I have a 3phase service with the breaker in the meter socket. I ran 2/0 to a main lug panel. Commercial office building. Inspector says I can't reduce wire size from 3/0 in commercial. Not sure hel is correct? Can anyone help with code locations to support my side? I thought it was okay for under 400 amp. And wouldn't the wires be considered service lateral? Or even branch circuit?
Service entrance conductors
- Thread starter kluchon
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hurk27
Senior Member
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- Portage, Indiana NEC: 2008
the allowance in 310.15(B)(6) is for dwellings only, there is another thread that where Bob (iwire) explained where in 240 it doesn't allow 2/0 on a 200 amp service, and 230 where it also spell this out, I see if I can find the thread.
Here post 56
3/0 is already sized for 200 amp so there is no rounding up as allowed in 240.4(B) as allowed in the exception #2 to 230.90(A) and 230.90 does not allow us to use calculated load unless we meet the exception #3 requirments, for using 500kcmil the yes we can use the rounding up to next breaker size for the 500's on a 400 amp service
Here post 56
3/0 is already sized for 200 amp so there is no rounding up as allowed in 240.4(B) as allowed in the exception #2 to 230.90(A) and 230.90 does not allow us to use calculated load unless we meet the exception #3 requirments, for using 500kcmil the yes we can use the rounding up to next breaker size for the 500's on a 400 amp service
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It's more that 2/0 is good for 175A with 75?C terminations, which is also a standard ocpd rating. There is nothing to round up. :blink:
If one could prove to AHJ, however unlikely, an ambient temp of 77?F or less, that would push the allowable ampacity of 2/0 to over 175A, which could then have an ocpd rounded up to 200A... provided the calculated load is less than the temperature-corrected ampacity of the 2/0.
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jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
Long answer: see above, short answer: nope.
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