Protect NM cable with conduit

bcarlson78248March 16, 2014

I want to put two light switches on an unfinished concrete wall in my basement. The NM cable will run across the room inside a dropped ceiling, and then I need to run it down the wall to a double switch box mounted on the concrete wall.

What is the best way to protect the two NM cables that run from the dropped ceiling down to the wall-mounted switch? I seem to recall that there are some restrictions on running NM cable inside standard metal conduit. The conduit will be very short, since it only runs from the ceiling down to the wall switch.


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You are talking about a sleeve for protection. This is not considered a conduit run. NM IS allowed in conduit, but with restrictions and is frowned upon.

You do need a bushing or fitting at the top of the conduit where the cable enters.

    Bookmark   March 16, 2014 at 8:59AM
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To me, plastic seems safer than ungrounded metal. Is a bushing needed with the plastic?

    Bookmark   March 17, 2014 at 2:03PM
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The conduit will be painted the same color as the wall, and I think it will look better with metal than with plastic. However, I could go either way.

I also planned to use a metal box for the switches and ground the NM to the box, which means the conduit will also be grounded. I will have to look at what is available for bushings to protect the wire where it exits the metal conduit and goes into the dropped ceiling area.


    Bookmark   March 17, 2014 at 3:04PM
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Arlington makes the simplest bushing for the open end of the EMT. But buying just one may be a problem.
There are other code compliant ways to protect the cable. An EMT connector plus a threaded bushing could be used.

Here is a link that might be useful: Arlington

    Bookmark   March 18, 2014 at 8:43AM
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You can find NM couplings for EMT at Lowes (and others). I do just that for a 4ft run down my basement wall to power my drill press.

Here is a link that might be useful: EMT NM coupling

    Bookmark   March 18, 2014 at 10:08AM
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"To me, plastic seems safer than ungrounded metal."

If the switch box is metal the emt will be grounded.

    Bookmark   March 18, 2014 at 10:04PM
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