Home Improvement : Tap Into Earth to Heat, Cool House

QUESTION: I need to replace my old central air conditioner. Are the new super-efficient geothermal heat pumps, that use the energy in the earth to cool and heat a house, very efficient and how do they work?

ANSWER: Geothermal heat pumps (often called ground-source or ground-coupled) are one of the most efficient central air-conditioning and heating systems available. Compared to your old air conditioner, a geothermal heat pump can cut your air-conditioning costs as much as 50%.

They are also very efficient for heating in the winter. Using the earth as the source of heat, a geothermal heat pump can provide 4 BTUs of heat for each 1 BTU you pay for on your electric bill. In cold climates, it can eliminate the need or greatly reduce the use of the backup heating units.

The new super-high-efficiency geothermal heat pumps use the newest technologies. Some use scroll compressors that are very quiet and reliable. Others use multi- and variable-speed blowers to better control heating and cooling for improved comfort.

You can also get a desuperheater option to produce free hot water in the summer.

Ground temperature stays fairly constant year-round (from 50 to 75 degrees F) depending on your area. It is much more efficient to pump the heat from inside your house to the 55-degree ground than to the 90-degree outdoor summer air. In the winter, it is easier for the heat pump to draw heat from the warm ground than from the cold outdoor air.

There are several methods to use the earth as a heat source (winter) or heat sink (summer). If you have a lake or well nearby, the constant-temperature water can be circulated directly through the heat pump.

Another method uses a geothermal closed-loop pipe filled with a water and antifreeze solution. This heat exchange solution flows through small plastic pipes buried in the ground. There, it either gives off heat in the summer or absorbs it in the winter.

These pipes can be buried horizontally or vertically in the ground. For horizontal pipes, the several-foot-deep trench need only be six inches wide. Little damage is done to your landscaping during installation.

Since a geothermal heat pump transfers heat with lake or well water or the heat-exchange solution, it can be located entirely inside your house. It does not need a noisy condenser fan as on standard air conditioners or heat pumps. This also is an advantage for servicing and reduces the chance of damage and corrosion.

You can write to me at the address below for Utility Bills Update No. 388 showing a list of names, addresses and telephone numbers for manufacturers of super-high-efficiency geothermal heat pumps and specifications on several models. Please include $1 and a self-addressed stamped business-size envelope.

Geothermal Heat Pump

While it is one of the quietest and most efficient air conditioners on the market, the geothermal heat pump can be located indoors and protected from vandalism and weather elements.

Evaporator coils Geothermal water heat exchanger High-efficiency compressor