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Operation
23 Liebert
®
NX
™
3. If using a key interlock system,
a. The “OK to transfer” lamp on the key-release unit will light.
b. Depress the key-release unit push button.
c. Turn the key and remove it from the key-release unit.
d. Insert the key into the lock for the Maintenance Bypass Breaker (MBB).
e. Retract the bolt.
4. Close the Maintenance Bypass Breaker (MBB).
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:,
a. Remove the key from the lock for the Maintenance Isolation Breaker (MIB).
b. Replace the key into the solenoid.
7. Open the MOB breakers of each module.
8. If UPS bypass shutdown is required, open the Bypass Input Breaker (BIB). This breaker is
external to the UPS; it may be in the Maintenance Bypass Cabinet.
2.5.10 Load Transfer-1+N System: Remove a UPS from System (Collective)
1. Ensure there are enough modules online to support the load before proceeding.
2. Open the MOB breaker of the module to be removed.
2.5.11 Load Transfer-1+N System: Add a UPS to the System (Collective)
NOTICE
Risk of loss of power to the critical load. Can cause equipment damage.
Do not turn On control power to an offline module if the collector bus is being fed by the
bypass line(s) of the UPS module(s) connected to the collector bus. Doing so will turn Off the
static switch(es) of any module connected to the collector bus and remove power from the load
bus.
This section lists typical step-by-step instructions. The touchscreen will list all steps required for the
process, based on the unit's condition and other factors.
1. Provide power to all the UPS controls to permit the display touchscreen and system logic to
function properly.
a. Close the Bypass Input Breaker (BIB)—This breaker is external to the UPS, possibly in the
Maintenance Bypass Cabinet. The display touchscreen should startup.
b. Close the Rectifier Feed Breaker (RFB)—This breaker is external to the UPS, possibly in the
Maintenance Bypass Cabinet.
c. Bypass Circuit Breaker (BFB)—This circuit breaker should be open (see Figures X and X for
the location).
d. Optional Module Output Breaker (MOB)—This circuit breaker should be open. This breaker
is external to UPS, possibly in the paralleling gear.
2. Apply power to the module.
• If the equipment does not have CB1 installed, the rectifiers of all modules will start
automatically.
• If CB1 is installed, close CB1 for all modules and allow the rectifiers on all modules to start.
• Verify the rectifier has started and that the LCD is fully functional before proceeding.
• The Inverter and BPSS will be Off.
3. Close the MOB breaker associated with this module.
a. Inverter will automatically start when MOB is closed.
b. Once the inverter has started and synchronized to the rest of system, the module will add
itself to the critical bus.