User's Manual

Service Menu Parameters
125 Liebert
®
iCOM
®
S126 Humidity Control Type—The left hand value selects the humidity control calculation.
Setting this parameter to Relative will control the humidity without considering any temperature
deviations. Predictive and Absolute control consider the temperature deviation from temperature
setpoint so that a constant level of moisture is kept in the area based on the humidity sensor reading
and the temperature deviation from setpoint. The factory default is Predictive (see 3.7 - Humidity
Control). The right hand value provides two options for controlling components during
dehumidification if S102 Temperature Control Sensor is set to Supply or Remote. If the S102 is set for
either of these values, the right hand value will be shown and can be selected as Supply or Return. If
S102 is not set to Supply or Remote, both humidification and dehumidification will operate using the
sensor assigned on S124.
S127 Humidity Proportional Band—Adjusts the activation points of the humidifier and
compressors or cooling valves for dehumidification based on the actual sensor values deviation from
setpoint. The smaller this number, the faster the compressors, cooling valves and humidifier will
increase capacity. Too small of a number may cause the unit to short cycle or overshoot or undershoot
the setpoint.
S128 Humidity Integration Time—Adjusts the capacity of the unit based on time away from
setpoint so that accurate humidity control can be maintained. If the integration time is set to 0, the
humidity control operates as a “proportional only” control. When an integration time is set, the
control mode changes to “PI” control.
S129 Humidity Deadband—Prevents overshooting or undershooting the setpoint and cycling
between humidification and dehumidification. This value will be split in half by the humidity
setpoint.
S130 Dehum Temp Act/Set—Lowers the temperature control sensor reading to a predefined value
during the call for dehumidification. The unit must be in supply air or remote humidity control. This
should be set below the accepted dew point threshold of the conditioned space.
S131 Dehum Setpoint Adjust/Filter—Sets the amount that the Dehum Temp Setpoint is adjusted
when the reheats activate. Example: If the unit is equipped with a reheat device, this parameter will
increase the dehumidification temperature as the call for reheats are increased until the reheat call is
at 100%. When the reheats are at 100%, the full Dehum Setpoint Adjustment will be applied.
S132 Dehum Reheat/LL Sensor/Set—The left hand value sets the temperature control sensor used
for activating reheat during dehumidification and low limits in and out of dehumidification. To
prevent the unit’s heating and cooling modes from activating simultaneously, Return Sensor is the
only allowable setting when S102 Temperature Control Sensor is set to Return. Supply Sensor is
selectable only when S102 Temperature Control Sensor is set to Supply and Remote Sensor
is
sel
ectab
le only when S102 Temperature Control Sensor is set to either Remote or Supply.
The right hand value is the user-programmed temperature setpoint used to activate reheat during
dehumidification and low limits.
S133 Dehum Low Limit 1 LL1/LL2—Low limit 1 (left hand value) will disable one of the two
compressors used for dehumidification in dual compressor dehumidification applications. If the
humidity control sensor is set to Supply or Remote (S126 right hand value) or the unit is configured
for single compressor or chilled water dehumidification, the LL1 value will not be visible and will be
inactive.
Low Limit 2 will disable both compressors for dehumidification on units configured for dual
compressor dehumidification. This parameter will disable the chilled water valve or compressor on
units configured for single compressor dehumidification.
See 3.7.2 - Dehumidification for more information on Low limit interaction.
S135 Estimated Aisle Temp—Sets an estimated cold aisle temperature when humidity control
sensor is set to remote and no remote temp sensors are installed at the unit. This estimated
temperature will be used to determine the humidity versus using an actual temperature in the cold
aisle that may fluctuate during modes of dehumidification or load changes of the IT equipment. This
provides a stable control point to reference the actual measured dew point from the return sensor.