User Manual 10H52192UM60 - Rev. 1 - 09/2011 51
Operating Instructions Liebert NX
4. For a single UPS, open the maintenance switch QS3; for a 1+N parallel system, open the external maintenance switch.
5. Press and hold the INVERTER ON button for 2 seconds.
The inverter starts up and the inverter indicator flashes green. When the inverter is ready, the UPS transfers from bypass to inverter,
the bypass indicator turns off, and the green inverter indicator remains on (not flashing). The UPS is in normal mode and the UPS
indicator states are as listed in Table 6-2.
6.4 Procedure for Completely Powering Down the UPS
Caution
The following procedure will switch off all power to the load.
Warning: Hazardous battery voltage
The UPS battery and connecting terminals remain energized at hazardous voltage levels at all times.
The following procedure is used to completely power down the UPS and load. All power switches, isolators, and circuit breakers will
be opened and the power will be removed from the load. In a parallel system, perform each step of the procedure on every UPS
module before proceeding to the next step.
1. Press and hold the INVERTER OFF button on the operator control and display panel for 2 seconds.
At this point, the inverter indicator turns off, the bypass indicator turns on, and the status indicator changes to amber,
accompanied by an audible alarm. The load transfers to the bypass and the inverter shuts down.
2. Open the internal and/or external battery circuit breakers (internal QS6 and QS7).
3. Open the input switches QS1 (mains input) and QS2 (bypass input) of the UPS.
At this point, in parallel systems the other UPS modules report Parallel Comm. Fail, which is normal. Other UPS modules continue to
supply the load through the inverter.
All of the indicators and the LCD on the operator control and display panel will be switched off as the mains-driven internal power
supplies decrease.
4. Open the output switch QS4 on the UPS.
6.5 Procedure for Completely Powering Down the UPS While Maintaining the
Power Supply to the Load
Caution
Ensure that the UPS has been installed with an external maintenance bypass cabinet before carrying out this procedure.
The following procedure is used to completely power down the UPS while maintaining the power supply to the load. In a parallel
system, perform each step of the procedure on every UPS module before proceeding to the next step.
1. Use the procedure in 6.3.4 Transfer from Normal Mode to Maintenance Mode to transfer the UPS to maintenance mode.
2. Close the maintenance switch on the external maintenance bypass cabinet.
3. Open the external circuit breakers or other protective devices at the input of the UPS.
4. Open the external output switch on the UPS.
6.6 Isolation Procedure (for One UPS in a Parallel System)
Caution
The following procedure will switch off all power to the load.
Warning: Hazardous battery voltage
The UPS battery and connecting terminals remain energized at hazardous voltage levels at all times.
The following procedure is used to isolate one UPS in a parallel system.
1. Press and hold the INVERTER OFF button on the operator control and display panel for 2 seconds.
2. Open the input switches QS1 and QS2 on the UPS and disconnect the battery.
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