I would think that you would ordinarily be allowed to utilize future NEC rules, and still make a safe installation. Unless the AJH in question has a specific concern with any given future rule. I can't speak for your AHJ, but if it were up to me, I would allow utilization of most future NEC rules.
I agree with you, but I have run into some pretty idiotic plans reviewers/inspectors before that don't interpret codes with logic. I had one plans reviewer burn me one time on a job where I read him the commentary out of the code book and how it is meant to be interpreted and he just said "well that's not how we interpret it." So really it always can fall back on the AHJ just requiring you to do whatever he/she wants. That's the short version of the story. I'll explain the detailed story below because, hey, why not?
So this was a tenant fit out design for a retail store, so imagine a strip center. The real "service" came from a utility transformer, underground to the building's main electric room. The service (208/120v, 3ph, 4w) terminated into a switchgear with a main disconnect, and then each switch on the switchgear supplied a seperate tenant in the strip plaza. If I'm remembering correctly each breaker in in the switchgear was 200A.
So what our client did was took over two of the tenant spaces, demo'd walls and turned it into one big space. They then utilized both 200A
FEEDS (not services) to the tenant space. This is pretty standard on the retail side of things. I used to do jobs like this all the time. I'm pretty sure the total load on Feed 1 was about 160A and Feed 2 was about 170A.
So the job goes out for permit, goes through a couple rounds of building department comments (none of which mentioned this design being an issue). Finally months later we get a call from the contractor that said the inspector (also the plans reviewer) came out to do a walk through and told us that we couldn't do what we were trying to do. He said you can only have one service to the building. We called the inspector multiple times and plead our case. We used the code to explain that the "Service" was what came in from the utility and not what he was describing. As I said above at one point I literally read the commentary to him, and he still didn't agree.
So the inspector essentially told them that they had to demo the one 200A feed to the space so that it only had "One service". The issue with this being - The remaining 200A feed did not have enough capacity to handle our client's electrical demands. So the only thing that they could possibly do was to run a new (single) feed to the tenant space and demo both existing 200A feeds that were in their space (All underground btw). Obviously this is a HUGE expense on a project of this size. We tried to tell our client to get their lawyers involved because we thought they had a real case considering the installation was code compliant. In the end the client didn't want to waste the time it would take to fight it so they took the cost in the teeth, and needless to say, they were not happy about it.
So long story short - I learned my lesson that the AHJ will always have more authority than the code.
-Drew
