# derated multiconductor neutral



## Shockdoc (Mar 4, 2010)

In a recent wiring of a deli with a single phase service I decided to pull six # 12 conductors to one # 8 neutral to my splice out boxes from my panel. I found this to save material and conduit fill.


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## Ray Cyr (Nov 21, 2007)

Shockdoc said:


> In a recent wiring of a deli with a single phase service I decided to pull six # 12 conductors to one # 8 neutral to my splice out boxes from my panel. I found this to save material and conduit fill.


Um, I'm not seeing how this would fit the definition of a multiwire branch circuit. I'm also not seeing how this could be a legal install since that #8 has a maximum rating of 55 amps and could see 60 amps if the #12's are on 20 amp breakers.


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## Wingnut (Jan 31, 2010)

Shockdoc said:


> In a recent wiring of a deli with a single phase service I decided to pull six # 12 conductors to one # 8 neutral to my splice out boxes from my panel. I found this to save material and conduit fill.


 
You would need a 6 pole breaker under '08


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## rlc3854 (Dec 30, 2007)

Wingnut said:


> You would need a 6 pole breaker under '08


 
Why can't you use handle ties?

I guess what the OP did would be good for future service and repair work when the neutral burns up when some one else ties into the system on the opposite buss.


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## Bkessler (Feb 14, 2007)

I worked in St Thomas for a year in 1995 and their were some guys from new york that I worked for for a while that did stuff like that all the time, I was a two year guy then. They didn't think twice about a running #12 in parallel to get up to 100 amps, Run uf across a parking lot and make at speed bump over it, and in 1995 were still installing "refurbished" FPE panels.


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## Shockdoc (Mar 4, 2010)

Wingnut said:


> You would need a 6 pole breaker under '08


Were still in 05 out here...except for two towns ..... Theres code, theres safe and then theres practical. Its my personal opinion code is edging 
towards corporate profit over safety and practical . Naturally , I'm a rebel.


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## Shockdoc (Mar 4, 2010)

rlc3854 said:


> Why can't you use handle ties?
> 
> I guess what the OP did would be good for future service and repair work when the neutral burns up when some one else ties into the system on the opposite buss.


A good splice will never burn, an incompetant electrician can burn anything.


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## Shockdoc (Mar 4, 2010)

Ray Cyr said:


> Um, I'm not seeing how this would fit the definition of a multiwire branch circuit. I'm also not seeing how this could be a legal install since that #8 has a maximum rating of 55 amps and could see 60 amps if the #12's are on 20 amp breakers.


I look at it this way...when I run a 60 amp sub panel, I derate the neutral on size down . what is the difference of six properly phased out circuits over a sub panel where some might improperly balance there loads. 80% continuos load rates 16 amps per circuit max . I prefer to be different. Running all two wire can get expensive and makes it easy for the simpleton HI guy, HO and novice to figuire out.


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## kbsparky (Sep 20, 2007)

We have installed "super neutrals" before, but only for one set of hots each ...

Now in the case of an old service panel that was converted to a junction box, we have used a single larger neutral instead of multiple smaller ones, but that is a different animal.


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## Dennis Alwon (May 9, 2009)

I see it this way. First what is the load. If the load is not fixed then I would assume 20 amps for each MWBC concept-- what I mean here is that I see 3 sets of MWBC's that this neutral must support or simply put there are 3 conductors on each of the 2 phases in the panel. 

If you wired it that way then I would want a #6 neutral that is capable of 60 amps. 20*3=60


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## wildleg (Apr 12, 2009)

whether its single or 3 phase, some of the loads will cancel on the neutral, so there will never be 60 amps on it. maybe if I get time I'll figure out a formula for that, or maybe someone here already knows it (?), but my brain guesses that something around 45 would have to be the max amps possible (?). Anyhow, I generally pull standard mwbc's (one neutral per set), without some special circumstances I don't see any compelling advantage to doing it this way.


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## Shockdoc (Mar 4, 2010)

Dennis Alwon said:


> I see it this way. First what is the load. If the load is not fixed then I would assume 20 amps for each MWBC concept-- what I mean here is that I see 3 sets of MWBC's that this neutral must support or simply put there are 3 conductors on each of the 2 phases in the panel.
> 
> If you wired it that way then I would want a #6 neutral that is capable of 60 amps. 20*3=60


Thier all motor/ heating loads for a kitchen . I'm sure that that neutral will never carry more than 26 amps at any given time. I have two commercial microwaves, two slicers, two refrigerators, etc. per run. they should all cancel each other out depending on run intervals. One run might carry lighting, exit, sign, showcase, exhaust


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## Bob Badger (Apr 19, 2009)

Shockdoc said:


> Were still in 05 out here...except for two towns ..... Theres code, theres safe and then theres practical. Its my personal opinion code is edging
> towards corporate profit over safety and practical .* Naturally , I'm a rebel.*


Or a fool but it is hard to tell from here. :laughing:

Usually if you are re-inventing normal wiring practices you have not found a better way.


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## Shockdoc (Mar 4, 2010)

Bob Badger said:


> Or a fool but it is hard to tell from here. :laughing:
> 
> Usually if you are re-inventing normal wiring practices you have not found a better way.


Call me what you'd like, 25 years with no fires or injuries . What is conventional these days, buying more and more expensive items to make my proffesion look so easy a caveman can do it. Check out all the HI guys and HO s buying 14/2,12/2 and doing all that simpleton wiring themselves. I save myself money , time and give my proffesion a challenge for the inexperienced to try to understand. Times are hard enough, Problem with America these days are the people are afraid to speak and act up. Like you they just do what their told...


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## Bob Badger (Apr 19, 2009)

First off we are just talking, I don't expect to change a rebels mind and what you decied to do in CA is not likley to impact me in MA. 



Shockdoc said:


> Call me what you'd like, 25 years with no fires or injuries .


Which means nothing. 

I have been on this planet 45 years and have not been hit by lightning. Am I immune? 



> What is conventional these days, buying more and more expensive items to make my proffesion look so easy a caveman can do it. Check out all the HI guys and HO s buying 14/2,12/2 and doing all that simpleton wiring themselves.


What does that have to do with how you do your work?



> I save myself money , time


I would always save money if I never used the right size conductors.




> and give my proffesion a challenge for the inexperienced to try to understand.


Yeah that makes sense. :no:





> Times are hard enough, Problem with America these days are the people are afraid to speak and act up. Like you they just do what their told...


Baaaa


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## micromind (Aug 11, 2007)

I've seen the single oversize neutral used in a few buildings around here. 

Usually, they're ancient buildings, old enough to have solder and tape splices. Most of them are a #10 with two or a #8 with 3 sets of hots. Not one has shown even the slightest sign of a problem.

Considering the fact that some of these buildings have been in existence for a very long time, and have seen several different types of occupancies, if this practice were actually hazardous, it would be obvious by now. 

Rob


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## micromind (Aug 11, 2007)

Shockdoc said:


> Were still in 05 out here...except for two towns ..... Theres code, theres safe and then theres practical. Its my personal opinion code is edging
> towards corporate profit over safety and practical . Naturally , I'm a rebel.


Agree Completely!

Rob


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## oldtimer (Jun 10, 2010)

micromind said:


> I've seen the single oversize neutral used in a few buildings around here.
> 
> Usually, they're ancient buildings, old enough to have solder and tape splices. Most of them are a #10 with two or a #8 with 3 sets of hots. Not one has shown even the slightest sign of a problem.
> 
> ...


 It might not be hazardous, but I don't think it's legal. :blink:

I have seen it done in K and T wiring, and also seen a wire soldered to the neutral of K and T and run to the ground of an added three pin receptacle.


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## Shockdoc (Mar 4, 2010)

micromind said:


> I've seen the single oversize neutral used in a few buildings around here.
> 
> Usually, they're ancient buildings, old enough to have solder and tape splices. Most of them are a #10 with two or a #8 with 3 sets of hots. Not one has shown even the slightest sign of a problem.
> 
> ...


I actually came this practice while working on some buildings in NYC constructed back in the '40s while I was a helper years back


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## Shockdoc (Mar 4, 2010)

Bob Badger said:


> First off we are just talking, I don't expect to change a rebels mind and what you decied to do in CA is not likley to impact me in MA.
> 
> 
> 
> ...


 I'd personally rather make the money instead of handing it over to supply houses and corporations. what happened to all you yankees ? forgot about the Boston Tea Party ?


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## nitro71 (Sep 17, 2009)

So, is it NEC compliant to run one neutral sized properly?


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## micromind (Aug 11, 2007)

nitro71 said:


> So, is it NEC compliant to run one neutral sized properly?


I've yet to find anything in the code that would prohibit the practice, but 'properly sized' is a point of contention. 

On one hand we have the worst possible case of all circuits on one phase being simultaneously loaded to the sum of the breakers. The chances of this ever becoming reality?.......

On the other hand, the code clearly allows far less capacity for multiple dryers, ranges, and a few other things. So the code obviously recognizes the possibility that all circuits will not be loaded at the same time. 

The 08 code makes it somewhat difficult though, you'd have to tie all the breaker handles together. 

Rob


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