Confused about Wire Sizes

[jonny1982]

Does this configuration sound correct???

A 400 amp breaker feeding a piece of equipment that has it's own cabinet. Inside the cabinet is a 225 amp breaker feeding the piece of equipment. The wire size from the 400 amp breaker to the 225 amp breaker is one set of 250's, copper.

I understand that if an overload would occur, the 225 amp breaker would trip, but are the conductors sized correctly from the 400 amp breaker to the 225 amp breaker??? 250's only good for 230 amp.

Thanks

 

[jaggedben]

Technically what you have there are tap conductors, and they have to follow the rules in 240.21(B).

So for example, if the wire run is less than 10 feet, it's probably okay, otherwise likely not.

240.21(B) goes into a lot of specifics.