PATH - A Public Private Partnership for Advancing Housing Technology

PATH Case Study

Rising Fuel Costs Power Geothermal Heat Pumps


Continued from Page 2


A GHP system consists of indoor heat pump equipment, a vertical or horizontal ground loop, and a flow center to connect indoor and outdoor equipment.

GHPs are appropriate for retrofit or new homes and can be used for virtually any size home in any region, provided the site has enough room to allow installation of a vertical well or horizontal ground loop.

Ground loops can be installed in a vertical boring or a horizontal trench. Vertical boring holes are usually more expensive and used where limited property is available, and there isn't enough space to run horizontal loops.

Read a PATH Field Evaluation:

Carl Franklin Homes: The Vista at Kensington Park, Dallas, TX


This project included the following PATH-profiled technologies:

[IMAGE: A homeowner in Colorado shows off his geothermal heat pump. Photo courtesy of the U.S. Department of Energy's Office of Energy Efficiency and Renewable Energy.] "In a retrofit project such as this, you also have to be concerned with the duct system. It is almost never practical to tear out and re-duct a house. It wouldn't be economically feasible. For as long as we've been doing this in retrofits, we've come across old or small duct systems where you would like a lot of heating capacity, but you don't have a lot of airflow capacity available to install a large cooling unit."

"We then have to match our GHP system to how much airflow the duct system can handle. We solve this problem with a two-speed system. You have the flexibility to push a little bit more heating or cooling when it's needed, even though the ducts aren't perfectly sized for the larger load. The system spends most of its time operating at a low speed that the ducts are sized for. That's the beauty of the two-speed: it's like having two units in one."

"On the cooling side, we are required to have a minimum SEER (seasonal energy efficiency ratio) of 13 in Wisconsin," Green says. "With the two-speed unit in her home, the heat pumps run at high speed around 18 SEER, while at low speed they run at about 25 SEER, which is nearly double the state requirement. With any of our geothermal units, the SEER ratings are right off the charts. This is what draws many customers to us in the first place. And with increasing fuel costs, we expect more and more interest."

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Content updated on 9/25/2006

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