A split-system air conditioner is composed of the evaporator (indoor unit) and the condenser (outdoor unit). Copper tubes facilitate refrigerant exchange between these units, making them work more efficiently together than apart. The condenser unit is what cools your home when the summer heat gets too unbearable. It contains an outside compressor that starts up in response to demand for cooling and pulls all of the hot air out by moving cold refrigerant through a coil, which then blows it back onto you so that you can enjoy some relief from this oppressive Australian climate. The evaporator unit is the indoor unit. The coil of your air conditioner is usually located inside a metal cabinet containing the furnace or heat pump. The refrigerant expands when it comes in contact with the coil and then becomes so cold that you feel cool just by standing next to it!