Will I Need a Horizontal or Vertical Loop Geothermal System?

November 29, 2013
Ross and Witmer

A geothermal, or ground-source, heat pump can be a highly energy efficient choice for residential and commercial heating and cooling in the Charlotte area. A geothermal system uses loops of buried tubing to take advantage of the relatively constant ground temperature a few feet below the surface. The ground loop system can be installed in horizontal trenches dug with a backhoe or trenching machine, or it can be inserted into boreholes drilled vertically beneath the property to a depth of 100 to 400 feet. Whether a horizontal loop or vertical loop system is best for your home or commercial building depends on a number of factors, including the nature of the soil beneath your property and the size of your lot.

Here is a look at the advantages and disadvantages of horizontal loops and vertical loops.

  • Surface footprint: A vertical loop system requires a much smaller surface area than a horizontal loop system. A horizontal system needs loops that are 150 to 200 feet long for each ton of heating and cooling capacity (a ton of capacity is 12,000 BTU per hour), so it requires a large amount of surface area for trenching. Vertical boreholes are typically spaced about 20 feet apart, so it is possible to install several 100- to 200-foot-long loops in a small surface area.
  • Installation cost: It is significantly cheaper to install a geothermal system with horizontal loops than one with vertical loops. Digging trenches in soft soil or clay is much easier than boring holes in hard rock.
  • Soil characteristics: If the depth to bedrock on your lot is only a few feet, you may have to install vertical loops using drilled holes to reach the zone of stable ground temperature. If the soil extends deeper than about 6 feet before it gets too rocky for trenching, it would be feasible to bury the horizontal loop system deep enough to be in a stable temperature zone.

Contact Ross & Witmer for help with your heat-pump system design, installation and maintenance. We work with homeowners and businesses in the Charlotte area and throughout central North Carolina.

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