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How do Geothermal heating and cooling systems 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 consistent 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.
How long is the payback period for a 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 a conventional heating system and central air conditioner. We have tools that can help you calculate these savings. 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 immediate positive cash flow. This theory also rings true in the case of a refinance on an existing property.
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 Geothermal system?
A Geothermal system is three to five 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 average?
All heating and cooling systems have a rated efficiency from a U.S. governmental agency based on laboratory conditions. For 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 Envision Series is rated up to 5). That means for every one unit of energy used to power the system, 3-5 units are supplied as heat. Where a fossil fuel furnace may be 78-90 percent efficient, a geothermal heat pump is about 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.
Do Geothermal systems require much maintenance?
No. Geothermal systems are practically maintenance-free. When installed correctly, the buried loop will last for generations. And the other half of the operation, the unit’s fan, compressor, and pump, are housed indoors, protected from the harsh weather conditions. Usually, periodic checks and filter changes are the only required maintenance.
What does Geothermal mean for the environment?
Geothermal systems work with nature, not against it. They emit no greenhouse gases, which are linked to global warming, acid rain and other environmental hazards. WaterFurnace provides an earth-loop antifreeze that will not harm the environment in the unlikely event of a leak.
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 area 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 degrees Fahrenheit 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). When the heat is absorbed the refrigerant evaporates into a gas. The gaseous refrigerant is then passed through a compressor where the coolant is pressurized, raising its temperature to more than 180 degrees Fahrenheit. Hot gas then circulates through a refrigerant-to-air heat exchanger where heat is removed and pumped into the building at about 100 degrees Fahrenheit. 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. When working as an air conditioner, the system’s flow is reversed.
Does a Geothermal system heat and cool?
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 from indoors and transfers it to the cooler earth through either groundwater or an underground earth loop system. The process is reversed for heating mode.
Can a geothermal system also heat water?
Yes. Some geothermal pumps can provide a large portion 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.
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.
Does the underground pipe system really work?
The buried pipe, or earth loop, was a significant technical advancement in heat pump technology. The idea of burying pipe in the ground to gather heat energy originated in the 1940s. 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.
What types of geothermal loops are available?
There are two main types: open and closed. Closed-loop systems include the Horizontal Loop, the Pond Loop, and the Vertical Loop.
What is an open-loop system?
An open-loop system uses groundwater from a conventional 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.
How much groundwater does an open-loop system require?
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 gpm 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 domestic water requirements. You probably will need to enlarge your pressure tank or modify the plumbing to supply adequate water to the heat pump.
What do I do with the discharge water?
There are several 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. One of these alternatives must be readily available and can accept the amount of water used by the heat pump before open discharge is feasible. The second means of water discharge is the return well. A return well is a second wellbore that returns the water to the ground aquifer. This 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.
Are there any laws that apply to open-loop installations?
All or part 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.
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. The only change in the water returned to the environment is a slight increase or decrease in temperature.
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.
What problems can be caused by poor water quality?
Poor water quality will cause serious problems in open-loop systems and water should be tested for hardness, acidity and iron content before a heat pump is installed. Your contractor or equipment manufacturer will tell you what level of water is acceptable. Mineral deposits can build up inside the heat pump’s heat exchanger. A periodic cleaning with a mild acid solution is all that’s needed to remove the build-up. Impurities, particularly iron, will 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.
What is a closed-loop system?
A closed-loop system uses a continuous loop of buried polyethylene pipe and is the preferred method. 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 re-circulates its heat-transferring solution in a 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 sufficient square footage will work.
What if I don’t have room for a horizontal loop?
Closed-loop systems can also be vertical. Holes are bored up to 250 feet per ton of heat pump capacity, depending on where you live. U-shaped loops of pipes get inserted in the holes. The holes get backfilled with a sealing solution. A professional well driller bores the holes.
How long will the loop pipe last?
Only high-density polyethylene pipe is used to install closed-loop systems. Properly installed, these pipes will last for many decades. They are inert to chemicals typically found in soil and have good heat conducting properties. Never use PVC pipe.
How deep and long will my trenches be?
Trenches usually are six to eight feet deep and up to 400 feet long, depending on the number of pipes in a trench. One advantage of a horizontal loop system can lay the trenches according to the shape of the land. As a rule of thumb, each ton of system capacity requires 500-600 feet of pipe. A well-insulated 2,000 square-foot home would need about a three-ton system with 1,500-1,800 feet of pipe.
How are the pipe sections of the loop joined?
Pipe sections are joined by thermal fusion. Thermal fusion involves heating the pipe connections and then fusing them to form a joint that’s stronger than the original pipe. This technique creates a secure connection to protect from leakage and contamination.
Will an earth loop affect my lawn or landscape?
No. Research has proven that loops have no adverse effect on grass, trees, or shrubs. Most horizontal loop installations use trenches about 24 inches wide. Initially, you will have bare areas that can be restored with grass seed or sod. Vertical loops require little space and result in minimal lawn damage.
I have a pond nearby. Can I put a loop in it?
Yes, if it’s deep enough (min of 6ft deep at the lowest seasonal level) and large enough. The amount of surface area required depends on the heating and cooling load of the structure. Opt against an open-source system if you are 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.
Can I install an earth loop myself?
We do not recommend installing it yourself. Good earth-to-coil contact is essential for successful loop operation, and nonprofessional installations may result in less-than-optimum system performance.
How do I know if the dealer and loop installers are qualified?
Don’t be afraid to ask for references for previous projects that the contractor has completed. A reputable contractor won’t hesitate to provide you with this information. Also, ask the contractor how many geothermal projects they have completed in the previous 12 months.
Can a geothermal heat pump be added to my fossil fuel furnace?
Split systems 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 primary heating source and a fossil fuel furnace as a supplement in frigid weather if additional heat is needed.
I have ductwork, but will it work with this system?
In all probability, yes. We can determine your ductwork requirements and any minor 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.
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