Applications Manual Bosch Geothermal Heat Pumps
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Bosch Thermotechnology Corp.
Data subject to change
9.10 Underground Piping Installation Criteria
Piping, ttings and joints must be compatible with the
heat transfer uid, antifreeze and must be corrosion
resistant. All piping, ttings, joints and other materials
used in closed-loop ground heat exchangers should meet
the standards referenced by the National Groundwater
Association (NGWA) in its Guidelines for the Construction
of Vertical Boreholes for Closed Loop Heat Pump
Systems. All underground piping joints should be either
socket or butt joints, thermally fused according to the
piping manufacturer’s speci cations. Glued or clamped
joints should never be used below ground with closed-
loop ground heat exchangers. Joints must not leak after
assembly.
Flushing, air purging and pressure testing are part of
the standard installation process for closed-loop ground
heat exchangers. Pressure testing should be conducted
at a minimum of 100 psi for at least 30 minutes with no
observed leaks.
Underground piping should be installed following
standards set by the International Ground Source Heat
Pump Association (IGSHPA) in Closed-Loop / Geothermal
Heat Pump Systems - Design and Installation Standards.
Fig. 50 Reverse return piping
Special attention should be paid to avoid sharp bends in
piping and remove sharp-edged rocks or other material
in the trench back ll. Either can cause damage to the
piping, potentially causing loss of system integrity and
uids. Trenches should be constructed and back lled in
accordance with manufacturer’s speci cations. Back ll
should be seeded and covered after settling has taken
place. Filled excavations should be periodically monitored
and erosion controls should be maintained until settling is
complete and permanent ground cover is in place.
All horizontal closed-loop trenches and vertical boreholes
must be constructed to prevent contamination from
occurring or spreading to groundwater. Underground
horizontal closed-loop ground heat exchangers should be
installed parallel to surface contours whenever possible.
The recommended design today for closed-loop ground
heat exchangers is the reverse return header layout
(Fig. 50). This approach distributes the ows and
pressures more evenly across the system, making it more
inherently balanced.
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