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View Full Version : Embedding conduit/raceway in Plaster wall



sbaitso
07-29-2008, 01:43 PM
Has anyone had any experience embedding a cable / conduit / raceway in a solid plaster wall (its solid plaster on masory - no lathe, no gap between the plaster and the brick on the other side)?

I'm thinking I'll have to cut a channel in the wall and put in a piece of conduit to use as a raceway for NM cable, then plaster over the channel. I could also go with a true conduit system and use THHN cable, but I'd like to avoid that.

I was hoping to use the Carlon NonMetallic Tubing (the corrugated blue stuff), but am a little unsure of its code-worthiness for such an install.

Has anyone tackled a project like this... any pitfalls to look out for?

I appreciate any advice.

Bob NH
07-29-2008, 02:29 PM
I believe you would be better served if you used MC (Metal clad cable) which is smaller than ENT ("Smurf tube", the corrugated blue stuff). It is flexible, already contains the wires, and if it is in a wet location you can get it with THWN insulated wires.

Chris75
07-29-2008, 07:54 PM
I believe you would be better served if you used MC (Metal clad cable) which is smaller than ENT ("Smurf tube", the corrugated blue stuff). It is flexible, already contains the wires, and if it is in a wet location you can get it with THWN insulated wires.

You still need to protect MC. (Actually I change my mind.) I still would not use MC.

Bob NH
07-29-2008, 09:35 PM
You still need to protect MC. (Actually I change my mind.) I still would not use MC.

MC is permitted per 330.10(10) or 330.10(11)c.

If I have to cut a groove in a brick wall smaller is better and I don't think anything else legal is smaller than MC.

Why would you not use it? What is better for the application?

sbaitso
07-30-2008, 09:55 AM
Hmm, looks like MC is the other choice.

I guess ultimately I'd feel better if I could have some sort of raceway that I could run cable through in the future if the needs of the circuit change, so I'd like to stay away from something where the wire is integral to the cable. Of course that's overkill and will ultimately just make more work for me.

Thanks for the advice.

Bob NH
07-30-2008, 05:36 PM
If you want to plan for expansion you can run a 20 Amp circuit now.

If you really want to plan for expansion you can run 12/3 with ground which will support a multi-wire branch circuit equivalent to two 20 Amp circuits. 4800 Watts will support an immense multimedia surround-sound system.

sbaitso
08-04-2008, 05:13 PM
I went with the MC cable... the shallowness of the trench (~1" deep) pretty much meant it was the only way to go, but it definitely was the best/easiest solution (thanks!). I went ahead and ran 12-3 in case of future expansion needs as well.

I've been reading parts of the 2008 NEC that seem to indicate that I'll need to protect the wire since this is a shallow channel with a steel plate at least 1/16" thick, but I can't determine if that applies to MC cable, or other, less protected cables.

Would i be crazy to go ahead an put a steel plate in the channel over the cable, or is that overkill?

jwelectric
08-04-2008, 07:31 PM
deleted .

Bob NH
08-04-2008, 07:40 PM
You don't need the metal protection unless the cable is in some place where it is likely to have nails or screws driven into it. Unless you have shallow furring strips on the masonry wall that will be covered with some kind of screwed or nailed material you don't need to do anything.

jwelectric
08-04-2008, 07:42 PM
Yes I agree.
I didn't read the original post good on first read and posted 300.4 (A)(2) which addresses notches in wood studs. If it is in studs then the nail plate would be required.