He noted that the architect and engineer on the project were opposed to geothermal at first, but it has worked well and “They are now believers in the technology.”

Vanderford asserted that geo-thermal heat pumps are an easier retrofit compared to installing rooftop units and they are more energy efficient. They also reduce greenhouse gas emissions, he said.

He also maintained that a geothermal system does not have to cost more. “You just have to design it right,” he said.

A Sure Thing

Chris Pamplin, sales and marketing manager, American Geo-thermal DX, Murfreesboro, TN, gave a presentation on “Direct GeoExchange — Horizontal and Vertical Ground Coil Test Results in Retrofit Applications.”

Pamplin explained that, instead of a glycol/water-filled ground coil, a Direct Geo-Exchange (DX) system uses a refrigerant coil made of copper tubing that is buried in the ground. So, rather than transferring energy from a glycol/water coil to a refrigerant coil in the heat pump unit, the DX system’s refrigerant coil gets energy directly from the earth.

In two residential DX test installations, both Knoxville, TN, houses showed “significant im-provement over air-to-air heat pumps,” said Pamplin.

The two homes were monitored by the University of Tennessee in collaboration with Virginia Power, Tennessee Valley Authority, Copper Development Association, American Geother-mal, and Oak Ridge National Laboratory.

The first house was a 1,200-sq-ft ranch-style home with a 2-ton DX system using a horizontal loop. It was determined that the house had a heating COP (coefficient of performance) of 3.6. That means that for every one unit of electricity, it delivers 3.6 times that amount of heating energy. The cooling COP was 2.8.

The second home was also a 1,200-sq-ft ranch home with a 2-ton system, this time using a vertical loop. Here the heating COP was 3.0 because this system had less coil in the ground. The cooling COP was again about 2.8.

Traditional air-to-air heat pumps for this area are measured at approximately 2.0 for heating, while for cooling they average about 2.9.

Although air-to-air units do slightly better for cooling, DX systems do much better for heating. Overall, DX technology only uses about 70% as much electricity as traditional heat pumps.

Pamplin said that the DX units provide consistent performance year to year, and no auxiliary heat was needed. “It never came on during the test period,” he said.

Bottom-Line Benefit

Mike Housh, owner, Mike Housh Heating and Air Conditioning, Middletown, OH, followed and described his experience with geothermal systems. He stated that he has installed a total of 4,000 tons of capacity over the last 10 years. “I believe DX is the future of residential Geo-Exchange,” said Housh.

DX advantages, he said, include higher conductivity, more Btu/sq ft, and lower cost. It’s also contractor friendly, he maintained.

Disadvantages include: corrosion potential depending on soil conditions; use of R-22; no major manufacturer; ground dehydration (it can dry out the ground); and lack of market awareness.

Phil Schoen, president and ceo, Geo-Enterprises, Inc., Tulsa, OK, which specializes in the design and application of geothermal systems, then covered “Using Ground-Source Heat Pumps in Radiant Panel Installations.”

He said that he started using radiant heating six to seven years ago. “It’s a great product for warehousing,” Schoen remarked. He has also used it for upscale housing.

PEX tubing sizes that he uses range from ½ to 1 in. Hydronic considerations include:

Radiant floor heating, he said, should not be put under kitchen islands, refrigerators, freezers, or any permanent structure. And he suggested using a higher temperature for the bathroom floor, because when people get out of the shower, “They like it toasty.”

Publication date: 08/27/2001