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Bosch Geothermal Heat Pumps
Bosch Thermotechnology Corp.
Data subject to change
Applications Manual
Typical horizontal loop design parameters:
f
Limited tonnage due to land area
f
Backhoe or trench excavation typical (Fig. 82)
f
In areas with any rock typically backhoe only
f
One circuit and 3 Gallon per Minute (GPM) per ton of
cooling capacity
f
¾
" HDPE piping
f
Pipe per ton of cooling capacity:
—
Cold climates: 400 to 1,000 Feet
—
Warm climates: 700 to 1,800 Feet
Fig. 82
Courtesy of International Ground Source Heat Pump Association/Oklahoma
State University
A horizontal ground coupled system with the piping buried
in a trench will typically have different depths based the
location of the system in a colder or warmer climates. For
the U.S., this is identi ed in the map provided (Fig. 83).
Pipe depths in the Northern Zone should be 3 to 5 feet,
as excessive depth will reduce the ability of the sun to
recharge the heat used in winter. The Bosch Geo Solutions
software program will help determine the appropriate
depth for these applications.
Fig. 83
Pipe depths in the Southern Zone should be 4 to 6 feet, so
that the high temperature of the soil in late summer time
will not seriously affect system performance. The Bosch
Geo Solutions software program will help determine the
appropriate depth for these applications.
Antifreeze will be necessary in the Northern Zone to
prevent freezing of the circulated water and to allow
the system to gain capacity and ef ciency by using large
amounts of heat released when the water contained in the
soil is frozen.
Installers should always back ll a trench by hand when
changing direction.
If it is necessary to join two pipes together in a trench,
always use the fusion technique for greater strength and
durability. Then mark tting locations for future reference
by magnetic tape or wire, or by inserting a steel rod just
below grade. These marking devices allow the use of a
metal detector to nd joints in pipes.
Trenches can be located closer together if a pipe in the
previous trench can be tested and covered before the next
trench is started. This also makes back lling easier. Four
to ve feet spacing is typically a good recommendation.
In those areas with dry climates and heavy clay soil,
heat dissipated into the soil may reduce the thermal
conductivity of the soil signi cantly. In such cases, the
installer may need to specify additional feet of pipe per
ton of capacity. A few inches of sand may also be added in
with the pipe, or a drip irrigation pipe buried with the top
pipe to add occasional small amounts of water.
