Sizing neutral for 30 amp service disconnect

[cppoly]

230.42 gives minimum conductor sizing requirements and for the neutral, section 230.42(C) refers you to 250.24(C).

250.24(C)(1) says then refers to you to table 250.102(C)(1) to size the neutral.

Table 250.102(C)(1) says the minimum size would be a #8 and I can’t find any exceptions here.

However going back to 230.42(C), the commentary says “the code does not prohibit sizing the grounded conductor simply by using the same size as the ungrounded (hot) service conductors”.

But this is just commentary. Does anyone know where it says this in the code??

Side note – if you originally just wanted to go to one section in the NEC to get an answer (as in 230.42), you are then referred to two other places.

 

[Malywr]

30A and less grounded conductor I would use same size as ungrounded conductor


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[cppoly]

30A and less grounded conductor I would use same size as ungrounded conductor


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Yup exactly.. just need help finding this in the code because from what I can find it points to a minimum #8 grounded conductor.

 

[kwired]

30A and less grounded conductor I would use same size as ungrounded conductor


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I would as well, but after looking I'm not finding where it says it can be smaller than the #8 given in T250.102(C)(1) either. Makes sense it shouldn't need to be larger than ungrounded conductors - haven't yet found any wording stating that though.

 

[Dennis Alwon]

Odd it is but technically you would need a #8 neutral because it is supposed to be sized to T. 250.102 as stated. But in some cases you can have service conductors as smaller as #12 but I don't see an exception from the #8 for neutral. Surely that cannot be the intent.:?

 

[cppoly]

So does it look like a #8 is required for the neutral even if using #12 hot?

 

[Little Bill]

Although the word "grounded conductor" is in the title of 250.102, I don't see it anywhere else in the article except in the table C1. Seems the whole intent was geared towards bonding jumpers. I'm certainly not going to install a #8 neutral with #10 or #12 ungrounded conductors unless forced to by an inspector. What would you do if using a cable method such as NM, MC, etc.?