ground heat-pump loop installation

Ground heat pump loop installation is a professional job. Installers should be certified and experienced when assessing and defining the heat pump loop.

The efficiency of this type of heat pumps depends largely on their ground loop (the series of underground piping). Assuring a correct design and a proper installation is critical, but the issues involving the loop are particularly important.

Defining its extension, configuration and placement isn’t a DIY. It requires architectural, mechanical, electrical, structural and engineering knowledge. Only knowledgeable contractors can assess and define the multiple factors associated with the soil and the most suitable loop type and length.

Image credit: KCP&L, Kansas City Utility

The characteristics and properties of the ground

Factors such as the amount of the soil available and its properties and composition should be properly assessed when designing the loop.

Your soil may or may not have good heat transfer properties (poor transfer properties will require more piping). Your soil may involve hard rock, requiring a vertical ground loop. Or underground water… Or it can be too shallow to trench, requiring the installation of vertical ground loops instead of horizontal loops.

Hydrology and open loop pipes

If your home is close to a well, pump, lake or other type of water source you may consider to use it. In fact, underground heat pump loops can be located in such water sources as long as the volume, depth and water quality satisfy some preconditions.

Open and closed-loop systems designs are possible, when using water sources. In the first case the system uses the water drawn from the well or other source in their pipes. The water is the heat exchanger and is discharged after being used…

Note: closed-loop systems are rather uncommon in residential solutions and pose issues like the quality of the water, its disposal and regulations.

Main options

Loops involve different options that should be carefully assessed. The option closed vs. open ground heat pump loop systems is just one of them. Other more important options include its configuration, extension and the horizontal vs. vertical loop choice…

Horizontal ground heat pump loops

Heat Pump Water Loop Horizontal loops are often less expensive and easier to install than vertical ones. They require trenches at least 4 feet deep and 2 pipes, buried at about 5 feet side by side (or one buried at about 4 feet and the other at 6 feet). These layouts involve at least a two-foot wide trench.

Vertical ground heat pump loops

Vertical loops are typically used when trenches are difficult to drill or when the landscape constraints limit drilling larger trenches, and also when the land is too costly or insufficient.

Installing a Vertical Heat Pump Loop Vertical systems involve holes approximately 4 inches in diameter, drilled 100–400 feet deep and about 20 feet apart. The schematic on left depicts a vertical ground heat pump loop (open design).

The existence of a rock shell can make the vertical ground heat pump loop a convenient choice.

Polyethylene pipe

The loops used in residential close-loop solutions are typically high density polyethylene pipes filled with an eco-friendly mix solution of antifreeze and water.

Ground heat pump loop configuration

Heat Pump Loop with a spiraled design The configuration of the loop depends on the type of soil, the availability of land and cost considerations. Straight loops are still dominant, but spiraled shaped loops are becoming increasingly common (see image on left). They have a big advantage: they allow more pipe in a shorter trench, cutting down on installation costs. That can make horizontal solutions – using more extensive pipes – a better solution… See images from Energy Savers depicting these configurations.

For more technical information, see: Virginia Department of Mines, Minerals and Energy Geo4VA.