Copyright Goodheart-Willcox Co., Inc. Chapter 32 Residential Split Air-Conditioning Systems 821 10 the metering device for the unit. Some indoor units may have a condensate pump or a heating unit. The thermistors measure the coil temperature and air temperature. These readings are continuously communi- cated back to the control board. Based on these readings, the system can adjust EEVs and the compressor output. As an indoor unit operates, moisture condenses on the coil and flows into a condensate pan. Some units are designed to drain by gravity, and other units use a conden- sate pump. This moisture usually drains out. However, if the drain line becomes blocked or the condensate pump fails, water could overflow the pan. The overflowing water could damage walls, ceilings, flooring, and furnishings. To avoid an overflowing drain pan, many indoor units are equipped with an overflow switch. See Figure 32-35. When the overflow switch senses, it opens a switch to shut off operation to the indoor unit. With no more refrigerant moving through the refrigeration coil, water stops con- densing on the coil and draining into the pan. Some indoor units include an occupancy sensor. An occupancy sensor senses when a room is occupied and when a room is not occupied. A system with occupancy sensors can be programmed to one temperature set point for an occupied room and a different set point when the room is unoccupied. Typically, an indoor unit is controlled with a remote control, Figure 32-36. The remote control may be used to turn the unit on or off, change the temperature setting, change the fan speed, and change the direction of the sup- ply air. Note that the thermostat is located in the unit, not in the remote control. Wall-mounted thermostats are also available with most systems. A line set typically contains the refrigerant lines, elec- trical wiring, and a condensate drain. Electrical power is Overflow switch RectorSeal Figure 32-35. This overflow switch mounts to the condensate pan and turns off the indoor unit when an accumulation of condensate is sensed. supplied to the indoor unit through the line set, so a sep- arate electrical connection is not needed for the indoor units. One common component that is typically not included in ductless systems is a filter-drier. Since ductless systems do not contain a filter-drier, extra care is needed to ensure that con- taminants are not introduced into the refrigerant lines. 32.6.2 Ductless System Installation Compared to installing a central air-conditioning system, installing a ductless system is generally much easier. How- ever, with ductless systems, all installation instructions provided by the manufacturer must be followed. These instructions may vary from manufacturer to manufac- turer and even from unit to unit, so always be sure to have the correct installation guides. Indoor Unit Disconnect Some building codes and building inspectors may determine that the outdoor electrical disconnect is too far from one or more indoor units. In these cases, an electrical disconnect for the indoor unit must be installed in a location acceptable to the authority having jurisdiction. Code Alert Fujitsu General America, Inc. Figure 32-36. Ductless split systems are easily programmed using a remote control or a smartphone app using WiFi.