Emerson Liebert DS Precision Cooling System 28-105kW Manuel D’Utilisation

Parameters SA23 through SA33 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 13).
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 dewpoint 57.5 / Lower dewpoint 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.

Economizer (page 3 of 3)

to change parameter

to confirm

to select parameter

for next/previous unit
then 

UNIT   01

SA23
SA24
SA25
SA26
SA27
SA28
SA29
SA30
SA31
SA32
SA33

PASSWORD   (Actual Level  3)

????

Return Damper Open

2.0V

Return Damper Closed

10.0V

Return Damper Minimum Limit At

15%

Outdoor Damper Open

10.0V

Outdoor Damper Closed

2.0V

Outdoor Damper Position

0%

Return Damper Position

100 %

and