Geo-Xergy Systems Inc.

Ground-coupled heat exchanger (GHX)

A GHX is underground piping that is in contact with the earth in order to store or retrieve energy. These are either closed or open loop underground piping systems.

Closed loops

Closed loops are sealed pipes buried underground which use environmentally friendly solution to carry energy in or out of the heat pump system inside the building. Closed loops are very reliable and require low maintenance. The required amount of piping depends on the characteristics of the building.

There are three types of closed loop systems:

  • Horizontal loops (and slinky)
  • Vertical loops
  • Pond/lake loops

GHX_v006-02Horizontal loops

  • Used when there is land space available; typically in rural or new construction areas.
  • These shallow systems generally found within the first 20 to 40 feet below the earth’s surface. They can be installed in two different ways:
    • digging a trench and then covering the piping with the earth
    • using a horizontal pipe drilling machine to drill a network of pipes underground at one end of a field and then re-emerge to the surface at the other end of the field. The exposed ends are then fused together and buried underground. This method sees very little disruption to the siteGHX_v006-01.
  • If more piping is needed but there is limited space, the pipes can be coiled horizontally, like a “slinky”.

Vertical loops

  • Used when there is limited space; mainly for commercial buildings and small residential spaces.
  • Vertical drilling of piping can be anywhere from 50-600 ft in depth, depending on the amount of piping needed, as well as the type of soil/rock (geological make-up) of the area.


Pond/lake loops

  • Used when a building is near a pond, lake or ocean.
  • Piping is typically run horizontally underground to the water source, where it is then coiled and submerged in sections under the water.


Open loops

  • Open loops are sealed pipes buried underground which carry water from a well (aquifer), transferring heat to or from the heat pump system inside the building. Once the energy is exchanged, the water leaves the building and goes into the same aquifer through a second well.

Putting it all together

This four-minute video shows you how ground source energy works with different types of loop systems: