Types of Geothermal HVAC Systems

Written by Anita Alvarez
Updated September 14, 2015
Geothermal ground loops
Geothermal ground pipes come in a variety of layouts. (Photo courtesy of Angie's List member Roger R. of Swisher, Iowa)

Look for equipment that works with your lot's soil, thermal capacity and water availability.

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Geothermal heating and cooling operates on the principles of heat transfer, and unlike traditional HVAC equipment, geothermal systems are a two-in-one: They heat and cool the home.

The type of system that will work for your home depends largely on three factors: soil conditions, the presence of rock and the availability of water. The underground geothermal loops must be able to access sufficient heat in order to transfer it to the home. If conditions limit your options for one type of system, there's likely another system that will work in your climate region.

Work with an HVAC contractor who specializes in geothermal to discuss the viability of these primary types of geothermal systems.

• Horizontal loops. You must have a fairly large lot to install a horizontal-loop system. In this configuration, the installer digs shallow trenches 3 to 6 feet in depth to bury the loops. Most systems require at least 400 and 600 feet of looping for every 1 ton of heating/cooling capacity required, so the lot must be large enough to accommodate the snaking loops.

• Vertical loops. When lot space is limited or digging horizontal trenches isn't feasible to due landscaping or structures on the lot, a vertical loop may work. However, this type of geothermal system tends to run high in terms of labor costs because the installer must dig trenches from 150 to 450 feet deep to accommodate the loops.

• Pond/lake loops. If you have access to a pond or lake, you might opt for what is generally a low-cost option: a lake or pond system. The installer submerges piping deep into the water where the temperature remains constant as compared to surface temperatures. Connecting the loops underwater generally requires some digging underground in order for the looping to attach to the indoor components, like the heat exchanger and ductwork.

• Well-water loops. Often the least-costly system, if you have access to well water, the installer can simply submerge the access loop into one well, which draws water through the pipes to source energy. The discharge pipe, submerged deep into the other well, allows water to circulate out of the geothermal system, and it's directed back into the ground.

Closed and Open Loops

Both the horizontal and vertical systems are always "closed." This means that the loops are sealed or closed, and the liquid solution that transfers energy circulates continuously through this closed loop. Pond or lake systems are also generally closed systems.

A well-water system is generally open, where one end of the loop allows water to enter it, and the other end of the loop acts as the point of discharge. This option requires that your installer follow federal guidelines when installing the system to prevent contamination of groundwater.

The investment you make upfront in geothermal equipment will pay you back tenfold for many decades. Work with an experienced geothermal contractor to investigate the best system for your home, and your budget.

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