Window-mounted heat pumps operate by transporting a refrigerant that has the ability to capture heat and store it until it is released. Unlike central heat pump systems, window-mounted units only need to move refrigerant a short distance. This refrigerant captures external heat and releases it through a coil located on the interior side of the unit to provide heat. When cooling, this process is reversed with heat being expelled from the exterior side of the unit.
Window-mounted heat pumps and air conditioning units function using many of the same principles. Heat pumps are able to provide both heating and cooling functions by reversing the flow of refrigerant. Unlike a heater or furnace, a heat pump does not need to burn oil or gas to generate heat. Pumps move heat from the outside air into the interior environment very efficiently, making them popular equipment choices for moderate climates.
Window-mounted heat pumps function by storing environmental heat within a refrigerant such as Freon. The position of the unit's reversing valve determines the directional flow of this refrigerant. Units make use of both an indoor and outdoor coil. Depending on the operation, each coil may function as either a condenser or a radiator in order to expel heat internally or externally.