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Interlock Application - Uninterrupted Power Sources

Scheme # 39
To prevent improper maintenance bypass of Uninterruptible Power Supply.

Solenoid Key Release Unit (SKRU) shown with A-1 Key held captive. UPS output breaker A is closed supplying the critical load through the UPS. Key B-1 is held captive in the L-O interlock on breaker A. Maintenance bypass breaker B cannot be closed until the UPS is placed in bypass mode, sending a signal to the SKRU allowing release of key A-1. The SKRU has an apartment lock that will accept either key A-1 or B-1.

To supply critical load through the maintenance bypass breaker, proceed as follows:

Reverse sequence to restore equipment to original condition.

Note: Refer to UPS manufacturer's operation and maintenance manual for instructions regarding transferring the load to the UPS maintenance bypass source. Persons not familiar with the operation of the UPS system should not attempt to change the position of the above devices.

Scheme # 25
Scheme # 26
Scheme # 27 Scheme # 28
Scheme # 29
Scheme # 30
Scheme # 31
Scheme # 32
Scheme # 33 Scheme # 34
Scheme # 35
Scheme # 35A
Scheme # 36