Emerson Liebert iCOM Manual De Usuario

To avoid the dehumidification lockout:

• Increase the heat load for efficient operation
• Decrease S133 LL settings slightly
• Where applicable, decrease the reheat proportional band. This will allow the reheats to activate 

sooner, helping to prevent the low return condition.

Under Factory Settings in the Advanced menu there is an item called Dehumidification With Comp. 

This will be set to either 1, 2, 1 or 2, or BOTH. This setting determines which compressors are used 

for dehumidification. It also determines if Low Limit 1 will be available and impacts how the reheats 

will operate during dehumidification. The Dehumidification With Comp field is set when the cooling 

unit is built and should not be adjusted without first consulting the factory. Table 9 outlines which 

Low Limit settings will be available, based on the Dehumidification With Comp selection.

Low Limit 1 and 2 will be available only on cooling units with two compressors when 

Dehumidification With Comp is set to BOTH.
Low Limit defines the sensor and the setpoint used to determine the low limit thresholds for all 

cooling and dehumidification modes.
The value of the selected sensor is compared with the setpoint set in S132 + the LL1 / LL2 settings 

(S133).
Possible selections are:

• 0 = Supply Sensor (selectable only when S102 Temperature Control Sensor is set to “Supply”)
• 1 = Remote Sensor (selectable only when S102 Temperature Control Sensor is set to either 

“Remote” or “Supply”)
Falls back to “Supply” when all Remote Sensors are set to “Disabled”

• 2 = Return Sensor - Default for all configurations, and the only allowable setting when S102 

Temperature Control Sensor is set to “Return.”

Defaults: Any time the S132 sensor setting changes (away from the default “Return” or back to 

“Return”), the setpoint will take the same value of what is set in S103 Temperature Setpoint.

The parameter Electric Reheat Operation in Service Menus>Options Setup defines how the heaters 

react if the temperature decreases during dehumidification. This parameter does not affect SCR 

reheat operation. The Electric Reheat Operation parameter is in the Advanced and should not be 

changed without factory approval.
No—No electric reheat allowed during dehumidification process.
Delayed—This setting applies only to two-compressor units with BOTH compressors selected for 

dehumidification. The electric reheats are prevented from turning On until Low Limit 1 is reached. At 

this condition, one stage of dehumidification is disabled and the reheats are activated. At 

Low Limit 2, both stages of dehumidification are disabled. When Delayed is selected on units with a 

single compressor selected for dehumidification (Dehumidification With Comp Setting: 1, 2, and 1 or 

2), the reheats will operate the same as they do for Staged as described below. Delayed is the default 

setting for Liebert DS units.
Staged—This setting applies to one or two compressor units. Electric heaters will stage as illustrated 

in Figure 47. Staged is the default setting for Liebert Challenger 3000 units. On two-compressor 

units with Staged reheat selected and Dehumidification With Comp set to BOTH, the control allows 

operating two compressors and reheats simultaneously. The electrical service to the unit must be 

sized and wired for this option if selected.

Low Limit 2 only

[blank] (units without compressors)

All Chilled Water Units

1 or 2 (Compressor 1 and 2 alternate)

Liebert DS

™

Low Limit 1 & 2

Both (both compressors dehumidify)

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