transformer disconnecting menas

[mayanees]

450.14 calls out the need for "a disconnecting means" for a transformer.
Does this mean one disconnecting means? Or can the transformer, in this case an outdoor 750 kVA oil-filled padmount, be fed from two MV breakers, such that in order to lock it out you'd need two locks, one for the emergency MV breaker feeder, and the other the Normal 15 kV source?

Thanks for any comments.

John M

 

[augie47]

Good question.
Probably an AHJ call when the dust clears.
Since 450.14 allows "remote" location AND marking at the transformer one might be allowed to mark the transformer and each switch with the need to lock out both, especially since any such system is probably being maintained by highly trained personnel, however, the Code does say "disconnect" (singular) so a literal interpretation would probably be one switch.

 

[mayanees]

thanks for the input Augie.

 

[mayanees]

FYI

FYI

.. as followup to anyone interested in this thread, our AHJ okayed the installation.

John M

 

[jumper]

Good question.
Probably an AHJ call when the dust clears.
Since 450.14 allows "remote" location AND marking at the transformer one might be allowed to mark the transformer and each switch with the need to lock out both, especially since any such system is probably being maintained by highly trained personnel, however, the Code does say "disconnect" (singular) so a literal interpretation would probably be one switch.

Gus, I do not see a singular "disconnect" term in 450.14.

450.14 Disconnecting Means. Transformers, other than
Class 2 or Class 3 transformers, shall have a disconnecting
means located either in sight of the transformer or in
a remote location. Where located in a remote location,
the disconnecting means shall be lockable, and the location
shall be field marked on the transformer.

Disconnecting Means. A device, or group of devices, or
other means by which the conductors of a circuit can be
disconnected from their source of supply.

 

[augie47]

good point... I did not go back to the definition. I was going by the term "a disconnecting means".

I can see his AHJ pondering this one.