Components of a Geothermal Heating System: Some Information From Audubon

A geothermal heating system has three basic components and some add-on ones as well.

Its most distinguishing feature is the ground loops. The most common is the “closed” ground loop system, which is a series of pipes that are buried underground. These pipes contain a heat transfer fluid, comprised of antifreeze and water. This fluid absorbs heat from the ground and carries it to the home. This fluid also absorbs heat from the house and sends it into the ground to keep the home cool.

Examples of closed loop systems include the horizontal closed loop, which can be used in larger parcels of land (over an acre for example). The loops are placed typically placed horizontally 6-to-10 feet below the surface. A vertical closed loop design is recommended for smaller parcels of land and loops are often buried vertically approximately 20 feet underground. Other types of ground loop designs use well water to transfer heat in an open loop configuration, or have a closed loop submerged underwater in a pond or lake.

The next component is the heat pump, which draws the fluid from the ground loop. In a heat pump, heat energy is exchanged with the ground to heat or cool the home. In the heating mode, fluid warmed from underground flows through the heat pump. A fan blows across the pipe warmed by the fluid. Because the fluid is much warmer than the air inside the heat pump, heat energy is released into the cooler air. The cool air is warmed and distributed inside the home. The process is reversed for cooling. Cool fluid in the pipe absorbs heat from the warm air inside the home. Once pumped underground, the excess heat in the fluid is absorbed by the cooler earth.

The final component is the air handling or distribution system. Here, a fan in the heat pump’s furnace blows air over a fan coil and the heated cooled air is distributed through the home’s ductwork. Some distribution systems are hydronic, where hot water is circulated through radiators or radiant floor heat tubing. This water absorbs heat from the heat pump and then distributed throughout the home.

In some homes, both a forced air and hydronic system, often referred to as a “hybrid system” work together.

Optional components include a heat pump “desuperheater,” which is used to help with domestic hot water heating. In warm weather, the desuperheater recovers some of the heat – that would otherwise be sent to the ground loop – to help produce hot water. In cold weather, some of the heat pump capacity may be diverted from space heating for the same purpose. Desuperheaters save approximately 25% on domestic water heating costs.

Another component is an auxiliary electric heater, which is built into the geothermal heat pump This auxiliary electric heat is installed to allow heating and cooling technicians to size – or resize – a home’s geothermal heat pump system to assist the system during the few coldest days of the year. Auxiliary electric heat is also an emergency backup heat source if there are any operational issues with the geothermal heat pump system.