The ground lends itself particularly well to be the thermal source from which to subtract or to which to yield the heat necessary to operate a machine in reverse cycle operating respectively as a heat pump or as a chiller. This action can be carried out by removing or releasing heat directly to the land mass itself. This technique is widely used in many European and non-European countries. The research work consists in the characterization of horizontal probes in "slinky" configuration as the geometry of the probe and the operating conditions change, the depth of laying in the ground.