A central air conditioner, also called AC condensing units or condensers, are one part of a split cooling system. That big box outside of your house with a fan on top is called the condensing unit! It connects to an evaporator coil, mounted inside an air handler or gas furnace, through a set of refrigerant tubes commonly referred to as a copper lineset. Central ACs transfer heat from one area to another. Refrigerant, commonly called Freon and most widely recognized as R22 or R410A (in residential systems), transfers heat out of your home. Most people think that the air being pumped through the vents comes from outside, it doesn’t.
The existing air in your home is cooled by passing it across the evaporator coil, transferring that heat into the refrigerant and circulating the warm refrigerant to the outdoor condenser to disperse it. The cycle continues until the temperature set on the thermostat is reached. Central ACs are also very powerful dehumidifiers. As warm air is passed over the evaporator coil, it no longer retains the level of moisture that it can at higher temperatures. The condensate released from the air stays on the outside fins of the evaporator coil, runs down into a built-in drain pan and gets carried away through a condensate draining system.