Definition A ground source heat pump is also known as a geothermal heat pump. These words are used

Photo Jan 08, 7 50 26 PM (1)interchangeably to mean the same kind of heat pump system. A geothermal heat pump system uses the earth as a source of heat since the earth’s temperature at certain depths remains constant. This kind of heat pump system will transfer heat from a cool space to a warm one and also enhance the natural flow of heat from a warm space to a cool one.Earth’s TemperaturesThe temperatures of the earth are moderate at various depths and the sun’s rays also keep the earth at constant temperatures. To get an idea of the temperature underground, it may help to understand that a ground source heat pump takes advantage of the fact that at approximately 20ft below the surface of the ground, the temperature is equal to the mean annual air temperature for that latitude. The temperature below this 20ft will remain between 50 and 60F.Photo Jan 08, 7 50 25 PMCoefficient of Performance

The measurement of the efficiency of a ground source heat pump is expressed in terms of the coefficient of performance or COP=Q/W. Further, Q is the heat supplied to or removed from the original source and W is the work being done by the system to provide the heat. Ground source heat pumps are able to achieve a very high COP as compared to an air source heat pump. Ground source heat pump systems are among the most efficient ways of providing heating and cooling to a 21st century dwelling.

It is important to add that the initial cost of installation is more than an air or fuel source heat pump system since digging in the earth is required along with the accurate laying of a supply grid of piping below the surface of the ground. However, if the tax credits at the federal and state level are subtracted from the cost and the overall energy savings over a period of a year are calculated, then the system will not only pay for itself, but save you money for years to come.

Variety of Systems

Direct Exchange systems are the oldest form of heat transfer mechanisms being used with ground source heat pumps. There is one, continuous loop of underground piping that circulates water and some form of refrigerant. The piping is in direct contact with the earth. The direct exchange refers to the fact that the heat transfer does not require an additional fluid.

Photo Jan 08, 7 50 25 PMClosed Loop

In a closed loop ground source heat pump system, there are two loops of piping and fluids to be considered. There is a primary refrigerant loop that is contained inside the heat pump appliance and that is where the heat exchange takes place. There is another series of piping that is buried in the ground. The fluid leaving the heat exchanger flows through the secondary loop and exchanges heat with the earth. The closed loop system requires two pumps. The closed loop ground source heat pump system is not as efficient as the direct exchange system as it requires larger and longer pipes and additional pumps to be effective.

Vertical Closed Loop Systems

The pipes in this kind of ground source heat pump system Photo Jan 08, 7 50 26 PMare installed in the earth vertically. The hole that is placed in the ground to contain these pipes can run as deep as 400 feet depending on the climate and the average temperature of the soil in that geographic space on the earth. The pipes in this installation are then surrounded by a bentonite grout that increases the level of conductivity between the pipes and the surrounding soil. Vertical installations are useful on properties that are not large and the homeowner is limited in terms of acreage.


Horizontal Closed Loop System

Photo Jan 08, 7 50 26 PM (2)The pipes in the kind of ground source heat pump system are placed in the ground horizontally. A trench is dug below the frost line and pipes are laid horizontally in the trench. The depth at which these horizontal pipes are placed must be calculated in order to achieve an optimum level of efficiency. If the trench is not deep enough the pipes may draw more heat from the sun’s impact on the surface of the soil instead of the constant temperatures at deeper levels. In areas of the world where the sun does not shine for a full 12 hours or winter prevents powerful sunshine from heating the soil, the system will be less efficient.


A ground source heat pump system is a powerful and efficient way to heat and cool a dwelling. It is environmentally friendly, extremely cost efficient, and will significantly decrease the carbon footprint on the earth.

Don JohnsonDon Johnson is the President of Freedom Heating and Cooling in Birmingham, Alabama which offers home owners tools including:

9 Things to Check Before Calling for Service on Your Air Conditioner or Furnace”,  a resource to help home owners save on HVAC problems
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The Ultimate Home Owner’s Guide to Designing an HVAC System , a 59-page eBook covering the 9 steps to building a Complete Home Comfort System.   Find More free eBooks at or contact him at 205-444-4444 or connect on facebook,   LinkedIn or Google +