I've got a general question in reference to table 450.3(b).
For example, the goal is to size primary protection for a 1.5kva single phase 480/120 transformer, assume correct secondary protection so the 250% rule applies.
Primary current = 3.13 amps,
250% * 3.13 = 7.81 amps
Taking in account standard breaker sizes start at 15, 20, 25, etc. and standard fuse sizes include 1, 3, 6, and 10...
My question is, what if fusing is not possible and I'm forced to use breakers (for whatever reason) can I use a 15 amp breaker because the code says to use standard sizes? Or do I HAVE to make provisions to install a 6 amp fuse (largest standard size that does not exceed 250%)?
For example, the goal is to size primary protection for a 1.5kva single phase 480/120 transformer, assume correct secondary protection so the 250% rule applies.
Primary current = 3.13 amps,
250% * 3.13 = 7.81 amps
Taking in account standard breaker sizes start at 15, 20, 25, etc. and standard fuse sizes include 1, 3, 6, and 10...
My question is, what if fusing is not possible and I'm forced to use breakers (for whatever reason) can I use a 15 amp breaker because the code says to use standard sizes? Or do I HAVE to make provisions to install a 6 amp fuse (largest standard size that does not exceed 250%)?
