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-   -   Burying MC cable in wall? (http://www.diychatroom.com/f18/burying-mc-cable-wall-29727/)

dc4nomore 10-10-2008 08:39 PM

Burying MC cable in wall?
 
The 4 exterior walls of my house are solid brick. 2 layers of regular brick, then a layer of cinder block, then the plaster wall material applied directly to the cinder block. Because of the difficulty of installing them I imagine, the builder (in 1938) only put two receptacles on the outer walls, and both are in the living rooms.

I needed more, obviously, so I dug out a few square holes for new outlet boxes with my hammer drill. I also dug small trenches (about 1") in the plaster/brick going down from the box holes, past the floor and into the basement. I attached the boxes in the holes with tapcons, and ran MC cable through the trenches and into a junction box directly below in the basement, where it meets up with regular 12/2 romex and heads to the service panel. I then filled in the trenches with drywall mud, completely engulfing the MC cable, sanded it down, reattached the trim, and painted.

I did all this a few months ago but never got around to actually hooking the lines up to the service panel. I was going to finish this project up (finally!) tomorrow and I thought about something that I don't think I ever thought about before...would the MC cable have any sort of issue with heating up because it is completely buried in the drywall mud? Now this is 12/2 cable for a 15 amp circuit, so it won't be overloaded by any means. But I just didn't know if it would be an issue.

I ran a similar line for a low voltage receptacle and I actually buried a piece of conduit in the wall so that I could slip the wires through it and possibly add lines if I wanted to upgrade something later. Now I'm thinking it might have been better to simply run romex through a piece of buried EMT, because then it would have more space to breathe. What do you all think?

Thanks in advance!

J. V. 10-11-2008 09:44 AM

330.10 Uses Permitted.
(A) General Uses. Type MC cable shall be permitted as
follows:
(1) For services, feeders, and branch circuits
(2) For power, lighting, control, and signal circuits
(3) Indoors or outdoors
(4) Exposed or concealed
(5) To be direct buried where identified for such use
(6) In cable tray where identified for such use
(7) In any raceway
(8) As aerial cable on a messenger
(9) In hazardous (classified) locations as permitted
(10) In dry locations and embedded in plaster finish on brick
or other masonry except in damp or wet locations

(11) In wet locations where any of the following conditions
are met:
a. The metallic covering is impervious to moisture.
b. A lead sheath or moisture-impervious jacket is provided
under the metal covering.
c. The insulated conductors under the metallic covering
are listed for use in wet locations.
(12) Where single-conductor cables are used, all phase
conductors and, where used, the neutral conductor
shall be grouped together to minimize induced voltage
on the sheath.

dc4nomore 10-11-2008 10:17 AM

Good to know...thank you. :thumbsup:

And also....How do you know if MC cable is suitable for wet locations? Would it specifically say that on the package? And if it doesn't say anything, I'd assume it is not ok?

SD515 10-11-2008 11:35 AM

In general, a sheathing that is 100% solid on the outside, usually flat or round, will be impervious to moisture. Interlocking type sheathing isn't impervious to moisture. It should say on the package or tag that comes with it if it's rated for wet locations. See # 11 in J.V.'s post above.

dc4nomore 10-11-2008 10:41 PM

Quote:

Originally Posted by SD515 (Post 170917)
In general, a sheathing that is 100% solid on the outside, usually flat or round, will be impervious to moisture. Interlocking type sheathing isn't impervious to moisture. It should say on the package or tag that comes with it if it's rated for wet locations. See # 11 in J.V.'s post above.

Yeah that makes sense...thanks a lot for the clarification!


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