The process of elevating low-temperature heat to over 100°F and transferring it indoors involves a cycle of evaporation, compression, condensation and expansion. A refrigerant, like Freon, 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 a gas as heat is absorbed. The gaseous refrigerant then passes through a compressor where the refrigerant is pressurized, raising its temperature to over 180°F. The hot gas then circulates through a refrigerant-to-air heat exchanger where heat is removed and pumped into the building at about 100°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 again. To become an air conditioner, the flow is reversed.

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.

How does a geothermal system work?
Throughout the year, outdoor temperatures fluctuate with the changing seasons. However, underground temperatures do not. In fact, about six to eight feet below the earth's surface, temperatures remain relatively constant year-round. A geothermal system, which consists of an indoor unit and a buried earth loop, capitalizes on these constant temperatures.

In the 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 the summer, the system reverses, pulling heat from the building, carrying through the earth loop and depositing it in the cooler earth.

What makes a geothermal system different from conventional systems?
A geothermal system utilizes the energy from the sun, which is stored in the earth, to heat and cool homes and buildings. Typically, electric power is used only to operate the unit's fan, compressor and pump. So, unlike conventional systems, geothermal systems do not burn fossil fuel to generate heat--they simply transfer heat to and from the earth.

Will a geothermal system provide 100% of heating/cooling needs?
Yes, a properly designed system will provide 100% of heating and cooling needs.

How efficient is a geothermal system?
A geothermal system is more than five times as efficient as the most efficient conventional system. Because geothermal systems do not burn combustible fuel to make heat, they provide three to five units of energy for every one unit used to power the system.

What does geothermal mean to the environment?
Because geothermal systems work with nature, not against it, they minimize the threats of acid rain, air pollution and the greenhouse effect. An environmentally friendly fluid is used in the closed, continuous loop.

Do geothermal systems require much maintenance?
No. In fact, geothermal systems are practically maintenance free. When installed properly, the buried loop will last for generations. And the other half of the operation--the unit's fan, compressor and pump--is housed indoors, protected from the harsh weather conditions. Usually, periodic checks and filter changes are the only required maintenance.  

Are the dealer and loop installers qualified?
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. Check that the installer is certified by IGSHPA (International Ground Source Heat Pump Association).  http://www.igshpa.okstate.edu/

How long is the payback period for your geothermal heat pump system?
To figure this accurately, you must know how much per year you'll save in energy costs with a geothermal system and the difference in costs between it and the alternative heating system and central air conditioner. To calculate your return on investment (payback in number of years) divide the annual savings into the additional cost. When you install a geothermal system in a new home, the monthly savings in operating costs will generally offset the additional monthly cost in the mortgage, resulting in a monthly positive cash flow immediately. Keep in mind that energy savings is only one of the many benefits you receive from a geothermal system.

How is heat transferred between the earth and the home or building?
The earth has the ability to absorb and store heat energy. 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 the air. In summer, the process is reversed and indoor heat is extracted from indoors and transferred to the earth through the liquid.

Does it do both heating and cooling?
One of the things that make 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. 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.

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 vice versa, is that the flow of heat is reversed.

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.

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

How deep and long will my trenches be?
Trenches are normally 7 to 8 feet deep and up to 100 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, 800 feet of pipe is required per ton of system capacity.

What if I don't have enough room for a horizontal loop?
Closed-loop systems can also be vertical. Holes are bored to about 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.

How long will the loop pipe last?
Closed-loop systems should only be installed using high density polyethylene pipe. Properly installed, these pipes will last for many decades and are backed by a 50 year warranty. They are inert to chemicals normally found in soil and have good heat conducting properties.

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 glue joints is certain to result in loop failure due to leaks.

I have a pond nearby. Can I put a loop in it?
Yes, if it's deep enough and large enough. A minimum of 8 feet in depth at its lowest level during the year is needed for a pond to be considered. The amount of surface area required depends on the heating and cooling load of the structure.

Are all geothermal heat pumps alike?
No. There are different kinds of geothermal heat pumps designed for specific applications. Many geothermal 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°F which are possible in closed-loop systems.

Most geothermal heat pumps provide summer air conditioning, but a few brands are designed only for winter heating. Sometimes these heating-only systems incorporate a groundwater cooled coil that can provide cooling in moderate climates.

Geothermal 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.

Will I have to add insulation to my home if I install one of these systems?
Geothermal heat pumps will reduce your heating and 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 and cooling system.

Can a geothermal heat pump also heat water?
Yes. Using what's called a desuperheater, some types of geothermal heat pumps can save you up to 65 percent on your water-heating bill by preheating 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.

Is a geothermal heat pump difficult to install?
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.

I have ductwork, but will it work with this system?
In all probability, yes. Your installing contractor should be able to determine 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. Your electric utility or contractor can determine your service needs.