Is it possible to use earth loops that are longer than 100 feet?
Except for horizontal loop systems, the maximum is 100 feet of earth loop length. Refrigerant flowing through the system must maintain a certain minimum velocity in order to entrain and return the compressor lubricating oil to the compressor. A loop length greater than 100 feet results in an excessive pressure drop and reduction in flow velocity. In the cooling mode, the hot refrigerant gas condenses into a liquid as it gives up its heat to the earth. To return that vertical column of liquid to the heat pump would require an auxiliary pump.
