Motor Feeder Circuits

[rbparks]

I need clarification on some Motor Feeder circuits we recently installed in an Industrial environment. We have 60amp fuse protection on (10) motor feeds from a distribution block in the main panel. All the motors are 2HP or less, we ran 12AWG THHN to all, they each have line of sight to the panel, and their own disconnect and fusing at each motor. (3) are about 10', (3) are about 25', (3) are about 50', and one of them is about 100'. I was told to look up the following sections, but I am really rusty on the all the tap rules, and don't want to twist them to suit my needs.
240.21(c)(2) 240.21(c)(6) 240.21(b)(1)(4)
Do we need individual fusing on each motor after the distribution block in the main panel because 60amps is too much for all of them? Maybe for the 100' footer, but everyone reads the sections different for the rest of them, and now we are arguing about it hotly. Anyone?

 

[kiloamp7]

Re: Motor Feeder Circuits

Wouldn't 430.28 tap rules be more appropriate since this is motor circuitry?

 

[rbparks]

Re: Motor Feeder Circuits

Originally posted by kiloamp7:
Wouldn't 430.28 tap rules be more appropriate since this is motor circuitry?

Yeah. Any of the 430, 430 part2, 430.28,430.102(a), 430.102(b). The problem is that we are engineers, you guess the rest. I was hoping someone that actually runs wires could plug our engineering loopholes. We think too much.

 

[don_resqcapt19]

Re: Motor Feeder Circuits

The tap rules make the 25' and less taps ok. The 50' and 100' taps are in violation.
Don

 

[jim dungar]

Re: Motor Feeder Circuits

Tap rules are usually easier if you only do what the code says, not what you think it says.

240.21(C) is for transformer secondary conductors and is not applicable to your example, you need 430.28 (like kiloamp7 said), which is almost identical to 240.21(B). You have three types of motor circuits, <=10', <=25', and >25'

Start with sizing the multi-motor feeder conductor per 430.24.

430.28(1)- taps not more than 10', tap conductor not less than the OCPD/10, in your case 60/10=6A which requires #14 minimum.

430.28(2)- taps not more than 25', tap conductor = feeder conductor/3, in your case 60/3=20A which requires #12 conductor minimum.

430.28(3)- taps 50' and 100' runs need 60A conductor.