Your thermostat monitors indoor temperatures and activates the AC when cooling is needed. Warm air is pulled through return ducts, filtered, and passed over a cold evaporator coil, where the refrigerant absorbs heat. The refrigerant then travels to the outdoor unit, where the compressor pressurizes it and the condenser coil releases the heat outside. It then returns indoors through an expansion device to restart the cooling cycle, keeping your home comfortable.