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Designing a Liebert XD Solution
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3.12 Liebert XD Refrigerant
The refrigerant used in the Liebert XD system is HFC-134a (1,1,1,2-tetrafluoroethane), made by a
number of manufacturers. The amount of refrigerant used by the Liebert XD system may be signifi-
cantly higher than in typical DX cooling systems.
All the major components of a Liebert XD system must be installed in a space with a volume of at
least 1,000 ft
3
(28.3m
3
) for each 13 pounds of refrigerant in that system from Table 1, ASHRAE Stan-
dard 15-2001, Safety Standard for Refrigeration Systems. If the Liebert XDP/Liebert XDC is placed in
a separate area, such as a machine room, then this area must also meet the volume requirement.
Inside the critical space, this includes the space under the raised floor, and the space between the top
of the raised floor and the bottom of a suspended ceiling. If the suspended ceiling is all open grates,
then this additional space, up to the overhead deck, would also be included.
Example
A space is 5,000 square feet, with an 18" raised floor and an 8' 6" suspended ceiling. Liebert XDOs
and a Liebert XDP are to be placed in this raised-floor area.
The volume of the space is (1.5 + 8.5) x 5,000 or 50,000 cubic feet.
The maximum amount of R-134a refrigerant that can be used in a single Liebert XDP/Liebert
XDC/Liebert XD module system within this space is 16 * (50000/1000) = 16 * 50 = 800 lb.
Multiple Liebert XD systems can be installed in this space, as long as the amount of R-134a
refrigerant in any one system does not exceed 800 lb.
3.13 Liebert XD Piping System Design
All piping must be ASTM (American Society for Testing and Materials) Type “L” copper pipe. The typ-
ical maximum operating pressure in the system is 90 psi (620kPa).
Piping for the Liebert XD system is arranged in a manner similar to piping for a chilled water system.
Liebert XD cooling modules (Liebert XDCF, Liebert XDH, Liebert XDO or Liebert XDV) are connected
in parallel between the main return and supply pipes going to and from the Liebert XDP/Liebert XDC.
Figure 23 represents a typical configuration. 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. Each must be minimized.
!
CAUTION
Risk of improper oil use. Can cause equipment damage.
The Liebert XD pumped R-134a refrigerant circuits do not use refrigerant oil. Do NOT put oil
in the R-134a system.
NOTE
Local codes might permit exceeding the maximum refrigerant limit stated above if refrigerant
detector and an exhaust system are installed. As an alternative, oxygen sensors may be
installed to meet some local codes.