Neutral sizing when EGC is upsized

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solarscuba

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I've heard contradictory information on this question and I was hoping someone could shed some light.

Article 705.95(B) provides the opportunity to have a neutral that is smaller than the ungrounded conductors at the inverter output if the neutral doesn't normally carry current. The neutral in that case can be sized to the same size as the EGC. However, 250.122(B) states that when the ungrounded conductors are upsized due to voltage drop the EGC also has to be upsized per 250.122(B).

Does this mean that the neutral must be upsized to match the EGC in these cases?

Thanks for your assistance.
 
I agree with Dennis. For this reason the 705 allowance only becomes meaningful for circuits above 50A or so. I look on the bright side and figure that on smaller jobs it's not worth setting up arguments with inspectors over a couple bucks of copper.

iwire said:
I can see this topic running 200 posts. :)
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:lol: I hope not.
 
Dennis Alwon said:
The neutral must be sized no smaller than the equipment grounding conductor. 215.2(A)(2)
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I think OP understands that, and I believe the question is if the minimum size EGC needs to be increased for some reason does that also mean the minimum size grounded conductor needs increased as well? IMO yes, and my reasoning is you have an adjusted result from 250.122 when you have over sized ungrounded conductors, and 215.2(A)(2) sends you to 250.122 - not just the table but the entire section needs to be applied.

Now the OP was specifically mentioning a 705.95(B) application - last part of that section says "shall be sized equal to or larger than the equipment grounding conductor." Which is determined by 250.122, all of 250.122 not just the table.
 
The rationale underlying increased EGC size (though validity can be debated) is to provide an effective fault current path. As all conductors may be a fault current path, it stands to logic the neutral conductor should be sized no less than the EGC when increased in size.
 
kwired said:
I think OP understands that, and I believe the question is if the minimum size EGC needs to be increased for some reason does that also mean the minimum size grounded conductor needs increased as well? IMO yes, and my reasoning is you have an adjusted result from 250.122 when you have over sized ungrounded conductors, and 215.2(A)(2) sends you to 250.122 - not just the table but the entire section needs to be applied.

Now the OP was specifically mentioning a 705.95(B) application - last part of that section says "shall be sized equal to or larger than the equipment grounding conductor." Which is determined by 250.122, all of 250.122 not just the table.
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The op was asking about a minimal size grounded conductor matching the equipment grounding conductor, and then asked if the neutral conductor must be increased if the equipment grounding conductor was increased. I stated the neutral cannot be smaller than the equipment grounding conductor so it had to be increased also. I don't see where my answer did not address the question.
 
If the neutral was already larger then the equipment grounding conductor when it was increased then I don't see why the neutral would need to be increased as long as it carried the load and was either equal to or larger than the equipment grounding conductor.
 
Dennis Alwon said:
If the neutral was already larger then the equipment grounding conductor when it was increased then I don't see why the neutral would need to be increased as long as it carried the load and was either equal to or larger than the equipment grounding conductor.
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And in most cases where the hot conductors are up sized to reduce VD you will be upsizing the grounded conductor too. Unless the grounded conductor is a neutral and there is no load on the neutral in the first place. :)
 
ActionDave said:
The way I read it the neutral can not be smaller than the EGC sized off of 250.122.

If you run larger than required EGC you don't have increase the size of the neutral.
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If you are saying that an equipment grounding conductor can be larger the the neutral then I disagree unless you install a larger equipment grounding conductor than required when the ungrounded conductors were upsized

250.122 also includes 250.122(B)
 
It states if the ungrounded conductors are increased then the equipment grounding conductor must be. If the equipment grounding conductor must be increased then you need to increase the neutral otherwise the conductor may not be able to carry a fault. The reason to increase the equipment grounding conductor is to insure that the overcurrent protective device trips when you have long distances. If the neutral is smaller then you have an issue. How do you account for 215.2(A)(2) as I mentioned earlier
 
GoldDigger said:
IMHO you can. The code refers to the size of the "required" EGC, not the size you actually install.
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Okay, how 'bout this then...

If the EGC is a combined EGC/GEC according to 690.47(C)(3), then a neutral meeting the requirements of 705.95(B) does not have to be larger than the EGC requirement of 250.122, even if the EGC/GEC actually installed is larger as required by 250.166.
 
jaggedben said:
Okay, how 'bout this then...

If the EGC is a combined EGC/GEC according to 690.47(C)(3), then a neutral meeting the requirements of 705.95(B) does not have to be larger than the EGC requirement of 250.122, even if the EGC/GEC actually installed is larger as required by 250.166.
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Where does 690.47(C)(3) mention neutral or grounded conductor
 
Dennis Alwon said:
Where does 690.47(C)(3) mention neutral or grounded conductor
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It does not, but it mentions the required size of the EGC when it is also serving as the GEC, and so might be considered to have side effects on the separate rule about the neutral being at least the size of the required EGC.
Just another edge case that illuminates whether the rules in question are well written or not.
 
But it only states that the combined conductor must be the larger of the two tables for grounding electrode conductor or equipment grounding conductor. What am I not seeing
 
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