Copyright Goodheart-Willcox Co., Inc. 798 Air-Conditioning Systems Germicidal light Supply air duct Humidifier Return air duct Fresh air intake ERV/HRV Condensing unit Indoor coil Thermostat Filtration device Furnace and air handler Rheem Manufacturing Company Figure 32-1. A complete residential central air-conditioning system. Indoor cooling unit Outdoor condensing unit Refrigerant line set containing suction and liquid lines Mitsubishi Electric, HVAC Advanced Products Division Figure 32-2. A ductless split system. A refrigerant line set connects the indoor and outdoor units. This room is being cooled by its cooling unit.