User manual

Operation
Liebert
®
iCOM
®
52
Dehumidification Compressor Quantity
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 7 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.
Reheat During Dehumidification
Hot gas reheat or hot water reheat will start as described in 3.5 - Temperature Control—Reheat,
when the temperature decreases during the dehumidification process.
The parameter Electric Reheat Operation defines how the heaters react in case the temperature
decreases during the dehumidification process. This parameter does not impact SCR reheat
operation. The Electric Reheat Operation parameter is in the Advanced menu under Factory Settings
and should not be adjusted 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 in the same manner 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 described
in 3.5.1 - Electric, Hot Gas and Hot Water Reheat. Staged is the default setting for Challenger
3000 units. On two compressor units with staged reheat selected and Dehumidification With Comp
set to BOTH, the control allows for operating two compressors and reheats simultaneously. It is
important that electrical service to the unit be sized and wired for this option if selected.
Table 7 Dehumidification With Comp settings
Available to Set Value Dehumidification With Comp Setting Default Setting On
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) —