I know the depth under cement is normally 4 " with RNC, but just wondering if the depth could be the same with paving stones? The job I'm on is having pavers put down around their pool ( proffesionally ) with gravel etc. and the installer said you would have to drill the pavers out. As far as I know the code don't specify this as an option, but what do you think an inspector might say about this?? I'll probably go the 12" rule for circuits that are GFI protected and rated 20 amps or less, but in this case it would be NICE to have it the same as concrete. I hate to bug the inspectors any more than I have to. I've called on them quiet a bit lately. Thanks, Steve
300.5 uses the words "concrete" and "slab". That can't be confused with pavers. I won't say your AHJ won't go along but I am not sure how. RNC is only 6" anyway so he might consider 2" of paver as being part of the 6" cover. Keep it 5' away from the water if at all possible.
I agree with Greg on 300.5, as concrete is more of a continuious material, and more "permenant" in a sense.
However, I have SEEN RNC laid to about 6" below paver bottoms and also have seen it pass inspection. As far as "drilling out" the pavers, I'd have to question the logic in this, if I'm getting what you mean.
If acheiving a 12" depth is an issue, you might have to bite the bullet and inquire with the AHJ as to how he inturprets 300.5. A screw up here could cause a re-do, and nobody wants to work for free!
Using RNC I am not sure when it ever needs to be more than 6" down if you aren't going under a road, runway or parking lot. Look at 680.10 for a more specific answer. You still see 6" and I could see how an AHJ might measure from the top of the paver.
I really hate to sound like a broken record .... but does not Section 90 of the NEC plainly state "this is not a design manual?"
So, how deep should the pipe be buried? Well, as deep as it needs to be when it exits from the protection of the slab, would be a good start. Or, do you plan on changing the trench depth every time you have a change of the surface material? Lots of luck sanding the angled parts.
Or, consider this: what's a likely cause for the pipe being damaged? Besides the gardener using his shovel to look for irrigation lines ... how about frost heave? I don't care how well the pavers are laid .... give them a few frost cycles, and they'll be all over the place. Maybe the angled pavers will now even act like scissors on your pipe.
Whatever depth you decide upon, make it an honest depth. That is, to the top of the pipe, after it's properly bedded in sand - and NOT the rough depth of the trench! This means a 6" burial depth starts off with a 12" ditch.