Ground Wire NEC 250.122

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Zyb

Zyb

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Design Engineer
Hi,

Am I right interpreting NEC 250.122 here? I'm confuse for my first ground wire if I based the sizing to the 20A breaker or 80A fuse. We usually use #8 for the whole run but I just want to understand the code. Thank you

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Not enough information to provide accurate answers. The equipment ground size might need to be adjusted based on the phase conductors.
The #10 for #1 might be oversized but again depends on the conductor size connected to the 20 amp breakers,. The #8 for #2 is likely correct but might need adjustment. EGC #3 would depend on the phase conductor size and protection ahead of the switch,
 
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The 80A breaker is not considered for sizing EGC #1. #10 would be correct if you're using #10 circuit conductors, otherwise #12 is okay. (Dumbest rule in the code, in my opinion, but it's the rule.)

The #8 for EGC #2 is probably fine.
#3 is probably a supply side bonding jumper, see table 250.102.
 
The #3 wire is not required. On a supply-side interconnection, there would be a N-G bond in the disconnect. The grounded conductor between the disconnect and the supply side tap takes care of the ground path. Now this will be a 3 page topic, job done. :cool:
 
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pv_n00b said:
The #3 wire is not required. On a supply-side interconnection, there would be a N-G bond in the disconnect. The grounded conductor between the disconnect and the supply side tap takes care of the ground path. Now this will be a 3 page topic, job done. :cool:
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Isn't that what I said? Yes, you are correct, this will stir things up!:D
 
Regarding the last three posts, they state correctly what is in the 2020 NEC, which makes it clear. See 250.25. Previous code cycles don't make it clear at all.
 
jaggedben said:
Regarding the last three posts, they state correctly what is in the 2020 NEC, which makes it clear. See 250.25. Previous code cycles don't make it clear at all.
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I take the stance that when the NEC is not clear on something and makes an effort to clarify it in a new version, that should also clarify all previous versions. Someone who says a clarification in a new version of the NEC does not also clarify previous versions is suffering from cognitive dissonance and I've seen it far too often.
 
pv_n00b said:
I take the stance that when the NEC is not clear on something and makes an effort to clarify it in a new version, that should also clarify all previous versions. Someone who says a clarification in a new version of the NEC does not also clarify previous versions is suffering from cognitive dissonance and I've seen it far too often.
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Yeah, that's very reasonable in my opinion and I agree. And yet, I've run into AHJs who don't.
 
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