Geothermal heat pump nets savings, comfort

Dear Jim: I should replace my old heating and cooling system with a more efficient one. Is installing a geothermal heat pump wise and what types are best? Shel K.

Dear Shel: Making the significant investment in installing a geothermal heat pump does make sense. Keep in mind, a geothermal heat pump also becomes the most efficient central air-conditioning system during summer and provides free water heating.

I just replaced my old heat pump with a WaterFurnace 7-Series geothermal heat pump in my own home. Even though the overall installed cost is higher than other systems, it will pay back its cost in savings and the comfort level is excellent. Also, if one is installed by 2016, there is a 30 percent federal tax credit on the total cost.

I chose this WaterFurnace model because of its super-high heating and cooling efficiencies. It has a heating efficiency COP (coefficient of performance) of 5.3. Using the constant temperature underground, it produces more than $5 worth of heat for each $1 on my utility bill.

When cooling during summer, the energy efficiency ratio, known as EER, is as high as 41. This is more than twice as efficient as the best new standard heat pumps and central air conditioners. Instead of the heat from the house being exhausted through the outdoor condenser unit, it goes into the water heater for free heat.

For most homes, several 5-inch diameter holes are drilled about 150 feet deep for the tubing to use the earths heat. This is called a vertical loop. I have a large backyard, so I installed a long horizontal, 5-foot-deep loop. The loop replaces the outdoor condenser unit so there is no noise to bother neighbors. The indoor compressor is quiet.

The 7-Series model, because it uses a special variable-output compressor, fine tunes the heating and cooling output to the instantaneous needs of the house. This is the most expensive system design, but it provides the best savings and year-round comfort. The installation cost of the ground loop is the same no matter what geothermal system you install.

By constantly varying the output, it runs in more efficient slower, quieter cycles and the air from the register feels hot. A common complaint for standard heat pumps is it never feels warm.

The energy-guzzling backup resistance heating seldom, if ever, comes on. During very hot weather, the compressor can run in super-cooling mode to produce an extra 20 percent output.

The next step down in comfort and efficiency is a model with a two-stage compressor. Most of the time, it runs at the lower-output speed. When it cannot heat or cool your house to the thermostat setting, it automatically switches to the higher speed for more output. Its energy efficiency ratio is as high as 30.

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Geothermal heat pump nets savings, comfort