Residential Cooling

Air Conditioning

Air conditioning is one of those amenities that's easy to take for granted if you have it, and on a hot, humid, summer afternoon, easy to desire it if you don't.

A central air conditioner uses the furnace's blower to draw room air into the unit through return-air ductwork and a filter that removes dust, hair and lint. The room air moves past a chilled indoor coil-the evaporator-to release its heat. The resulting cold air travels on to the plenum, usually a large metal box at the top of the furnace, where it's channeled to air supply ductwork and returned to rooms.

With air conditioners, bigger is not necessarily better.

For one thing, the larger the capacity, the more a unit will cost; output is directly related to cost. Also, it's critically important to pick a size that is appropriate for the house.

An air conditioner that is too small can't keep up with load requirements on a particularly hot day. One that is too large will cycle off and on too frequently, doing a poor job of dehumidifying the air, which degrades comfort. In fact, it's better to slightly undersize an air conditioner than to oversize it.