Emerson 15-90KVA Manuel D’Utilisation

Follow the procedure below to transfer the load from the UPS inverter output to the Maintenance 

Bypass system.

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, the status indicator will turn amber and an audible alarm 

will sound. The load will transfer to static bypass (internal) and the inverter will shut off.

2. Open the Liebert BDC door to gain access to the bypass isolation breaker (BIB), maintenance 

bypass breaker (MBB) and maintenance isolation breaker (MIB).

3. When the lamp indicator on the BDC is illuminated, press and hold the adjacent push button and 

remove the Key from the lock (K0).

4. Insert the Key into the lock on the MBB and turn the Key.
5. Close the MBB.
6. Verify the MBB is closed. Failure to close the MBB will interrupt power to the load.
7. Open the MIB.
8. Remove the key from the lock on the MIB. Insert the key into the lock (K0) and turn the key.
9. The UPS system is now isolated from the critical load.
10. 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 48.

11. 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 64.

Risk of power loss to connected load. Can cause damageto equipment.
The load equipment is not protected from normal supply aberrations when the Liebert APM is 

operating in the maintenance bypass mode.

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.

NOTE
Pressing the Alarm Silence Switch cancels the audible alarm, but leaves the warning message 

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.

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

®

 APM

™

 system are 

still energized. Service must be performed by properly trained and qualified personnel only.