The inlet on my 2006 Trane furnace froze up. I found that the contractor installed the vent too close to the inlet, and didn't make the vent long enough; per Trane's installation instructions. He fixed the second and sorta fixed the first.

However I also found that the vent was 11" from an inside corner and 4" from an overhead deck. I am told that is grossly inadequate, but Trane simply says to follow local code on those.

I checked with the local building inspector. He says that the only applicable local code is the NYS building code. In 2007 that was changed to require vents to be 4' from inside corners; previous to that it wasn't mentioned. He finds nothing on distance from something overhead.

Is that correct? Was the contractor in compliance in 2006? I am hoping someone might be familiar with this.
The inspector is overworked and admits he doesn't know as much as he would like about furnaces as he would like; so I wonder if he is missing something.