Abstract: A heat and cooling system having an indoor air coil subcircuit, an outdoor air coil subcircuit, a geothermal subcircuit, and a control system for selectively operating the system in air-to-air heating, air-to-air cooling, geothermal heating, air-to-air defrost (optionally) and geothermal defrost modes. The various subcircuits may be connected to one another in parallel. The heating and cooling system may include a control system that permits refrigerant to be selectively routed through any two of the heat exchangers to provide the various modes of operation. In one embodiment, the control system may generally include a circuit having a single reversing valve, a plurality of check valves, a plurality of solenoid valves and a plurality of expansion devices.

Abstract: A heat pump system having a defrost subcircuit that draws heat from a geothermal heat source. The defrost subcircuit is connected to the outdoor air coil in parallel with the indoor coil. The system includes a control mechanism for selectively circulating refrigerant through the defrost subcircuit but not the indoor air coil during the defrost mode. The heat pump system further includes components which permit the defrost subcircuit to be pumped down when the system leaves the defrost mode.

Abstract: A geothermal subcircuit for use with a conventional air conditioning unit. The subcircuit includes a geothermal heat exchanger that is buried in the ground or submerged in a lake, river, well or geothermal heat sink. The geothermal subcircuit is connected with the geothermal heat exchanger in parallel with the outdoor air coil. The control mechanism operates to selectively move refrigerant through the outdoor air coil during the cooling mode or through the geothermal heat exchanger during the heating mode.