Emerson Xtreme Density Liebert XDO Placement, Determining Spacing of Liebert XDOs in an Aisle

Designing a Liebert XD Solution

3.6Liebert XDO Placement

3.6.1Determining 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

XDO	Hot air is	XDO
	drawn into
	the XDO for
	cooling

Critical

Equipment

Critical

Equipment

Cooled air enters the

rack...

Hot air goes into the hot aisle

COLD AISLE

Critical	Critical
Equipment	Equipment
Cooled air
enters the
rack...
Hot air goes
into the hot
aisle
HOT AISLE	COLD AISLE

Cold Aisle Spacing

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	B
(10% to 25% of A is recommended)
	C	Required cooling capacity, kW = A + B
Existing/planned Liebert Deluxe/DS unit	D
sensible capacity, kW
	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,	J
typically 12-16 ft (3.7 to 4.9m)
	K	Spacing between each Liebert XDO = (I ÷ J) - 2
		Required Liebert XD system cooling density = E x 1000 ÷ H
	L	OK if under 640; otherwise, additional cooling is required from
		Liebert Deluxe or Liebert DS units.

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