Bryant 50YEW Design Manual page 54

Water-to-Water System Design Guide
Part III: Source Side Design / Closed Loop Installation Guidelines
CAUTION! This manual is not intended for
commercial loop design.
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 3-7 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.
Figure 3-7: Typical Horizontal 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 [4.6 meters] is required. Commercial installations
may require more distance between bores. This manual is not
intended for commercial loop design.
52
CAUTION!
Bryant: Whatever It Takes.
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 3-8 illustrates common vertical bore
heat exchangers.
Use an IGSHPA design based software such as GeoDesigner for
determining loop sizing and confi gurations.
Figure 3-8: Typical Vertical Loop Confi gurations