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Figure 14. Typical Horizontal Loop Configurations
2 ft
Two-Pipe
Back-Hoe Loops
Two-Pipe
Trenched Loops
When multiple pipes are laid in a trench, space pipes
properly and backfill carefully to avoid disturbing the
spacing of the pipes in the trench. Figure 14 details
common loop cross-sections used in horizontal loops.
Vertical Applications
To install Vertical earth couplings, 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 apart, In southern or cooling dominated climates 15
feet is required.
The minimum diameter for 3/4 inch or 1 inch U-bend
well bores is 4 inches. Larger diameter boreholes may be
drilled if convenient, unless local code requires an
expensive method of backfilling. Assemble each U-bend
assembly, fill with water and 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 filled with
water or drilling mud solutions, since a water filled pipe
is buoyant under these circumstances. Tape the pipes
together approximately every 10 feet to prevent the
assembly from separating under downward pressure and
bowing out against the borehole wall.
Carefully backfill the boreholes to within 10 feet of the
surface. Follow IGSPHA specifications for backfilling
unless local codes mandate otherwise.
When all U-bends are installed, dig the header trench 4
to 6 feet 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
2 ft
2 ft
Four-Pipe
Six-Pipe
Four-Pipe
Extended Slinky
Figure 15. Typical Vertical Loop Configurations
One Pair
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 15
illustrates common vertical bore heat exchangers.
Pond/Lake Applications
Pond loops are one of the most cost effective applications
of geothermal systems. Typically 1 coil of 300 ft of PE
pipe per ton is sunk in a pond and headered back to the
structure. Minimum pond sizing is 1/2 acre and 8 ft deep
for an average residential home. Actual area can be 1500-
3000 ft 2 per ton of cooling. In the north, an ice cover is
required during the heating season to allow the pond to
reach an average 39 F. Winter aeration or excessive
wave action can lower the pond temperature preventing
proper operation of the geothermal system. Direct use of
pond or lake water is discouraged because of the
potential problems of heat exchanger fouling and pump
suction lift. Heat exchanger may be constructed of either
multiple 300 ft coils of pipe or slinky style Figure 16. In
northern applications the slinky or matt style is
recommended due to its superior performance in heating.
Due to pipe and antifreeze buoyancy pond heat
exchanger will most likely need weighted down to
prevent floating. 300 foot coils require two 4" x 8" x 16"
blocks (19 lbs. each) or 8-10 bricks (4.5 lbs each) and
every 20 ft of 1-1/4" pipe requires 1 three hole brick.
Coils are supported off of the bottom by the concrete
blocks or bricks. The supply/return trenching should
begin at the structure and work toward the pond. Near the
pond the trench should be halted and back filled most of
the way. A new trench should be started from the pond
back toward the partially backfilled first trench to prevent
pond from flooding back to the structure.
Seal and protect the entry point of all earth coupling
entry points into the building using hydraulic cement.
18
When Loops are
shallower than
one ton per loop
Two Pair
Series/Parallel One Pair
Vertical Bores
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