ECN Forum Forums General Topics of the Trade General Discussion Area What's a nipple??

OK,
NEC'99 310-15(b)(2)(a)

Exception No. 3: Derating factors shall not apply to conductors in nipples having a length not exceeding 24 in. (610 mm).

So what exactly constitutes a nipple??

A pipe not over 24" is a nipple.

<<CENSORED>>

Never mind. George's answer is probably more appropriate for this forum!

I like George's answer. It is easy to overthink this. A 90 degree bend can be a nipple if it is less than 24".

At first read you say why?

Why can I stuff 24" of pipe with wires and not derate?

I believe the answer lies in coppers ability to readily conduct heat.

Say you have a 24" nipple between a panel and a contactor enclosure, you will have conductors hanging out of both sides of the nipple acting like heat sinks limiting how hot the conductors in the nipple will get.

That's my story and I am sticking to it.

After all there has to be logic behind this exception.

Bob

i am leaing more to bob's answer there .

yes any pipes included the ell sweep[s] if 24 inch or less but i am still consering about the abilty of heat build up in there.

and for short pipe nipples 24 inch or less.

I have see few place some peoples did use 24 inch pipes and jamed many romax[s] wire in the pipe and i have one call not too long ago and have to replace bunch of romax wire they were brittle in few spots.

Really IMO,, i dont know if they did change the code or not about derating the wires in the nipples at all but i wish they change the length limit to more like 4 inch or less that can clear up some of the mess we have to deal with it ..

merci , marc

I like both George and Ryan's descriptions.
(the elbow was what I was looking for).

We had an inspector proclaim that by (his own) definition a nipple must be a straight piece of rigid conduit. (Although he couldn't explain the term "offset nipple")

Thanks...S

Elbow and nipple:



[This message has been edited by ThinkGood (edited 04-23-2004).]

Guy's if you want my input into the frey, a nipple as I understand it is a Male-Male Threaded coupling.
Ask any plumber what a nipple is, provided they are civilised, that will be thier answer.
Cue Russ!.

That would be my thought too Trumpy.

If it doesn't have threads at both ends most plumbers wouldn't call it a nipple,just a 24" length of pipe.

Russell