Q: What is a geothermal heat pump?
A: 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.
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 that the flow of heat is reversed.
Q: How does the underground pipe system work?
A: The idea to bury pipe in the ground to gather heat energy began in the 1940’s. But steady improvements in heat pump design, more robust pipe materials and worry-free pipe joining methods have been combined to make geothermal heat pumps the most efficient and reliable heating and cooling systems available.
Q: What is a closed-loop” system?
A: 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 existing natural sources, a closed-loop system recirculates its heat transferring solution in pressurized pipe.
Q: Where can this loop be located?
A: That depends on land availability and terrain. Some 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 to seven 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, 600-1,000 feet of pipe is required per ton of system capacity. A well-insulated, 2,000-square-foot home would require approximately a four-ton system with 2,400-4,000 feet of pipe.
Q: How many pipes are in a trench?
A: Normally, two runs of pipe are laid at six feet then looped back over itself at four 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?
A: Closed-loop systems can also be vertical. Holes are bored to about 150-250 feet per ton of heat pump capacity. U-shaped loops of pipe are inserted in the holes. The holes are then grouted with a bentonite slurry. Subsurface rock normally does not pose a problem, although extremely hard rock or unconsolidated material can make a vertical loop difficult to install.
Q: How long will the loop pipe last?
A: Closed-loop systems should only be installed using high-density polyethylene with the correct cell classification. This pipe has a half-life of 100 years and is inert to chemicals normally found in soil and have good heat conducting properties. PVC pipe should not be used under any circumstances.
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-twelve feet in depth at its lowest level during the year is needed for a pond to be considered.
Q: If the ground is only 55 degrees, how does it heat my home to 72 degrees?
A: The earth stores a vast amount of heat energy from our sun. This heat energy is spread out over a large area and captured into the loop system. Inside the geothermal heat pump unit, the heat is concentrated via a refrigeration process and delivered to your home at temperatures in excess of 100 degrees F.
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 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 effect on grass, trees or shrubs. You will of course notice 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: This practice is typically discouraged. An earth loop may 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?
A: No. The antifreeze solution in the loop will prevent freezing down to approximately 15 degrees F. Three types of antifreeze solution are acceptable: propylene glycol, ethyl alcohol 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. Non-professional installations may result in less than optimum system performance.
Q: What is an “open-loop” system?
A: 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.
Q: Can a geothermal heat pump also heat water for my home?
A: Yes. Using what’s called a desuperheater, some types of geothermal heat pumps can save you up to 75 percent on your water-heating bill by pre-heating tank water. Desuperheaters are standard on some units, optional on others. Some geothermal models can provide all of your hot water needs on demand at the same high efficiencies as the heating/cooling cycles.
Q: Can a geothermal 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 installing contractor should be able to determine ductwork requirements and any modifications, if needed.