Air-Conditioning and Refrigeration
• Residential buildings, including single-family and multifamily low-rise buildings of three or fewer
stories above grade
• Manufacturing buildings, which manufacture and store products
Types of Air-Conditioning Systems
In institutional, commercial, and residential buildings, air-conditioning systems are mainly for the
occupants’ health and comfort. They are often called comfort air-conditioning systems. In manufacturing
buildings, air-conditioning systems are provided for product processing, or for the health and comfort
of workers as well as processing, and are called processing air-conditioning systems.
Based on their size, construction, and operating characteristics, air-conditioning systems can be
classified as the following.
Individual Room or Individual Systems. An individual air-conditioning system normally employs
either a single, self-contained, packaged room air conditioner (installed in a window or through a wall)
or separate indoor and outdoor units to serve an individual room, as shown in Figure 9.1.1. “Selfcontained, packaged” means factory assembled in one package and ready for use.
FIGURE 9.1.1 An individual room air-conditioning system.
Space-Conditioning Systems or Space Systems. These systems have their air-conditioning—cooling,
heating, and filtration—performed predominantly in or above the conditioned space, as shown in Figure
9.1.2. Outdoor air is supplied by a separate outdoor ventilation system.
Unitary Packaged Systems or Packaged Systems. These systems are installed with either a single selfcontained, factory-assembled packaged unit (PU) or two split units: an indoor air handler, normally with
ductwork, and an outdoor condensing unit with refrigeration compressor(s) and condenser, as shown in
Figure 9.1.3. In a packaged system, air is cooled mainly by direct expansion of refrigerant in coils called
DX coils and heated by gas furnace, electric heating, or a heat pump effect, which is the reverse of a
Central Hydronic or Central Systems. A central system uses chilled water or hot water from a central
plant to cool and heat the air at the coils in an air handling unit (AHU) as shown in Figure 9.1.4. For
energy transport, the heat capacity of water is about 3400 times greater than that of air. Central systems
are built-up systems assembled and installed on the site.
Packaged systems are comprised of only air system, refrigeration, heating, and control systems. Both
central and space-conditioning systems consist of the following.
Air Systems. An air system is also called an air handling system or the air side of an air-conditioning
or HVAC&R system. Its function is to condition the air, distribute it, and control the indoor environment
according to requirements. The primary equipment in an air system is an AHU or air handler; both of
these include fan, coils, filters, dampers, humidifiers (optional), supply and return ductwork, supply
outlets and return inlets, and controls.
© 1999 by CRC Press LLC