Emerson Liebert NX 10-30kVA - Manual (Page 91)

Operating Instructions
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9.14 Commissioning a Parallel System
Check the input and output wiring of each UPS module. Ensure that the phase rotation sequence of
the main inputs and the bypass inputs and outputs of each UPS module are the same. Ensure the
parallel cables are connected firmly.
It is assumed that the installation is complete, the system has been commissioned by authorized per-
sonnel and the external power isolators are closed. Before start up, disconnect the load.
9.15 Maintenance Bypass Cabinet Operating Procedures
9.15.1 Start Up and Initialization
Follow these steps to start the UPS while connected to the Maintenance Bypass.
1. Set Maintenance Bypass switch to the Normal position on Maintenance Bypass Cabinet.
2. Close the system input circuit breaker.
3. Start the UPS as instructed in 9.2 - UPS Start Up.
4. Close system output circuit breaker.
9.15.2 Shutting Down the UPS
Use the following procedure to power down the system.
1. Turn the NX off by following the procedures in 9.4 - Powering Down the UPS
2. Open system output circuit breaker.
3. Open system input circuit breaker.
9.15.3 Transferring System from UPS to Maintenance Bypass Operation
1. Turn the bypass switch (SW) to the bypass position on the Maintenance Bypass Cabinet. The UPS
will switch to bypass mode.
The connected equipment is now powered from the bypass source and is NOT protected.
2. To isolate the UPS from the system, rotate the bypass switch to the maintenance position.
9.15.4 Transfer the System from Maintenance Bypass to UPS Operation
1. Turn the bypass switch (SW) to the Normal position on the Maintenance Bypass Cabinet. The
UPS will go to bypass mode.
2. Press the “Inverter On” button on the UPS and allow the UPS to go to normal mode.
3. The connected equipment is now powered and protected by the UPS.
9.15.5 Transfer the System from UPS Operation to Maintenance Bypass
If the UPS needs to be shut down completely while maintaining power to the load, follow these steps:
1. Perform Steps 1 through 5 in 9.3 - Switching the UPS from Normal to Maintenance
Bypass.
2. Rotate Maintenance Bypass Switch to Maintenance position.
3. Post a label on the primary input distribution panel, which often is installed outside the UPS
area, advising personnel that the UPS circuit is under maintenance.
The UPS is now completely powered down.
!
CAUTION
The operations described in this section must be performed by authorized electricians or
qualified technical personnel. If you have any difficult, do not hesitate to contact Liebert
Global Service at 1-800-LIEBERT.
!
WARNING
Wait 5 minutes for the internal DC busbar capacitors to discharge.
NOTE
The Maintenance Bypass power switch may be operated at any time while the UPS is powered
down to connect the load to the maintenance bypass supply.