stjohnbarleycorn
Senior Member
I can't seem to find where you round down on the feeder circuit for the next standard size breaker. Thanks for any help.
sorry, for a single motor when you figure out the OCPD size from the table, 430.52 430.52(c) states you can't go over the amperage in the table, and then in 420.52(C) ex. 1 it states you can go to the next standard size up. If I am reading it correctly.
If you are feeding multiple motors you take 125% of the first and then the sum of FLC of the rest. I think there is a reference that says you can't round up to the next size in this case because of the multiple motors on the circuit. But I may be wrong. thanks.
sorry, for a single motor when you figure out the OCPD size from the table, 430.52 430.52(c) states you can't go over the amperage in the table, and then in 420.52(C) ex. 1 it states you can go to the next standard size up. If I am reading it correctly.
If you are feeding multiple motors you take 125% of the first and then the sum of FLC of the rest. I think there is a reference that says you can't round up to the next size in this case because of the multiple motors on the circuit. But I may be wrong. thanks.
I can't seem to find where you round down on the feeder circuit for the next standard size breaker. Thanks for any help.
I was reading over the info, I think what I am getting at is that for a feeder for multiple motors , and using a IT breaker, you take the largest motor FLC, times 250%, then the other motors FLC added to that. The final number you come up with should be rounded down, not up as with a branch circuit.
I'm sorry, but I don't read it that way. I may be missing it but I can find no reference in 430.62 for feeders to allowing "a higer size"as I do in 430.52 for branch circuits.In article 430.62(A) ex 1 it does say for instantaneous trip circuit breakers that we can not exceed the Values of T430.52.
But for all other fuse or standard breakers, (Inverse Time) we can still round up on the feeder.
Is that what your looking at?
that might be what I am thinking of.
So there is no difference in feeding a single motor or multiple motors on a feeder, as far as the rating of the OCPD, You can go with the next size up standard breaker, unless it exceeds 400%? thanks for the help.
I'm sorry, but I don't read it that way. I may be missing it but I can find no reference in 430.62 for feeders to allowing "a higer size"as I do in 430.52 for branch circuits.
I can't seem to find where you round down on the feeder circuit for the next standard size breaker. Thanks for any help.
430.62 Rating or Setting ? Motor Load.
(A) Specific Load. A feeder supplying a specific fixed motor
load(s) and consisting of conductor sizes based on
430.24 shall be provided with a protective device having a
rating or setting not greater than the largest rating or setting
of the branch-circuit short-circuit and ground-fault protective
device for any motor supplied by the feeder [based on
the maximum permitted value for the specific type of a
protective device in accordance with 430.52, or 440.22(A)
for hermetic refrigerant motor-compressors], plus the sum
of the full-load currents of the other motors of the group.
Disregarding exceptions, this is the code you're looking for. You take the largest OCPD and add the full load current of the remaining motors. then you go down to the next standard size. (See bolded portion).