Geothermal FAQs

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.

Heating and cooling systems carry an efficiency rating which is certified by the Air-Conditioning, Heating, and Refrigeration Institute (AHRI). Fossil fuel furnaces use AFUE. Air conditioners use SEER while heat pumps use HSPF and SEER.

Geothermal heat pumps rate heating efficiencies 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. The WaterFurnace 7 Series holds the highest recorded certified performance of 5.3 COP in a closed loop and 5.9 in an open loop. That means for every dollar of energy used to power the system, up to $5.90 of energy are supplied as heat. Where a fossil fuel furnace may be 78-98% efficient, a geothermal heat pump is over 500% efficient.

For cooling, geothermal units are rated in Energy Efficiency Ratio (EER). This is a measure of the instantaneous energy efficiency of cooling equipment. The higher the EER, the more efficient the unit. The WaterFurnace 7 Series carries a certified rating of 41 EER for closed loop and 53.2 EER for open loop. This is more than twice as efficient as any traditional heat pump or air conditioner and a third higher than any other two-stage geothermal heat pump.

A geothermal system is over five times more efficient in heating and more than twice as efficient in cooling as the most efficient ordinary system. Because geothermal systems move existing heat rather than creating it through combustion, they provide four to five units of energy for every one unit used to power the system.

No. Geothermal systems are practically maintenance free. The buried loop will last for generations. The unit’s fan, compressor and pump is housed indoors, protected from the weather and contamination. Usually, periodic checks and filter changes are the only required maintenance.

While WaterFurnace does offer an outdoor geothermal unit for jobs where space is limited, its rugged housing is sealed so that no components are exposed to the elements.

Geothermal systems work with nature, not against it. They emit no greenhouse gases – which have been linked to pollution, acid rain, and other environmental hazards. WaterFurnace’s earth-loop antifreeze will not harm the environment in the unlikely event of a leak. And all of the current WaterFurnace product lines use R-410A, a performance-enhancing refrigerant that will not harm the earth’s ozone layer.

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 (such as the WaterFurnace Envision Series Split) allow the coil to be added to a forced-air furnace and utilize the existing blower.

Heat pumps don’t create heat. They take existing heat and move it. Anyone with a refrigerator has witnessed the operation of a heat pump. Refrigerators collect heat from the unit’s interior and move it to the exterior for cooling purposes. Unlike a refrigerator, a heat pump can reverse itself. An air-source heat pump, for example, can extract heat from outdoor air and pump it indoors for heating purposes.

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 gasseous 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.

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.

Yes. Some geothermal heat pumps can provide all of your hot water needs 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.

The buried pipe, or earth loop, was an important technical advancement in heat pump technology. The idea of burying pipe in the ground to gather heat energy originated in the 1940’s. New heat pump designs and more durable pipe materials have been combined to make geothermal heat pumps the most efficient heating and cooling systems available.

An open loop system uses groundwater from an ordinary well as a heat source. The groundwater is pumped into the heat pump unit where heat is extracted and the water is disposed of in an environmentally safe manner. Because groundwater is a relatively constant temperature year-round, wells are an excellent heat source.

The water requirement of a specific model is usually expressed in gallons per minute (gpm) and is listed in the unit’s specifications. Generally, the average system will use 1.5 gmp per ton of capacity while operating, but the amount of water required depends on the size of the unit and the manufacturer’s specifications. Your contractor should be able to provide this information. Your well and pump combination should be large enough to supply the water needed by the heat pump in addition to your domesting water requirements. You’ll probably need to enlarge your pressure tank or modify your plumbing to supply adequate water to the heat pump.

There are a number of ways to dispose of water after it has passed through the heat pump. The open discharge method is easiest and least expensive. Open discharge simply involves releasing the water into a stream, river, lake, pond, ditch, or drainage tile. Obviously, one of these alternatives must be readily available and have the capacity to accept the amount of water used by the heat pump before open discharge is feasible.

A second means of water discharge is the return well. A return well is a second well bore that returns the water to the ground aquifer. A return well must have enough capacity to dispose of the water passed through the heat pump. A new return well should be installed by a qualified well driller. Likewise, a professional should test the capacity of an existing well before it is used as a return.

No. They are pollution free. The heat pump merely removes or adds heat to the water. No pollutants are added. The only change in the water returned to the environment is a slight increase or decrease in temperature.

Poor water quality can cause serious problems in open loop systems. Your water should be tested for hardness, acidity and iron content before a heat pump is installed. Your contractor or equipment manufacturer can tell ynou what level of water is acceptable. Mineral deposits can build up inside the heat pump’s heat exchanger. Sometimes a periodic cleaning with a mild acid solution is all that’s needed to remove the build-up.

Impurities, particularly iron, can eventually clog a return well. If your water has high iron content, make sure that the discharge water is not aerated before it’s injected into a return well.

A closed loop system uses a continuous loop of buried polyethylene pipe. The pipe is connected to the indoor heat pump to form a sealed underground loop through which an environmentally friendly antifreeze-and-water solution is circulated. A closed loop system constantly recirculates its heat-transferring solution in pressurized pipe, unlike an open loop system that consumes water from a well. Most closed loops are trenched horizontally in areas adjacent to the building. However, where adequate land is not available, loops are vertically bored. Any area near a home or business with appropriate soil conditions and adequate square footage will work.

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

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.

Pipe sections are joined by thermal fusion. Thermal fusion involves heating the pipe connections and then fusing them together to form a joint that’s stronger than the original pipe. This technique creates a secure connection to protect from leakage and contamination.

Yes, if it’s deep enough and large enough. A minimum of six feet in depth at its lowest level during the year is needed for a pond to be considered. The amount of surface area required depends on the heating and cooling loads of the structure. You should opt against using water from a spring, pond, lake or river as a source for an open loop system unless it’s proven to be free of excessive particles and organic matter. They can clog a heat pump system and make it inoperable in a short time.