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.
This is what I have typically seen for instructions on installing NM cable clamps:
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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.
Best Answer
Approved Installations
The NEC often states "Approved method" of installation, which in other words is what the manufacture instructs. In the case of the non metallic NM wire connector, Halex© offers an online manual.
Other Items That Should Be Fixed
The metal stud looks to be 3.5" inch and Code requires no less than 1.25" from the edge of the stud. In other words, the wire needs to be moved to the center of the stud or use FHA straps to protect it from sheetmetal screws. See NEC 2014 300.4 Protection Against Physical Damage Cables and Raceways Parallel to Framing Members and Furring Strips.
Also NEC 2014 300.4 B Requires protection for NM cable passing through metal stud bored holes.
Excerpt....."where nonmetallic-sheathed cables pass through either factory- or field-punched, cut, or drilled slots or holes in metal members, the cable shall be protected by listed bushings or listed grommets covering all metal edges that are securely fastened in the opening prior to installation of the cable."