Guys -
With all due respect, I believe you are trying to use the NEC as a design manual.
JAO - 445 is written with the understanding that gen installations are not cookie cutter. They need to be designed. There are very few minimums. Most of it reads (paraphrased), "Put it in so it works, doesn't burn up and you can work on it safely." Having put in/designed a few (or more
), I don't remember a one that went in marginal - generally all they got is barely enough.
I remember a thread a few months ago where the OP was looking for reasons that he could cheap on the copper from the gens. As I recall, he was replacing burned up conductors, likely from overload. Hummmm - this reasoning eludes me.
tryinghard -
200kw, 480V, 3ph, .8pf (likely), gives 300A FLA (continuous). I would agree with previous posters, everything after the gen 400A CB is not under 445.
Most installations I deal with, the gen does not have a CB. So 445.13 applies to the conductors from the gen to the CB. I've always felt there was no magic occuring at the gen CB and one should install 125% ampacity from the gen to the first OCPD (JAO). Disenting thought: It's pretty hard to run a gen at 100% output, and hold freq and voltage, so maybe that was the reasoning for the 115% rule.
Looking at the 250AL conductors (205A per steve), no way can you use the continuous output of the gen (300A X 1.25 = 375A). If that is okay, good deal - but this is a design issue - not an NEC issue.
steve is correct that the 25' tap rule does not allow upsizing the CB. So you are stuck with a 200A CB at the end of the 250AL (240.21B).
The installation you have described is pretty marginal for a 200kw gen. You may wish to consider some redesign.
note to steve: Per 240.4B, I think one could use a 225A CB to feed 250AL. (but I'm thinking you already knew that
carl