Two questions that came up on a job in relation to 450.3(B)
In providing transformer primary protection at 250%, there is no "Note 1" to the Table as there is with the 125%. On a 75kva transformer (480v primary), your current is 156.25 amps X 250%=390 amps. Would you be allowed to go to a 400 amp breaker as far as Art 450 is concerned.
Same transformer, 250% primary protection, 240/120 secondary, 450.3(B) allows 125%, 312 amps X 125% = 390 amps. There is a "Note 1", so next higher is allowed. Could the secondary connect to (2) 200 amp main breaker panels ? (Note 2 seems to allow that)
In providing transformer primary protection at 250%, there is no "Note 1" to the Table as there is with the 125%. On a 75kva transformer (480v primary), your current is 156.25 amps X 250%=390 amps. Would you be allowed to go to a 400 amp breaker as far as Art 450 is concerned.
Same transformer, 250% primary protection, 240/120 secondary, 450.3(B) allows 125%, 312 amps X 125% = 390 amps. There is a "Note 1", so next higher is allowed. Could the secondary connect to (2) 200 amp main breaker panels ? (Note 2 seems to allow that)
