Troubleshooting guide

1. Parallel system connection
2. Adding one new unit into the parallel system
3. Removing one unit from the parallel system
Switch on the input breaker and the UPS will enter Bypass mode. If the UPS is in maintenance Bypass mode, turn the
maintenance switch to the “UPS” position before turning on the system.
You cannot add one new unit into the parallel system while the whole system is running. First, all loads and each UPS in
the system must be shutdown
Make sure all of the UPS are parallel models, and follow the wiring scheme shown earlier in this manual. .
Install the new UPS and follow instructions in the previous section for proper connection, testing and startup.
Press the OFF button twice for about 0.5 second each. The UPS will enter into bypass mode without output.
After turning off the output breaker, do the same with the input breaker of the UPS.
After the UPS shuts down, remove the parallel cable and parallel current cable. You can now remove the unit out from
the parallel system.
Warning: (parallel system only)
If the bypass is abnormal, you cannot remove the UPS without interruption. You must first power down the load and shut
down the UPS system.
Enable the Bypass setting in each UPS and then power off the running UPS. All UPS units in the parallel system will
transfer to Bypass mode. Remove all maintenance bypass covers and change the maintenance switches from UPS to
BPS. Next, turn off input breakers and battery breakers.
Remove the desired UPS.
Turn on the input breaker of the remaining UPS and the system will transfer to Bypass mode.
Set the maintenance switches from BPS to UPS and replace the maintenance bypass covers. Turn on the remaining
UPS and finish the parallel system connections.
Before turning on the parallel system to activate the inverter, make sure that every maintenance switch on the UPS is in
the same position.
When the parallel system is turned on to operate through the inverter, do not change the maintenance switch of any unit.
There are two methods that can be used to remove one UPS from the parallel system:
First method:
Second method:
Make sure all of the UPSs are designed for parallel operation and that all the wiring is done properly.
Turn off the input and output breakers of each UPS.
Remove all the maintenance bypass covers and change the maintenance switches from UPS to BPS. When done,
replace the maintenance bypass cover. With a multimeter, measure the L1-N1 and L2-N2 voltage difference between
each UPS. If the voltage difference is less than 2V, it means all connections are correct. If the difference is larger than
2V, check if the wiring has been done correctly.
Turn on the input breakers of each UPS in the parallel systems. Before turning on each UPS, check if PAR001~PAR003
are displayed in each UPS sequentially. If no “PAR××” exists in any UPS, check if the parallel cables are correctly
connected.
Turn on each UPS in sequence and make sure that AC mode LED or Battery mode LED display is lit in each UPS. Using
a multimeter, measure the output voltage of each UPS to make sure the voltage difference is less than 2V (typical 1V). If
the difference is larger than 2V, check that parallel cables and/ or parallel current cables are connected properly.
Turn off each UPS in sequence. After all of the UPS are transferred to Bypass mode, turn on the output breaker of each
unit.
Turn on the UPSs in the AC mode. Parallel system connections and configuration should now be complete.
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3-5. Parallel operation
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