rojay
Senior Member
- Location
- Chicago,IL USA
Would 310.12(A) permit 2/0 AWG conductors for a 400 amp service with 2 sets of service conductors each landing in a separate 200 amp MCB panel?
NEC 310.12(A)
- Thread starter rojay
- Start date
- Status
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
No, but many areas will allow it. I assume you are talking 2/0 copper
rojay
Senior Member
- Location
- Chicago,IL USA
Yes, 2/0 AWG copper. I was figuring that there may be an issue based on the fact that neither set of service conductors will be supplying the entire house load.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Exactly
Jerramundi
Senior Member
- Location
- Chicago
- Occupation
- Licensed Residential Electrician
I'd be careful applying that table in Chicago, buddy, lol. Just my opinion.
As far as I understand it, the moment you apply ANY correction or adjustment factors, ability to utilize that table is null and void.
That means anything as simple as being outside 78*-86*F, which Chicago most certainly is.
2% design temp. puts us at 91*F with a 1% high of 106*F.
When I was working underneath other guys here in Chicago, it was DRILLED INTO ME that 3/0 was the go to for 200A. No debate.
However, I'm even questioning that now because if you were to design the installation to account for that 1% temp. high, 3/0 THHN on 75*C terminations would not be sufficient... but I've never heard of anyone using 4/0 for 200A.
As far as I understand it, the moment you apply ANY correction or adjustment factors, ability to utilize that table is null and void.
That means anything as simple as being outside 78*-86*F, which Chicago most certainly is.
2% design temp. puts us at 91*F with a 1% high of 106*F.
When I was working underneath other guys here in Chicago, it was DRILLED INTO ME that 3/0 was the go to for 200A. No debate.
However, I'm even questioning that now because if you were to design the installation to account for that 1% temp. high, 3/0 THHN on 75*C terminations would not be sufficient... but I've never heard of anyone using 4/0 for 200A.
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