Geothermal Installation II
A successful horizontal ground
loop configuration will have the
1. Pipe is type 3408 (SDR 11 -
160 psig.) high density
The number 3408 or PE3408
defines the type of resins used
to manufacture the
SDR 11 (Standard Dimension
Ratio) is the pipe size.
Psig is pounds per square inch
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.