Liebert Refrigerant Distribution Unit XDP - Manual (Page 18)

Piping
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2.3 Liebert XDP Interconnection with Liebert XD Cooling Modules
All piping must be ASTM (American Society for Testing and Materials) Type L copper pipe.
The Liebert XDP may be connected to Liebert XD cooling modules with either Liebert’s XD prefabri-
cated piping assembly or with rigid, off-the-shelf piping. In either setup, piping for the Liebert XD
system is arranged in a manner similar to piping for a chilled water system. Liebert XD cooling mod-
ules are connected in parallel between main return and supply pipes going to and from the Liebert
XDP/Liebert XDC. For piping details, refer to Liebert’s XD System Design Manual, SL-16655. The
guidelines provided for pipe size must be strictly followed. Failure to size the main lines
and connection lines adequately may result in reduced cooling capacity. The critical aspects
of pipe sizing are related to refrigerant volume and pressure drop. Both must be minimized.
Figure 16 Piping arrangement for Liebert XDP/Liebert XDC used with Liebert XD cooling modules
2.4 Piping Installation Method
The assembly and connection means used for piping in the Liebert XD system are similar to that of
conventional refrigeration systems. All piping should be installed with high-temperature brazed
joints. Brazing material may be used, but soft soldering is not recommended. If brazing material is
used, the lines being brazed MUST be filled with flowing dry nitrogen during brazing to prevent
excessive oxidation and scale formation inside the piping. Prevailing good refrigeration practices
should be employed for piping supports, leak testing, dehydration and charging.
Insulate all piping lines to prevent condensation in applications where the dew point approaches the
R-134a refrigerant temperature.
2.4.1 Bypass Flow Controller
Some installations require one or more bypass flow controller(s) to ensure that the Liebert XDP’s
pumps operate within the optimum range. 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 and the first Liebert XD module
in the circuit. See Figures 17 and 18 for piping details of the bypass flow controller.
Refer to Table 4 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.
Table 4
Bypass flow controllers for a Liebert XDP-based system
Cooling Modules -
Cumulative Model Size
Required Number
of Bypass Flow Controllers
Liebert XDP
32 to 63 3
64 to 95 2
96 to 127 1
128 to 160 0
Liebert XD
Cooling
Modules
Liebert XD
Cooling
Modules
Liebert XD
Cooling
Modules
Liebert XD
Cooling
Modules
Liebert XD
Cooling
Modules
Liebert XDP/
Liebert XDC
SLOPE—The main supply and return lines to and from the Liebert XDP/Liebert XDC
must be sloped downward toward the Liebert XDP/Liebert XDC at a rate of 1-2" per
20 feet (25.4-51mm per 6m) of pipe run. Horizontal connector lines should also be
sloped downward from the cooling modules toward the main supply and return lines.
All supply and
return mains
must be level with
or above the top
of all Liebert
XD modules