Room-air-conditioner servicing is similar to refrigerator servicing. An air conditioner is a refrigerant system that removes heat from a room. (In a refrigerator, the heat is removed from the food.) An evaporator is employed to remove the heat, and a condenser is used to liquefy the refrigerant. Air movement over the evaporator and condenser surface is accomplished by a fan. Hot air usually contains a greater percentage of moisture than colder air. When the evaporator fan moves hot humid air over the cold surface of the evaporator, a quantity of the moisture in the air will condense (form water droplets) in addition to the air itself being cooled. In this manner, the relative humidity of the recirculated air is also reduced. The condensate water is drained into the condenser section, where it is dissipated.
Servicemen who have a good knowledge of refrigeration combined with the understanding that an air conditioner removes heat and humidity from a room by the process of refrigeration will be able to competently service air conditioners. Since most portable air conditioning units of present design contain compressors of the hermetic or sealed type, the only parts that can be serviced in the field are the relay, control switch, fan, fan motor, starting and running capacitors, air filters, and cabinet parts. The refrigerating system (consisting of the cooling unit, condensers, compressors, and connecting lines) generally cannot be serviced in the field.