I know about the plates that one installs onto a stud where wiring passes through it, but that is possible only on the side that is not yet finished. What about the other side, the already-finished side? My brother-in-law says that in Canada they use metal sleeves through the studs, and the wiring then goes through the sleeve and is protected from both sides. When I've asked here in the US, people say it sounds like a great idea but they've never seen such a thing.
I know about the plates that one installs onto a stud where wiring passes through it, but that is possible only on the side that is not yet finished. What about the other side, the already-finished side? My brother-in-law says that in Canada they use metal sleeves through the studs, and the wiring then goes through the sleeve and is protected from both sides. When I've asked here in the US, people say it sounds like a great idea but they've never seen such a thing.
In the US, code says you don't need a metal plate unless the wire is less than 1 1/4 inches from the edge of the stud. There are no circumstances in a regular 2x4 wall that would require a plate on both sides. Most of the time you don't need one at all, if you drill your hole in the middle of the stud. Usually people use these when you have to notch to run the wire near the edge for some reason.
If the holes are drilled at least 1&1/4" from the face of the stud on both sides then there is little likelihood of damage to the cable. Drywall screws are 1&1/4" long so even if over driven clean through the drywall they cannot reach a hole that is at least that far from the face of the stud. 3/4" holes that are drilled in the center of the stud should work fine.
There's also at least 3/8" of drywall between you and that wire... and chances are the wire is really more like 1.5-1.75" from the edge if it's in the middle. So you're talking a minimum of 1 5/8" and probably over 2".
This is the code... it's how every house in the U.S. is built. I wouldn't get in the habit of pounding 3" framing nails into finished walls. You'd probably go through any wire protection with that anyway.
He's in Woodstock, Ontario, and I saw him using them in a partition wall he was building in his basement. Where he saw them being used I have no idea -- perhaps when his new condo was still under construction.
Way back in the 20th century before the Florida Unified Building Code most local AHJs wanted to see cables sleeved in EMT if the 1.25" could not be maintained in any dimension. Now they are OK if the cable is secured 1.25" horizontally from the furring strip, even if the void (to the block) is only
3/4" deep. It is fairly unlikely that a sheetrock installer will miss by that far but a homeowner will just start driving nails when they hang pictures and such.
On Mon, 11 Oct 2004 08:28:22 -0700, Minnie Bannister wrote (in article ):
The code is concerned with protecting the wiring from sheetrock screws. As other posters have observed, a standard 1-5/8" drywall screw driven through
1/2" drywall and indented 1/8" will penetrate the stud 1". There is no reqirement to protect NM cable (or AC or MC for that matter) from every eventality, such as someone hanging a heavy wall-shelf or similar with 3-1/2" screws. It's just common sense to check for hidden electrical or plumbing when using long fasteners. You can't be expected to take that precaution when hanging sheetrock, due to the number of screws involved.
If you expect the wiring is going to be subject to damage, the code requires that it be protected in an EMT or similar sleeve. For example, if you knew that a set of shelving was going to be hung right over the wiring run this precaution would make sense.
I suppose you could use 1-1/2" long sections of 3/4" or 1/2" EMT press-fit into the holes in the studs, but I have never done this. It seems an unnecessary amount of work. Where damage to concealed NM was a concern, I have sleeved it in EMT or steel flex.
I would even go so far as to say running NM through sections of EMT could increase the overall risk because of the potential for damaging the wire during installation. You'd probably have to flare the ends of each section in order to safely pull NM through a run of several studs, because otherwise you'd risk gouging the cable as you pulled it through the sharp edges of the EMT pieces. It would be a lot of work to do it properly, probably much easier/cheaper to just use MC instead.
And, you'd probably be violating code if you used 1/2" EMT technically, since you can't legally install 12/2 (and probably not even 14/2) in 1/2" EMT due to fill limits.
Anyway your basic point is the same.. the code can't protect against everything. There is a balance between reasonable precautions, common sense, and cost of installation.
Actually, I don't believe this is true. With a single cable, the NEC allows 53% conduit fill, and 1/2" EMT has an interior diameter of about 5/8". This yields 0.161 in^2 of usable area. The 12/2 NMB cable sample I measured is 0.39" x 0.18", and it has to be treated as a circle of diameter 0.39". This yields a cross-sectional area of
0.119 in^2, which is less than 0.161 in^2. BTW, my sample of 12/3 NMB cable has a diameter of 0.37", so a single 12/3 NMB cable is OK too. I don't have a sample of 12/4 here.
Newer NM-b is smaller than the old TW NM but whenever I have seen EMT sleeves the run was a single straight section with no bends so it is pretty easy to do. You do have to ream the burrs off the EMT to avoid damage but you should really be using a Romex to EMT connector on the end.
Right... of course I still wonder what kind of situation lends itself to a half-EMT, half-exposed romex installation between boxes? Why not just go EMT the whole way, or, if it's too complicated for pipe bending, just use MC.
In may case, I have an unfinished basement, and I ran NMB between the floor joists above for a lighting circuit. I used EMT sleeve risers on the boxes I installed for switches.
Yep, what Wayne said. They also used to run EMT sleeves down furred walls against block since the wire was right behind the drywall. The EMT stopped at the ceiling line and the NM continued through the attic. Now they have a "hold your nose" legal loophole/interpretation of the NEC that allows them to simply put the wire on a standoff away from the furring strip but still in a 3/4" void against the block.
On Mon, 11 Oct 2004 11:40:32 -0700, J T wrote (in article ):
"Nipples" meaning pipe segments less than 24" are exempt from conduit fill limitations. You can sleeve 12/3 NM for short straight lengths in 1/2" EMT or Rigid for that matter without difficulty. This is often done (and required) when running NM up through a floor.
And yes, you have to carefully ream the cut ends so you don't damage the cable, but you're always required to do that...
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