Copyright Goodheart-Willcox Co., Inc. 820 Air-Conditioning Systems 32.6.1 Ductless System Components Ductless systems include three primary components: an outdoor unit, an indoor unit, and a line set that connects the two. Some systems, including VRF systems, include Y-fittings and distribution boxes in the line set distribu- tion system. The outdoor unit contains the compressor, condens- ing coil, and condenser fan. Outdoor units for heat pump systems include a reversing valve and often a defrost heater to prevent ice buildup in cold conditions. In single- zone mini-split systems, an EEV is typically contained in the outdoor unit. Several types of indoor units can be used in ductless systems. See Figure 32-33. These indoor units are often called “heads.” Wall-mount units are installed in the upper part of walls. Floor units are wall-mount units positioned on the lower part of the wall. Ceiling cassettes can be installed flush with the ceiling or can be installed below the ceiling. Small ducted air handler units can also be included in a “ductless” system. Each indoor unit has its own refrigerant coil, coil thermistor, air thermistor, blower, air filter, condensate pan, condensate drain, and electrical connection. See Figure 32-34. Indoor units on some systems will contain Air filters Mitsubishi Electric, HVAC Advanced Products Division Figure 32-34. This indoor unit is shown with its cover and air filters removed. Fujitsu General America, Inc. Figure 32-33. The selection of an indoor unit type in the ductless system may be influenced by design, installation, or utility concerns. Various types of indoor units can be used in a single ductless system, providing flexibility. Wall-mount unit Ceiling cassette In-line duct unit Floor unit