These are the questions we get from customers exploring geothermal as an alternative to conventional HVAC. There is a great deal of information here. Please scroll to scan all the FAQs.
What government-based incentives are available for geothermal heat pump installation?
A growing number of loan and grant programs is making it easier to invest in a geothermal system for your home or business. The following is a list of programs that further reinforce the national and international movement towards adopting more efficient, environmentally friendly and cost effective energy alternatives for heating and cooling your home or business.
United States Government: As part of the American Recovery and Reinvestment Act of 2009 (ARRA)There is an uncapped 30-percent tax credit for residential investments in geothermal heat pump systems through 2016. REHAU's RAUGEO PEXa geothermal ground loop heat exchange system qualifies under this program. For more information, contact Public Information at the Internal Revenue Service at www.irs.gov or by phone at 1.800.829.1040.
State-by-State (U.S.): The Database of State Incentives for Renewables & Efficiency (DSIRE) is a comprehensive source of information on state, local, utility, and federal incentives and policies that promote renewable energy and energy efficiency. Established in 1995 and funded by the U.S. Department of Energy, DSIRE is an ongoing project of the N.C. Solar Center and the Interstate Renewable Energy Council. For more information, visit www.dsireusa.org.
Geothermal Heat Pumps
What is a geothermal heat pump?
A geothermal heat pump is an electrically-powered device that uses the natural heat exchange ability of the earth and/or the earth's groundwater to heat and cool your home or building.
How does it work?
Like any type of heat pump, it simply "pumps" or moves heat energy from one place to another. Your refrigerator works using the same principle and type of equipment, on a smaller scale. By using the refrigeration process, geothermal heat pumps remove heat energy stored in the ground and/or the earth's groundwater and transfer it indoors in the winter and back outdoors in the summer.
How is heat transferred between the earth and the home or building?
The ground has the ability to absorb and store heat energy. To use that stored energy, heat is extracted from the ground through a liquid medium (groundwater or an environmentally friendly anti-freeze solution) and is circulated to the heat pump or heat exchanger. There, the heat is used to heat the building through traditional warm air distribution or - even better - through radiant floor heating. In summer, the process is reversed and indoor heat is extracted from the air and transferred to the ground through the liquid. Certain commercial buildings also utilize the radiant piping network to collect heat from the building and reject it to the earth.
Does a heat pump generate both hot and cool air?
One of the things that makes a heat pump so versatile is its ability to be a heating and cooling system. You can change from one mode to another with a simple flick of a switch on your indoor thermostat, or automatically with the right intelligent thermostat. In the cooling mode, a geothermal heat pump takes heat from indoors and transfers it to the cooler ground through either groundwater or an underground piping loop system. in some systems, it is possible to do simultaneous heating and cooling within the building, transferring heat from one section to another.
Do I need separate ground loops for heating and cooling?
No. The same ground loop works for both operations or modes. All that happens when changing from heating to cooling, or vice versa, is that the flow of heat is reversed automatically.
What types of ground loop configurations are available?
There are two main configurations of ground loops: open and closed.
Does the underground loop system really work?
YES, from Alaska to Miami and all throughout Canada (extremes of ground temperatures) geothermal earth exchange systems can be designed and installed to meet demanding building loads, either full peak loads or partial loads, according to the customer and designer intentions.
What are the components of a geothermal heat pump system?
The three main parts are the heat pump, the ground loop (open or closed piping loop and the fluid within), and the heating/cooling distribution systems - either air-based or fluid-based.
Are all geothermal heat pumps alike?
No. There are different kinds of geothermal heat pumps designed for specific applications. Many geothermal heat pumps are intended for use only with higher temperature ground water encountered in open-loop systems. Others will operate at entering ground water temperatures as low as 28°F (-2°C) which are possible in closed-loop systems.
Most geothermal heat pumps provide summer air conditioning, but a few units are designed only for winter heating. Sometimes these heating-only systems incorporate a groundwater cooled coil that can provide cooling in moderate climates.
Geothermal heat pumps can also 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.
Will I have to add insulation to my home if I install one of these systems?
Geothermal heat pumps will reduce your heating and cooling costs regardless of how well your home is insulated. However, upgrading insulation and building efficiency will reduce peak heating and cooling demands, allowing the designer and installer to supply a smaller, less expensive system.
Can a geothermal heat pump also heat domestic water?
Sometimes. Using an extra heat exchange coil (sometimes called a "desuperheater") within the heat pump unit, some types of geothermal heat pumps can save you up to 50 percent on your water-heating bill by preheating the incoming cold water. Desuperheaters are standard on some units, optional on others. Some heat pump units can provide all of the domestic hot water needs during cooling cycles, using heat from the indoor air.
Is a geothermal heat pump difficult to install?
The indoor heat pump units are compact and easily installed by an experienced contractor. They can be installed in areas unsuitable for fossil fuel furnaces because there is no combustion, thus, no need to vent exhaust gases or provide fuel piping or combustion air. The outdoor piping is installed by contractors who specialize in that type of work, whether it be for open- or closed-loop systems.
Can a geothermal heat pump be added to my fossil fuel furnace?
Partial-load of split systems can easily 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.
I have forced-air heating (ductwork), but will it work with this system?
In all probability, yes. Your installing contractor should be able to determine ductwork requirements and any 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 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. Depending upon your geographical location, it may be most cost-effective to size the ground source heat pump system for 80-100 percent of the peak heating load. Sizing the heat pump to handle the entire heating load may impractically increase costs due to the requirement of a larger heat pump unit and outdoor ground loops. Also, an over-sized unit can cause dehumidification problems in the cooling mode, resulting in a loss of summer comfort.
Do geothermal heat pumps have outdoor units?
The buried piping loop is the only part of the system which is outdoors. The heat pump equipment goes inside the building, usually in the basement, garage, crawl space, or mechanical room. Because it's indoors, the life spans of the compressor and major components are greatly extended, most having a life span of 20 years or more.
How does a ground source earth energy or geothermal system work?
Unlike outdoor temperatures that fluctuate with the changing seasons, the temperature of the soil four to six feet beneath the ground remains relatively consistent year-round for a given location. A ground source or earth energy geothermal system taps into earth’s natural heating and cooling properties through an underground loop heat exchanger system connected to an electric heat pump within in your home or business.
In the winter, a fluid with antifreeze and water circulating through the ground loop system absorbs stored heat from the ground and carries it indoors. The heat pump, using the same refrigeration principle as your refrigerator, then compresses the heat to a higher temperature for distribution throughout the building. In the summer, the heat pump works in reverse, drawing heat from the building and carrying it through the loop system for rejection back into the earth.
What makes a geothermal system different from conventional heating and cooling systems?
A ground source or earth energy geothermal system uses solar energy from the sun, which is stored in the ground, to heat homes and buildings and to help generate domestic hot water. In warm weather, heat pumps quietly and efficiently collect heat from the building and "pump" it into the earth, which is much cooler than the air in summertime.
Unlike conventional systems, geothermal systems don’t burn fossil fuels (i.e. natural gas, oil, propane) to generate heat. They simply exchange heat to and from the ground, depending on the conditions. Electricity is used to operate the heat pump's compressor, a circulating pump for the fluid in the ground loops and the electronics. According to the International Ground Source Heat Pump Association, ground source heat pumps can reduce energy consumption by up to 50% when compared to conventional systems.
How efficient is a geothermal system?
In heating mode, a geothermal system can be three-to-four-times as efficient as the most efficient conventional system. Because geothermal systems do not burn fossil fuel (i.e. gas, oil, propane) to make heat, they provide three to four units of energy for every one unit used to power the system through electricity. In cooling mode, geothermal systems can be two-to-three-times more efficient than traditional air conditioners or air-to-air heat pumps. This improved efficiency translates directly to reduced operating costs.
What does geothermal mean to the environment?
Because geothermal systems work with nature, not against it, they minimize the threats of acid rain, air pollution and the greenhouse effect. An environmentally friendly fluid called “Geo-Therm” is used in the closed, continuous loop.
Do geothermal systems require much maintenance?
Closed-loop geothermal systems are practically maintenance free. When installed properly, the buried ground loop of crosslinked polyethylene piping will last for generations. And the other half of the operation--the heat pump's compressor and circulating pump--is housed indoors, protected from the harsh weather conditions. Usually, periodic checks and air filter changes (for forced air distribution) are the only required maintenance.
With open-loop systems, the water quality may impact the condition of the heat pump's indoor heat exchanger. Periodic cleaning or replacement of the indoor heat exchanger may be required.
The Heat Pump Process
Anyone who has 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 which 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, like Freon, 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 (liquid 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 over 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 become an air conditioner, the flow is reversed.
Geothermal Loop Systems – Closed
What is a closed-loop system?
The term "closed-loop" is used to describe a geothermal heat pump system that uses a continuous loop of special buried plastic pipe as a heat exchanger. The pipe is connected to the indoor heat pump to form a sealed, underground loop through which an antifreeze solution is circulated. Unlike an open-loop system that consumes water from a well, a closed-loop system recirculates its heat-transferring solution in pressurized pipe.
Where can this loop be located?
That depends on land availability and terrain. Some closed-loops are installed horizontally in trenches near the home or building. Many closed-loops are installed vertically through deep "boreholes". Drilled with special equipment, these are typically 300 feet or more deep and 5 to 6 inches in diameter.
How deep and long will my trenches be?
Trenches are normally four to six feet deep and up to 400 feet long, depending on how many pipes are in a trench. One of the advantages of a horizontal loop system is being able to lay the flexible pipes according to the shape of the land.
How many pipes are in a trench?
Normally, a run of pipe is laid at five feet then looped back over itself at three feet once the bottom pipe is covered with soil. This allows more length of pipe to be put in one trench and has no adverse affect on system efficiency. Other loop designs use four or six pipes and allow for shorter trenches if land area is limited.
What if I don't have enough room for a horizontal loop?
Closed-loop systems are often vertical. Vertical boreholes are drilled from 200 to 400 feet deep. U-shaped loops of approved pipe are dropped in the holes. The holes are then backfilled with a grouting mixture to create contact between the pipes and the earth surrounding the borehole.
How long will the loop pipe last?
Properly installed, approved pipes (PE and PEXa) will last for many decades. They are inert to chemicals normally found in soil and have good heat conducting properties. PVC pipe should not be used under any circumstances.
Will an earth loop affect my lawn or landscape?
No. Research has proven that loops have no adverse effect on grass, trees, or shrubs. The buried pipe loops will be invisible and reliable.
Can I reclaim heat from my septic system disposal field?
No. An earth loop will reach temperatures below freezing during extreme conditions and may freeze your septic system. Such usage is banned in many areas.
Can I install an earth loop myself?
It's not recommended. In addition to the special equipment and certification required, good earth-to-coil contact is very important for successful loop operation. Nonprofessional installations may result in less than optimum system performance.
I have a pond nearby. Can I put a loop in it?
Sometimes, 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 load of the structure.
Geothermal Loop Systems – Open
What is an open-loop system?
The term "open-loop" is commonly used to describe a geothermal heat pump system that uses groundwater from a conventional well as a heat source. The groundwater is pumped into the heat pump unit where heat is extracted, then the water is disposed of in an appropriate manner. Since groundwater is a relatively constant temperature year-round, it is an excellent heat source.
What do I do with the discharge water?
There are a number of ways to dispose of water after it has passed through the heat pump. The open discharge method is the 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 must possess 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.
How much groundwater does an open-loop system need?
Geothermal heat 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 heating contractor should be able to provide this information. Generally, the average system will use 1.5 g.p.m. per ton of capacity while operating.
Your well and pump combination should be large enough to supply the water needed by the heat pump in addition to your domestic water requirements. You will probably need to enlarge your pressure tank or modify your plumbing to supply adequate water to the heat pump.
What problems can be caused by poor water quality?
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 you 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 a high iron content you, should be sure that the discharge water is not aerated before it's injected into a return well.
Finally, you should opt against using water from a spring, pond, lake or river as a source for your heat pump 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.
Does an open-loop system cause environmental damage?
No. They are pollution free. The heat pump merely removes or adds heat to the water. No pollutants are added whatsoever. The only change in the water returned to the environment is a slight increase or decrease in temperature. Some people are concerned that open-loop systems contribute to the depletion of our ground water resources. This issue is not critical in some parts of North America because of abundant supplies of ground water.
Are there any laws that apply to open-loop installations?
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.
|Selecting the Right System|
Is the efficiency rating actual or just a manufacturer's average?
All types of heating and cooling systems have a rated efficiency according to industry-regulated test methods and third-party testing. Fossil fuel furnaces have a percentage efficiency rating. Natural gas, propane and fuel oil furnaces have efficiency ratings based on laboratory test conditions. To get an accurate installed efficiency rating, factors such as flue gas heat losses, 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 efficiency ratings according to their coefficient of performance or COP. It's a standardized scientific way of determining how much energy the system produces versus how much it uses.
Most geothermal heat pump systems have COPs of 3.0 - 4.0, and some are even better. That means for every one unit of energy used to power the system, three to four units are supplied as heat. Where a fossil fuel furnace may be 80-90 percent efficient (80-90% of the energy is delivered as heat to the building), these geothermal heat pumps are 300 to 400 percent 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.
How do I know a dealer or loop installer is qualified?
Always ask for references. A reputable dealer won't hesitate to give you names and contact numbers so you can confirm his capabilities. The same applies to the loop installer. In the US, certification for installers from International Ground Source Heat Pump Association (IGSHPA) is available and often required by local regulations. In Canada, certification for installers from the Canadian Geoexchange Coalition (CGC) is available and often required by local regulations.
How long is the payback period (ROI) for a geothermal heat pump system?
To figure this accurately, you must know how much per year you'll save in energy costs with a geothermal system and the difference in costs between it and the alternative heating system and central air conditioner. To calculate your return on investment (payback in number of years), divide the annual savings into the additional cost. When you install a geothermal system in a new home, the monthly savings in operating costs will generally offset the additional monthly cost in the mortgage, resulting in a monthly positive cash flow immediately. Keep in mind that energy savings is only one of the many benefits of a geothermal system. Many heat pump manufacturers have so-called "payback calculator" tools available on their websites.
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, one room unit would provide most of the heating and cooling needs. Ceiling cable or baseboard units could then be used for supplemental heat.