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Designing a Liebert XD Solution
13
3.0 DESIGNING A LIEBERT XD SOLUTION
Liebert XD systems are intended for use with precision air conditioning equipment, such as the Lie-
bert Deluxe System/3 and Liebert DS. The precision air conditioning equipment is required to control
the room’s humidity and to filter the air.
The Liebert XD systems provide efficient, highly effective heat removal (sensible cooling only), and
provide no dehumidification. 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 lim-
ited 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, the industry’s
most highly recommended method for dealing with extremely high heat loads.
Refer to the technical data manual of either the Deluxe System/3 (SL-18100) or the
Liebert DS (SL-18810) 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 units
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 sensi-
ble 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.
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 150 watts per square foot (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 limita-
tions may reduce this to less than 50 watts per square foot (500 watts per 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.
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.