Bosch Geothermal Heat Pumps Applications Manual page 82

8 2 | Bosch Geothermal Heat Pumps
11.3 "Slinky™" Ground Heat Exchangers
A variation of the horizontal ground heat exchanger often
used today is the "Slinky™" loop horizontal closed-loop
system (Fig. 85). This arrangement ties the pipe into large
coils that overlap each other, allowing for large lengths
of pipe to t into much smaller trenches. This design is
a horizontal closed-loop array for area of less land and
shorter trenching. The ground heat exchanger is typically
laid at in a circular pattern at the bottom of a trench.
Fluid circulates through the ground loops.
Fig. 85 "Slinky™" loop system
Courtesy of International Ground Source Heat Pump Association/Oklahoma
State University
For example, 800 ft. of ¾ in. pipe can be tied into a
"Slinky™" loop with 3 ft. diameter coils and be buried into
a trench that is typically 125 - 150 ft. long.
The "Slinky™" design allows the installer to increase the
density of the pipe in the trench by coiling it to achieve
more pipes per foot of trench.
When rst introduced, the "Slinky™" design included both
horizontal (Fig. 86) and vertical (Fig. 87) applications.
Vertical "Slinky™" loops were designed for installation with
a trencher. This design in less popular today as it has been
found to be extremely dif cult to back ll unless ne soil
(e.g. sand) or owable back ll is used. Today, horizontal
"Slinky™" loops are used more frequently than vertical
"Slinky™" loops because they are easier to install.
Fig. 86
Courtesy of International Ground Source Heat Pump Association/Oklahoma
State University
Data subject to change
Fig. 87
Courtesy of International Ground Source Heat Pump Association/Oklahoma
State University
""Slinky™" loops may be a compact or extended design
(Fig. 88). The "Slinky™" design typically provides one
circuit per trench. Like the horizontal two-pipe loop,
the""Slinky™" loop is typically designed with one trench
per ton when ¾" HDPE is used. Pressure drop must be
considered when using the compact "Slinky™" or the
extended "Slinky™" design, as circuits can be lengthy.
Fig. 88
Courtesy of International Ground Source Heat Pump Association/Oklahoma
State University
Applications Manual
Bosch Thermotechnology Corp.