Copyright Goodheart-Willcox Co., Inc. Chapter 32 Residential Split Air-Conditioning Systems 817 10 means of distributing cooled air. Like a traditional split system, a ductless split system has an outdoor unit (com- pressor and condenser) outside a building that is con- nected by a line set to an indoor unit (evaporator) inside the building. Ductless split systems often use multiple indoor units throughout a building. These cool the air in individual rooms. The cooling units use fans to pull in warm air, absorb heat into the refrigerant in the evapora- tor, and blow cool air back into the room. No ductwork is used, Figure 32-32. Ductless split systems are popular for adding air con- ditioning to both new construction and to older buildings that are not equipped with air duct systems. Ductless systems are frequently used in offices, motels, multi- family dwellings, and houses that use hydronic heating, electric baseboard heat, or space heaters. Ductless split systems offer a convenient solution for providing heat- ing and cooling to room additions and small apartments, where extending or installing distribution ductwork for a central air conditioner or heating system may not be an option. Ductless split systems can be categorized into three groups: Flame Furnace, Inc. Figure 32-30. Checking suction and discharge pressures at the condensing unit. System Problems with Corresponding Measurement Change Problem Suction Pressure Discharge (Head) Pressure Superheat Subcooling Compressor Amps Undercharge ↓ ↓ ↑ ↓ ↓ Overcharge ↑ ↑ ↓ ↑ ↑ Liquid line restriction ↓ Normal ↓ ↑ ↑ ↓ Suction line restriction ↓ ↓ ↑ ↑ Normal ↓ Heavy load ↑ ↑ ↑ ↑ Normal ↑ Light load, low evaporator airflow ↓ Normal ↓ ↓ Normal ↓ Normal ↓ Noncondensables, condensing coil restriction ↑ ↑ ↓ ↓ ↑ Low outdoor ambient temperature ↓ ↓ ↑ ↑ Normal ↓ High outdoor ambient temperature ↑ ↑ ↑ Normal ↑ Dirty condenser, low outdoor airflow ↑ ↑ Normal ↓ Normal ↓ ↑ Evaporator coil restriction ↓ ↓ ↓ ↓ ↑ Overfed metering device ↑ ↓ ↓ ↓ ↑ Underfed metering device ↓ ↓ ↑ ↑ ↓ Goodheart-Willcox Publisher Figure 32-31. This chart provides a list of some common air-conditioning system problems and their impact on various system measurements.