Emerson Liebert NX 480V - Manual (Page 88)

Operating Instructions
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9.10 Parallel System Start Up
1. Start each UPS normally as described in 9.2 - UPS Startup
2. Turn on the inverter of each UPS module one at a time.
3. Apply the load after the last UPS module transfers to inverter. The total load can be determined
through the LCD of either UPS.
4. Verify the load rate of each UPS module. If the load rates are roughly the same, then the parallel
system may be assumed to be operating normally.
NOTE
If one module cannot transfer to inverter mode long after its inverter is on, its output
connection may not be good or its output phase rotation may not be coincident with other
modules. At this time, the LCD for the UPS module will display “inverter asynchronous” and
the inverter indicator will flash continuously. If either UPS module makes abnormal noise
after it transfers to inverter, its parallel cables may be incorrectly connected.