Emerson Liebert NXL 250 kVA, Operation And Maintenance Manual

Page: 47 / 112

Operation
39 Liebert
®
NXL
™
Maintenance Bypass Load Transfers—Single Module System: If Load is on UPS Bypass
1. Transfer the UPS system to bypass (see 2.15.4 - Load Transfer and Retransfer—Single
Module System ). The “OK to transfer” lamp on the key-release unit will light.
2. If using a key interlock system, depress the key-release unit push button, turn the key and
remove from key-release unit.
3. If using a key interlock system, insert the key into the lock for the Maintenance Bypass Breaker
(MBB); retract the bolt.
4. Close the Maintenance Bypass Breaker (MBB).
NOTICE
Risk of improper operation sequence. May cause equipment damage.
Failure to close the Maintenance Bypass Breaker (MBB) will interrupt power to the load.
5. Open the Maintenance Isolation Breaker (MIB). The UPS system is now isolated from the critical
load, and the load is now on Maintenance Bypass.
6. If using a key interlock system, remove the key from the lock for the Maintenance Isolation
Breaker (MIB).
7. If the maintenance bypass cabinet or switchboard has an optional two-key interlock system,
replace the key into the solenoid.
8. If UPS bypass shutdown is required, open the Bypass Input Breaker (BIB).
Maintenance Bypass Load Transfers—Single Module System: If Load is on Maintenance
Bypass
1. Close the Bypass Input Breaker (BIB) or verify that it is closed. Note that the UPS Bypass circuit
breaker (motorized) must also be closed. Refer to 2.15.1 - Startup—Single Module System .
2. If using a key interlock system, depress the key-release unit push button, turn the key and
remove it from the key-release unit.
3. If using a key interlock system, insert the key into the lock for the Maintenance Isolation Breaker
(MIB); retract the bolt.
4. Close the Maintenance Isolation Breaker (MIB).
NOTICE
Risk of improper operation sequence. May cause equipment damage.
Failure to close the Maintenance Isolation Breaker (MIB) will interrupt power to the load.
5. Open the Maintenance Bypass Breaker (MBB). Load is now on UPS Internal Bypass.
6. If using a key interlock system, remove the key from the lock for the Maintenance Bypass Breaker
(MBB) to lock it open.
7. If the maintenance bypass cabinet or switchboard has an optional two-key interlock system,
reinsert the key into the solenoid.
8. The UPS system may now be transferred from bypass to UPS (see 2.15.4 - Load Transfer and
Retransfer—Single Module System ).
NOTE
If the maintenance bypass cabinet or switchboard has any other type of custom interlock, follow
the specific instructions for that interlock system to remove the key.
NOTE
The UPS system is now locked in bypass and cannot be retransferred to the Inverter until the
key is reinserted.
NOTE
The UPS system is now locked in bypass and cannot be retransferred to the Inverter until the
key is returned.