6.4 Operation Procedures for Parallel System
6.4.1 Before startup
WARNING! These procedures result in mains voltage being applied to the UPS output terminals.
WARNING! If any load equipment is connected to the UPS output terminals, check with the user that it is safe
to apply power. If the load is not ready to receive power, disconnect the downstream load switch, and paste a
warning label on the connection point of the load.
1. Check and confirm that the UPS power distribution mode is correct, that the power cables and signal cables are
correctly connected, and there are no short circuits.
2. Check that the batteries are properly installed, the cables are correctly connected, and the positive and negative
battery poles are correct.
3. Check all the operating status of the parallel system, ensure that the phase sequence of the main, bypass and
output of each UPS is correct and consistent, that the connection of the parallel cable is reliable, and that the
user load is not connected during power on.
4. Measure the mains voltage and frequency and verify that they are correct.
5. When the UPS is switched on, the UPS output terminals are energized. If the load has already been connected to
the output terminals, make sure that it is safe to apply power to it.
6.4.2 Parallel system parameters setting
NOTE: The parameters of parallel system must be set by Vertiv engineer through Vertiv setting software.
6.4.3 Power on procedures for parallel system
WARNING! During the parallel power on, confirm that the external output MCB of each UPS has been closed,
and that all the inverter output of the UPSs is connected parallelly.
WARNING! During the parallel power on, confirm that the system is working normally, and then feed power to
the load, to void load power failure.
WARNING! To avoid misreporting as faults, all operations relating to disconnection or connection must follow
the following steps.
1. Set the parallel parameter of each UPS in the parallel system, then commission the inverter. The specific
commissioning procedures are as follows:
a. Ensure that the total external maintenance bypass switches are open in the parallel system. Open the front
door of each UPS, ensure that the internal maintenance bypass switch Q3 is off, and that the input cables
and PE terminals are securely connected.
b. Close the total bypass input switch Q2.
50 Proprietary and Confidential ©2023 Vertiv Group Corp. 6 Parallel System and LBS System
Vertiv™ Liebert® EXS Installer/User Guide
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