Geothermal Installation II
Outdoor Corn Boilers
A successful horizontal ground
loop configuration will have the
following characteristics:

1. Pipe is type 3408 (SDR 11 -
160 psig.) high density
polyethylene.

The number 3408 or PE3408
defines the type of resins used to
manufacture the polyethylene
pipe.

SDR 11 (Standard Dimension
Ratio) is the pipe size.

Psig is pounds per square inch
gauge pressure.
2. 500 ft. of pipe is required for each ton of capacity in a horizontal configuration.

3. A typical configuration consist of a two pipe per trench system wherein a 250 ft. x 4 ft.
wide trench is dug and a 500 ft. roll of 3/4" plastic pipe is rolled out as a "U" tube with 4
ft. of horizontal pipe separation.

4. Multiple parallel loop systems must employ a reverse return (first pipe out is last one
back) header technique to insure even flow through all loops.

5. Horizontal loop systems may also be constructed as a single continuous length of
1 1/2" plastic pipe.

6. Installers have generally gravitated to the multiple loop parallel system since the 3/4"
pipe is easier to handle, less expensive and produces a lower pressure drop in the
system allowing for the use of a smaller circulator pump.

7. A geothermal loop system does not allow the use of mechanical joints of any kind
outside the building. All underground joints are made by fusing the plastic pipe with
socket or butt fusion techniques.
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