There are five basic types of ground loop systems. Four of these -- horizontal, slinky, basket and vertical -- are closed-loop systems. The fifth type of system is the open-loop option. Which one of these is best, depends on the land available, climate, soil conditions, geology, hydrogeology, and local installation costs at the site. All of these approaches can be used for residential and commercial building applications. The ground loop is INDEPENDENT of the inside components selection, i.e. radiators, duct air, fan coil units, or underfloor piping systems.
Water well loop
This type of system uses well or surface body water as the heat exchange fluid that circulates directly through the GHP system. 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, and all local codes and regulations regarding groundwater extraction and discharge are met.
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 1.5 meter deep. The most common layouts either use two pipes, one buried at 2.5 meters, and the other at 1.5 meter, or two pipes placed side-by-side at 1.5 meter in the ground in a 0.6 meter wide trench. 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. Every loop is connected to a header that leads to heat pump. Headers are placed in trenches.
A slinky loop of fluid-filled pipe, that performs the same function as any other horizontally-deployed ground loop pipe in a ground source heat pump system. But the slinky is different than straight pipe runs , because for the same amount of ditch length, one can alter the spacing between pipes more uniformly than with multiple pipe loops at the same depth, and with better thermal performance than straight pipe runs at multiple depths in the same ditch. Slinky type of loops are designed in order to save space and increase performance. However, slinkies require technical knowledge in order to be contructed correctly. The pitch in every slinky coil should be maintained constant. Each slinky is connected with a horizontal pipe that is placed within trenches and is connected to the heat pump.
Basket loops are mainly conical loops and are installed in batches. They are very similar to the cylindrical loops but they tend to be more efficient due to heat rejection which is easily succeeded. Basket loops are excavated in batches not trenches. Every single excavation is approximately 3.5 meters in depth and the land requirement for every single basket is less than 5 square meters. Each basket is connected with headers, that are placed in trenches, and connected to the heat pump in the building.
Large commercial buildings 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 to five inches in diameter) are drilled about 5 meters apart and 50 to 150 meters deep. Into these holes fit two or four pipes that are connected at the bottom with a U-bend to form a loop. The vertical loops are connected with horizontal pipe, placed in trenches, and connected to the heat pump in the building.