EQUIPMENT

The foundation of any GHP system is the heat pump unit itself. The most commonly used unit in these systems is the single package water-to-air heat pump. All of the components are contained in a single enclosure, about the size of a small gas furnace.

The unit includes a refrigerant-to-water heat exchanger, refrigerant piping and control value, compressor, air coil (heats in winter; cools and dehumidifies in summer), fan and controls (Figure 2).

The single package design is a major advantage over the so-called "split" system used for air- ource heat pumps (ASHP). The lack of an outside unit reduces the amount of refrigerant required and the potential for leaks--a major enhancement to reliability.

Virtually all GHP units use refrigerant R-22, an HCFC. R-22 is considered a transition refrigerant and has a ODP (ozone depletion value) of 0.05--only 5% of the most damaging refrigerants R-11 and R-12. R-22 is not scheduled for phase out until 2030.

Domestic hot water heating capability can be added to most equipment. The components are installed in the cabinet by some manufacturers and supplied as a small add-on cabinet by others. The domestic hot water heating components consist of a refrigerant-to-water heat exchanger and a small circulating pump. Field installed piping connects this unit to your domestic hot water heater.

High efficiency equipment generally contains a high efficiency compressor, larger air coil, higher efficiency fan motor, and sometimes, a larger refrigerant-to-water heat exchanger.

Manufacturers also offer split systems, water-to-water heat pumps, multi-speed compressors, dual compressor, and rooftop versions of this equipment to suit various applications.