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Designing a Liebert XD Solution
15
3.6 Liebert XDO Placement
3.6.1 Determining Spacing of Liebert XDOs in an Aisle
Liebert XDO units should be placed in rows directly above the cold aisles of a room for optimum cool-
ing. Each Liebert XDO serves an area equal in width to the cold aisle spacing, typically 12 to 16 feet
(3.7 to 4.9m). The length of the area served includes any space between Liebert XDO modules in a
row. Depending on the cooling capacity to be achieved, spacing between Liebert XDO modules in a
row may vary from zero to as much as 6 feet (1.8m). When the spacing increases to more than 6 feet
(1.8m), overall performance of the system may be negatively affected and gaps in cooling may occur.
Emerson recommends installing one Liebert XDO at the end of each aisle being cooled and to space
the remainder between these end units in pairs as shown in Figure 15. This layout will block the
incursion of hot air around the side of the end cabinets.
Figure 14 Liebert XDO placement over cold aisle
Table 3 can be used to determine the correct number and spacing of Liebert XDOs.
Table 3 Calculating quantity and spacing of Liebert XDO modules (example below is Liebert XDO20)
Input Information Step Result
Total heat load in the room, kW A
Reserve capacity needed
(10% to 25% of A is recommended)
B
C Required cooling capacity, kW = A + B
Existing/planned Liebert Deluxe/DS unit
sensible capacity, kW
D
E Required Liebert XD system cooling capacity, kW = C – D
F
Number of Liebert XDO20s required = E ÷ 20, rounded up (60Hz)
= E ÷ 16, rounded up (50Hz)
G
Number of Liebert XDP
/Liebert XDC modules required = F ÷ 8,
rounded up (60Hz and 50Hz)
Room area, square feet H
I Area served by each Liebert XDO20 = H ÷ F
Spacing of cold aisles, center-to-center,
typically 12-16 ft (3.7 to 4.9m)
J
K Spacing between each Liebert XDO = (I ÷ J) - 2
L
Required Liebert XD system cooling density = E x 1000 ÷ H
OK if under 640; otherwise, additional cooling is required from
Liebert Deluxe or Liebert DS units.
HOT AISLE
Cold Aisle Spacing
Hot air is
drawn into
the XDO for
cooling
XDOXDO
Critical
Equipment
Critical
Equipment
Critical
Equipment
Critical
Equipment
COLD AISLE
Hot air goes
into the hot
aisle
Cooled air
enters the
rack...
Hot air goes
into the hot
aisle
Cooled air
enters the
rack...
COLD AISLE