How Does Central Air Conditioning Work?

By Josienita Borlongan

Converting Heat into Cool Air

How Does Central Air Conditioning Work?

An air conditioner works by using energy to convert heat into cold air by using a compressor cycle much like a refrigerator, only in bigger spaces. This cycle allows heat to be transferred from the inside of the house to the outside of the house. A special fluid called a refrigerant is used in this process, whereby heat is absorbed and released as it goes outside. The refrigerant changes in state between gas and liquid during this cycle. Whenever the refrigerant changes from liquid to gas, it absorbs heat; then when it changes back from gas to liquid state, it releases heat. This liquid is passed through an expansion device that changes the liquid in to a low-pressure mixture of liquid/gas. This is why some of the air conditioning units have water droplets or "perspiration" on the equipment that is sticking on the outside. The remaining liquid in the indoor coils absorbs heat from the inside air, which turns into a low-temperature gas cooling the indoor air.

Three Main Parts of an Air Conditioner

The compressor, located on the outside air portion of the air conditioner, is the one responsible for compressing the gas.

The condenser, also located outside like the compressor, is responsible for condensing the vapor.

The evaporator is the part that heats up the furnace when the heater portion of your central air is used. It is normally located inside the indoor coil or as part of the furnace.

How the Cycle Works

The compressor compresses the low-temperature gas--reducing its volume and increasing its temperature and pressure--which causes it to turn into a vapor. The vapor then goes into the condenser (outdoor coil), which transfers the heat outdoors. This process then causes the refrigerant to condense into a liquid state, which then returns to the expansion device repeating the cycle.

As air passes through the indoor coil, the air inside is cooled and dehumidified. During the dehumidification stage, the moisture is removed from the air becoming a liquid form which then gets collected in a pan located at the bottom of the indoor coil of the air conditioner. The liquid or moisture eventually gets drained outside.