Unfinished bsmnt: max distance from NM in ceiling joists to junction box on wall

I’m adding circuits to an unfinished basement. I’m using NM wherever I move through/along the ceiling joists. When I want to move vertically down the exposed, poured-foundation wall, I’m adding a box, pigtailing to THHN, and running the THHN through EMT. I’m having trouble finding the maximum distance from the top of the wall that I can mount the box. That is, it would be silly to mount the box three feet below the top of the wall and let the NM run down that length to it. But am I being overly pedantic in making sure the top of the box is as high as the top of the wall? Or can it be within six inches of the top? My concern is with drilling into the concrete that close to its edge—securing the boxes would mean drilling within an inch or so of the top of the wall.

Thanks!

 

Six inches from the top of the wall should be fine. The NM should be pretty well protected with only the top 6" exposed on the wall.

 

Thanks. I'll be paying for a (voluntary) inspection once everything is all done, and this kind of echos what the inspector was telling me when I had him out for a preliminary look---when asking about a different area, he stressed the protection of the cables from snagging or hanging much more than anything else.

 

You could just sleeve the cable in a conduit sleeve down the wall and just skip the splice.

 

I was under the impression that I could only run NM cable through conduit if the wires were properly labelled/stamped (I'm out of my element terminology-wise). That is, when I strip off some of the sheathing of the NM cable the insulation of the inside wires do not carry any markings. Hence I went with a splice to THHN that is individually rated (again, my apologies for sloppy use of words).

Is this a hyper-technical reading of the code? A mistaken reading of the code? If it's technically part of code, is it a safety factor or to make it easier for the next person working?

Work/effort aside, am I actually introducing a weak point (e.g. risk of sheathed cable inside conduit versus an added splice))?

 

That applies if the sheath is removed and only the wires are use.

Always best practice but not a code violation to put NM in conduit, just harder to pull. In fact it is a good practice and sometimes required to use short sections of non continuous conduit as a protective sleeve.

 

NM cables can be run through a short length of EMT conduit as a sleeve for protection. When you do this, the open end of the EMT needs to have a bushing to protect against cutting the cables. A simple drive-on bushing is typically the best way to go. DO NOT strip the sheathing from the cables till the cables enter the box.

Arlington EMT100-100 EMT Insulating Conduit Bushing for Electrical Metal Tubing, White, 1-Inch, 100-Pack - Amazon.com

 

No. Actually the junction you proposed would be the *weak* point --- so to speak.