How GeoExchange^SM Systems Work

Introduction

**GeoExchange Systems (Geosource) provide space conditioning -- heating, cooling, and humidity control. They may also provide water heating -- either to supplement or replace conventional water heaters.

GeoExchange Systems work by moving heat, rather than by converting chemical energy to heat. Every Geothermal Heating and Cooling System includes three major subsystems or parts:

	Earth Connection to transfer heat between its fluid and the earth.
	Geothermal Heat Pump to move heat between the  fluid in the earth connection and the building.
	Distribution Subsystem to deliver heating or cooling to the building. GeoExchange systems may also include a ++Desuperheater to supplement the building's Water Heater, or a full-demand water heater to meet all of the building's hot water needs.

 ** GeoExchange is a Service Mark of  the GHPC
++ An extra piece of equipment used to preheat and deliver hot water

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Earth Connection

GeoExchange systems use the earth as a heat source and heat sink. A series of pipes, commonly called a "loop," carry a fluid used to connect the GeoExchange system's heat pump to the earth. Most commonly, the loops contain only water or a water and antifreeze mixture.  The technical term for this part of the system is "ground heat exchanger."

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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 distribute 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 geothermal heat pump cabinet is usually located in a basement, crawl space, attic, or closet.

In commercial installations, it may be hung above a ceiling or installed as a self-contained console, refrigerant-to-air heat exchanger, and condensate removal system for air conditioning. For home installations, the geothermal heat pump cabinet is usually located in a basement, attic, or closet.

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Distribution Subsystem

Most residential GeoExchange systems use conventional ductwork to distribute hot or cold air and to provide humidity control. Hydronic or circulating fluid systems use a special water-to-water heat pump 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).

GeoExchange 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 allows each area of the building to 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.

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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 desuperheater 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 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 "on demand" systems that use a separate heat exchanger to meet all of a household's hot water needs. This system usually involves a subsystem in the heat pump that uses GeoExchange^SM to heat the water when the main unit is not heating or cooling the building as well as when the main system is operating. These units provide cost-effective hot water heating as quickly as any competing system.

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