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Pittsburgh Geothermal Guide: Types of Loop Systems

Energy resources are changing rapidly.  The conventional oil, gas and coal fuels are giving way to alternative sources like wind, solar and hydro.  Geothermal energy is less understood by consumers, but potentially the most abundant source available, nearly as huge a supply as the Earth itself. Many people are considering installing geothermal heating and cooling in Pittsburgh.

From the Greek word “geo” for “earth”, geothermal energy is generated by the natural process of heat gravitating toward cooler temperatures.  The by-product can be captured and utilized simply as heat or converted to electricity. In small, self-contained residential or large commercial applications, this typically happens in either closed or open looped systems.

Closed Loop Geothermal Systems

Systems using water or anti-freeze that run from the pump into the ground and back to the pump continuously are closed looped.  Most efficient for smaller residential systems where land is available, two or three horizontal loops are side by side just a few feet underground.  Sometimes the loops are spiraled underground to extend the overall length in a shorter area.

Where the need for length may be prohibitive to run alongside the building, large commercial buildings and schools often use vertical systems.  A series of holes four inches in diameter are drilled about 20 feet apart and 100–400 feet deep and filled with two pipes connected at the bottom to form a loop. Each loop is connected with a horizontal manifold pipe in a trench which connects to the heat pump in the building. Vertical loops are also the choice when the soil is too shallow for trenching.  This system minimizes the disturbance to existing landscaping.

If the site has an adequate water body, a pond/lake loop may be the lowest cost option where a supply line is run underground directly to the water and coiled into circles at least eight feet under the surface to prevent freezing before looping back to the building.

Open Loop Geothermal Systems

An open loop system takes surface water or a well to use as the heat exchange fluid that circulates directly through the GHP system instead of a piped fluid passing through the surface. Once circulated through the system, the water returns to the ground through the well or a discharge over the surface.

Hybrid systems using a combination of a geothermal loop underground and outdoor air (i.e., a cooling tower), are another technology option, particularly effective when cooling needs are significantly higher than heating needs. Where local geology permits, the “standing column well” is a variation of an open-loop system with one or more deep vertical wells drilled.

Whichever loop is used, it is clear the face of energy is changing and geothermal energy is beginning to play an increasing role of supply to meet the new demand.

For more information about getting geothermal heating and cooling installed in your Pittsburgh home, give Boehmer Heating & Cooling  a call today!

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