They are usually used to pull heat out of the air or ground to heat a home, or they can be switched into reverse to cool a building. If you know how an air conditioner works, you already know a lot about how a heat pump works, because heat pumps and air conditioners operate in very similar ways.

Heat pumps are a unique kind of heating system, because they can do the work of both a furnace and an air conditioner. Thus, there’s no need to install separate systems to heat and cool your home. Heat pumps work extremely efficiently, because they simply transfer heat, rather than burn fuel to create it.

Heat pumps work best in moderate climates, and using a heat pump instead of a furnace and air conditioner may help you save money on your utility bill. Most heat pumps are somewhat limited by the cold, however, so it is important that you learn which kind of heat pump is best for your area before installing one in your home or office building.

Air-source heat pumps

One of the most common types of heat pumps is the air-source heat pump, which takes heat from the air outside your home and pumps it inside through refrigerant-filled coils. Inside this basic heat pump, you’ll find two fans, refrigerator coils, a reversing valve and a compressor. With the proper modification, air-source systems can also work with other types of indoor heating systems.

The reversing valve reverses the flow of the refrigerant, so that the system begins to operate in the opposite direction. Instead of pumping heat inside your home, the heat pump releases it, just like an air conditioner. The refrigerant now absorbs heat on the indoor side of the unit and flows to the outside, where the heat is released and the refrigerant cools and flows back indoors to pick up more heat.

Ductless heat pumps

If your home doesn’t have air ducts to distribute heat, you could use a special kind of heat pump called a mini-split heat pump. A mini-split heat pump connects an outdoor air-source unit to multiple indoor units that in turn connect to water heat or space heaters. Ductless mini-split systems are useful for retrofitting a home with a heat pump system, as their locations outside and inside the home are flexible, and installation only requires a three-inch (7.6 cm) conduit to come through the wall. The indoor air handlers for a mini-split system may be installed in the wall, ceiling, or on the floor, and are relatively small.

Article by: Cowan, Laura.  “How Heat Pumps Work”  13 May 2009.  HowStuffWorks.com. <http://home.howstuffworks.com/home-improvement/heating-and-cooling/heat-pump.htm>  18 May 2011.