Vertiv Liebert XD Series, System Design Manual

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3 DESIGNING A LIEBERT XD SOLUTION
Liebert XD systems are intended for use with precision air conditioning equipment, such as the Liebert
Deluxe System/3 and Liebert DS™. The precision air conditioning equipment is required for the
humidification and filtration of the room air.
The Liebert XD systems provide efficient, highly effective heat removal (sensible cooling only), without
providing humidity control. The Liebert XD control system maintains the refrigerant temperature just
above the dew point of the space to prevent condensation. Since the capacity of the system is limited by
the dew point in the space, sufficient dehumidification and an adequate vapor barrier must be provided
to maintain the dew point at or below the level necessary to achieve the required capacity.
The Liebert XD system is optimized for hot aisle/cold aisle equipment configurations, an industry best
practice for dealing with extremely high heat loads. Room and equipment designs that preclude the hot
aisle/cold aisle configuration are often well-suited to cooling with the Liebert XDR system.
Refer to the technical data manual of either the Deluxe System/3 (SL-18100) or the Liebert DS (SL-18827)
for additional installation and application guidelines that apply to all critical space cooling applications.
3.1 Determine Cooling Requirements and Select Liebert XD System
1. Calculate the total cooling required
2. Determine placement of the Liebert XD modules
3. Determine required pipe sizes
4. Calculate the refrigerant volume of the Liebert XD systems
5. Complete design details including, electrical, mounting, piping, etc.
3.2 Calculate the Heat Load to be Handled by Liebert XD System
When designing a cooling solution using the Liebert XD system, the initial steps are similar to those
required to cool a conventional critical space. The total heat load must be calculated, including sensible
and latent cooling requirements. These should be increased by the reserve capacity needed for pull-
down situations where the room temperature must be reduced and to provide for unexpected increases
in heat load.
NOTE: Reserve capacity is distinct from redundant capacity in that redundant capacity may or may not
be available concurrently with normal operating capacity. Reserve capacity is available concurrently
with normal operating capacity.
The next step is to determine how much of the required cooling capacity is to be provided by Liebert
Deluxe™ or Liebert DS units. If the facility is new, typically up to 150W/ft
2
(1500W/m
2
) of cooling can be
obtained from Liebert precision air conditioning units supplying air through a raised floor. In existing
facilities, such factors as raised floor height, under-floor obstructions or other limitations may reduce this
to less than 50W/ft
2
(500W/m
2
).
Once the total required sensible cooling capacity is known, subtract the sensible cooling portion to be
provided by Liebert Deluxe or Liebert DS units. This yields the cooling capacity to be provided by the
Liebert XD system. Confirm the minimum heat load for the Liebert XDP/Liebert XDC is still present in the
data center (48kW and 64kW respectively).
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