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Basics of Geothermal Heat Pumps

As homeowners are constantly looking for ways to save on their energy bills, there is a very good opportunity to save money on typically the largest energy expense in homes, which is heating and cooling.

Many areas of the country use air-to-air heat pumps, which can save the homeowner money and provide a comfortable means of heating and cooling.  However, another great option is a Geothermal Heat Pump.

Geothermal or GSHP (Ground Source Heat Pumps) are similar to ordinary air-to-air heat pumps, but instead of using heat found in the outside air, they rely on the heat of the earth to provide heating and cooling as well as hot water. Although outside temperatures vary across the country, at six feet underground the temperatures are relatively consistent and range from 45 degrees to 75 degrees F.

The earth’s constant temperature is what makes geothermal heat pumps one of the most efficient, comfortable, and quiet heating and cooling technologies available today. While geothermal heat pumps are more expensive to install than regular heat pumps, they produce much lower energy bills.  Since geothermal heat pumps are mechanically simple and their outside parts are below the ground and protected from the weather, maintenance costs are often lower as well.

Another benefit to a geothermal heat pump is that they can be equipped with a device called a desuperheater. A desuperheater is a small, auxiliary heat exchanger that uses superheated gases from the heat pump's compressor to heat water. This hot water then circulates through a pipe to the home's storage water heater tank.  In winter, the desuperheater can reduce water heating costs by about half, while a conventional water heater provides the rest of the households needs. In the spring and fall when temperatures are mild and the heat pump may not be operating at all, the regular water heater provides the hot water. Some manufacturers also offer triple-function geothermal heat pump systems, which provide heating, cooling, and hot water. They use a separate heat exchanger to meet all of a household's hot water needs.

A geothermal heat pump does not create heat by burning fuel, like a furnace does. Instead, in winter it collects the Earth's natural heat through a series of pipes, called a loop, installed below the surface of the ground, or submersed in a pond or lake. Fluid circulates through the loop and carries the heat to the house. There, an electrically driven compressor and a heat exchanger concentrate the Earth's energy and release it inside the home at a higher temperature. Ductwork distributes the heat to different rooms.

In summer, the process is reversed. The underground loo draws excess heat from the house and allows it to be absorbed by the Earth. The system cools your home in the same way that a refrigerator keeps your food cool - by drawing heat from the interior, not by blowing in cold air.
The geothermal loop that is buried underground is typically made of high-density polyethylene, a tough plastic that is extraordinarily durable but which allows heat to pass through efficiently. When installers connect sections of pipe, they heat fuse the joints, making the connections stronger than the pipe itself. The fluid in the loop is water or an environmentally safe antifreeze solution that circulates through the pipes in a closed system.

Another type of geothermal system uses a loop of copper piping placed underground. When refrigerant is pumped through the loop, heat is transferred directly through the copper to the earth.
Typical geothermal heat pump installations include horizontal ground closed loops, vertical ground closed loops, open-loops, and pond closed loops.

Information provided by Energy.gov, consumerenergycenter.org, and AHIT

 

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