Piping and Filling with Refrigerant: R-134a and R-407c Circuits
18
Bypass Flow Controllers
To ensure the Liebert XDC pumps operate within the optimum range, some installations require one
or more bypass flow controller(s). These devices are added to the field piping, and simulate the flow of
additional cooling modules.
Each bypass flow controller should be installed with one shutoff valve to allow the controller to be dis-
abled when cooling modules are added to a Liebert XD system.
If bypass flow controllers are required, they should be connected between the main supply and the
main return lines of the field piping. The connection points to the main supply and return lines should
be in a convenient and accessible location between the Liebert XDP/Liebert XDC and the first Liebert
XD module in the circuit. See Figures 20 and 21 for piping details of the bypass flow controller.
Refer to Table 5 to determine the number of bypass flow controllers needed, based on the total nomi-
nal cooling capacity of the cooling modules in each Liebert XD system.
Figure 20 Bypass flow controller details, dimensions
Figure 21 Bypass flow controller arrangement
Table 5 Bypass flow controllers for a Liebert XDC-based system
Cooling Modules -
Cumulative Model Size
Required Number
of Bypass Flow Controllers
Liebert XDC
32 to 63 N/A
64 to 95 2
96 to 127 1
128 to 160 0
7/8”
(22mm) ID
4”
(102mm)
Return
Main
7/8" Refrigerant Grade
Full Port Ball Valve
Field-Supplied and Field-Installed
Supply
Main
Bypass Flow Controller
(Field-Installed)
Flow Direction