The Geothermal Process

The geothermal process is based on a simple premise: The earth below the frost line – usually about four feet deep – is a constant temperature of about 50 degrees all year long.

During the winter, a geothermal heat pump absorbs heat from the ground and uses it to warm the air in your home. In the warmer summer months, the process is reversed, taking heat from your home and transferring it back into the ground.

The loops of piping are buried in the ground near your home or business, either vertically or horizontally. That ground loop is connected to a pumping module inside your home.

The pump circulates a mixture of water and the antifreeze through the ground loop, where it absorbs heat from the earth. When the heated liquid reaches the heat pump inside your home, the heat is multiplied and used to warm the air inside the air-handling system. A blower sends the warmed air throughout the building through ductwork. To cool your home or business during the summer, the system simply works in reverse with the flip of a switch on your thermostat.

During the summer, a reversing valve switches the indoor coil to act as the "evaporator" and the underground pipes to act as the condenser.

In addition to the primary equipment, other components are integral, including:

Not all geo systems are alike - most provide summer air conditioning, but some models are designed only for winter heating.

Geothermal heat pumps also can be different in the way they're designed. Self-contained units combine the blower, compressor, heat exchanger and coil in a single cabinet.

All components of a geothermal system - except the underground loops - are placed inside a building, usually in the basement, garage or crawl space. Because they're indoors, the compressor and other vital parts are protected, with most having a life span of 20 years or more.

In most cases, installation of a geothermal system is easy, especially when it's replacing another forced-air system. It can be installed in locations unsuitable for natural gas or propane furnaces - there is no combustion, and thus no need to vent exhaust gases.

In fact, geothermal components can be added to existing heating equipment for those wishing to have a dual-fuel system. A conventional furnace can be kept as a backup in extremely cold weather if additional heat is needed.

A standard 200-amp electrical service will have more than enough capacity to power a geothermal heat pump. Your contractor should contact an electrical expert to determine proper distribution loading.

If you're replacing a forced-air system, a geo system can use the existing ductwork. If you currently have a boiler system with radiators, the conversion will be more complex.

Like any other heating and cooling system, good maintenance is a key part of getting the most value for your energy dollar. Checking the system periodically and having it professionally inspected regularly will help ensure that it stays in peak operating condition.

The first step is to read through the owner's manual. It's important to be able to identify key parts and how they work.

Your contractor will show you how to do simple maintenance on your geothermal heat pump, which might include:

Have the whole system checked by a service technician once a year. This should include a visual inspection, refrigerant leak test, evaporator coil cleaning, and a check of the compressor, fan and pump motors. The technician will record operating data in a logbook so a deteriorating condition can be detected easily.

Rarely, a geothermal system may need emergency service. The most common cause of emergency service calls is electrical problems.

Lyle Sell is a licensed Pennsylvania Real Estate Salesperson, License #: RS210676L