Emerson Liebert Challenger With Liebert iCOM Control 3000/ITR - Manual (Page 34)

Operation
28
Autorestart
When there is a loss of power to the cooling unit and power comes back, the unit will return to its pre-
vious operating status—On if it was On before the power failed, Off if it was Off.
When power returns, the autorestart time—time-selectable: Single Unit Auto Restart (Service Menu,
Options Setup)—controls the start of the unit. The autorestart time runs in a loop, starting the next
unit each time when elapsed. With units in a U2U network, the autorestart will begin with Unit #1.
Loss of Power Alarm
A Loss of Power Alarm is activated when power is restored after an interruption. If acknowledged, the
alarm resets automatically after 30 minutes. This alarm can be set to different event types (Message,
Alarm or Warning) and can be disabled under menu item Loss of Power (Service Menu, Set Alarms).
Fan Alarm / Fan Protection Settings
The fan operation is protected by two devices: motor protection (optional) and a differential pressure
switch. The differential pressure switch ensures that the blower(s) are moving air and the motor pro-
tection monitors for main fan overload. If either protection device triggers, an alarm will be
announced by a buzzer, alarm relay and event to monitoring after an adjustable time-delay (Main
Fan Overload and Loss Of Airflow in Service Menu, Set Alarms).
The time delay at the unit start is always five seconds shorter than the control delay (to avoid short
component starting when the fan is not working). During operation, the fan delay is fixed to
15 seconds.
There are two selection possibilities for both, Loss Of Airflow and Main Fan Overload:
• Shutdown—stops the unit (intended for DX models).
• Disable—stops the humidifier, electrical heaters and dehumidification; allows cooling and
free-cooling only (intended for chilled water models / external cooling).
5.1.2 General Compressor Requirements
Low-Pressure Time Delay
When the compressor starts, the low-pressure input is ignored for a selected period of time based on
the setting of the Low Pressure Alarm Delay (Service Menu, Options Setup). This permits the pumps
to begin operating normally without nuisance alarms at startup.
!
WARNING
Risk of electric shock. Can cause injury or death.
The Liebert iCOM microprocessor does not isolate power from the unit, even in the “Unit Off”
mode. Some internal components require and receive power even during the “Unit Off” mode
of Liebert iCOM control.
The only way to ensure that there is NO voltage inside the unit is to install and open a remote
disconnect switch. Refer to unit electrical schematic.
NOTE
Loss of power alarm will be activated only on units that had the fan on before power was lost.
NOTE
When the Main Fan Overload alarm is active, the Loss of Airflow alarm is masked out. If a loss
of airflow occurs, the compressor, heaters and humidifier will all turn Off until airflow is
restored.
NOTE
Low-pressure condition could be read through contacts or through pressure transducers with
threshold setting.