Geothermal heat pumps:
Parts of the system

Q: What are the components of a geothermal heat-pump system?
A: The three main parts are the heat-pump unit, the liquid heat-exchange medium (open or closed loop), and the air-delivery system (ductwork).

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Q: Are all geothermal heat pumps alike?
A: No. There are different kinds of geothermal heat pumps designed for specific applications. Many geothermal heat pumps, for example, are intended for use only with higher temperature ground water encountered in open-loop systems. Others will operate at entering water temperatures as low as 25 degrees F which are possible in closed-loop systems.

Most geothermal heat pumps provide summer air conditioning, but a few brands are designed only for winter heating. Sometimes these heating-only systems incorporate a groundwater-cooled coil that can provide cooling in moderate climates.

Geothermal heat pumps can also differ in the way they are designed. Self-contained units combine the blower, compressor, heat exchanger and coil in a single cabinet. Split systems allow the coil to be added to a forced-air furnace and utilize the existing blower.

Q: Will I have to add insulation to my home if I install one of these systems?
A: Geothermal heat pumps will reduce your heating and cooling costs regardless of how well your home is insulated. However, insulating and weatherizing are key factors in realizing the most savings from any type of heating and cooling system.

The illustration below shows typical insulating standards suggested by many electric utilities. You may wish to contact your utility for recommendations on your home.

Q: Can a geothermal heat pump also heat water for my home?
A: Yes. Using what's called a desuperheater, some types of geothermal heat pumps can save you up to 50 percent on your water-heating bill by pre-heating tank water. Desuperheaters are standard on some units, optional on others. Some geothermal models can provide all of your hot water needs on demand at the same high efficiencies as the heating/cooling cycles.

Q: Is a geothermal beat pump difficult to install?
A: Most units are easy to install, especially when they are replacing another forced-air system. They can be installed in areas unsuitable for fossil fuel furnaces because there is no combustion, thus, no need to vent exhaust gases.

Ductwork must be installed in homes that don't have an existing air distribution system. The difficulty of installing ductwork will vary and should be assessed by a contractor.

Q: Can a geothermal heat pump be added to my fossil fuel furnace?
A: Split systems can easily be added to existing furnaces for those wishing to have a dual-fuel heating system. Dual-fuel systems use the heat pump as the main heating source and a fossil fuel furnace as a supplement in extremely cold weather if additional heat is needed.

Q: I have ductwork, but will it work with this system?
A: In all probability, yes. Your installing contractor should be able to determine ductwork requirements and any minor modifications, if needed.

Q: Do I need to increase the size of my electric service?
A: Geothermal heat pumps don't use large amounts of resistance heat, so your existing service may be adequate. Generally, a 200-amp service will have enough capacity, and smaller amp services may be large enough in some cases. Your electric utility or contractor can determine your service needs.

Q: Should I buy a beat pump large enough to heat my home with no supplemental heat?
A: Your contractor should provide a heating and cooling load calculation (heat loss, heat gain) to guide your equipment selection. Geothermal heat pumps are sized to meet your cooling requirements. Depending on your heating needs, a geothermal heat pump will supply 80-100 percent of your design heating load. Sizing the heat pump to handle your entire heating needs may result in slightly lower heating costs, but the savings may not offset the added cost of the larger heat-pump unit. Also, an oversized unit can cause dehumidification problems in the cooling mode, resulting in a loss of summer comfort.

Q: Do geothermal heat pumps have outdoor units?
A: No. The equipment goes inside your home, usually in the basement, garage or crawl space. Because it's indoors, the lifespans of the compressor and major components are greatly extended, most having a lifespan of 20 years or more.