Geothermal

Frequently Asked Questions

Q: How does it work?
A: Like any type of heat pump, it simply moves heat energy from one place to another. Your refrigerator works using the same scientific principle. (See mechanics of the heat pump process on page 3.) By using the refrigeration process, ground source heat pumps remove heat energy stored in the earth and/or ground water and transfer it to the home.

Q: How is heat transferred between the earth and home ?
A: The earth has the ability to absorb and store heat energy. Heat is extracted from the earth through a liquid medium (ground water or an anti-freeze solution) and is pumped through an heat exchanger inside the heat pump. There, the heat is elevated by a cycle of compression and evaporation of a refrigerant to heat your home. In summer the process is reversed and indoor heat is extracted from your home and transferred to the earth through the liquid.

Q: You mentioned heating and cooling. Does it do both?
A: One of the things that makes a heat pump so versatile is its ability to be a heating and cooling system in one. You can change from one mode to another with a simple flick of a switch on your indoor thermostat (this switchover can be optionally automated). In the cooling mode, a ground-source heat pump takes heat from indoors and transfers it to the cooler earth through either ground water or an underground loop system.
 

Q: Do I need separate ground loops for heating and cooling?
A: No. The same loop works for both. All that happens when changing from heating to cooling, or vice versa, is the flow of heat is reversed.

Q: What types of loops are available?
A: There are two main types: open and closed. The next two sections will give you specifics about each.

Q: Does the underground pipe system really work?
A: The buried pipe, or "ground loop," is the most recent technical advancement in heat pump technology. The idea to bury pipe in the ground to gather heat energy began in the 1940's. But it's only been in the last 10 years that new heat pump designs and improved pipe materials have been combined to make ground-source heat pumps the most efficient heating and cooling systems available.

Mechanics of the system

Q:  What are the mechanics of the heat pump process?

A: Anyone who has a refrigerator or an air conditioner has witnessed the operation of a heat pump, even though the term heat pump may not be familiar. These machines, rather than making heat, take existing heat and move it from a lower temperature location to a higher temperature location (hence the term heat "pump"). 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 ground-source heat pump works the same way, except that its heat source is the warmer warmth of the earth. The process of elevating low-temperature heat to over 100 degrees F and transferring it indoors involves a cycle of evaporation, compression, condensation and expansion. A refrigerant, usually R-22 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 (liquid from the ground loop). The refrigerant evaporates into as heat is absorbed- the gaseous refrigerant then passes through an electric compressor where the refrigerant is pressurized, raising the temperature to over 180 degrees f. The hot gas then circulates through a refrigerant-to-air heat exchanger where heat is removed and pumped into the home at about 110 degrees 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 over. To become an air conditioner, the flow is reversed. 

Closed loop system

Q: What is a closed-loop system?
A: The term "closed-loop" is used to describe a ground-source 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 recalculates it's heat transferring solution in pressurized pipe.

Q: Where can this loop be located?
A: That depends on land availability and terrain. Most closed-loops are trenched horizontally in yards adjacent to the home. But any area near a home or business with appropriate soil conditions and adequate square footage will work.

Q: How deep and long will my trenches be?
A: Trenches are normally four feet deep and up to 125 feet long with one trench for each "ton" (12,000 btu/hr) of heat pump capacity. One of the advantages of a horizontal loop system is being able to lay the trenches according to the shape OT the land. As a rule of thumb, 500 feet of pipe are required per ton of heat pump capacity. A well insulated, 2,000 square foot home would need about a 3 to 3 1/2 ton system with 1,500 feet of pipe.

Q: How many pipes are in a trench?
A: Normally, one 500 foot coil of pipe is made into an extended "slinky" is laid flat in the bottom of the 3 foot wide trench then covered with soil or sand this allows more length of pipe to be put in a shorter trench saving space and cost and has no adverse affect on system efficiency.

Q: What if I don't have enough room for a horizontal loop?
A: Closed-loop systems can also be vertical. Holes are bored to about 125-150 feet per ton of heat pump capacity. U-shaped loops of pipe are inserted into the well and backfilled with a sealing solution called grout.

Q: How long will the loop pipe last?
A: Closed-loop systems should only be installed using high-density geothermal rated polyethylene pipe. Properly installed, these pipes will last 75 to 100 years. In fact most manufacturers guarantee their loops for 50 to 55 years. This pipe material is inert to chemicals normally found in soil and has good heat conducting properties. Pvc pipe should not be used under any circumstances in the ground.

Q: How are the pipe sections of the loop joined?
A: The only acceptable method to connect pipe sections is by thermal fusion. Pipe connections are heated and fused together to form a joint stronger than the original pipe. Mechanical joining of pipe for an earth loop is never an accepted practice. The use of barbed fittings, clamps and glued joints underground is certain to result in loop failure due to leaks.

Q: Will an earth loop affect my lawn or landscape?
A: No. Research has proven that loops have no adverse affect on grass, trees or shrubs. Most horizontal loop installations use trenches about 3 feet wide. This, of course, will leave temporary bare areas that can be restored with grass seed or sod vertical loops require little space and result in minimal lawn damage.

Q: Can I reclaim heat from my septic system disposal field?
A: No. An earth loop will reach temperatures below freezing during extreme conditions. This may stop the digestion process and the New York state board of health prohibits such uses.

Q: If the loop falls below freezing, will it hurt the system?
A: No, the antifreeze solution in the loop will keep it from freezing down to about 20 degrees F. In fact, additional heat is available from the phase change of water into ice of ground moisture. In New York, three types of antifreeze solution are acceptable: GS-4, calcium chloride and methyl alcohol.

Q: Can I install an earth loop myself?
A: It's not recommended. In addition to thermal fusion of the pipe, good earth-to-coil contact is very important for successful loop operation. Nonprofessional installations may result in less than optimum heat pump performance. Thermal fusion should be done by personnel certified in the process in order to ensure leak free joints. Most closed-loop systems use trenched-in pipe as a heat source.

Q: I have a pond near my home. Can I put a loop in it?
A: Yes, if it's deep enough and large enough. A minimum of ten feet in depth at its lowest level during the year is needed for a pond to be considered. In pond loops copper, polyethylene or polybutylene pipe can be used.
 

Open loop systems:

Q: What is an open-loop system?
A: The term "open-loop" is commonly used to describe ground-source heat pump system that uses ground water from conventional well as a heat source. The ground water is pumped into the heat pump unit where heat is extracted, then the water is disposed of in an appropriate manner. Since ground water in New York is a relatively constant 48 to 53 degrees F all year, it is an excellent heat source.

Q: What do I do with the discharge water?
A: 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 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.

Q: How much ground water does an open-loop system need?
A: Ground-source 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 4 to 12 G.P.M. while operating. An extremely cold day might result in a usage of 4,000-10,000 gallons of water. 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.

Q: What problems can be caused by poor water quantity?
A: 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 dealer or equipment manufacturer can tell you what level of water quality is acceptable. Our heat pumps are available with Cupronickel heat exchangers for corrosive water situations. 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 buildup. Impurities, particularity 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.

Q: Does an open loop system cause environmental damage?
A: No. They are pollution free. The heat pump merely removes heat from or adds heat to the water. No pollutants are added whatsoever. The only change in the water returned to the environment is as light 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 most parts of New York because of abundant supplies of groundwater.

Q: Are there any laws that apply to open-loop installations?
A: 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.
Q: What are the components of a ground-source heat pump system?
A: The three main parts are the heat-pump system, the liquid heat exchange medium (open or closed loop), and the delivery system. Most systems heat and cool air and use ductwork. Some of our systems heat and cool water for distributing heat into hydronic radiant floors (concrete or wood) and fan coils for cooling.

Q: Are all ground-source heat pumps alike?
A: No there are different kinds of ground-source heat pumps designed for specific applications. Many ground-source 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 degrees F which are possible in closed-loop systems. Most ground-source heat pumps provide summer air conditioning, but a few are designed only for winter heating. Sometimes these heating-only systems incorporate a ground water cooled coil that can provide cooling in moderate climates. Ground-source 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.

Q: Will I have to add insulation to my home if I install one of these systems?
A: ground-source heat pumps will reduce your cooling costs regardless of how well your home is insulated. However, insulating and weatherizing are key factors in realizing the most savings from any type of heating system. The illustration below shows typical insulating standards suggested by many electric utilities. You may wish to ask your utility for recommendations for your home.
No matter what energy source with which you heat your home insulation is a very good investment.

Q: Can a ground-source heat pump also heat water for my home?
A: Yes. Using what's called a dhw condenser, some types of ground-source heat pumps can save you up to 65 percent on your water heating bill by heating tank water. DHW condensers are standard on some units, optional on others.

Q: Is a ground-source heat pump difficult to install?
A: Most units are easy to install, especially when they are replacing 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, fan coils or radiant floor tubing must be installed in homes that don't have an existing distribution system. The difficulty of installing ductwork or radiant floors will vary and should be assessed by a contractor.

Q: Can a ground-source heat pump be added to my fossil fuel furnace?
A: 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.

Q I have ductwork, but will it work with this system?
A: In all probability, yes. Your dealer should be able to determine ductwork requirements and any minor modifications, if needed.

Q: Do I need to increase the size of my electric service?
A: Ground-source heat pumps don't use large amounts of resistance heat, so your existing service may be adequate. Generally, a 200 ampere service will have enough capacity, and smaller amp services maybe large enough in some cases. Your electric utility or contractor can determine your service needs.

Q: Should I buy a heat pump large enough to heat my home with no supplemental heat?
A: PDG or the manufacturer will do a heating and cooling load calculation (heat loss, heat gain) to guide in equipment selection (copy available on request). Most ground-source heat pumps are sized to meet your heating requirements to an outdoor temperature of about 0 to 10 degrees F. For sustained temperatures below that point, some supplemental heat probably will be needed. Sizing the heat pump to handle your entire heating need may result in slightly lower heating costs, but the savings may not offset the added cost of the larger heat-pump unit. Also, an oversized unit can cause dehumidification problems in the cooling mode, resulting in a loss of summer comfort.

Q: Do ground-source heat pumps have outdoor units?
A: No. The equipment goes inside your home, usually in the basement, garage or crawl space. Because it's indoors and water is a better heat transfer media than air, the life spans of the compressor and major components are greatly extended, most having a lifespan of 20 years or more.

Q: How efficient is a ground-source heat pump?
A: They are more than three times as efficient as the most efficient fossil fuel furnace. Instead of burning a combustible to make heat, they simply move heat that already exists doing that, they provide at least three units of energy for every one used to power the heat-pump system.

Q: What does a system like this cost?
A: A system for the typical home will cost slightly more than if you bought a separate furnace and central air-conditioning system. But you wouldn't really be comparing apples to apples. To accurately compare the costs you need to consider the following: Payback, or how long it takes to recover the difference in costs between the two systems using energy savings. Payback for most ground-source heat-pump systems runs two to six years. Another way to look at payback is at its inverse which is the return on investment. With the return on investment you can compare the additional investment in the system with other investments such as CD's, bank accounts, stocks, bonds, etc. If the ground source system yields a higher rate of return on the investment then it is worth considering. Energy efficiency of the two systems. To get an accurate picture, make sure efficiency claims are substantiated. Your lifestyle and how well your home is insulated affect how economical a system will be. Total operating savings from heating, cooling and domestic hot water must be combined to get an accurate picture of total energy savings. Energy costs and availability of fuel, both in the present and the future.

Maintenance costs and system reliability. System lifespan.

Q: What about comfort?
A: A ground source heat pump system moves warm air (90 degrees to 105 degrees) or warm water (100 to 125 degrees) through out your home via a standard duct network or hydronic system. Typically, a very even comfort level is found through out the home. This is because the warm air is moved in slightly higher volumes and, therefore, saturates the home with warmth more evenly. This helps even out hot or cold spots and eliminates the cold air and hot air blasts common with fossil fuel furnaces. It's also a great comfort to know that you've reduced your energy consumption while using an inexhaustible energy source, the earth.

Q: Which system is best, open or closed loop?
A: The net results in operating cost and efficiency are virtually the same. Which system you choose depends on whether you have an adequate ground water supply and a means of disposal. If you do, an open system can be used effectively. If not, either a horizontal or vertical closed loop system is your best choice. Over a period of time the closed loop system offers less maintenance because it is sealed and pressurized, eliminating any possible build up of mineral deposits.
 

Questions you should ask about a new heating system:

Regardless of the type of heating system you may be considering for your home or business, there are specific questions you should ask the dealer installer. These questions deal with finding out the actual efficiency of the system, any operating limitations it may have, and the bottom line of operating costs. The answers here are meant as a guide for what you should try to find out with your questions.

Q: What is the Btu size of the furnace that's being proposed?
A: 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 know what size furnace you'll need, you must have a heat loss heat gain calculation done on your home. From that, an accurate determination can be made on the size of the heating system you'll need. Most fossil fuel furnaces are substantially oversized for home heating requirements, resulting in increased operating cost.

Q: Is the efficiency rating actual or just a manufacturer's average?
A: All types of heating and cooling systems have a rated efficiency. Fossil fuel furnaces have a percentage efficiency rating. Natural gas, propane and fuel oil furnaces have efficiency ratings based on laboratory conditions. To get an accurate installed efficiency rating, factors such as flue gas heat losses, cycling losses caused by over sizing, blower fan electrical usage, etc., must be included. ground-source 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 ratio of how much energy the system produces versus how much it uses. Most ground-source heat pump systems have COPs of 3.O-4.0. That means for every one unit of energy used to power the system, two and one-half to three and one-half units are supplied as heat. Where a fossil fuel furnace maybe 50 to 90 percent efficient, a ground-source heat pump is about 3OO percent efficient. Some ground-source heat pump manufacturers and electric utilities use computers to accurately determine the operating efficiency of a system for your home.

Q: Will the minimum entering water temperature have an affect on which heat pump I buy?
A: if you have an open-loop system your entering water temperatures (EWTs) will rarely fall below 5O degrees F- Almost all ground-source heat pumps will operate efficiently at those temperatures. A closed-loop system, on the other hand, will encounter EWTs below freezing. And not all ground-source heat pumps will operate at those low EWTs it's important to know what EWTs your heat pump will handle

Q: Are the dealer and loop installers qualified?
A : Don't be afraid to ask for references from dealers. A reputable dealer won't hesitate to give you names and numbers to call to confirm his capabilities the same with the loop installer.

Q: Will open or closed loop be best for you?:
A: Will the loop joints be heat fused? : The only acceptable method for joining sections of the special pipe used for closed-loop systems is heat fusion, any other method will eventually result in failure of the loop.

Q: How long is the payback period for your ground-source heat pump system?
A: To figure the- accurately, you must know how much per year you will save in energy costs with a ground-source system and the difference in costs between it and a conventional heating system and central air conditioner. As an example if you'll save $700 per year with a ground-source system and the cost difference is $2,000, your payback will be less than three years.