1. Confirm that the total external maintenance bypass switches are disconnected.
2. Open the front door of each UPS in turn.
3. Ensure that the internal maintenance bypass switch Q3 is disconnected.
4. Check all the input cables, parallel cables and copper bars are connected properly.
WARNING! In parallel UPS configuration, all operations related to disconnection or connection of the
maintenance bypass switch must be performed within three seconds to avoid overload situations and
damage to the maintenance bypass switch.
5. Close the total bypass input switches.
6. Close the output switch Q5, bypass input switch Q2, rectifier input switch Q1, and all external output isolating
switches (if any) of each UPS in turn.
When the above steps are complete, the system is powered on, and the startup screen pops up.
Wait 25 seconds and confirm that the Touchscreen shows that the rectifier power supply and the bypass power supply are
normal.
If not, check whether the Q1 and Q2 switches are closed. Then the rectifier starts up, about 30 seconds after the rectifier
enters normal operation, the bypass static switch is closed.
7. When the rectifier start process is finished and the rectifier indicator turns solid green, close the external BCB.
8. For each UPS, manually turn on the inverter. The inverter starts up, the whole UPS system will power the load.
8.3.2 Maintenance bypass procedures
WARNING! If the UPS system is composed of more than 2 parallel UPS modules, and the load capacity
exceeds the single module capacity, do not use the internal maintenance bypass switch.
Maintenance Bypass will transfer the load from UPS power supply protection state to direct connection with AC input bypass
state.
CAUTION: Power supply interruption danger. Before performing this procedure, should check the LED
information first and make sure the bypass is normal and inverter synchronized. Otherwise, it may result in
the load power interruption for a while.
1. Manually turn off the inverter of each UPS respectively. The power flow diagram shows Inverter Off, and the
buzzer alarms. The load transfers to the static bypass, and the inverter shuts down. At last, all UPS units are
transferred to Bypass Mode.
NOTE: Pressing the Silence Off button silences the alarm; however, the alarm message on the touch screen does not
disappear until the alarm status is cleared.
2. Close the UPS all the external maintenance bypass switches but, do not close the internal maintenance bypass
switch Q3 of each UPS. While you are closing these switches, all the external maintenance bypass should be
parallel connected with static bypass of each of the UPS's. The touch screen of each UPS should display Main
Switch Closed.
3. Disconnect the output switch Q5 of each UPS in turn, and the maintenance bypass can supply power to the load.
8 Parallel System and LBS System Proprietary and Confidential ©2023 Vertiv Group Corp. 147
Vertiv™ Liebert® APM2 30 to 120 kVA Modular UPS User Manual
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