Re: Protecting plastic nail on boxes.
Hey we have siders up here that will drive a 2" roofing nail through the back of a service!
I've been waiting for this to happen here in my area but haven't seen it yet. I've seen them nail through the back of the cabinet and miss the buss bar by 1/4" and even drop old siding and break the glass on the meter. I guess it's only a matter of time.
Anyway, back to the original question (good point or not), you're right - the AHJ is nuts but our opinions here are just that - opinions. If the CMP wants to make a change in the future and require PVC box mfrs. to make their boxes with rear metal plates then so be it. But as of right now, as far as I know, PVC boxes are approved for their use. (And, by the way, if we install a metal plate are we required to bond it with the EGC ?)
If we start making changes to our installation techniques so that the main intent of our installations switches from "neat and workmanlike" to "preventive and cautionary" we might as well pack up and open a 7-11 because we might all go broke doing this. Should tin knockers install shrouds so that their duct work isn't perforated ? Or plumbers for their pipes ? Why don't we just go back in time and require a/c cable and metal boxes instead of nmc and pvc boxes ??? That way we can be sure to satisfy everyone but especially that occasional AHJ who wants to over-enforce what he thinks the code should be.
I'm a proponent of requiring that all trades be licensed. That way if a sheet-rocker misses a stud and drives a nail through our wiring, he/she bears the onus of responsibility and not us because our wire extends beyond the 1 1?/4" rule at the entry point of the box. What I'd really like to see happen is a ban on sheet-rockers using roto-zips to cut out for electrical boxes. That way they won't rip up our wires inside the boxes.
Sorry. Just my opinion. Didn't mean to get up on the box !!!