# Neutral Size



## NolaTigaBait (Oct 19, 2008)

jack756 said:


> I'm installing a 800amp 3 phase 4 wire panelboard. This panel is being fed from a 1200 amp panel. The only load that requires a neutral is a 100 amp lighting panel that will be fed from the 800 amp panel. My question is, does the neutral from the 1200 amp panel to the 800 amp panel need to be same size as the ungrounded conductors?


No, but it can't be any smaller than 250.122 either...


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## Dennis Alwon (May 9, 2009)

NolaTigaBait said:


> No, but it can't be any smaller than 250.122 either...


250.122 is for th egc not the grounded conductor, 250.24 (c)(1) is what you need.

The grounded conductor can be as small as the GEC if the load calculates that low.


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## NolaTigaBait (Oct 19, 2008)

I know, I was simply stating that it can't be smaller than the ecg.


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## Dennis Alwon (May 9, 2009)

NolaTigaBait said:


> I know, I was simply stating that it can't be smaller than the ecg.


You should be saying it cannot be smaller than the GEC not the egc. 

Here is why. A 200 amp panel would require a #6 egc while a 200 amp service requires a #4 GEC. When you say it cannot be smaller than the EGC then you are saying it can be a size #8 for the grounded conductor-- this is not true- #4 is the smallest it can potentially be.

Don't confuse me I am confused enough.


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## JohnJ0906 (Jan 22, 2007)

For an 800 amp panel, odds are it will be a parallel feeder, which means each neutral parallel will have to be 1/0 minimum.


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## NolaTigaBait (Oct 19, 2008)

Dennis Alwon said:


> You should be saying it cannot be smaller than the GEC not the egc.
> 
> Here is why. A 200 amp panel would require a #6 egc while a 200 amp service requires a #4 GEC. When you say it cannot be smaller than the EGC then you are saying it can be a size #8 for the grounded conductor-- this is not true- #4 is the smallest it can potentially be.
> 
> Don't confuse me I am confused enough.


Luckily I've never had to do this...I understand now...gotcha:thumbsup:


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## JohnJ0906 (Jan 22, 2007)

Dennis Alwon said:


> 250.122 is for th egc not the grounded conductor, 250.24 (c)(1) is what you need.
> 
> The grounded conductor can be as small as the GEC if the load calculates that low.


Dennis, 250.24(C)(1) is for the service neutral. The OP has a sub panel.

220.61(A) is what applies here, IMO.


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## Dennis Alwon (May 9, 2009)

JohnJ0906 said:


> Dennis, 250.24(C)(1) is for the service neutral. The OP has a sub panel.
> 
> 220.61(A) is what applies here, IMO.


Thanks John, I just caught that reading one of the new responses. I then realized my oops and was about to correct it when I read yours.


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## Dennis Alwon (May 9, 2009)

So the way I read that is if the calculated load is 16 amps then we could pull a #12.


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## Magnettica (Jan 23, 2007)

> 220.61 Feeder or Service Neutral Load.
> (A) Basic Calculation. The feeder or service neutral load
> shall be the maximum unbalance of the load determined by
> this article. The maximum unbalanced load shall be the
> ...


So the way I read it, unless the OP has dryer and oven range loads for his 100 amp panel there are no reductions for the neutral feeder.


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## JohnJ0906 (Jan 22, 2007)

Dennis Alwon said:


> So the way I read that is if the calculated load is 16 amps then we could pull a #12.


This came up on a job a few months back. We had a 800 amp MDP (not a service) with no neutral loads. My contention was that there was no requirement for a neutral, and the job leader disagreed. The only article we could find was 220.61(A).

FWIW specs called for a full sized neutral, so that is what it got. We added 1 20 amp 277v circuit, so we have (3) 300 kcmil conductors carrying about 10 amps of neutral load.


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## JohnJ0906 (Jan 22, 2007)

Magnettica said:


> So the way I read it, unless the OP has dryer and oven range loads for his 100 amp panel there are no reductions for the neutral feeder.


True, but if there are a lot of loads that don't have a neutral load, he might not need a full sized one for the 100 amp feeder, and the 800 amp feeder neutral is not required to be larger than the one calculated for the 100 amp.


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## TOOL_5150 (Aug 27, 2007)

So, We are in agreement that the smallest grounded conductor to a sub panel would be a #14? Because there is no code stating we even NEED to run a neutral to a subpanel if it is not required.

~Matt


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## Dennis Alwon (May 9, 2009)

That is a common question that arises. EC's get turned down for not pulling a neutral to a panel even if one is not needed. The is no reason to pull a neutral. The only requirement we have, as EC's, is a neutral must be present at the structure 250.24(C)


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## Dennis Alwon (May 9, 2009)

TOOL_5150 said:


> So, We are in agreement that the smallest grounded conductor to a sub panel would be a #14? Because there is no code stating we even NEED to run a neutral to a subpanel if it is not required.
> 
> ~Matt


I would agree with that. Probably poor practice but compliant.


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## TOOL_5150 (Aug 27, 2007)

Dennis Alwon said:


> I would agree with that. Probably poor practice but compliant.


I agree with your agreement.

~Matt


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## Magnettica (Jan 23, 2007)

JohnJ0906 said:


> True, but if there are a lot of loads that don't have a neutral load, he might not need a full sized one for the 100 amp feeder, and the 800 amp feeder neutral is not required to be larger than the one calculated for the 100 amp.


And which article covers that? 

Wouldn't minimum be listed in 250.66?


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## Dennis Alwon (May 9, 2009)

Magnettica said:


> And which article covers that?
> 
> Wouldn't minimum be listed in 250.66?


250.66 is for GEC although it is also used to denote that where the neutral at the service cannot be smaller than what is denoted there. That is for service only. Sub panels have no restrictions that I know of.


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## Magnettica (Jan 23, 2007)

I never really gave it much thought that the only requirement for a sub panel is an EGC.


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## JohnJ0906 (Jan 22, 2007)

magnettica said:


> and which article covers that?
> 
> Wouldn't minimum be listed in 250.66?


220.61


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## Dennis Alwon (May 9, 2009)

Magnettica said:


> I never really gave it much thought that the only requirement for a sub panel is an EGC.


Many years ago I did a house that needed a 400 amp service mostly for the heating. I ran a 200 amp SEU cable to a 200 amp small circuited panel. No neutral necessary.


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## NolaTigaBait (Oct 19, 2008)

Dennis Alwon said:


> 250.66 is for GEC although it is also used to denote that where the neutral at the service cannot be smaller than what is denoted there. That is for service only. Sub panels have no restrictions that I know of.


That makes alot of sense. Thanks for clarifying.


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## Magnettica (Jan 23, 2007)

Dennis Alwon said:


> Many years ago I did a house that needed a 400 amp service mostly for the heating. I ran a 200 amp SEU cable to a 200 amp small circuited panel. No neutral necessary.


Like I said, I never really gave it much thought. Makes sense if you have no neutral load then there's no need for a neutral conductor. Simple enough. :thumbsup:


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## Dennis Alwon (May 9, 2009)

So after all this I learned that I am incorrect. There is a minimum size grounded conductor if one is needed. The grounded conductor may not be smaller than the EGC. This makes sense in the case of a line to neutral fault.



> 215.2 Minimum Rating and Size.
> (A) Feeders Not More Than 600 Volts.
> (1) General. Feeder conductors shall have an ampacity not less than required to supply the load as calculated in Parts III, IV, and V of Article 220. The minimum feeder-circuit conductor size, before the application of any adjustment or correction factors, shall have an allowable ampacity not less than the noncontinuous load plus 125 percent of the continuous load.
> Exception No. 1: Where the assembly, including the overcurrent devices protecting the feeder(s), is listed for operation at 100 percent of its rating, the allowable ampacity of the feeder conductors shall be permitted to be not less than the sum of the continuous load plus the noncontinuous load.
> ...


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## Mike Guile (Jan 14, 2010)

*Neutral*

Dag gone it. I wish I knew that about the lack of neutral to dedicated panels that didn't need one. I probably could of saved a few thousand bucks over last couple years. 

An inspector a long time ago told me you always needed 4 wires to any sub panel, and since he was in inspector I assumed he was right (back then). Now I know. 

Thanks for that one. 

Side note: I just ran an MC 4 wire 4/0-4/0-4/0-1/0 Cable for a 200 amp dedicated HVAC outdoor panel. It was a 250 ft run. That would of saved me a few bucks right there.


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## Magnettica (Jan 23, 2007)

Mike Guile said:


> Dag gone it. I wish I knew that about the lack of neutral to dedicated panels that didn't need one. I probably could of saved a few thousand bucks over last couple years.
> 
> An inspector a long time ago told me you always needed 4 wires to any sub panel, and since he was in inspector I assumed he was right (back then). Now I know.
> 
> ...


Holy smokes!

How much does 250' of that cost?


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## Mike Guile (Jan 14, 2010)

*$*

I think it was about a grand or so. MC Feeder

Well. We did need one outlet at panel area anyway. But, that's overkill for an outlet that will probably never get used. I would of just found some power inside and drilled out and made an outlet if I could of saved 250 ft of 4/0

I'm actually not even sure if I could of got a 3 wire in MC? I've only seen 4 wire and more.


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## boots 211 (Aug 21, 2009)

My question is why wouldn't you pull a neutral for any future use? it might you that needs to pull power from that panel for the next project. Seems easier to pull it now, and make the next project easier.


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## Dennis Alwon (May 9, 2009)

boots 211 said:


> My question is why wouldn't you pull a neutral for any future use? it might you that needs to pull power from that panel for the next project. Seems easier to pull it now, and make the next project easier.


In most cases you would but suppose you have 3 phase loads for Heat & A/c and wanted to pull a feeder panel specifically for that. Perhaps the unit need 480V and there is no 480 V there but there is a 120v/240v panel.. 

The resi I did I had all the heat and a/c in one panel which used up all the load for that panel. In the same room was the 120/240 circuit panels for the rest of the house. Why run a neutral in that panel. Unnecessary but of course it wouldn't hurt.


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