Residential Geothermal Heat Pump FAQ

A water/ethanol solution is piped through polyethylene loops to collect the earth's natural heat, which is circulated to a heat exchanger that reacts with a refrigerant to create more heat (like your refrigerator in reverse). The loops can be inserted in vertical boreholes, laid in horizontal trenches or sunk in a pond or lake. This heat is distributed to your home through existing ductwork or an in-floor radiant tubing system.

Why is it considered so environmentally friendly?

Nontoxic fluids are used in geothermal systems. Geothermal works with nature, not against it like conventional systems, so it reduces the threats of acid rain, air pollution and the greenhouse effect.

Are there other advantages to residential geothermal?

There are no noisy "on" cycles with blasts of hot or cold air, and no fluctuations in temperature. There are no flues or chimneys and no carbon monoxide concerns and no noisy outdoor units. Household costs are also reduced by partially heating your hot water supply. Above all else, geothermal systems are the most environmentally friendly available on the market today!

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What does a residential geothermal system cost to operate?

The incredible efficiency of geothermal energy make the systems highly cost-effective. Energy is coming from the ground and your only costs are for the electricity to run the heat pump, compressor and fan. Homes converting to a geothermal system from oil or electric resistance will cut about 70% off its yearly heating and cooling costs and as much as 80% when switching from propane.

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.

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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 residential geothermal system?

A residential 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.

Is the efficiency rating actual or just a manufacturer's average?

All heating and cooling systems have a rated efficiency from a U.S. governmental agency. Fossil fuel furnaces have a percentage efficiency rating. Natural gas, propane and fuel oil furnaces have efficiency ratings based on laboratory conditions. To get an accurate installed efficiency rating, factors such as flue gas heat losses and cycling losses caused by oversizing, blower fan electrical usage, etc., must be included.

Geothermal heat pumps, as well as all other types of heat pumps, have efficiencies rated according to their coefficient of performance or COP. It's a scientific way of determining how much energy the system produces versus how much it uses. Most geothermal heat pump systems have COPs of 3-4.5 (WaterFurnace's E Series is rated up to 4.7). That means for every one unit of energy used to power the system, 3-4.5 units are supplied as heat. Where a fossil fuel furnace may be 78-90% efficient, a geothermal heat pump is about 400% efficient. Some geothermal heat pump manufacturers and electric utilities use computers to accurately determine the operating efficiency of a system for your home or building.

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Do Geothermal systems require much maintenance?

No. Geothermal systems are practically 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.

Are all Geothermal heat pumps alike?

No. There are different kinds of geothermal heat pumps designed for specific applications. Many geothermal heat pumps, for example, are intended for use only with higher temperature ground water encountered in open-loop systems. Others will operate at entering water temperatures as low as 25°F, which are possible in closed-loop systems. Most geothermal heat pumps provide summer air conditioning, but a few brands are designed only for winter heating. Geothermal heat pumps also can differ in the way they are designed. Self-contained units combine the blower, compressor, heat exchanger and coil in a single cabinet. Split systems allow the coil to be added to a forced-air furnace and utilize the existing blower.

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How does a Geothermal heat pump work?

Anyone with a refrigerator or an air conditioner has witnessed the operation of a heat pump, even though the term heat pump may be unfamiliar. All of these machines, rather than making heat, take existing heat and move it from a lower temperature location to a higher temperature location. Refrigerators and air conditioners are heat pumps that remove heat from colder interior spaces to warmer exterior spaces for cooling purposes. Heat pumps also move heat from a low-temperature source to a high-temperature space for heating.

An air-source heat pump, for example, extracts heat from outdoor air and pumps it indoors. A geothermal heat pump works the same way, except that its heat source is the warmth of the earth. The process of elevating low-temperature heat to over 100°F and transferring it indoors involves a cycle of evaporation, compression, condensation and expansion. A refrigerant is used as the heat-transfer medium which circulates within the heat pump. The cycle starts as the cold, liquid refrigerant passes through a heat exchanger (evaporator) and absorbs heat from the low-temperature source (fluid from the ground loop). The refrigerant evaporates into a gas as heat is absorbed.

The gaseous refrigerant then passes through a compressor where the refrigerant is pressurized, raising its temperature to more than 180°F. The hot gas then circulates through a refrigerant-to-air heat exchanger where heat is removed and pumped into the building at about 100°F. When it loses the heat, the refrigerant changes back to a liquid. The liquid is cooled as it passes through an expansion valve and begins the process again. To work as an air conditioner, the system's flow is reversed.

Does a Geothermal system heat and cool too?

One thing that makes a geothermal heat pump so versatile is its ability to be a heating and cooling system in one. With a simple flick of a switch on your indoor thermostat, you can change from one mode to another. In the cooling mode, a geothermal heat pump takes heat from indoors and transfers it to the cooler earth through either groundwater or an underground earth loop system. In the heating mode, the process is reversed.

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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.

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.

How do I know if the dealer and loop installers are qualified?

Don't be afraid to ask for references from dealers. A reputable dealer or loop installer won't hesitate to give you names and numbers to call to confirm his capabilities.

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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.

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If a home has ceiling cable heat or baseboard heat, do air ducts need to be installed?

Not always. It may be desirable to install geothermal heat pump room units. For some small homes, a one-room unit would handle the heating and cooling needs. Ceiling cable or baseboard units could be used for supplemental heat if desired.

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.

What is the BTU size of the furnace that's being proposed?

Furnaces are designed to provide specific amounts of heat energy per hour. The term "BTUH" refers to how much heat can be produced by the unit in an hour. Before you can determine what size furnace you'll need, you must have a heat loss/heat gain calculation done on the structure. From that, an accurate determination can be made of the size of the system you'll need. Most fossil fuel furnaces are substantially oversized for heating requirements, resulting in increased operating cost and unpleasant temperature swings.

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Should I buy a Geothermal heat pump large enough to heat with no 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 residential 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.