Types of Geothermal Systems

Horizontal Loop

Vertical Loop

Open Loop

1. Closed Loop. Loops of pipe are buried at a depth of 6 ft (2m) or greater in the ground. Pipes are placed horizontally or in deep, vertically-drilled holes, often 200 ft (60m) or greater below ground level. Water and antifreeze (or other transfer fluid) are circulated through the heat exchanger (heat pump) and back out through the loops continuously. Some closed loop systems bleed off a portion of their working fluid to keep the source temperature stable.

a . Horizontal Loop: If adequate land area without hard rock is available, a horizontal loop installation is usually the most economic. Horizontal loops are often used for newly constructed homes and commercial buildings. A horizontal system uses a number of trenches. The piping can be configured in the trenches in several ways:
- A single pipe;
- Multiple pipes in a narrow trench;
- Multiple pipes in a wider trench.
The trenches are normally four feet deep or more, and vary in length depending on the number of pipes to be buried. One of the advantages of a horizontal loop system is being able to lay the trenches according to the size of the lot.

b. Vertical loops: If the land area available is limited, a vertical loop may be installed for the geothermal piping. Vertical installations might also be used where the land is too rocky for trenching, for existing buildings, and for large commercial or educational facilities.

To install a vertical loop, a contractor will bore holes into the ground. Long, hairpin-shaped loops of pipe are then inserted. The hole is backfilled, plugged or grouted, and the pipes are connected to headers in a trench leading back to the building.

The drilling depth is determined by the lowest total cost based on the conditions at the job site. A typical borehole depth is 150 to 250 feet. The objective of a vertical borehole is to install a specific amount of pipe, not to reach a certain depth. If 1,200 feet of pipe are required, three 200-foot boreholes are acceptable and may be more cost-effective. Drilling boreholes for geothermal loops is much simpler than drilling to find well water. The borehole is generally smaller, which reduces drilling time, and no casing is required because the hairpin-shaped loop is the casing.

2. Open Loop- Geothermal heat pump system that uses groundwater from a conventional well as a heat source. The groundwater is pumped into the heat pump unit where heat is extracted, then the water is disposed of in an appropriate manner. Since groundwater has a relatively constant temperature year round, it is an excellent source of heat.

You must have a large volume of water to use an open loop system. You typically need about 7-15 gallons of water per minute. This will depend on the size of system required to heat your home. The water can be pumped from one well to another well or pond. This replenishes the aquafier. The only thing that happens to the water is that heat is taken from the water or injected into the water.

Absolute Service Co.
46105 Garrett's Lk. Rd
Shawnee, OK 74804
p. 405.275.7305 or 405-382-6600