CAUTION: Load is not secured on the maintenance bypass anymore unless there is power generator running
instead of normal grid utility.
4. Pressing the EPO button of each UPS stops the operation of rectifier, inverter, static switch and battery, but this
action will not affect the maintenance bypass power the load normally.
NOTE: In maintenance mode, the load is directly fed by the mains power instead of the pure AC power from the
inverter.
5. Disconnect the rectifier input switch Q1 and bypass input switch Q2 of each UPS in turn.
After all the internal power supply is disconnected and the touch screen does not display will also be turned off.
NOTE: Wait for 10 minutes before maintenance for the internal DC bus capacitance to get discharged.
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.
8.3.3 Procedures for isolating one UPS module from parallel system
IMPORTANT! The isolation procedures should be carried out only by Vertiv certified service personnel.
NOTE: After isolating one UPS module, when the parallel system is not overload, then proceed with steps below.
To isolate the UPS module from the parallel system for any major repairing activity, follow the below steps.
1. Turn off the rectifier, inverter, static switch and battery with the EPO button on the GHMI.
NOTE: Turning off the rectifier, inverter, static switch, and battery will not affect all the other UPS in parallel system
and the load will remain powered normally.
2. Disconnect the external power mains switch, rectifier input switch Q1, external power bypass switch, bypass
input switch Q2, output switch Q5, BCB and single module external output switch.
WARNING! Place a notice at the AC input distribution (generally far away from the UPS) to alert that UPS
maintenance is being performed.
NOTE: Wait 10 minutes for the internal DC bus capacitance discharging. Then the UPS is completely shutdown.
8.3.4 Procedures for inserting one isolated UPS module in parallel system
IMPORTANT! These procedures must only be carried out by service personnel of Vertiv or under their guidance.
The following procedures are used to reintegrate a UPS module that has been previously isolated from the parallel system:
1. Confirm that the I/O cable, battery cable and parallel cable of the single module are correctly connected.
2. Confirm that the maintenance bypass switch Q3 or the single module external maintenance switch is
disconnected.
3. Close the output switch Q5, external output switch, external power bypass switch, bypass input switch Q2,
rectifier input switch Q1, and external power mains switch of each UPS in turn.
148 Proprietary and Confidential ©2023 Vertiv Group Corp. 8 Parallel System and LBS System
Vertiv™ Liebert® APM2 30 to 120 kVA Modular UPS User Manual
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