797 10 ▲ RectorSeal Introduction The ability to comfortably and cost effectively condition the air within multiple rooms in homes has led to an increased demand for central air conditioning. What was once considered a luxury for homeowners is now a standard feature. Therefore, it is important for the technician to be familiar with these systems. 32.1 Split Air-Conditioning Systems A split air-conditioning system has its components in two or more separate loca- tions. A split system’s condensing unit is typically located outdoors, and its evapo- rating unit is placed indoors. Most split systems fall into one of two categories: • Central air-conditioning system. Often simply called split systems, a central air-conditioning system uses a single indoor unit connected to a duct system. A blower distributes the conditioned air through supply air ducts into multiple rooms. A return air duct system allows air from the conditioned spaces to return to the air handler to be conditioned. See Figure 32-1. • Ductless air-conditioning systems. In ductless systems, the indoor unit with an evaporator and fan is placed within the room or area to be cooled. No ductwork is needed. Ductless air-conditioning systems can be further classified as mini-split systems that provide cooling to a single indoor unit, multi-split systems that provide cooling to multiple indoor units, and VRF systems that provide cooling to a larger number of indoor units. See Figure 32-2. The table in Figure 32-3 provides a comparison of a central air-conditioning system and the three types of ductless air-conditioning systems. These systems are discussed in detail in this chapter. Heat pump systems are split systems that can provide both cooling and heating. Heat pumps include a reversing valve that changes the flow of refrigerant. When a heat pump is in heating mode, the high-pressure vapor leaving the compressor flows to the indoor unit. The coil in the indoor unit, which serves as the evapora- tor in cooling mode, serves as the condenser in heating mode. Heat is released as the vapor condensing to liquid, and this heat is released in the indoor unit. Liquid refrigerant then flows to the outdoor unit, where the coil serves as the evaporator. Heat pumps are covered in Chapter 40, Heat Pumps. access valve lock biocide tablet blank-off plate central air-conditioning system ductless split system overflow switch quick-connect coupling Technical Terms