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-   -   Mixing NM and rmored cable (http://www.diychatroom.com/f18/mixing-nm-rmored-cable-30103/)

n0c7 10-17-2008 04:27 PM

Mixing NM and rmored cable
 
I need to run a wire to a light fixture in a finished ceiling where I know there are steel studs, self tapping screws, and air vent ducts(all bad for an NM cable). I think my best bet would be to run armored cable to the new light fixture. Power to the light switch is 14/2 NM. Whats the best way to make both types of cables work in a similar box? I plan to use a remodel style switch box as well as a remodel style light box.

teamo 10-17-2008 04:34 PM

You need a metal box for this one because ac/bx cannot go into a plastic box. Use a non metallic cable clamp for the nm and a bx type clamp with an anti-short (red head) bushing for the armored cable. other than that the wiring is the same. If the switch leg is nm then you can use a plastic box for that part of it. The hard part will be fastening the metal box into the ceiling. If there is a joist, strapping, or wood lathe in the ceiling then you can attach it to the wood with screws.

chris75 10-17-2008 06:33 PM

Quote:

Originally Posted by teamo (Post 173356)
The hard part will be fastening the metal box into the ceiling. If there is a joist, strapping, or wood lathe in the ceiling then you can attach it to the wood with screws.

They make metal and plastic round old work boxes.

n0c7 10-17-2008 07:47 PM

So will any metal workaround box work to fit the BX or do I need a specific box that accepts the various cable clamps? Just trying to visualize this as I'm only familiar with running NM cable and using the screw type clamps.

chris75 10-17-2008 08:10 PM

Quote:

Originally Posted by n0c7 (Post 173412)
So will any metal workaround box work to fit the BX or do I need a specific box that accepts the various cable clamps? Just trying to visualize this as I'm only familiar with running NM cable and using the screw type clamps.

Being in the trade, I just swap out the straps if needed. But you must use the correct strap and box for the wiring method being used.

n0c7 10-20-2008 01:27 AM

I found the right romex ends as well as the BX(ac90) ends, and ended up with a metal conduit box which had 10 different knockout locations on it, and screw holes in various locations making it very easy to attach inside a finished ceiling. Thanks for the help, was an interesting fit. :thumbup:

One question on the BX though - I had trouble shoving those plastic red anti shorts into the cable. It seemed to be very difficult to get over the paper inside the cable. It took me a lot of effort. Does it matter if the anti short goes inside or on top of the paper inside the cable and how far should they insert into the cable?


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