Conscious Choice: Heat Pumps

May 2001 | Sensible Home

Heat Pumps

by James Dulley

Dear Jim: We have a gas furnace with central air-conditioning, and my son has an all-electric house. He is planning to install a super-efficient geothermal heat pump. Would this make sense for my home too? — Paul G.

Dear Paul: When people hear the word heat pump, they often think heat pumps are only for all-electric homes. With rising costs of natural gas, propane, and oil, geo- thermal heat pumps may be a money-saving option for any home. They produce warmer, more comfortable air than standard air-type heat pumps.

A geothermal heat pump both heats and cools your home like an air-type one, but that is where the similarities end. It pulls free heat from the earth for super-high efficiencies. For example, with a coefficient of performance (COP) of 4, it produces an extra $3 of free heat for each $1 on your utility bills.

In the summer, the savings can be as high as 60 percent. Some models have efficiencies as high as 22, as compared to your old air conditioner at about 8. The dehumidification is also better for improved indoor air quality.

In the air-conditioning mode, most geothermal heat pumps use the heat from your house to heat your hot water for free, instead of exhausting it outdoors. The newest models use ozone-friendly R410A refrigerant instead of freon.

Geothermal heat pumps are so efficient because they use the ground as the source of heat in the winter; and in the summer, they deposit heat to the ground. Since the ground temperature, several feet below the surface, stays relatively constant, the heat pump requires less electricity to heat and cool.

Even though it feels cold outdoors when it is 30 degrees, there is still energy in the air that a standard heat pump can "pump" into your house. At the same time, the ground temperature may be 55 degrees. It makes sense that it is easier to pull heat from 55-degree ground than from 35-degree air.

To install a system, a small pipe is placed in a narrow trench in your yard. (Vertical holes can be used instead.) A solution runs through the pipe that is connected to a heat exchanger in the heat pump. Another efficient design (DX) uses copper tubing with the refrigerant running directly through it.

Since a noisy outdoor condenser fan is not needed, most geothermal units are located entirely inside your house. There are designs to fit utility rooms, basements, or attics. This makes servicing them easier. New outdoor units are also available if you plan to keep your gas furnace.

For ultimate comfort and efficiency, select a two-stage model with a variable-speed blower. This allows it to constantly fine-tune the heating and cooling (and electricity usage) to the varying needs throughout the day.

Write for (or instantly download) Update Bulletin No. 644, buyer’s guide of thirteen single/two-stage geothermal heat pump manufacturers listing efficiencies, heat/cool outputs, features, fuel cost comparison chart, and ground loop details. Please include $3.00 and a business-size SASE. James Dulley, Conscious Choice, 6906 Royalgreen Dr., Cincinnati, OH 45244.

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