c. Close the output switch Q5, bypass input switch Q2, main input switch Q1 and all the external output
isolating switches (if any) in turn. Now, the system is powered on, and LCD screen is activated.
d. The UPS internal cooling fan starts, and the rectifier executes self check and starts to run. The rectifier
runs in normal state for about 30 seconds, after which the rectifier startup phase is complete. Confirm that
the LCD displays bypass and main input normally, and that the current log window generates an alarm of
PowerCAN Comms. Abnormal or Discrete Bus Comms. Abnormal, otherwise you should check that the
switch Q2 and switch Q1 have been closed, and that parallel cables of each UPS have been well connected.
The alarm indicators (red) are always off till all the UPSs in parallel system are rectified.
e. Refer to Parallel system parameters setting on the previous pagefor the parallel parameters setting for
each UPS. Carry out the following procedures if the UPS is running normally.
f. Press the power button of one UPS and press the Enter key to start the UPS. The run (green) indicator
blinks, and the inverter will start, then the run indicator comes on. If the battery is not connected, the alarm
indicator will be solid on, and the buzzer will beep every second. If the battery is connected, the alarm
indicator will turn off.
g. If the UPS is working normally, press the power button of this UPS for 2 seconds to turn off the inverter.
h. Repeat steps a to g to power on and commission the inverter of other UPSs respectively.
NOTE: Carry out the parallel commissioning after each UPS is working normally.
2. After confirming that the inverter of each UPS is normal, commission the parallel system, the specific procedures
are as follows:
a. Close the external and internal I/O switch of each UPS, and all UPSs are powered on at the same time.
After the start of the rectifier is finished, press the power button of one UPS to start the inverter, and then
the run indicator (green) comes on.
b. Start the inverter of the second UPS, check whether there is an alarm on the LCD, and confirm that the
UPS parallel works normally.
6.4.4 Maintenance bypass procedures
If the UPS system consists of more than 2 parallel UPS modules, and the load capacity exceeds that of the single module
capacity, do not use the internal maintenance bypass switch.
This operation will make the load transfer from UPS power supply protection state to direct connection with AC input bypass
state.
WARNING! Power supply interruption danger of the load.
Before performing this procedure, check the LCD information first, and ensure that the bypass is normal, and
inverter synchronized. Otherwise, it may result in the load power interruption for a while.
WARNING! If the maintenance is required, wait 10 minutes for the internal DC bus capacitance discharging.
WARNING! The parts of UPS circuits also have hazardous voltage, though the rectifier input switch, bypass
input switch and battery switch are disconnected. Therefore, the UPS maintenance is applicable to qualified
personnel only.
6 Parallel System and LBS System Proprietary and Confidential ©2023 Vertiv Group Corp. 51
Vertiv™ Liebert® EXS Installer/User Guide
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