hour. Conditioned
supply air is preferable. Some designs transfer air into the apart-
ments through acoustically lined louvers to provide kitchen and toi-
let makeup air, if necessary. Supplying air to, instead of exhausting
air from, corridors minimizes odor migration from apartments into Fig. 3 Typical Installation of Heating and Cooling
corridors. Equipment for a Manufactured Home
Residences 1.7
required if large forced-air systems are installed close to sleeping condensate collected at the evaporator is drained by a flexible hose
areas. Gas, oil and electric furnaces or heat pumps may be installed (10), which is routed to the outdoors through the floor construction
by the home manufacturer to satisfy market requirements. and connected to a suitable drain.
Gas and oil furnaces are compact direct vent types that have
been approved for installation in a manufactured home. The special REFERENCES
venting arrangement used is a vertical through-the-roof concentric
ACCA. 1970. Selection of distribution systems. Manual G. Air-Condition-
pipe-in-pipe system that draws all air for combustion directly from
ing Contractors of America, Washington, DC.
the outdoors and discharges the combustion products through a
ACCA. 1995. Duct design for residential winter and summer air condition-
windproof vent terminal. Gas furnaces must be easily convertible
ing and equipment selection. Manual D, 3rd ed. Air-Conditioning Con-
from liquefied petroleum to natural gas and back as required at the tractors of America, Washington, DC.
final site. ACCA. 1986. Load calculation for residential winter and summer air condi-
Manufactured homes may be cooled with add-on split or single- tioning. Manual J, 7th ed. Air-Conditioning Contractors of America,
package air-conditioning systems when the supply ducts are ade- Washington, DC.
quately sized and rated for that purpose according to HUD require- ARI. 1984. Application of sound rated outdoor unitary equipment. Standard
ments. The split-system evaporator coil may be installed in the 275-84. Air Conditioning and Refrigeration Institute, Arlington, VA.
integral coil cavity provided with the furnace. A high static pressure ARI. 1995. Sound rating of outdoor unitary equipment. Standard 270-95.
Air Conditioning and Refrigeration Institute, Arlington, VA.
blower is used to overcome resistance through the furnace, the
ARI. 1988. Selection, installation and servicing of residential humidifiers.
evaporator coil and the compact air duct distribution system. Supply
Guideline F-1988. Air Conditioning and Refrigeration Institute, Arling-
air from a single-package air conditioner is connected with flexible
ton, VA.
air ducts to feed existing factory in-floor or overhead ducts. Damp-
ARI. 1989. Central system humidifiers for residential applications. Standard
ers or other means are required to prevent the cooled, conditioned 610-89. Air Conditioning and Refrigeration Institute, Arlington, VA.
air from backflowing through a furnace cabinet. ARI. 1993. Packaged terminal air-conditioners and heat pumps. Standard
A typical installation of a downflow gas or oil furnace with a 310/380-93. Air Conditioning and Refrigeration Institute, Arlington, VA.
split-system air conditioner is illustrated in Figure 3. Air returns to ARI. 1993. Residential air filter equipment. Standard 680-93. Air Condi-
the furnace directly through the hallway (1), passing through a lou- tioning and Refrigeration Institute, Arlington, VA.
vered door (2) on the front of the furnace. The air then passes ASHRAE. 1989. Ventilation for acceptable indoor air quality. Standard 62-
through air filters (3) and is drawn into the top-mounted blower (4), 1989.
which during the winter months forces air down over the heat ASHRAE. 1992. Gravimetric and dust spot procedures for testing air-clean-
ing devices used in general ventilation for removing particulate matter.
exchanger, where it picks up heat. For summer cooling, the blower
Standard 52.1-1992.
forces air through the split-system evaporator coil (5), which
ASHRAE. 1992. Thermal environmental conditions for human occupancy.
removes heat and moisture from the passing air. During heating and
Standard 55-1992.
cooling, the conditioned air then passes through a combustible floor
ASHRAE. 1993. Energy-efficient design of new low-rise residential build-
base and duct connector (6), before flowing into the floor air distri- ings. Standard 90.2-1993.
bution duct (7). The evaporator coil is connected via quick-connect Bose, J.E., J.D. Parker, and F.C. McQuiston. 1985. Design/Data manual for
refrigerant lines (8) to a remote air-cooled condensing unit (9). The closed-loop ground-coupled heat pump systems. ASHRAE.
CHAPTER 2
RETAIL FACILITIES
General Criteria ....................................................................... 2.1 Department Stores ..................................................................... 2.5
Small Stores .............................................................................. 2.1 Convenience Centers ................................................................. 2.6
Discount and Big Box Stores .................................................... 2.2 Regional Shopping Centers ....................................................... 2.6
Supermarkets ............................................................................ 2.2 Multiple-Use Complexes ........................................................... 2.7
T
HIS chapter covers the design and application of air-con- to offset the greater cooling and heating requirements. Entrance ves-
ditioning and heating systems for various retail merchandising tibules and heaters may be needed in cold climates.
facilities. Load calculations, systems, and equipment are covered Many new small stores are part of a shopping center. While exte-
elsewhere in the Handbook series. rior loads will differ between stores, the internal loads will be sim-
ilar; the need for proper design is important.
GENERAL CRITERIA
Design Considerations
To apply equipment properly, it is necessary to know the con-
struction of the space to be conditioned, its use and occupancy, the System Design. Single-zone unitary rooftop equipment is com-
time of day in which greatest occupancy occurs, the physical build- mon in store air conditioning. The use of multiple units to condition
ing characteristics, and the lighting layout. the store involves less ductwork and can maintain comfort in the
The following must also be considered: event of partial equipment failure. Prefabricated and matching curbs
simplify installation and ensure compatibility with roof materials.
• Electric power—size of service The heat pump, offered as packaged equipment, readily adapts to
• Heating—availability of steam, hot water, gas, oil, or electricity small-store applications and has a low first cost. Winter design con-
• Cooling—availability of chilled water, well water, city water, and ditions, utility rates, and operating cost should be compared to those
water conservation equipment for conventional heating systems before this type of equipment is
• Internal heat gains chosen.
• Rigging and delivery of equipment Water-cooled unitary equipment is available for small-store air
• Structural considerations conditioning, but many communities in the United States have
• Obstructions restrictions on the use of city and ground water for condensing pur-
• Ventilation—opening through roof or wall for outdoor air duct, poses and require the installation of a cooling tower. Water-cooled
number of doors to sales area, and exposures equipment generally operates efficiently and economically.
• Orientation of store
Retail facilities often have a high sensible heat gain relative to
• Code requirements the total heat gain. Unitary HVAC equipment should be designed
• Utility rates and regulations and selected to provide the necessary sensible heat removal.
• Building standards
Air Distribution. The external static pressures available in
Specific design requirements, such as the increase in outdoor air small-store air-conditioning units are limited, and ducts should be
required for exhaust where lunch counters exist, must be consid- designed to keep duct resistances low. Duct velocities should not
ered. The requirements of ASHRAE ventilation standards must be exceed 6 m/s and pressure drop should not exceed 0.8Pa/m. Aver-
followed. Heavy smoking and objectionable odors may necessitate age air quantities range from 47 to 60 L/s per kilowatt of cooling in
special filtering in conjunction with outdoor air intake and exhaust. accordance with the calculated internal sensible heat load.
Load calculations should be made using the procedure outlined in Attention should be paid to suspended obstacles, such as lights
Chapter 28 of the 1997 ASHRAE Handbook—Fundamentals. and displays, that interfere with proper air distribution.
In almost all localities there is some form of energy code in effect The duct system should contain enough dampers for air balanc-
that establishes strict requirements for insulation, equipment effi- ing. Dampers should be installed in the return and outdoor air duct
ciencies, system designs, and so forth, and places strict limits on for proper outdoor air/return air balance. Volume dampers should be
fenestration and lighting. The requirements of ASHRAE Standard installed in takeoffs from the main supply duct to balance air to the
90 should be met as a minimum guideline for retail facilities. branch ducts.
The selection and design of the HVAC for retail facilities are nor- Control. Controls for small stores should be kept as simple as
mally determined by economics. First cost is usually the determin- possible while still able to perform the required functions. Unitary
ing factor for small stores; for large retail facilities, operating and equipment is typically available with manufacturer-supplied con-
maintenance costs are also considered. Generally, decisions about trols for ease of installation and operation.
mechanical systems for retail facilities are based on a cash flow Automatic dampers should be placed in the outdoor air intake to
analysis rather than on a full life-cycle analysis. prevent outdoor air from entering when the fan is turned off.
Heating controls vary with the nature of the heating medium.
SMALL STORES Duct heaters are generally furnished with manufacturer-installed
safety controls. Steam or hot water heating coils require a motorized
The large glass areas found at the front of many small stores may
valve for heating control.
cause high peak solar heat gain unless they have northern expo-
Time clock control can limit unnecessary HVAC operation.
sures. High heat loss may be experienced on cold, cloudy days. The
Unoccupied reset controls should be provided in conjunction with
HVAC system for this portion of the small store should be designed
timed control.
Maintenance. To protect the initial investment and ensure max-
The preparation of this chapter is assigned to TC 9.8, Large Building Air- imum efficiency, the maintenance of air-conditioning units in small
Conditioning Applications. stores should be contracted out to a reliable service company on a