Heat Pump Inspection – Main Types of Heat Pumps
The most common type of heat pumps are air-to-air systems, which extract heat from the outside air and transfer it to the inside air. Other types of heat pumps include solar-assisted, water-source and ground-source heat pumps. Explained below are the principles for air-to-air systems, but the same principles apply to other types of heat pumps.
While it may seem rather hard to imagine the heat from outside air can actually heat your home during freezing weather, air-to-air heat pumps are in fact very effective. As long as the air temperature is greater than absolute zero, -460 degrees F, there is some heat in the air. At 32 degrees F air possesses 88 percent of the heat that it has at 100 degrees F.
Heat pumps disperse heat by moving a refrigerant with a boiling point around -20 degrees F, such as Freon, between indoor and outdoor coils or heat exchangers. Like any fluid, the cold refrigerant absorbs heat when the outside air heats it to a boil. Then, a compressor compresses the vaporized refrigerant and raises its temperature to more than 100 degrees F. The heated refrigerant then passes through a pipe to the inside heat exchanger, transferring its heat to the inside air and condensing to a warm liquid.
That warm liquid passes through an expansion valve, reduces the refrigerant’s pressure, expands its volume and lowers its temperature – the reverse of compression. The cold refrigerant can now absorb heat from the outside air again and repeat the whole cycle.
During the heating cycle, the air at your registers may seem cool because a heat pump does not deliver sudden bursts of hot air like conventional furnaces. A heat pump delivers a more constant flow of 85 to 90 degrees F, at a tighter velocity. The air will seem cool because it is less than the human body temperature, however it is sufficiently warm to heat your home and keep you comfortable.