There are several types of air conditioners, including self-contained window units, portable air conditioners with window exhaust kits, split central air conditioning systems and split ductless air conditioners. In addition, there are reversible air conditioners called heat pumps that can warm a home in the winter months.
The central part of any air conditioning system is a pair of connected coils filled with a refrigerant. The evaporator coils are situated indoors and absorb heat as warm air passes over them. This causes the refrigerant inside to expand and turn into a gas. This gas is pressurized and pumped to condenser coils, where it expels heat into the outside environment before flowing back to the evaporator coils. In some cases, both sets of coils are mounted in a single wall-mounted or window-mounted unit, while in others, the refrigerant passes from an indoor unit to an outdoor unit via metal pipes.
Ducted units, such as central air conditioners, chill the air at a central point and blow it through ventilation ducts in the home. Ductless units have evaporator coils and air handlers in individual rooms, each passing refrigerant to a single condenser unit outside. Portable units use a hose or duct to transfer the warm air from the condenser through a vent to the outdoors.