System information

Carrier Geothermal Heat Pump Systems
33
Residential Products Technical Guide
Horizontal Applications
For horizontal earth loops, dig trenches using either a chain-type
trenching machine or a backhoe. Dig trenches approximately
8-10 feet [2.5 to 3 meters] apart (edge to edge of next trench).
Trenches must be at least 10 feet [3 meters] from existing utility
lines, foundations and property lines and at least 50 feet [15.2
meters] minimum from privies and wells. Local codes and ordinances
supersede any recommendations in this manual. Trenches may be
curved to avoid obstructions and may be turned around corners.
When multiple pipes are laid in a trench, space pipes properly and
backfi ll carefully to avoid disturbing the spacing between the pipes
in the trench. Figure 7 details common loop cross-sections used in
horizontal loops. Actual number of circuits used in each trench will
vary depending upon property size. Use GeoDesigner software to
determine the best layout.
 CAUTION! 
CAUTION! This manual is not intended for
commercial loop design.
Figure 7: Typical Horizontal Loop Confi gurations
Figure 8: Typical Vertical Loop Confi gurations
Vertical Applications
For vertical earth loops, drill boreholes using any size drilling
equipment. Regulations which govern water well installations also
apply to vertical ground loop installations. Vertical applications
typically require multiple boreholes. Space boreholes a minimum of
10 feet [3 meters] apart. In southern or cooling dominated climates
15 feet is required. Commercial installations may require more
distance between bores. This manual is not intended for commercial
loop design.
The minimum diameter bore hole for 3/4 inch or 1 inch U-bend
well bores is 4 inches [102 mm]. Larger diameter boreholes may be
drilled if necessary. Assemble each U-bend assembly, fi ll with water
and perform a hydrostatic pressure test prior to insertion into the
borehole.
To add weight and prevent the pipe from curving and digging into
the borehole wall during insertion, tape a length of conduit, pipe or
reinforcing bar to the U-bend end of the assembly. This technique is
particularly useful when inserting the assembly into a borehole fi lled
with water or drilling mud solutions, since water fi lled pipe is buoyant
under these circumstances.
Carefully backfi ll the boreholes with an IGSHPA approved Bentonite
grout (typically 20% silica sand soilds by weight) from the bottom
of the borehole to the surface. Follow IGSPHA specifi cations for
backfi lling unless local codes mandate otherwise. When all U-bends
are installed, dig the header trench 4 to 6 feet [1.2 to 1.8 meters]
deep and as close to the boreholes as possible. Use a spade to
break through from ground level to the bottom of the trench. At
the top of the hole, dig a relief to allow the pipe to bend for proper
access to the header. The “laydown” header mentioned earlier is a
cost effective method for connecting the bores. Figure 8 illustrates
common vertical bore heat exchangers.
Use an IGSHPA design based software such as GeoDesigner for
determining loop sizing and confi gurations.
Closed Loop Design/Installation Guidelines