Skip to main content
3 of 3
Commonmark migration

Is it against NEC to reverse NM cable clamps?

Is the following installation method for NM cable clamps prohibited by the NEC for receptacle outlets?

Note: I know it would be more functional and less awkward to screw in the NM clamps had I used one of the knockouts on top of the box (indicated by the green arrow), right side, or bottom of the box. However, this was the only box I had laying around that already had a knockout punched out for an example and I was able to use a right angle driver to secure the NM clamps for this example setup. Also, since I know I will receive comments if I don't clarify: I know the metal box needs to be grounded (e.g. green ground screw and pigtail) even though it is not shown in the pictures below.

NM cable clamp screws inside box -- seen from outside box NM cable clamp screws inside box -- seen from outside box

This is what I have typically seen for instructions on installing NM cable clamps:

NM cable clamp screws outside box -- seen from outside box NM cable clamp screws outside box -- seen from outside box**

Reason for Question:

While I know the "reversed" method of installing cable clamps will take up additional space inside the box, if I use a 4"x4"x2+" box for a single gang outlet (using a single gang mud ring) then crowding the box is definitely not an issue. Also, if I leave a few inches of slack in the cable outside of the box, I can loosen the clamp to give me some "wiggle room" if I (or a future owner) is doing some work and needs extend the cable a little for any reason without having to tear open the drywall around the box or splice in pigtails.

statueuphemism
  • 5.3k
  • 13
  • 50
  • 65