ECN Forum Forums Code Related Discussion NEC & other Code issues Derating NM cable

George regardless of your profession this is an NEC forum and if you are not basing your response on a code section you should state plainly that you response is an opinion.

People come here to learn the NEC.

FWIW It is possible to fully load twenty 120 volt 2 wire circuits from a 200 amp 240/120 service. Therefore you could have 40 fully loaded current carrying conductors in a single raceway.

Just My Opinion, Bob

Bob, I see where George is going and I tend to agree with the sentiment. From what Tom is saying, Wisconsin does too.
Load diversity in residential circuits does make a lot of this derating somewhat moot.
If you really had 20 fully loaded 20a circuits, the 2 ga al service conductors would burn up.

All this said your point is still valid.

We have to go to war with the code we have not the code we wish we had.

Greg I agree that in residential circuits some changes could be made.

I am still going to be a stickler for NEC facts in a forum called NEC & other Code issues

Everyone is more than welcome to post their opinions on NEC issues all I ask is do not present an opinion as code fact.

That is IMO

Bob

Bob- I'm with you. I have to enforce the code. I can't afford the insurance needed to enforce my opinion on code issues. Maybe I don't think it's necessary to run conduit when feeding a swiming pool panel I think you should be able to run SER. - I have to enforce the installation of conduit. Derating applies to all. No exception. When I review plans I expect to see atleast minimum code.

iwire ---

The question concerned NM run through holes in joists. I suspect that the question was asked because the code is silent on what constitutes bundling.

My response was that I could not bundle NM tight enough for derating to be necessary.

You are not allowed to make up a definition of bundling and enforce it as part of the NEC.

Actually this would also go against real world work ethics. You cant run that tight of a bundle through a hole in joists without pulling individual wires. That tight would burn the insulation on the NM. Also would make it alot harder ( I am referring to running many NM's though a single hole)

Stovepiping is the bain of every Sparky out there doing service changes. It is absolutely stupid.

Am I the only sparky that uses yellow #77 to help reduce cable sheath friction burn?

310.15(B)(2) says "stacked or bundled" so the degree of tightness becomes a non issue IMHO. NM cable pulled through 2x4 studs whether steel or wood could qualify for derating.

again in real world conditions...you would NOT run that many NMs through a joist. You would drill more holes just to make it easier. I would NEVER have to lube an NM cable to get it through a hole...grab a drill and drill the joists.

Yes a joist is considered a conduit...just remember the next sparky after you, leave him/her a nice place to work in.

This means:
an open/not filled conduit, an easy way to run wire, a CLEAN job, a nice cut in, ACCURATE information...etc

I am in the real world. You'd be shocked at the bundles of wires I see run through the same holes. That's what triggered this post.