At the heart of a geothermal system is the earth loop. This earth loop is the vehicle that transfers heat to or from the ground, distinguishing geothermal from conventional equipment.
Earth loops come in two basic types: closed and open. Closed loops, made of durable plastic pipe, are buried in the earth or submerged in a lake or pond, and transfer heat by circulating a solution through the system.
Open loops use ground water pumped from heat source such as a well. The decision on which loop configuration to use depends on the land terrain, the cost of trenching or drilling, the availability of quality ground water and the availability of land. This technique allows the loop to be placed underneath homes, basements, wooded lots or even swimming pools without disrupting grass or landscaping. Because water transfers heat better than soil, closed loops can be coiled and placed on the bottom of a pond or lake where it transfers heat to or from the water. A 1/2 acre, 8-foot-deep pond is usually sufficient.
Pond or lake loops often require less excavation than vertical and horizontal loops; therefore, they are often less expensive to install. Horizontal Loops are used where adequate land is available. One or more trenches are dug using a backhoe or chain trencher. Pipes are inserted and the trenches are back filled.
Vertical LoopsVertical Loops are installed where space is limited. Holes are bored using a drilling rig, the pipe is inserted, and the holes are filled. The pipes are connected horizontally a few feet below the surface.
Horizontal LoopsHorizontal Loops are often used when adequate land surface is available. Depending on geothermal system needs and space available, pipes are placed in trenches that range in length from 100 to 400 feet.
Pond LoopsPond Loops can be installed if an adequately sized body of water is located close to the home. A series of coils are sunk to the bottom, connected by a header with supply and return pipes leading to the home.
Open Loops are used where there is an abundant supply of quality well water. The well must have enough capacity to provide adequate flow for both domestic use and the geothermal system.