GHPs operate on the same principle as a refrigerator. There is a cooling mode, and hot water is produced when the pump is in operation. The pump interacts with the ground instead of an air source. It uses a set of pipes or loops buried in the ground. Other components of a GHP include the indoor heat pump equipment and flow unit to connect indoor and outdoor equipment. The indoor unit of the pump is typically called an air handler, with a blower and filter as with a regular air conditioner. Heated and cooled air enters the home evenly through ductwork and the blower.
Most commonly used geothermal heat pumps are closed loop systems, such as horizontal pumps, which are typically used in homes. In this type of system, there is a system of pipes buried in the ground. The heat transferred is captured in this closed pipe system. Trenches for a horizontal GHP must be at least four feet deep. One pipe is buried at six feet and the other at four feet. The two pipes may also be placed side-by-side at five feet.
Open loop GHPs can use a lake, pond or another body of water. The body of water is the heat transfer fluid, and water is pumped into a heat exchange pump. A supply line is run underground from the building or home to water. The supply line is coiled into circles eight feet under the surface to prevent freezing. Coils have to be placed in water bodies that meet minimum volume, depth and quality requirements.