Geothermal heat pumps: Open loop systems FAQ

Q: 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, and 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.

Q: 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.

Q: 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 ~10 g.p.m. 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.

Q: 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 quality 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
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?
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 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 groundwater.

Q: 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.

Geothermal Heat Pumps: Closed loop systems FAQ

Q. 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 systemthat consumes water from a well, a closed-loop system re-circulates its heat transferring solution within a pressurized piping system.

Q: Where can this loop be located?

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?

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 trenches according to the shape of the land. As a rule of thumb, 500-600 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 1,500-1,800 feet of pipe.

Q: 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.

Q: What if I don't have enough room for a horizontal loop?
Closed-loop systems can also be vertical. Holes are bored to about 120 - 150 feet per ton of heat pump capacity. U-shaped loops of pipe are inserted in the holes. The holes are then backfilled with a sealing solution.

Q. How long will the loop pipe last?
Closed-loop systems should only be installed using high density polyethylene or polybutylene pipe. Properly installed, these pipes will last 50-75 years. They are
inert to chemicals normally found in soil and have good heat conducting properties. PVC pipe should not be used under any circumstances.

Q: How are the pipe sections of the loop joined?

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 is certain to result in loop failure due to leaks.

Q: 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 six inches 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?
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.

Q: If the loop falls below freezing, will it hurt the system?
No. The antifreeze solution in the loop will keep it from freezing down to about 10
degrees F. Three types of antifreeze solution are acceptable: propylene lycol, calcium chloride and methyl alcohol.

Q: Can I install an earth loop myself?

It's not recommended. In addition to thermal fusion of the pipe, good earth coil contact is very important for successful loop operation. Non-professional installations may result in less than optimum system performance.

Q: I have a pond near my home. Can I put a loop in it?

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. In pond loops, copper, polyethylene or polybutylene pipe can be used.

FAQ: What is a closed loop system?

Q. 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 re-circulates its heat transferring solution within a pressurized piping system.

FAQ: Does the underground pipe system really work?

Q. Does the underground pipe system really work?
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 its only been in the last few years that new heat pump designs and improved pipe materials have been combined to make geothermal heat pumps the most efficient heating and cooling systems available.

FAQ: What types of loops are available?

There are two main types: open and closed. The next two sections will give you specifics about each.

FAQ: Do I need separate ground loops for heating and cooling?

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

FAQ: You mentioned heating and cooling - does it do both?

Q. You mentioned heating and cooling - does it do both?
One of the things that makes a heat pump so versatile is it's ability to be both 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 thermostats. 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 loop system.

FAQ: How is the heat transferred between the earth and home?

Q. How is the heat transferred between the earth and home?
The earth has the ability to absorb and store heat energy from the sun. To use that stored energy, heat is extracted from the earth through a liquid medium (groundwater or an anti-freeze solution) and is pumped to the heat pump or heat exchanger. There, the heat is used 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.

FAQ : How does the heat pump work?

Q. How does it work?
Like any type of heat pump, it simply moves heat energy from one place to another. Your refrigerator works using the same scientific principle. By using the refrigeration process, geothermal heat pumps remove heat energy stored in the earth and/or the earth's groundwater and transfer it to the home.

FAQ: What is a geothermal heat pump?

Q: What is a geothermal heat pump?

A: geothermal heat pump is an electrically powered device that uses the natural heat storage ability of the earth and/or the earth’s groundwater to heat and cool your home or business.

Most efficient and economical resource for heating and cooling

May be you don't know but the most efficient and economical resource for heating and cooling your home is right in your own backyard.

Although temperatures in the atmosphere can vary considerably over the course of a year (or even a day), the temperature underground remains fairly constant. At about six feet under, the soil measures from 45 degrees to 75 degrees fahrenheit, depending upon latitude. And this consistency, it turns out, can be a resource for keeping one's home warm in the winter and cool in the summer. ground source heat pump

In winter, ground source heat pump transfer heat from the earth into building to heat up the rooms. In summer, the ground source heat pump transfer heat from building into the earth to keep the rooms cool.

Economics of a Heat Pump

A heat pump can move 3 to 4 times more heat to or from a building than the energy required to operate it.

The energy efficiency of heating equipment can be compared by looking at the rated COP or Coefficient of Performance of the unit. COP is the ratio of energy output to energy input thus a higher COP rating indicates a more efficient unit. The COP of an electric furnace is 1, since each watt of electricity put into it produces the equivalent of 1 watt of heat energy out. The COP of a NORDIC unit is 3 or greater. Each watt the heat pump uses to run its transferring mechanism enables it to draw 2 or more from the earth thus giving a total of 3 or more units
out for every 1 unit put in. The heat pump supplies more than 2/3 of your energy requirement from free energy stored in the earth and reduces your heating cost by at least 66% One of the innovative features of the NORDIC unit is its ability to provide "free" hot water during summer operation. Btu output actually increases during hot water making cycles and the recovery rate is similar to that of a 40 gallon electric hot water heater. Hot water is also provided during winter operation at a saving of 65-70% less than the cost of heating the water with an electric hot water heater. A typical homeowner can expect this feature alone to save him 20 to 30% of his present electric bill.

Definition of a Heat Pump

Simply stated a heat pump is an electrically driven mechanical device which absorbs heat energy at one location and transfers it to another. Geothermal heat pumps use the natural heat storage ability of the earth or the earth's groundwater to heat and cool your home or business.

Energy can exist around us in the form of heat, light, mechanical, electrical or chemical energy, and although energy can neither be created nor destroyed, it can be changed from one form to another and moved from place to place. A heat pump derives its name from its ability to "pump" or move heat from one area to another.

Heat pumps do not produce energy by themselves any more than a well water pump can produce water by itself. The well pump needs to be attached to a source of water before it can pump any water. Similarly a heat pump will not produce any heat if not connected to an energy source such as the earth; however, if an energy source is available and the heat pump is able to tap it then vast amounts of energy can be moved at very little cost.

Geothermal Heat Pumps are ...

The geothermal heat pump, also known as the ground source heat pump, is a highly efficient renewable energy technology that is gaining wide acceptance for both residential and commercial buildings. Geothermal heat pumps are used for space heating and cooling, as well as water heating. Its great advantage is that it works by concentrating naturally existing heat, rather than by producing heat through combustion of fossil fuels.