Geothermal FAQ
Q1: What is a Geothermal Heat transfer pump (GHP)?
Q2: How does a Geothermal heat transfer pump (GHP) actually work?
Q3: How do I get the heat from the ground into my home?
Q4: What is an open-loop system?
Q5: How much groundwater does an open-loop system need?
Q6: What problems can be caused by poor water quality?
Q7: Does an open-loop system cause environmental damage?
Q8: Are there any laws that apply to open-loop installation?
Q9: What is a closed-loop system?
Q10: How long will the pipe last?
Q11: How are the pipe sections of the loop joined?
Q12: What is the fluid in the loops?
Q13: What type of Geothermal heat transfer pumps are available?
Q14: Can a heat pump provide 100% of my heating and cooling needs?
Q15: Can a geothermal heat transfer pump heat my hot water for my home?
Q16: Do I need to increase the size of my electric service?
Q17: Where is the Geothermal heat transfer pump installed?
Q18: How efficient is a Geothermal heat transfer pump?
Q19: Can geothermal do snow melting?
Q20: Can I heat my pool?
Q21: What kind of maintenance can I expect?
Q22: Is there improved indoor air quality with this system?
Q23: How do I know what size system is best for me?
Q24: How do geothermal heat pumps compare to conventional systems?
Q25: Will this system add value to my home?
Q26: Is it true that geothermal heat pump systems have the lowest impact on the environment?
Q27: What is the life of a system?
Q1: What is a Geothermal Heat transfer pump (GHP)?
A geothermal heat pump is an extremely efficient machine used for heating and cooling which extracts heat from one place and moves it to another place. It works like a refrigerator which has a type of heat pump in it that extracts heat from the food compartment or freezer thus making the temperature inside drop and keeping your food cold. The extracted heat is then moved to the coil (the one that gets warm) in back of the refrigerator where the heat radiates into the air. A Geothermal system is like that except on a bigger scale. In the winter a GHP extracts heat from the earth and moves it into your home or building. In the summer a GHP can extract heat from your home or building and moves it into the earth and stores it there. When winter rolls around again, the GHP will extract that stored summer heat and moves it back into the house.
Q2: How does a Geothermal heat transfer pump (GHP) actually work?
Heating: fluid is circulated through the pipe loops in the ground where it comes into contact with earth that is at a constant temperature of somewhere between 45-55 degrees Fahrenheit. The GHP extracts some heat from this circulating fluid which then returns to the earth at a lower temperature but reabsorbs heat from the earth again. A refrigerant is used as the heat transfer medium which circulates within the GHP. The cycle starts as the cold liquid refrigerant passes through a heat exchanger (evaporator) and absorbs heat from the low temperature source (liquid from the ground loop). The refrigerant evaporates into a gas as heat is absorbed. The gas then passes through a compressor where it is pressurized causing its temperature to rise over 160º F. The hot gas then circulates through a refrigerant-to-air heat exchanger coil where a blower removes the heat and circulates it into the home or building at about 100º 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.
Cooling: the process reverses; heat is absorbed from the house or building and transfers through the heat exchanger into the ground loop circulating fluid then moved to the earth and released there thus warming up a large mass of material which acts as a type of 'thermal battery'. This stored heat can be reabsorbed into the house or building when the heating cycle begins again. Think about it! You get to literally enjoy summer heat in the winter!
Q3: How do I get the heat from the ground into my home?
The most commonly used are open-loop and closed-loop systems.
Q4: What is an open-loop system?
An open-loop system may be employed cost-effectively if ground water is plentiful. This type of system uses ground water from an aquifer and is piped directly from the well to the building, where it transfers its heat to a geothermal heat pump. After it leaves the building, the water is disposed of by either
- drainage to a low area such as a pond, river, lake or stream,
- to a dedicated drainfield sized to the required volume of water of the heat pump or
- water is pumped back into the same aquifer through a separate discharge well.
Q5: How much groundwater does an open-loop system need?
Geothermal heat transfer pumps used in open-loop systems need differing amounts of water depending on the size of the unit and the manufacturer's specifications. The water requirement of a specific model is usually expressed in gallons per minute (g.p.m.) and is listed in the specifications for that unit. Your water well and heat pump combination should be large enough to supply the water needed by the heat pump in addition to your domestic water requirements
Q6: What problems can be caused by poor water quality?
Poor water quality will cause serious problems in open-loop applications. Your water should be tested for hardness, acidity and iron content before the heat pump is installed. Poor water quality can cause mineral deposits to build up inside the GHP heat exchanger and periodic cleaning will be required. Water from flowing springs, ponds, lakes or river sources are not recommended for heat pump use, unless proven to be free of excessive particulate and organic matter. These sediments will contaminate the heat exchanger heat pump system and make it inoperable.
Q7: Does an open-loop system cause environmental damage?
No, the heat pump only moves heat from one source to another, therefore no pollution is generated. The only change in the water after it's used by the heat pump is a slight increase or decrease in temperature.
Q8: Are there any laws that apply to open-loop installation?
In some localities, all or parts of the installation may be subject to local ordinances, codes, covenants or licensing requirements. Check with local authorities to determine if any restrictions apply in your area.
Q9: What is a closed-loop system?
Closed-loop systems are becoming most common. There are 5 types of closed loop systems. All types use a continuous loop where the heat transfer fluid is circulated. A horizontal loop is usually the most cost effective when adequate yard space is available and trenches are easy to dig. Using trenchers or backhoes digging trenches three to six feet below the ground, you then lay a series of parallel plastic pipes. The trench is then back filled, taking care not to allow sharp rocks or debris to damage the pipe. A typical horizontal loop will have 400-600 feet of pipe per ton of heating and cooling capacity.
Vertical loops are preferred in many installations where yard space is insufficient and where preservation of existing landscaping is desirable. Contractors bore vertical holes in the ground 150-450 feet deep. Each hole contains a single loop of pipe with a U-bend at the bottom. The hole is then backfilled or grouted to improve the thermal conductivity. Each vertical pipe is then connected to a horizontal pipe underground to and from the heat pump. Vertical loops are generally more expensive to install, but require less piping than horizontal loops.
Slinky loops are used to reduce the heat exchanger per foot trench requirements but require more pipe per ton of capacity. This pipe is coiled like a slinky, overlapped and laid in a trench. Two-pipe systems may require 200-300 feet more pipe per ton of nominal heat exchange capacity. The trench length decreases as the number of pipes in the trench increases or as slinky overlap increases.
Pond loops are a special kind of closed loop system. Where there is a pond or stream that is deep enough and with enough flow, closed loop coils can be placed on the bottom. Geothermal transfer fluid is pumped just as a closed loop ground system. First cost economics are very attractive and there is no aquatic environmental impact.
Q10: How long will the pipe last?
A high-density polyethylene pipe is used in a closed loop system and has a 50-year warranty. Independent tests show a useful life span of over 200 years.
Q11: How are the pipe sections of the loop joined?
Thermal fusion and stab fittings are the only acceptable method used to connect pipe sections. Thermal fusion connections are either socket or butt fused together to form a joint stronger than the original pipe. Stab fittings are fairly new but are proving themselves to be reliable. Using barbed fittings, clamps and glued joints are unacceptable and will eventually cause the loop to leak and fail.
Q12: What is the fluid in the loops?
There are two types of antifreeze solutions that are used: propylene glycol and methyl alcohol. These heat transferring solutions are mixed with water to form a solution for your specific climate and ground conditions. Geothermal fluid (GTF) is a mixture of methyl alcohol and water and is commonly used.
Q13: What type of Geothermal heat transfer pumps are available?
- Forced air systems distribute conditioned air using conventional ductwork.
- Hydronic systems provide heated or chilled water used in various distribution systems such as fan coils, radiant flooring, baseboards, and cast iron radiators.
- Combination systems combine forced air and hydronic into one unit.
- Domestic hot water heaters designed for both residential and commercial applications have the ability to provide more hot water over extended periods at a fraction of the operating cost of conventional systems.
- Console heat pumps are free standing units that do not require a distributing system. They are aesthetically appealing, as are used in applications such as: hotel rooms, class rooms, churches, warehouses and industrial work areas.
Q14: Can a heat pump provide 100% of my heating and cooling needs?
Yes. Heat pumps can provide 100% of your heating and cooling requirements.
Q15: Can a geothermal heat transfer pump heat my hot water for my home?
Domestic hot water is available with the use of a heat pump for pennies a day or even free. A hot water desuperheater is a heat exchanger built into the heat pump and is designed to remove high temperature heat from the refrigerant gases. A typical hot water desuperheater will generally provide 120° F water and can supply the majority of the domestic water needs depending on the amount of consumption. Other units such as Geothermal hot water heaters can provide 100% of domestic hot water needs.
Q16: Do I need to increase the size of my electric service?
Most homes already have adequate electrical service.
Q17: Where is the Geothermal heat transfer pump installed?
They are located indoors in spaces that do not get colder than 45 degrees Fahrenheit. This is very appealing for many reasons. Indoor installations free up outdoor space allowing better architectural design and yard usage. Noise normally associated with outdoor condensers is eliminated and because the electrical controls and heat exchanger coils are protected from the elements this then allows greater system longevity. The Geothermal units take up less space than conventional equipment.
Q18: How efficient is a Geothermal heat transfer pump?
Depending on individual circumstances and the type of GHP unit, efficiencies can range from 300% to 500%. On average operating costs are about 75% less than electric heating devices and 50% less than air source heat pumps. Cooling costs are 25% - 50% lower than for conventional air conditioners. In addition, because hot water is supplied by the heat pump at these efficiencies and higher, your overall savings are increased even more.
Q19: Can geothermal do snow melting?
Yes. Snow melting on sidewalks and driveways is becoming more fashionable and can be incorporated into the overall geothermal system design.
Yes. Indoor and outdoor pools are easily heated inexpensively with Geothermal systems.
Q21: What kind of maintenance can I expect?
A properly installed closed-loop heat pump requires very little maintenance aside from regularly maintaining the air filter and air blower assembly. Water coil maintenance is recommended on open-loop installations as water quality can greatly affect the heat exchanger efficiency. Use only a contractor certified by the manufacturer to service the geothermal unit.
Q22: Is there improved indoor air quality with this system?
Yes. An all-electric heat pump system produces no products of combustion therefore no indoor air pollutants are possible. Conventional gas and oil systems require chimneys to vent away harmful carbon monoxide and other dangerous gases.
Q23: How do I know what size system is best for me?
Ask a qualified, trained dealer contractor certified by the manufacturer to assess your home or building and perform an accurate heating and cooling analysis. Factors like the type of windows and insulation R. values are taken into account and an accurate heating and cooling load will be determined. The geothermal heat transfer pump and ground loop are then designed to fit the exact characteristics of your home or building. It is important to note any future home expansion you might contemplate so that the ground loops can be sized for the added capacity up front.
Q24: How do geothermal heat pumps compare to conventional systems?
Although heat pumps normally cost more to install than conventional systems the increased comfort, lower energy and maintenance costs result in customer satisfaction. A survey published by the National Rural Electric Cooperative Association found that 97% of geothermal system owners would purchase one again, and 99% would recommend one to a friend.
Q25: Will this system add value to my home?
Yes. More and more Home Appraisers and Real-estate Agents are educated and acknowledge a geothermal system as a renewable energy source with greater value.
Q26: Is it true that geothermal heat pump systems have the lowest impact on the environment?
Geothermal systems provide the most efficient heating and cooling that you can buy, and according to the U.S. Department of Energy and the Environmental Protection Agency, they create the lowest attributable emissions.
Q27: What is the life of a system?
Experts believe 18-23 years of serviceable life is expected from a geothermal heat pump. It is not unusual for such geothermal heat pumps to last 30-40 years. This is nearly double that of conventional systems.
A heat pump can be easily and economically replaced when it is worn out. Reputable manufacturers perform extensive tests on the heat pump before it leaves the factory, to insure the highest quality system.
