How deep are the pipes of a ground-source heat pump?

Q:
How deep are the pipes of a ground-source heat pump?

A:

When geothermal lines are installed in the ground they are usually placed at a depth of about 8 feet. At 8 feet the temperature of the ground stays fairly consistent all year around. The frost in the ground usually doesn’t penetrate more than 4 feet into the ground, at a depth of 8 feet you do not have to worry about the lines ever freezing. Also when you are using the geothermal lines in the summer for air conditioning the ground at the 8 foot depth stays cool no matter how hot it gets at the surface.

There is also drilled well geothermal installations. This is where several vertical wells are drilled into the ground; the depth of the wells depends on the size of the system that you are installing. Installing a vertical system allows you to have geothermal heating on a smaller foot print and access to a larger source of cool or warm earth. This is ideal for in-town use or small country lots.

The third way to install geothermal lines is to install them into an existing pond or large body of water like a lake or a large river. These lines are weighted down so that they sit at the bottom where the temperature of the water never changes from summer to winter. Being at or near the bottom allows for boat traffic to drive over the area without effecting them.

More important than the depth of the geothermal piping is the amount of water that is in the ground at that level. The more water you have where the lines are buried the more heat exchange you can have. The lines absorb the temperature from the soil surrounding the pipes; water replaces that warm or cold when it is absorbed by the piping. The more water the more constant the temperature is around the buried geothermal lines.

Rob Abbott
Operations Manager
Village Builders Inc.