Ryan's correct for circuits that include the B phase, read 240.85. Of course the single phase circuits that only use the A and C phases can use the slash rated circuit breakers since they are using just a single phase transformer. Since we serve a lot of residential customers with open delta banks (we use the three phase to serve a small business that is next to the residential area), the residential customers would all have to use full rated circuit breakers if that wasn't permitted.
By the way,
Charlie, are you talking about using a single pole breaker on the high phase ("wild leg") that is prohibited?
I would be interested in the reference in the Code that prohibits that installation, I have never been able to find the reference.
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Charlie Eldridge, Indianapolis,
Utility Power Guy
