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Abstract

Geothermal Heating and Cooling Systems provide space conditioning -- heating, cooling, and humidity control. They may also provide water heating -- either to supplement or replace conventional water heaters. Geothermal Heating and Cooling Systems work by moving heat, rather than by converting chemical energy to heat like in a furnace.

Every Geothermal Heat ing and Cooling Systems has three major subsystems or parts: a geothermal heat pump to move heat between the building and the fluid in the earth connection, an earth connection for transferring heat betwee n its fluid and the earth, and a distribution subsystem for delivering heating or cooling to the building.

Each system may also have a desuperheat er to supplement the building's water heater, or a full-demand water heater to meet all of the building's hot water needs. Geothermal Heat Pump The geothermal heat pump is packaged in a single cabinet, and includes the compressor, loop-to- refrigerant heat exchanger, and controls.

Systems that distribut e heat using ducted air also contain the air handler, duct fan, filter, refrigerant-to-air heat exchanger, and condensate removal system for air conditioning. For home installations, the geothe rmal heat pump cabinet is usually located in a basement, attic, or closet. In commercial installations, it may be hung above a suspended ceiling or installed as a self-contained console.

Distribution Subsyst em Most residential geothermal systems use conventional ductw ork to distribute hot or cold air and to provide humidity control. (A few systems use water-to-water heat pumps with one or more fan-coil units, baseboard radiators, or under-floor circulating pipes.) Properly sized, constructed, and sealed ducts are essential to maintain system efficiency.

Ducts must be well insulated and, whenever possible, located inside of the building's thermal envelope (conditioned space). Geothermal heating and cooling systems for large commercial buildings, such as schools and offices, often use a different arrangement. Multiple heat pumps (perhaps one for each classroom or office) are attached to the same earth connection by a loop inside the building. This way, each area of the building can be individually controlled.

The heat pumps on the sunny side of the building may provide cooling while those on the shady side are providing heat. This arrangement is very economical, as heat is merely being transferred from one area of the building to another, with the earth connection serving as the heat source or heat sink only for the difference between the building's heating and cooling needs.

Water Heating Many residential-sized systems installed today are equipped with desuperheaters to provide domestic hot water when the system is providing heat or air conditioning. The desuperheate r is a small auxiliary heat exchanger at the compressor outlet. It transfers excess heat from the compressed gas to a water line that circulates water to the house's hot water tank.

In summer, when the air conditioning runs frequently, a desuperheater may provide all the hot water needed by a household. It can provide four to eight gallons of hot water per ton of cooling capacity each hour it operates. A desuperheater provides less hot water during the winter, and none during the spring and fall when the system is not operating. Because the heat pump is so much more efficient than other means of water heating, manufacturers are beginning to offer "triple function," "full condensing," or "full demand" systems that use a separate heat exchanger to meet all of a household hot water needs. These units cost-effectively provide hot water as quickly as any competing system.

The water heating system that is installed in the Finger Lakes Institute is an on demand system. This system provides hot water as soon as there is a demand for it. Using this type of system eliminates the need to heat stored water like a conventional hot water tank requires