Geothermal - Frequently Asked Questions Return to Geothermal products

 
 

How does a geothermal heating and cooling system work?

Outdoor temperatures fluctuate with the changing seasons but underground temperatures don't. Four to six feet below the earth's surface, temperatures remain relatively constant year-round. A geothermal system, which typically consists of an indoor unit and a buried earth loop, capitalizes on these constant temperatures to provide "free" energy. In winter, fluid circulating through the system's earth loop absorbs stored heat and carries it indoors. The indoor unit compresses the heat to a higher temperature and distributes it throughout the building. In summer, the system reverses, pulling heat from the building, carrying it through the earth loop and depositing it in the cooler earth.

What makes a geothermal system different from ordinary systems?

Unlike ordinary systems, geothermal systems do not burn fossil fuel to generate heat; they simply transfer heat to and from the earth to provide a more efficient, affordable and environmentally friendly method of heating and cooling. Typically, electric power is used only to operate the unit's fan, compressor and pump.

What are the components of a geothermal system?

The three main parts consist of the heat-pump unit, the liquid heat-exchange medium (open or closed loop), and the air-delivery system (ductwork).

How efficient is a geothermal system?

A geothermal system is three to four times more efficient than the most efficient ordinary system. Because geothermal systems do not burn fossil fuels to make heat, they provide three to four units of energy for every one unit used to power the system.

Do geothermal systems require much maintenance?

No. Geothermal systems are virtually maintenance free. When installed properly, the buried loop will last for generations. And the other half of the operation—the unit's fan, compressor and pump—is housed indoors, protected from the harsh weather conditions. Usually, periodic checks and filter changes are the only required maintenance. (Note: WaterFurnace has developed a geothermal unit—the ES Split—that is so rugged and quiet, it can be placed outdoors when that's the best solution).

What does geothermal mean for the environment?

Geothermal systems work with nature, not against it. They emit no greenhouse gases, which have been linked to global warming, acid rain and other environmental hazards. WaterFurnace provides an earth-loop antifreeze which will not harm the environment in the unlikely event of a leak. And much of the WaterFurnace product line uses R-410A, a performance-enhancing refrigerant that will not harm the earth's ozone layer.

Can a geothermal heat pump be added to my fossil fuel furnace?

Split systems easily can be added to existing furnaces for those wishing to have a dual-fuel heating system. Dual-fuel systems use the heat pump as the main heating source and a fossil fuel furnace as a supplement in extremely cold weather if additional heat is needed.

Is a geothermal heat pump difficult to install?

Most units are easy to install, particularly when they replace another forced-air system. They can be installed in areas unsuitable for fossil fuel furnaces because there is no combustion, thus no need to vent exhaust gases. Ductwork must be installed in homes that don't have an existing air distribution system. The difficulty of installing ductwork will vary and should be assessed by a contractor. Another popular way to use geothermal technology is with in-floor radiant heating, in which hot water circulating through pipes under the floor heats the room.

I have ductwork, but will it work with this system?

In all probability, yes. Your installing contractor should be able to determine ductwork requirements and any minor modifications if needed.

Do I need to increase the size of my electric service?

Geothermal heat pumps don't use large amounts of resistance heat so your existing service may be adequate. Generally, a 200-amp service will have enough capacity and smaller amp services may be large enough in some cases. Your electric utility or contractor can determine your service needs.

Should I buy a geothermal heat pump large enough to heat without any supplemental heat?

Your contractor should provide a heating and cooling load calculation (heat loss, heat gain) to guide your equipment selection. Geothermal heat pumps typically are sized to meet your cooling requirements. Depending on your heating needs, a geothermal heat pump will supply 80-100 percent of your design heating load. Sizing the heat pump to handle your entire heating needs may result in slightly lower heating costs, but the savings may not offset the added cost of the larger heat pump unit and larger loop installation. Also, an oversized unit can cause dehumidification problems in the cooling mode, resulting in a loss of summer comfort.

How long is the payback period for a geothermal system?

To figure this accurately, you must know how much you'll save each year in energy costs with a geothermal system as well as the price difference between it and an ordinary heating system and central air conditioner. As an example: If you'll save $700 per year with a geothermal system and the price difference is $2,000, your payback will be less than three years. If you install a geothermal system in a new home, the monthly savings in operating costs generally will offset the additional monthly cost in the mortgage, resulting in an immediate positive cash flow.

Can a geothermal system also heat water?

Yes. Some geothermal heat pumps can provide all of your hot water needs on demand at the same high efficiencies as the heating/cooling cycles. An option called a desuperheater can be added to most heat pumps. It will provide significant savings by heating water before it enters your hot water tank.

Do I need separate earth loops for heating and cooling?

No. The same loop works for both. To switch heating to cooling, or vice versa, the flow of heat is simply reversed.

What if I don't have room for a horizontal loop?

Closed loop systems also can be vertical. Holes are bored up to 250 feet per ton of heat pump capacity, depending on where you live. U-shaped loops of pipe are inserted in the holes. The holes are then backfilled with a sealing solution.

How long will the loop pipe last?

Closed loop systems should be installed using only high-density polyethylene pipe. Properly installed, these pipes will last for many decades. They are inert to chemicals normally found in soil and have good heat conducting properties. PVC pipe should never be used.

How deep and long will my trenches be?

Trenches are normally four to six feet deep and up to 400 feet long, depending on the number of pipes in a trench. One advantage of a horizontal loop system is being able to lay the trenches according to the shape of the land. As a rule of thumb, 500-600 feet of pipe is required per ton of system capacity. A well-insulated 2,000-square-foot home would need about a three-ton system with 1,500-1,800 feet of pipe.

Will an earth loop affect my lawn or landscape?

No. Research has proven that loops have no adverse effect on grass, trees, or shrubs. Most horizontal loop installations use trenches about 24 inches wide. This, of course, will initially leave temporary bare areas, but they can easily be restored with grass seed or sod. Vertical loops require little space and result in minimal lawn damage.