Bosch Geothermal Heat Pumps, Руководство по применению

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7 8 | Bosch Geothermal Heat Pumps
Bosch Thermotechnology Corp. Data subject to change
Applications Manual
Fig. 76
The most common horizontal heat exchanger is two pipes
placed side-by-side in the same trench. Other horizontal
loop designs use four or six pipes in each trench, if land
area is limited. Regardless of the arrangement chosen, all
piping for antifreeze solution systems should be at least
polyethylene (or approved equal) with thermally fused
joints (as opposed to barbed ttings, clamps, or glued
joints), to ensure leak-free connections for the life of the
piping. Other piping materials also exist and must be
approved by IGSHPA for use with Bosch geothermal heat
pumps.
Properly installed, these pipes will last anywhere from 25
to 75 years. They are unaffected by chemicals found in soil
and have good heat-conducting properties.
Horizontal loop installations typically use trenches
anywhere from 6 to 24 in. wide. This leaves bare areas that
can be restored with grass seed or sod.
Generally, the more pipes that are added to a horizontal
trench (provided there is adequate spacing), the shorter
the trench. Since pipe is relatively inexpensive compared
to excavation, most horizontal loops have multiple pipes
in the trench to maintain shorter trenches. Available
excavation equipment however could change the number
of pipes that can be placed in a trench.
A single pipe loop is typically not common, but may be
used if there is plenty of land (Fig. 77). To complete the
circuit, each trench must go out and circle back to the
starting point. If using ¾" pipe, there is usually one trench
per ton of cooling capacity required for the structure. A
parallel circuit design might look like a ower petal. If
the ground loop is designed as one large series pipe (not
recommended except for 1-½ to 2 ton systems) the pipe
diameter must be larger, typically 1-¼" or larger.
Fig. 77
Courtesy of International Ground Source Heat Pump Association/Oklahoma
State University
The use of multiple pipes in a trench reduces total trench
length substantially. If a double layer of pipe is laid in the
trench, then the two layers should be set approximately 2
feet apart to minimize thermal interference (Fig. 78).
Fig. 78
Courtesy of International Ground Source Heat Pump Association/Oklahoma
State University
Example:
A 1-½ inch series horizontal system with pipes at 5 feet
and 3 feet is installed. After installing the rst pipe at
the 5 foot depth, the installer should partially back ll
to the 3 foot depth using a depth gauge stick or other
measurement device prior to installing the second pipe.
The return line will be running closest to the surface
and the supply line will be running beneath it. This
arrangement will maximize the overall system ef ciency by
providing warmer water in the heating mode and colder
water in the cooling mode.