Geothermal heat pumps consist of three or four main components. In a three-piece configuration you have the ground heat exchanger loop, the indoor unit (which contains the compressor section in the air handling device) and the ductwork.
In a four-piece configuration, you have the ground heat exchanger loop, a compressor section, an air handler and ductwork. There are two basic heat exchanger ground loop fields. Both have the same purpose – to extract heat from the ground or to expel heat into the Earth.
One type, called water source, uses water pumps, refrigerant-to-water heat exchangers and tubing buried in the ground. The other type, called direct geoexchange, places the copper refrigerant typing directly into the ground.
The direct exchange type is the more efficient heat transfer method. In the water-source setup, the water has to go through pumps, poly-tubing and a refrigerant-to-water heat exchanger to exchange heat. The efficient method of heat transfer employed by the direct geoexchange geothermal heat pumps means the system requires a smaller heat exchanger loop field.