Outdoor temperatures fluctuate with the changing seasons but underground temperatures don’t. Six to nine 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.
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.
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).
All heating and cooling systems have a rated efficiency from a U.S. government agency. 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 Envision holds the highest recorded certified performance of 5.4 COP in an open loop. That means for every dollar of energy used to power the system, $5.40 of energy are supplied as heat. Where a fossil fuel furnace may be 78-98% efficient, a geothermal heat pump is about 500% efficient. For cooling, geothermal units are rated by Energy Efficiency Ratio (EER). EER is a measure of efficiency in the cooling mode when measured at a constant temperature (95 degrees F). The higher the EER, the more efficient the unit. The WaterFurnace Envision holds the highest recorded certified performance of 30EER for closed loop and 32.1EER for open loop.
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 are housed indoors, protected from the weather and contamination. Usually, periodic checks and filter changes are the only required maintenance.
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. Our 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 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.
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.
No. The same loop works for both. To switch heating to cooling or vice versa, the flow of heat is simply reversed.
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.
There are two main types: open and closed.
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 – 2 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. We’ll 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 domestic water requirements.
There are a number of ways to dispose of water after it has passed through the heat pump. The open discharge method may be 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 have the capacity to accept the amount of water used by the heat pump before open discharge is feasible. In our area, freezing conditions have to be considered / overcome. A second, more common 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. We can tell you what level of water is acceptable based upon the equipment chosen for your home or business. 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 vertically in our area and in areas adjacent to the building. However, where adequate land is available, loops can be installed horizontally. Any area near a home or business with appropriate soil conditions and adequate square footage will work.
Our closed loop systems are 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.
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, 600-800 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 1,800-2,400 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. Stop in. We’ll show you a sample. 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.
It’s not recommended. Good earth-to-coil contact is very important for successful loop operation. Nonprofessional installations may result in inefficient system performance.
Closed loop systems also can be vertical. Holes are bored up to 150 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 has the dealer been around? How long has the dealer been installing geothermal systems? Look for dealers that have been leading the pack not jumping onboard the bandwagon. Look for dealers that have NATE Certified technicians and installers. Look for factory training and certification. Don’t be afraid to ask for references.
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.
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 but we can help you with that assessment. 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.
In all probability, yes. Our team of trained, professional, duct designers will be able to determine ductwork requirements and any minor modifications if needed.
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.
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. Our team of experienced electricians can determine your service needs.
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.
A good contractor will perform 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.
Geothermal systems are so energy-efficient that the payback period is remarkably brief. A study by the Air Force Institute of Technology calculated that it takes on average just seven to eight years to recoup costs. Your specific payback point depends on factors like local utility rates, excavation/drilling costs, how well your house is insulated, the efficiency of the model you choose, and what incentives your state or utilities provide. One of the best aspects about geothermal is cash flow. If you install a geothermal system, the monthly savings in operating costs generally offset the additional monthly financing cost, resulting in an immediate positive cash flow – especially in a new home. Again, your specific situation may vary.