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Operating Instructions
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11.4 Partially De-Energize the Liebert Nx 480 with Bypass Distribution Cabinet (BDC)
Follow the procedure below to transfer the load from the UPS inverter output to the Maintenance
Bypass line of the UPS. To partially de-energize Liebert NX 480V UPS with Liebert BDC:
NOTICE
Risk of load being dropped by the UPS. Can cause equipment damage.
This procedure must be performed by properly trained and qualified personnel who are
knowledgeable about the operation of this system. Failure to follow these instructions will
result in loss of power and possible damage to critical equipment.
Before performing this operation, read any 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.
1. On the Control Panel, press the INVERTER OFF button for 2 seconds.
2. Close the CB3 Maintenance Bypass Breaker.
3. Open the CB5 Output Breaker.
4. Manually open the external battery breaker(s).
5. Open the CB2 Bypass Input Breaker.
6. Open the CB1 Rectifier Input Breaker.
7. Verify that the indicator on the SKRU unit is illuminated.
8. Press and hold the “Alarm Present Silence” button while rotating and removing the key.
9. Insert the key into the lock on the MBB and turn the key.
10. Close the MBB.
11. Verify MBB is closed.
NOTICE
Risk of improper operation. Can cause property damage from loss of power to connected load.
Failure to close the MBB will interrupt power to the load. The load equipment is not protected
from normal supply aberrations when the Liebert
®
NX
™
is operating in the maintenance
bypass mode.
12. Open the MIB.
13. Turn the key to complete lockout of MIB.
14. Remove the key from lock on MIB.
15. Insert the key into the SKRU lock unit and turn the key.
UPS is now isolated from the critical load.
For a single-input system—The bypass isolation breaker (BIB) remains closed. This allows
power to remain present at the UPS input; refer to Figure 51.
For a single-source, dual-input system—The bypass isolation breaker (BIB) can be opened to
further isolate the UPS from input power; refer to Figure 21.
NOTICE
Risk of improper operation. Can cause property damage from loss of power to connected load.
The load equipment is not protected from normal supply aberrations when the Liebert
®
NX
™
is operating in the maintenance bypass mode.
!
WARNING
Risk of electrical shock and arc flash. Can cause property damage, injury and death.
Wait 5 minutes for the internal DC busbar capacitors to discharge before attempting to
remove the internal protective barriers.
!
WARNING
Risk of electrical shock and arc flash. Can cause property damage, injury and death.
Even with the UPS in maintenance bypass and Off, portions of the Liebert
®
NX
™
system are
still energized. Service must be performed by properly trained and qualified personnel only.