Contents | Introduction | Symbols Legend | Scheme Book

Interlock Application - Breakers and Generators

Scheme # 36
To prevent paralleling of any sources while allowing switching of the loads to alternate sources.

Breaker A is closed to supply load M. Breaker B is closed to supply load N. Tie-Breaker C and generator breakers G and H are locked open. Key A-1 is held in the L-O interlock on breaker A. Key B-1 is held in the L-O interlock on breaker B. Tie-Breaker C cannot be closed unless either breaker A or breaker B is locked open. Generator breaker G cannot be closed unless breaker B is locked open. Generator breaker H cannot be closed unless breaker A is locked open. Tie-Breaker C interlock has an apartment lock and can be unlocked for operation with either key A-1 or B-1. Generator G breaker interlock can be unlocked for operation with key B-1 only. Generator H breaker interlock can be unlocked for operation with Key A-1 only.

To transfer load N to breaker A, proceed as follows:

Reverse sequence to restore service through breaker B. Load M can be supplied through breaker B in a similar manner.

To transfer load M to generator H, proceed as follows:

Reverse sequence to restore service through breaker A.
Load N can be transferred to generator G using the B-1 key in a similar manner.

To transfer loads M and N to generator H, proceed as follows:

Reverse sequence to restore service through breakers A and B.
Loads M and N can be transferred to generator G in a similar manner. Open breakers A & B, then utilize the A-1 key to unlock tie-breaker C and utilize the B-1 key to unlock generator breaker G.

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