There are four basic types of ground loop systems.  Three of these - horizontal, vertical, and pond/lake - are closed-loop systems. The fourth type of system is the open-loop option. Factors affecting which one is best include:  climate, soil conditions, available land, and local installation costs at the site.  All of these systems can be used for residential and commercial building applications.

CLOSED-LOOP SYSTEMS

HORIZONTAL: This type of installation is generally most cost-effective for residential installations, particularly for new construction where sufficient land is available. It requires trenches at least four feet deep.  The most common layouts either use two pipes, one buried at six feet, and the other at four feet; or two pipes placed side-by-side at five feet in the ground in a two-foot wide trench. The Slinky^TM method of looping pipe allows more pipe in a shorter trench, which cuts down on installation costs and makes horizontal installation possible in areas it would not be with conventional horizontal applications.

VERTICAL: Large commercial buildings and schools often use vertical systems because the land area required for horizontal loops would be prohibitive.  Vertical loops are also used where the soil is too shallow for trenching, and they minimize the disturbance to existing landscaping. For a vertical system, holes (approximately four inches in diameter) are drilled about 20 feet apart and 100-400 feet deep.  Into these holes go two pipes that are connected at the bottom with a U-bend to form a loop. The vertical loops are connected with horizontal pipe (i.e., manifold), placed in trenches, and connected to the heat pump in the building.

POND/LAKE: If the site has an adequate water body, this may be the lowest cost option. A supply line pipe is run underground from the building to the water and coiled into circles at least eight feet under the surface to prevent freezing.  The coils should only be placed in a water source that meets minimum volume, depth, and quality criteria.

OPEN - LOOP SYSTEM

This type of system uses well or surface body water as the heat exchange fluid that circulates directly through the GHP system. This system can be installed if an abundant supply of high quality well water is available. A typical home will require 4 to 8 gallons of water per minute. A proper discharge area such as a river, drainage ditch, field tile, stream, pond, or lake must be present. Check your local codes for restrictions before selecting a specific discharge method.