User manual

Operation
Liebert
®
iCOM
®
44
Figure 39 Damper settings and limits screen
Parameters SA24 through SA30 of the Liebert Air Economizer screen show the return and outdoor
damper limits and current position. The return damper will receive a 2VDC signal when fully open
and an 8-10VDC signal at its most-closed position.
The outdoor damper will receive a 10VDC signal when fully open and a 2VDC signal when fully
closed. If the outdoor conditions do not permit Liebert Air Economizer usage, then the outdoor
damper will fully close and the return damper will fully open for normal operation of the primary
cooling unit.
The actual outdoor and return damper positions are shown at parameters SA29—Outdoor Damper
Position and SA30—Return Damper Position (see Figure 39).
Air Economizer activation relay—The K11 relay is activated when the Liebert iCOM determines
that the Liebert Air Economizer
™
is available for use. This relay will remain active during a BMS
remote deactivation of the Liebert Air Economizer.
Adjusting control limits with Air Economizer units—A cooling unit equipped with a Liebert Air
Economizer will be factory-set to utilize outdoor air based on the current ASHRAE standards. When
the outdoor damper is opened Liebert iCOM will automatically disable any humidification control as
humidification and dehumidification will not be able to overcome the amount of outdoor air being
used. However, other units not equipped with Liebert Air Economizers may continue to humidify and
dehumidify the data center. If the room is equipped with a mixture of Liebert Air Economizer and
other types of units, then follow these steps.
1. Identify the allowable outdoor air conditions entered into the Liebert iCOM control.
• Upper dew point 57.5 / Lower dew point 44.
• Dry bulb is limited, based on the selection in S135.
2. Set the deadband and proportional band of the units based on the allowable outdoor air.
• Setpoint = 41%
• Proportional band = 1%
• Deadband = 17%
• Return Temperature Setpoint = 75°F
3. The units should also be set for predictive humidity control which will compensate for any
deviation from the Return Air Temperature setpoint and Relative Humidity Control.
NOTE
Even when the return temperature setpoint is not being used for cooling control, it must be set
to operate in Compensated or Predictive humidity control.