Chapter 5 UPS Operation Instructions 49
Liebert
®
ITA 16kVA And 20kVA UPS User Manual
CB1
SW
CB2
Figure 5-1 Configuration of the UPS with external maintenance bypass
For the UPS system which the distribute power is accomplished by user, if you need to isolate the UPS from AC
power, disconnect the external input MCB. (If the main and bypass are independently powered, close the two input
MCBs).
Caution
Cut off the maintenance power, in order to prevent the physical injury.
5.4 EPO
EPO switch is designed to switch off the UPS in emergency conditions (such as fire, flood). The system will turn off
the rectifier, inverter and stop powering the load immediately (inverter and bypass output included), and the battery
stops charging or discharging.
If the mains input is present, the UPS control circuit will remain active; however, the output is closed. To remove all
mains power from the UPS, the external main input MCB should be disconnected.
5.5 Auto Restart
When the mains power failure, the UPS draws power from the battery to supply the load until the batteries are
depleted, then the UPS will shut down.
The UPS will automatically restart and recover output power supply:
After the mains power is restored.
The UPS Auto Restart function is enabled.
After the Auto Restart is delayed (default: ten minutes). During the Auto Restart delay, the UPS will charge the
battery to provide a safety margin for equipment shutdown if input power fails again.
If the Auto Restart function is disabled, you can restart the UPS manually by pressing the FAULT CLEAR button.
5.6 UPS Reset
The EPO action or the following reasons such as inverter overtemperature, power-off overload, battery overvoltage
and excessive switching may result in the UPS power-off. After all appropriate measures have been taken to clear the
faults indicated by the alarm message appearing on the LCD, you can carry out the following steps to restore the
UPS to normal operation state.
1. Press the FAULT CLEAR button to make the system exit the EPO state.
2. Press the ON button for two seconds.