Hello,
I have a 480V panel with a 225A breaker feeder a 150kVA transformer that provides 208/120V on the secondary. The primary feeder is 4/0 conductors and the secondary is 500 conductors. Secondary feeder of less than 10' goes to a distribution board with a 500A breaker.
The secondary breaker is properly sized per 450.3(B).
The inspector is having issue with the secondary feeder. Yes there is no overcurrent protection for it (500A breaker on 380A feeder), but doesn't 240.21(C)(2) relieve me of secondary overcurrent protection anyways? The feeder is less than 10', the ampacity of the conductor meets the calculated load of 357A, the conductors end at the switchgear, and conductors are in EMT conduit, and no the conductors do not leave the enclosure. Since I meet all those requirements, shouldn't 240.21(C)(2) basically say the main breaker isn't for secondary overcurrent protection? It is for mechanical loads so we don't want nuisance tripping anyways.
What am I missing?
I have a 480V panel with a 225A breaker feeder a 150kVA transformer that provides 208/120V on the secondary. The primary feeder is 4/0 conductors and the secondary is 500 conductors. Secondary feeder of less than 10' goes to a distribution board with a 500A breaker.
The secondary breaker is properly sized per 450.3(B).
The inspector is having issue with the secondary feeder. Yes there is no overcurrent protection for it (500A breaker on 380A feeder), but doesn't 240.21(C)(2) relieve me of secondary overcurrent protection anyways? The feeder is less than 10', the ampacity of the conductor meets the calculated load of 357A, the conductors end at the switchgear, and conductors are in EMT conduit, and no the conductors do not leave the enclosure. Since I meet all those requirements, shouldn't 240.21(C)(2) basically say the main breaker isn't for secondary overcurrent protection? It is for mechanical loads so we don't want nuisance tripping anyways.
What am I missing?
