Operating Instructions
21
3.5 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 3.3 - Switching the UPS from Normal to Maintenance
Bypass.
2. Close the external maintenance bypass switch, QextBYP.
3. To completely isolate the UPS from the AC supplies, the main external power input isolator (both
isolators, where separate supplies are provided for rectifier and bypass) should be opened (see
Figure 15).
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.
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
and after the external power switches (QINextBYP) have been closed. See the reference drawing of
Figure 15 for more information.
NOTE
An external Maintenance Bypass Cabinet must be installed before attempting to perform the
following procedure.
!
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.
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