ECN Forum Forums Code Related Discussion NEC & other Code issues Protecting NMD90 (loomex) after construction

Thanks gfretwell for your post.

Here in Canada, I tried to get the Canadian equivalent of the UL (here called CSA) to render an opinion on the adequacy of these plates for providing post-construction protection. They did not want to render an opinion and referred me to the local authority who enforces the code.

Comparing the risk of accidentally piercing Romex set back 1-1/4 inches from a stud face without a plate to the risk of piercing Romex installed closer than 1-1/4 inches with the use of a plate is like comparing apples and oranges.

For the first case, the code assumes that the prudent homeowner will never drill to a depth exceeding 1-1/2 inches and for the latter case, the code assumes that the homeowner attempting to drill to the same depth would upon hitting a metal protection plate cease to continue.


In a perfect world, electricians would always be able to route cables deeper than 1-3/4 inches behind the stud face, but in the real world we have been told that the use of a 1/16" metal plate will absolve us of any feeling of responsibility should an accident ever occur.

I guess every installer must establish their comfort level and then decide if they want to accept code or exceed it.

do you remember how thin your friend's sheet really was?

Pretty thick, better than 1/16" as I remember. Had him punch the screw holes, drilling wouldn't be easy.

-Hal

Hal,

Thanks for your answer.

I'm sure 1/16 inch or thicker stainless would be next to impossible to drill through without a carbide bit.

Hardness seems to vary with the percentage of nickel in the alloy and that affects how easily the metal retains stains.

If your friend needed a punch, it is probably a hard alloy. If I choose stainless over rolled steel, it will probably be a thinner guage.

I will probably ground the plate as well to the electrical ground so that if a drill bit goes through and hits a wire, at least the breaker will blow instantly.

I don't think we can protect wires from the determined DIY homeowner toting a drill any better than we could protect them from the same guy armed with a reciprocating saw and the gleam of an addition in his eye.

Larry,

I agree that I can't protect such a homeowner, but I want to do my part to assure that anytime I place wires buried in a sheetrock ceiling that are 1/2 inch closer to the surface than permitted by code, I, at least provide the mandatory 16 guage steel plate.

When I closed up this art deco style ceiling with its 5 layers,offset at different depths, I never imagined that someone would ever want to hang any object from it.

I even thought if I left a photograph showing the concentration of wires in this ceiling, that would be enough to discourage such a DIY guy from ever attacking it with a drill.

But this house has a good chance of surviving a hundred years, pictures and plans will be lost or ignored, and I have to do the minimum necessary to provide some protection.

Legally, in the deed of sale, I have to have declared that there is a hidden defect in the wiring for which a plate was added to compensate.