How Deep Are Geothermal Loops?
A geothermal heating and cooling system consists of two main components: the heat pump and the ground loop. While some people in the industry refer to the ground loop as the heat exchanger, many people simply refer to it as the loop or the loop field.
After a geothermal system has been installed for several months to a year, the grass from the drilling will have grown back a person could walk over the loop field and not even know that it exists. This is ironic considering how important of a part it plays in the geothermal system. It is the loop field that connects the geothermal heat pump to the ground and makes it the most efficient heating and cooling system available.
Many people often ask how deep the wells need to be dug for geothermal systems. The answer to this question is always, “It depends.” The reason it depends is because there are many different factors involved in the sizing of the geothermal loops, and many different designs as well. I have been to geothermal installations where the loops ranged from only six feet underground, to the 1,600 foot geothermal wells at the Peace Center in Philadelphia.
The real factor involved in how the geothermal wells are placed and the design that is chosen is driven by cost, the amount of space available, and the size needed to heat and cool a building. When there is a large amount of space available and cost is a consideration, horizontal geothermal loops may be chosen that range from six to twenty feet underground. Other than placing coils of loops in a body of water, this can be the most cost effective way to place geothermal loops. In the example of the Peace Center in Philadelphia, a large skyscraper needed to be supported by geothermal wells in a very limited space. This is where the 1,600 foot wells come in with a unique design known as standing water column.
With considerations regarding cost, the amount of space available, and the size of the system that is needed to heat and cool a building, a geothermal contractor or engineer will custom design a geothermal loop field. It is important to note that you should check to ensure that your geothermal contractor has been through a formal geothermal design or loop certification program such as IGSHPA (International Ground Source Heat Pump Association) or a certification offered through a geothermal manufacturer. For more information about the different geothermal loop designs available, feel free to refer to the Outdoor Portion section under Geothermal 101 on this site.