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Posted By: electure What's a nipple?? - 04/22/04 10:59 AM
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??
Posted By: George Corron Re: What's a nipple?? - 04/22/04 11:24 AM
A pipe not over 24" is a nipple.
Posted By: DougW Re: What's a nipple?? - 04/22/04 03:07 PM
<<CENSORED>>

Never mind. George's answer is probably more appropriate for this forum!
Posted By: Ryan_J Re: What's a nipple?? - 04/22/04 05:12 PM
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".
Posted By: iwire Re: What's a nipple?? - 04/22/04 07:39 PM
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. [Linked Image]

After all there has to be logic behind this exception.

Bob
Posted By: frenchelectrican Re: What's a nipple?? - 04/22/04 08:37 PM
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
Posted By: electure Re: What's a nipple?? - 04/23/04 12:36 PM
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
Posted By: ThinkGood Re: What's a nipple?? - 04/23/04 02:00 PM
Elbow and nipple:

[Linked Image from s91748743.onlinehome.us]

[This message has been edited by ThinkGood (edited 04-23-2004).]
Posted By: Trumpy Re: What's a nipple?? - 04/23/04 03:05 PM
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!. [Linked Image]
Posted By: ga.sparky56 Re: What's a nipple?? - 04/23/04 11:45 PM
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
Posted By: karlwayne Re: What's a nipple?? - 04/24/04 12:17 AM
probably refering mostly to RGC

A "chase nipple" would look like a romex connector except the clamp part would be an oversized smooth edged flange(only need one locknut)
A "close nipple" would be the shortest piece of conduit you could thread (or buy) without having running threads the entire length.
A "short nipple" would constitute anything else. ie: normally sold as 3", 3 1/2", 4", 4 1/2" etc.
I have never heard the term used in connection with an elbow, but believing heat dissapation is the subject,why not. (?)
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