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Bosch Geothermal Heat Pumps
Bosch Thermotechnology Corp.
Data subject to change
Applications Manual
14 Ground Loop Pumping
Package (GLP)
14.1 Flow Centers for Closed-Loop Ground
Heat Exchangers
Many closed-loop systems are connected to a “ ow
center” at the geothermal heat pump unit providing for a
common connection to the supply and return lines coming
in from the geothermal ground heat exchanger. These ow
centers are used as a one stop accessory for circulating
uid in a closed loop system. Flow centers can be either
pressurized or non-pressurized. The ow center is a eld
labor saving device that takes care of a number of issues
a loop installer should handle in a eld installed pump
station.
14.2 Pressurized Flow Centers
Pressurized ow centers are compact, insulated, and
easy to mount polystyrene or metal cabinets that contain
composite or brass 3-way valves and a pump or pumps
(Figure 105). These 3-way valves are used for attaching a
ush cart’s hose connections to ll, ush and purge the
ground heat exchanger; then the unit side; and then to add
antifreeze and circulate the entire system.
Polystyrene
Cabinet
Composite Valve
Brass Valve
Metal
Cabinet
Brass Valve
Fig. 105 Pressurized ow centers
Pressurized ow centers offer the advantages of being
equipped with ush/ ll ports and eliminating the
possibility of uid exposure to contaminants.
However, the thermal expansion of ground loop piping may
cause the circulating pump or pumps to cavitate without
the use of an expansion tank. Any entrapped air will not
leave the system over time. Additionally, a ush cart is
typically necessary for lling and ushing the ground heat
exchanger and ground loop system. Check and isolation
valves must also be eld installed.
Generally you will see what's referred to as a "one pump”
pressurized ow center or a "two pump" pressurized ow
center. For many pressurized ow centers, the pumps
are typically either a Grundfos UP 26-99 or a Grundfos
UP 116, but other brands exist as well. They are close
in characteristics but can have system saving, or system
detrimental effects.
Flow centers have the pump (or pumps) already installed
with all the piping and valves (Figure 106). They are also
typically insulated with foam. The connections at the
top and bottom of the ow center are for connection
to the ground heat exchanger and to the unit. The pipe
connections on the side are for the ush cart connections.
The front brass cap is for turning the 3-way valve.
Fig. 106
Proper ow through the ground heat exchanger is
extremely important. For example, a 9 GPM system
(nominally a 3 ton unit) may have 3 circuits with 3 GPM
through each circuit. A properly installed ground heat
exchange requires a minimum amount of turbulence
in the pipe - measured by the "The Reynolds Number",
for ef cient heat transfer. The ow in each circuit, size
and length of pipe, and antifreeze in the system, are all
variables in determining the Reynolds Number.
