Conductor sizing and SC protection sizing for motor

[samir]

Hello friends,

I am trying to catch up with NEC requirements. I understand the sizing of conductor (125% atleast of FLC) and short circuit protection(250% maximum of FLC) for a single motor. But what is when two motors or several motors are fed?

I have attached a snapshot of a scenario where someone could explain how the conductor sizing and overcurrent protection is done when a 75HP and 60HP (480V AC motor). In this case the a single AL conductor (250A) is foes into a wireway and separates into two separate cables to feed each 75HP and 60HP motor?

I am trying to figure out if this is within the NEC requirement or not.

 

[petersonra]

This is a motor feeder circuit.

see 430.24 and 430.62.

 

[augie47]

At first glance, the only potential problem I see is that your EGC from your wireway to your individual motor SCGF protection would need to be sized per the feeder GFSC device (300 amp).
The sketch, to me, was not clear on that point. After the individual OCP, the size can be adjusted to the downstream device.
The other numbers appear to fall within NEC guidelines, in fact, slightly oversized, but taking the length of run into account that might be necessary fro a voltage drop standpoint (I did not address that).