Copyright Goodheart-Willcox Co., Inc. Chapter 32 Residential Split Air-Conditioning Systems 799 10 32.2 Comfort Cooling Controls Controls for comfort cooling include operating controls and safety controls. Operating controls regulate the nor- mal operation of the system. Safety controls regulate safe operation by turning components on or off in order to pro- tect system components and building occupants. Operating controls can include thermostats, pressure switches, humidistats, motor starters, and relays. Safety con- trols can include electrical fuses, circuit breakers, thermal overloads, internal motor overloads, refrigerant pressure limit controls, and oil pressure controls. Many of these controls are described in Chapter 16, Electrical Control Systems. For more information on thermostats, see Chapter 36, Thermostats. Comparison of Residential Split Air-Conditioning Systems Central Air-Conditioning System Single-Zone Ductless System Single-Zone Multi-Split Ductless System VRF System Also Called Split System Mini-Split Multi-Split VRV System Outdoor Unit Single outdoor unit typically includes hermetic compressor, condenser, and condenser fan. Single outdoor unit includes inverter-driven compressor, EEV, condenser, and condenser fan. Single outdoor unit includes inverter-driven compressor, EEVs, condenser, and condenser fan. Single or multiple outdoor units include inverter- driven compressors, condensers, and condenser fans. Indoor Unit Single indoor air handler contains metering device, evaporator coil, and blower. Furnace may be contained in air handler. Single indoor unit contains evaporator and fan. Multiple indoor units, each containing an evaporator and a fan. Maximum number of indoor units may be 8. Multiple indoor units, each containing an EEV, an evaporator, and a fan. Maximum number of indoor units may be 64. Airflow Duct system distributes supply air from and provides return to the air handler. Air blown over evaporator in conditioned space. Air blown over each evaporator in conditioned space. Air blown over each evaporator in conditioned space. Metering Device TXV or fixed orifice in indoor unit, typically. EEV in outdoor units. EEVs for each indoor unit. EEVs in each indoor unit. Controls Single thermostat in central location controls cooling. Thermostat on indoor unit controls cooling. One indoor unit serves as the master thermostat for the system. Thermostats on each indoor unit control cooling. Each indoor unit can be set to a different temperature. In heat recovery systems, some indoor units can provide cooling while others provide heating. Other Notes • Single evaporator provides cooling to all conditioned space in building. • May be air conditioner or heat pump. • Duct system facilities installation of additional air treatment accessories such as humidifiers, air cleaners, and ERVs/HRVs. • Single evaporator provides cooling to a single conditioned space. • May be air conditioner or heat pump. • Multiple evaporators provide variable cooling to each conditioned space. • May be air conditioner or heat pump. • Multiple evaporators provide variable cooling or heating to each conditioned space. • May be heat pump system (all indoor units must cool or heat) or heat recovery system (some indoor units can cool while others can heat). • Available for residential applications, but more commonly used in commercial applications. Goodheart-Willcox Publisher Figure 32-3. This chart compares characteristics of central air-conditioning systems and three types of ductless air-conditioning systems.