Geothermal heat pumps take advantage of relatively consistent temperature of the ground or water sources. Geothermal loops are a pipe system that transfers water and heat to and from the ground to ultimately provide highly efficient heating and cooling in your home. Geothermal loops are often categorized into two different types; closed loops or open loops.
Geothermal closed loops allow the geothermal system to pump water into loops or pipes buried into the ground and return the same water back to the system after the heat transfer has been accomplished. Geothermal closed loop can be installed in either a horizontal, vertical or pond configuration. Horizontal loop systems require a larger amount of land spreading pipe between 4 and 6 feet deep throughout the lot. Vertical loop systems bury one loop per ton of cooling required roughly 150 feet into the ground. Vertical loops are less like to be affected by extreme climate and drought due to the depth of the loop. Pond loops are used when a water source is readily available. The loop is submerged into the body of water. The body of water considered for this type of loop must meet certain requirements to ensure consistent heat transfer, larger and deeper is better.
Geothermal open loops system is also commonly named pump-and-dump. Open loop systems uses a water pump within a well water source to pump water into the geothermal unit. After the water passes through the geothermal heat pump it is discharged to a determined location such as a small pond. Not all wells are suitable for geothermal use. The quality and amount of water available must be assessed to determine suitability.
Here is a great video explaining geothermal loops and the advantages of each.