Closed Loop

A Heat Exchanger within the Ground

Closed loop geothermal systems utilize a series of piping buried in the ground  or submerged in a pond to create a heat exchanger. This piping is filled with a water/antifreeze solution (loop solution) that allows the geothermal system to take advantage of the constant temperatures stored in the earth or pond.  There are several types of systems.  Horizontal, Pond & Vertical.

The loop solution which circulates in the closed piping system absorbs heat or rejects heat into the surrounding earth or water. Closed loops can be installed into ponds, excavated and buried in the ground in a horizontal configuration using a backhoe, or drilled vertically with drill rig. Closed loops are virtually maintenance free, recirculating the same loop solution, and having no need for a well or drain to discharge the water. Due to the excavation and loop piping material costs, closed loops systems are generally more expensive to install than open loop systems.


Types of closed loop systems:

Horizontal closed loop systems

Horizontal Closed Loop Systems are commonly installed using a backhoe which opens a trench 2 feet wide and 6 feet deep. Three rows of polyethylene pipe are installed into the bottom of the trench at 6 feet deep, covered by 2 feet of soil, and a second layer of pipe is installed at 4 feet deep. The entire trench is back-filled and the series of 6 pipes is joined by a heat fusion process into 2 larger pipes that serve as supply and return lines (extended header). The extended header is installed through the foundation and connected from the loop pump to the unit.

 

Pond-Coupled Closed Loop Systems

Ponds with at least 10 feet deep water and a minimum half acre surface area make an excellent choice for a closed loop application.  A pre-assembled heat exchanger made of polyethlyene plastic pipe is floated onto the surface of the pond, connected with an extended header, filled with a loop solution and submerged.  Pond-coupled systems can reduce excavation costs and provide a lower installation cost than other closed loop (horizontal or vertical ) system options.

 

Vertical Closed Loop Systems

Where land space is more limited or no pond is available, vertical closed loop systems can be installed into the ground by utiliizing a drill rig which bores open a series of vertical shafts or bore holes.  Two polyethylene coils connected at the bottom by a fusion U-Bend are pulled into each bore hole and then grouted closed.  Each pipe is connected into a central extended header and into the home.  Generally more expensive to install, a vertical closed loop system could be installed in nearly any location.