Liebert Crv Operation-Liebert Icom ® Control; Cooling; Heating; Air Flow - Emerson Liebert CRV User Manual

10.7 Liebert CRV Operation—Liebert iCOM

10.7.1 Cooling

The cooling control of the Liebert CRV can be managed from any of the temperature sensors. Emerson
recommends using the supply temperature sensor to control the cooling capacity of the Liebert CRV.
The supply temperature is an accurate representation of the actual heat rejection the Liebert CRV
needs to perform at an optimal level. A chilled water version of the Liebert CRV will modulate the
cooling capacity from 0% - 100% and the DX version of the Liebert CRV will modulate the cooling
capacity of the unit from 20% -100% compressor capacity.
To avoid short-cycling the compressor during room heat load changes, the Liebert CRV will not
deactivate the compressor until the air temperature is below 150% of temperature setpoint when in
Remote or Supply Air Control or below 200% of temperature setpoint when operating in Return Air
control.

10.7.2 Heating

The heating control is active only when the unit is in dehumidification mode. The reheats will begin
activation when the control temperature has dropped to -66% of the controls proportional band and
will deactivate when the temperature setpoint has been reached.

10.7.3 Air Flow

The Liebert CRV's airflow can be controlled manually or dynamically by temperature sensors.
Emerson recommends controlling the fan speed using the remote rack temperature sensors. The
remote rack sensors are an accurate representation of the delivery of the Liebert CRV's discharge air.
When using the remote rack temperature sensors, the fan speed will modulate from 50% to 100%
based on the remote rack temperature setpoint and the sensitivity of the proportional and integral
settings. Manually controlling the Liebert CRV's fan speed is also possible by setting a fixed fan speed
either from the front display or through a monitoring system. The manual control will be overridden
for freeze protection, humidification and reheat operation. In the event of a single fan failure the
Liebert CRV will ramp the remaining operating fan to 110% of its rated output to compensate for the
loss of airflow. In addition, an alarm will be triggered to report which fan failed.

10.7.4 Humidification

The Liebert CRV's humidification is activated when the measured temperature and humidity sensor
has been calculated to exceed the corresponding dew point setpoint. The dew point setpoint is
calculated based on the temperature and humidity of the sensor set to control the control setpoint and
relative humidity.
Example: Temperature Setpoint 72°F / Humidity Setpoint 50% = 52°F Dew Point
NOTE
The Liebert iCOM control monitors the condition of the air discharging from the unit to protect
neighboring electronic equipment. Liebert iCOM will prevent the humidifier from activating if
the discharge air is near its saturation point. This protects against discharging fog from the
unit or condensation forming on the unit's supply air baffles. This protection mode is activated
when the supply sensor reading is below 53°F (11.7°C) or above 55% relative humidity. When
this condition is met a message will display showing "humidifier" suspended.
The status of the humidifier lockout can be viewed in the Service/Diagnostics menu.
These protections do not apply to the external humidifier output.
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Liebert CRV
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Control
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Liebert iCOM Control