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