OT: NEC on motor feeders...

I was talking with a cow-orker about whether motor leads can be in the same conduit as power feed leads and need some clarification.

480V feeds will pass right by a 50 HP motor to a cabinet 20' away where the starter is, then return back to the motor. I spec'ed two seperate conduits but Bubba wants to put in a jbox where the feed conduit passes the motor instead of running two conduits. For some vague reason this strikes me as a deprecated practice but I'm not sure and couldn't find it in my code book. I said I would check on it.

The NEC does not care. They have very few restrictions on what can share the same raceway. About their only area of concern for motor circuits is mixing control wiring with power under article 725. The only other area might be when a manufacturer says not to mix VFD line and load circuits.

What would be your reason for not wanting them to install it this way?

Alaric,

While what Jim says is true, it's important to note that combining the feeder and the motor leads in the same conduit will require you to derate the ampacity of the wire. This will probably result in an increase in wire size for a 50 hp motor which will probably require a bigger conduit. The end result is that it is probably more economical to run separate conduits.

It's not a good idea for such a large load. As a matter of practice we never mix feeders and motor circuits in the same raceway.

I don't think I would do it...but thats just me, I looked around on mikeholt, this is what I found.


1)If you had more then 3 load carrying conductors then you would have to de-rate your conductors.


2)Also 230.7 might apply if it was before the disconnect.


But it sounds like preference...I would prefer not

On motor circuits I also like to think in terms of the future now. If for some reason in some far off distant future someone wasnt to change that starter to a VFD, then they would need to separate those circuits. I think it would be better to do it now. Besides, as others have mentioned the derate on all of the circuits may cost more than you might think with the cost of copper right now.

Cow-worker? LOL! Was that deliberate?