215-220 Min Feeder size

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mikeames

mikeames

Senior Member
Location
Gaithersburg MD
Occupation
Teacher - Master Electrician - 2017 NEC
Ok today I was working at a club that had a small 6 circuit panel feed with #8. one of our guys mentioned that there is a minimum feeder size and #8 is too small even though it was protected with a 40A bkr. The smallest allowed he said was #6. I did not recall reading this so I didnt say anything when he asked me if I knew that. I said I did not. Now I am at home and I read through art 215 and 220. Am I missing it or is he wrong? I always thought you could supply a panel with 10-3 if you wanted to if the conditions (loads) allowed.

(Assume the OCP is correctly sized))
 
A feeder can be 40 amps and #8. There is no #6 rule that I'm aware of. If your conductors are THHN in conduit or MC cable with 75 degree terminations you can use a 50 amp OCPD. What code section did they say prohibited this installation?
 
He just said it was two something he didnt know the specific article and section....... the section on feeders. I did not know so I looked and from what I can see I cant find anything.
 
Pierre C Belarge said:
Take a look at 225.39 for feeders, and 230.79 for services.
Click to expand...
Neither of those sections have anything to do with the size of the conductors. They only specify the minimum size of the means of disconnect. Of course if the means of disconnect is a breaker, then that would govern the conductor size.
 
I looked at the articles you posted but I don't think that applies to the situation.

Thanks I am going to plop the book down tomorrow and nicely ask where or why he thought what he did.
 
I was thinking like Pierre. 225.39(D). But I think that only applies to "outside" feeders. If it's a feeder within a structure (not TO the structure), I don't think that applies.
 
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