# derating in nipples



## Louieb (Mar 19, 2007)

We had a little discussion on the job about derating wires,here is the senario,exterior panel with a 24 inch nipple out the bottom to a LB and then a 24 inch nipple to a junction box in basement.I say even though art 100 says condulets are seperate from raceways it is still an enclosed part of the raceway and the wires must be derated.I would put a j box on the outside also to be in compliance,if I did not want to upsize my conductors to be within the realm,of the exception.

More than a sixpack involved! Thanks


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## BBQ (Nov 16, 2010)

Damn interesting question.


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## k_buz (Mar 12, 2012)

> (4) Where conduit or tubing nipples having a maximum
> length not to exceed 600 mm (24 in.) are installed between
> boxes, cabinets, and *similar enclosures*, the
> nipples shall be permitted to be filled to 60 percent of
> ...



The way I read that, I think you are correct. I don't consider a conduit body to be a "similar enclosure".


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## wildleg (Apr 12, 2009)

so you are saying if you put a line of 24" nipples and c condulets to forever, you could pack it with wires and not derate. I say fail.


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## Dennis Alwon (May 9, 2009)

IMO, it is part of the raceway and the heat buildup is the same throughout so de-rating is to be used. Think about the wires- they will be all together and bundled just as they would be in the conduit.


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## BBQ (Nov 16, 2010)

wildleg said:


> so you are saying if you put a line of 24" nipples and c condulets to forever, you could pack it with wires and not derate. I say fail.


I agree with the logic of what you say but find the NEC less than clear on it.


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## Louieb (Mar 19, 2007)

Okay ,I was winning, then read art 314.16(c)1 ;so if the condulet is double the cross sectional area ,would it not disapate heat faster!Remember we are talking about between two nipples.


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## TOOL_5150 (Aug 27, 2007)

Dennis Alwon said:


> IMO, it is part of the raceway and the heat buildup is the same throughout so de-rating is to be used. Think about the wires- they will be all together and bundled just as they would be in the conduit.


Please, for the electrons' sakes... think about the wires. :whistling2::thumbup:

I agree with you, 24" and C body and another 24" WOULD require derating.


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## 360max (Jun 10, 2011)

k_buz said:


> The way I read that, I think you are correct. I don't consider a conduit body to be a "similar enclosure".


can he splice in the LB?


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## TOOL_5150 (Aug 27, 2007)

This is one of those threads that never gets a real answer, just a bunch of opinions, and then a few days later it dies away only to be resurrected in a few years.


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## BBQ (Nov 16, 2010)

k_buz said:


> The way I read that, I think you are correct. I don't consider a conduit body to be a "similar enclosure".


After reading k_buz's post I am going to change my postion and say the NEC clearly requires derating of this run.


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## Semi-Ret Electrician (Nov 10, 2011)

Louieb said:


> Okay ,I was winning, then read art 314.16(c)1 ;so if the condulet is double the cross sectional area ,would it not disapate heat faster!Remember we are talking about between two nipples.


Louie I agree with you in principle, the larger cross sectional area (of the condulet) would reduce the bundle and serve as a heat sink, so less conductor heating should result. 

But, the Code hasn't gotten around to that yet. 

Code still says: if you have more than three current carrying conductors in one raceway (longer than twenty four inches) you must derate ..no matter if you have 4 #14 ccc in a 1/2" conduit (or cable) or in a 6" RMC. Go figure.

BTW, has anybody ever seen a temperature rise in resi wiring due to bundling?


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## 360max (Jun 10, 2011)

After reading some other sections, I agree that derating does apply.


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## 360max (Jun 10, 2011)

Semi-Ret Electrician said:


> Louie I agree with you in principle, the larger cross sectional area (of the condulet) would reduce the bundle and serve as a heat sink, so less conductor heating should result.
> 
> But, the Code hasn't gotten around to that yet.
> 
> ...


*
*


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## Semi-Ret Electrician (Nov 10, 2011)

Yikes! Was that due to bundling or overload?


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## Elephante (Nov 16, 2011)

360max said:


> [/B]


I have never seen that before.Holy crap! What happened there?


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## DEelectrician88 (Oct 14, 2011)

I asked my inspector today while he was at my job, he said its a very good question but after thinking about it he said he would fail it because the intent was to get around the code which is unsafe and inspectors have final jurisdiction


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