September 13, 2010

This is a subject every homeowner in Idaho Falls should understand, too, because earth loops are right at the heart of a geothermal system. They constitute its biggest advantage over conventional heating and cooling technologies.

So, what exactly does an earth loop do? It transfers heat to and from the ground – eliminating the need for fossil fuels. And that’s especially good news for Idaho Falls residents.

Earth loops come in two basic types. Closed loops are buried in the earth or submerged in a lake or pond. They transfer heat by circulating a solution of water and environmentally safe antifreeze. Open loops use groundwater pumped from a well as a heat source. Which type you use depends on the terrain, the cost of trenching or drilling, the availability of quality groundwater, and what space is available.

Horizontal Trench Loops

If you have enough useable land, horizontal loops can be installed. This is done by digging trenches with a backhoe or a chain trencher. Then, you insert polyethylene pipes backfill the trenches. Various horizontal loop configurations are possible, using one, two or three circuits per trench. The more pipes you have in each trench, the shorter the trench can be. Trenches normally range from 100 to 300 feet , depending on the design. A typical home requires 1⁄4 to 3⁄4 of an acre for the trenches.

A variation on the horizontal loop is the horizontal bore loop. This type of loop is most often used in a retrofit situation to minimize disruption to the landscape. It requires special equipment to bore holes horizontally under the surface. The operator can “steer” the drill head to go deeper or shallower, or turn right or left. This machine drills at a slight angle down to a typical depth of 10-12 ft., then back to the surface, typically 200 ft. away. At that point, two ends of pipe are attached to the drill bit and pulled back through the hole until the pipe is buried. This technique allows the loop to be placed.

Vertical Loops

Vertical loops are used where space is limited or where soil conditions make horizontal loops impractical. You need a drilling rig to install vertical loops. And you need to bore multiple holes about 10 feet apart. Then, you insert a double pipe connected with a U-bend into each hole, fill the hole with grout to seal it and provide good contact around the pipe and connect the pipe to a header system horizontally a few feet below the surface. The depth of the holes is dependent upon soil/rock conditions and the size of the system. Although most holes are bored about 100 to 250 feet deep, there’s no “magic depth” that needs to be reached. Capacity is not based on depth; rather how much pipe is in the ground and the overall thermal conductivity of the borehole.

Pond Loops

If an adequately sized body of water is close to your Idaho Falls home, we at Conan Heating & Air Conditioning can install a pond loop. A series of sealed pipes containing a mixture of water and antifreeze can be coiled and sunk to the bottom. Using pond water directly is never recommended. A 1⁄2-acre, 8-foot-deep pond is usually sufficient for the average home. Ideally, the pond should be close to the home (less than 200 ft.). If the pond is farther from the home, the benefit of using a pond loop is reduced due to added trenching, materials and pumping costs.

Pond loop coils are connected together on dry land, then floated into location. Once filled with fluid, they will sink to the bottom and remain there. Generally, a 300 ft. coil is used for each ton of capacity. This is less pipe than is used in an earth loop because water is a better conductor of heat energy. Pond loops are a cost-effective way to install a geothermal system because trenching is limited to only the supply and return piping from the pond to the house.

Open Loop (Well System)

If an abundant supply of quality well water is available, an open-loop system can be installed. A proper discharge site, such as a ditch, field tile, stream, or pond, must also be available. Be sure to check all local Idaho Falls codes before selecting a discharge method. This installation usually costs less to install and delivers the same high efficiency since groundwater maintains a relatively constant temperature year-round. Depending on water quality, periodic cleaning of the heat exchanger inside the unit may be necessary. Well water containing too many contaminants may not be suitable for use with a geothermal system as it may cause the unit’s performance to degrade over time. Proper testing of the water prior to installation is required.

For more information, contact Conan Heating & Air Conditioning, your geothermal heating and cooling authority in Idaho Falls, ID.

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