How do we know 240.21 overrides 310.12? I don't even see it as overriding really, 310.12 just changes the ampacity in some situations.
Electrofelon, You would allow the 83% rule for feeders that are tapped off a 400 amp breaker (read post #1) before replying, How would you have the contractor come into compliance.
I actually am not dead set on the 83% rule applying to feeder taps, just exploring the language and others opinions, it's an interesting idea. Regardless of that, as has been pointed out there are other issues like the conductors not being in a raceway and in this situation the 83% rule wouldn't apply anyway because each set of conductors is not carrying 100% of the load. I don't see any easy way to make this code compliant. You're probably going to need to add 200 amp ocpds at the start of the ser.
It's more that 240.21 requires OCPD at the source of supply, unless you meet one of the tap rules. If you choose to take advantage of 310.12, then as a side effect you won't meet the tap rules, so you must put the OCPD at the source of supply as usual.
Thanks for your responses, It sounds like we’re basically on the same page. I mentioned a few of these options to the contractor. And then shortly after he flew off the handle on me and called the Cheif who signed off on it. Just making sure that I haven’t lost my mind or anything. Thanks for everyone’s help I really appreciate it! Enjoy your weekend
I disagree with the "small enough" part. In multifamily applications you could have taps supplying individual dwelling units. If it supplies the entire load of a dwelling unit it is eligible to consider the 83% rule. There could be other reasons it ends up being disqualified though.
