There are four basic types of Ground Heat Pump loop systems. Three of these:
are closed-loop systems.
The fourth type of Heat Pump is the open-loop option. Which one of these is best depends on the climate, soil conditions, available land, & local installation costs at the site. All of these approaches can be used for residential or/and commercial building applications.
This type of installation is generally most cost-effective for residential installations, in particularly for new construction where sufficient land is available. It requires trenches at least four feet deep (1.2-4m – the deeper the better).
The most common layouts either use two pipes, one buried at six feet, & 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 The Slinky™ 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.
Large commercial buildings & 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 (30-120m) 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, & connected to the heat pump in the building.
A supply line pipe is run underground from the building to the water & 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 & quality criteria. In small pond near the house is not indicated !
Once it has circulated through the system, the water returns to the ground through the well, a recharge well, or surface discharge.
This option is obviously practical only where there is an adequate supply of relatively clean water, & all local codes & regulations regarding groundwater discharge are met.