Liebert Emerson NX UPS System - Manual (Page 57)

Operating Procedures
49
6.5 Powering Down the UPS and Maintaining Power to Load
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 6.3 - Switching the UPS from Normal to Maintenance
Bypass.
2. Close the external maintenance bypass rotary switch to Maint position.
The UPS is now completely powered down.
The procedure can be performed only after the installation has been completed (which includes the
maintenance bypass cabinet), after the system has been placed in operation by authorized personnel.
See Figure 30 for more information.
Figure 30 Example of configuration for single UPS with external maintenance bypass cabinet.
NOTE
An external Maintenance Bypass Cabinet must be installed before attempting to perform the
following procedure
!
WARNING
On the primary input distribution panel, which is often located distant from the UPS area, a
label should be posted advising service personnel that the UPS circuit is under maintenance.
!
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 if required
CB1 CB2 SW
3P