New ARI Standard Published for Testing and Rating Direct-Exchange Geothermal Heat Pump

January 14, 2000


D/X Installations Gaining Momentum with Passage of New Standard

NEW YORK, NY— Direct-exchange geothermal heating and cooling systems have been around for more than a decade. However installations are likely to increase significantly now that the Air Conditioning and Refrigeration Institute (ARI) has approved a new standard for such systems. The new standard establishes definitions and requirements for testing and rating direct geoexchange heat pumps. The recent approval of ARI 870: Direct Geoexchange Heat Pumps means that direct-exchange systems will be independently tested and monitored to meet strict operating and safety requirements. Ultimately the test data and rating information that result from the new ARI standard will allow meaningful comparisons of direct geoexchange system performance data with those of other heating and cooling systems.

Copper Tube is Key to Success of D/X GCH Systems
Direct-exchange geothermal systems use the earth as an energy reservoir, taking advantage of the constant temperature (about 55°F) 4 feet below the surface. Copper tubes run underground carry refrigerant that circulates into and out of a home. A compressor induces heat exchange, and heated or cooled air is distributed through an air handler.

The heat-transfer medium in geothermal systems always enters a home at the ambient below-grade temperature, unlike other systems in which the heat-transfer medium is exposed to much hotter or colder outside air temperatures. Once the refrigerant reaches the heat pump, which is situated inside the home, the compressor concentrates and delivers the heat.

To increase efficiency further in the air-conditioning season, waste heat can be transferred to the water heater. Research indicates that geothermal systems reduce heating and cooling costs by an average of 30 to 60 percent when compared to air-source heat pumps.

Direct-exchange geothermal heating and cooling systems are generally regarded as energy efficient and inexpensive to operate because they burn no fuel and consume no energy beyond the electricity required to operate the compressor and the fan used to circulate the air.

Benefits of D/X Systems vs. Water-based Geothermal Systems
What sets direct-exchange systems apart from other geothermal systems is the fact that only one transfer is required for heat exchange, compared to the two steps required in water-based systems. The copper tube used in direct-exchange systems is an excellent heat conductor-much more efficient than the plastic tubes used in water-based systems. This conductivity enables copper systems to work more efficiently and with smaller-diameter tubes than those used in plastic systems, so bore holes are smaller, reducing excavation and installation costs.

Manufacturers of direct-geoexchange heat pumps include: ECR Technologies, Inc., P.O. Box 3271, Lakeland, Fl 33802, phone: (941) 688-0880, and American Geothermal DX TM, 1037 Old Salem Road, Murfreesboro, Tennessee 37129-4936, phone: (615) 890-6985.

[Note: Further information and a case study documenting the installation of a direct-exchange geothermal heat-pump system at a Pennsylvania home site can be viewed by visiting the our Heat Pump section. Photos of the installation can be obtained by calling either of the contacts listed on the first page of this release.]


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