Switching The Ups From Normal To Maintenance Bypass; Powering Down The Ups - Liebert NX series Operation & Maintenance Manual

3.3

Switching the UPS from Normal to Maintenance Bypass

Follow the procedure below to transfer the load from the inverter output to the Maintenance Bypass
line of the UPS.
CAUTION
!
Before performing this operation, read the messages on the LCD to be sure that bypass supply
is regular and the inverter is synchronous with it. If those conditions are not present, there is
a risk of a short interruption in powering the load.
This procedure assumes that UPS is operating normally.
1. Press the INVERTER OFF button on the right side of the operator control panel for longer than
2 seconds.
The Inverter indicator will turn off and the alarm indicator (6) will turn amber and an audible
alarm will sound. The load will transfer to bypass and the inverter will shut off.
NOTE
Pressing the Alarm Silence Switch cancels the audible alarm, but leaves the warning message
displayed until the appropriate condition is rectified.
2. Open the UPS door to gain access to the main power switches, SW1 and CB1.
3. Turn the rotary switch to BYPASS position. The UPS Bypass Static Switch still supply power to
load.
4. Turn the rotary switch to TEST. The load is now on maintenance bypass.
5. Turn the rotary switch to MAINT.
6. Open rectifier switch CB1. All operator indicators and messages will turn off as the utility driven
internal power supplies decay. The unit will power down, but the load will continue to be supplied
by the manual Maintenance bypass.
WARNING
!
Wait 5 minutes for the internal DC busbar capacitors to discharge.
WARNING
!
Even with the UPS in maintenance bypass and "Off," portions of the unit are still energized.
Service is to be performed by qualified personnel only.
CAUTION
!
The load equipment is not protected from normal supply aberrations when operating in the
maintenance bypass mode.
3.4

Powering Down the UPS

To power down the UPS completely, follow the procedures in 3.3 - Switching the UPS from Nor-
mal to Maintenance Bypass.
To completely isolate the UPS from the AC supplies, the main external power input isolator (both iso-
lators, where separate supplies are provided for rectifier and bypass) should be opened (see
Figure 15).
WARNING
!
To prevent injury to personnel, lockout or tagout the service supplies.
20
Operating Instructions