I live in Sparks, Nevada, and the 2011 National Electrical Code applies to me. My work will be inspected when complete.

I am replacing a switch and have found that someone before me (accidentally?) sliced open the insulation on the hot wire for the switch and neglected to fix it.

The slice only goes down a few inches of the wire, so I am considering cutting this off and just adding a jumper wire to it to extend it the required three inches outside the box (there will be enough wire to add a nut). Is this legal (per NEC 2011)? Specifically I am unsure if this a violation of the amount of wire I have to have coming in to the box.

See picture below, the slice is visible in the hot wire. It only goes as far as you can see in the picture and is intact after that.

enter image description here

Edit: Or should I just wrap it in electrical wire rated for at least 120V? My understanding is this is legal because it is in a junction box.

  • You are also missing at least 1/4" of the outer NM cable assembly's insulation extending into the box for all of the NM cable assemblies in that box (except for the one where the insulation has not been stripped back yet at all); this is code violation that you are likely to get called on. Also, the accompanying neutral (white insulation) directly to the left of the hot wire is normally current carrying as well and therefore poses the same problem as the black/hot wire with too much stripped insulation. Mar 5, 2017 at 12:54
  • Can't the wire with the slashed insulation by covered with heat shrink tubing? Can the missing NM sheath be similarly repaired with heat shrink? Mar 5, 2017 at 16:20
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    @stateupeuphemism do you believe the inspector will cite the two violations you mentioned considering that they are existing work?
    – Tim Sweet
    Mar 5, 2017 at 16:37
  • What work did you get permitted exactly? It sounds like you are just replacing a switch if you are saying that all was existing. If your city requires a rough-in inspection with the wires exposed on a switch replacement (not just final inspection), I'd say you have high odds of being called on it as that inspection requirement itself is pretty strict. Mar 5, 2017 at 17:58
  • @statueuphemism I am installing bathroom fans, just for the context of this question I had hoped that description was enough. The full description of my project is in an older question: diy.stackexchange.com/questions/105565/…
    – Tim Sweet
    Mar 5, 2017 at 19:49

4 Answers 4


I think 300.14 is quite clear. You need at least 6" of free conductor, and the conductors must be long enough to extend 3" out of the box. If you can't pull more cable into the box, you're going to have to replace it.

As others have mentioned, 314.17(C) requires at least 1/4" of the cable sheath to be in the box. So the inspector might call you on that as well.

  • 1
    Those other issues seem to moot the issue with the nicked insulation near the end. Still, I wonder - is "pull a new cable" the only answer for nicked insulation this near the end of a wire? Mar 5, 2017 at 17:46
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    @Harper you could possibly insulate the wire, but even if you did, it's still too short to meet code. The best course of action, is to talk to the inspector, and ask them what they expect to see.
    – Tester101
    Mar 5, 2017 at 21:00

Thank your Grandfather...

Replacing a switch is regarded as general repair work. In other words, no altering, or replacing any electrical wires puts those wires in a grandfather category, assuming the gyp-board is not removed as to expose the old wires.

Some electrical tape around the slice insulation and a wire nut to extend it longer is all that is required. Though as mentioned by others, your grounding technique needs a lot of work!

As a tip of advice a large crimp rated for at least 5 #12s with two pigtails extending out for the two devices would be fab. Twist only slightly and make the formation smooth and even after the crimp is squeezed tight. Be sure to use the proper crimping device and non-insulated crimps.

  • Make sure the tape is equal to or greater than the insulation that is on the wire. Also, if you get a tight inspector, they might still flag this.
    – Tester101
    Mar 5, 2017 at 21:07

Tough problem. I have to say I would be tempted to just tape up the wire, though that tape is probably not legal to cure thee insulation fault. If you used brown, red, orange, yellow, blue or violet electrical tape, and also taped the other end of the same wire the same way, nobody could tell it wasn't just a wire marking, though unusual. If this was a white wire and you did that with black tape, nobody would look twice at it!

I don't think cutting it back inside the box and splicing is legal either. You need to have 3" coming out of the box.

  • -1 For recommendations on how to hide problems rather than fixing them. Mar 5, 2017 at 12:59
  • @statueuphemism. Fair enough, but you claim it hides a problem. Can you specify what problem? What about Jim Stewart's new proposal of heat shrink tubing? What I'm fishing for is whether such a tape-up/shrink-tube is a practical problem, a letter-of-the-law problem, both or neither. Code cites appreciated. Mar 5, 2017 at 17:44
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    I mistook your comments about "that would not quite be legal" to be related to the use of tape rather than the length of wire requirements. I will remove the -1 once I am allowed. I did not realize properly applied UL-listed insulating tape could be used to repair the insulation on individual conductors themselves: UL white book for Insulating Tape: "This category also covers thermoplastic tape intended for use as the sole insulation and covering of joints and splices in electrical conductors." Learn something new every day. Mar 5, 2017 at 18:57
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    Clarified, you may have had it right the first time. I'm not being snarky or defensive; whether tape is legal to repair wire insulation near a wire end is a question I am really curious about. Clearly tape does suffice as an insulator, as it is the official way to insulate hot or neutral splices which use solder, split-bolt or bare lugs. Mar 5, 2017 at 20:01
  • @Harper If you use the proper tape and technique, then yes, I believe tape can be used to repair insulation. However, DIYers may not be using the proper tape or technique.
    – Tester101
    Mar 6, 2017 at 13:16

Pretty sure you can add a jumper with a wire nut. I actually had to do that in my breaker panel for a feeder wire that was a few inches too short. Honestly though, that seems like less of an issue than that grounding mess you've got going on.

  • Thanks, I'll fix the grounding wires. Any idea on what parts of the NEC apply?
    – Tim Sweet
    Mar 5, 2017 at 3:17
  • FYI I cleaned up the grounds, see picture which also has a better view of the slice.
    – Tim Sweet
    Mar 5, 2017 at 3:26
  • The grounds used to have a green "through" wirenut with a hole in the top for one of the ground wires to extend through the wirenut and go to the device yoke. Common and normal. Mar 5, 2017 at 6:04
  • Guess I'm not common or normal. Never liked nor used those green wire nut pigtails lol
    – Kris
    Mar 5, 2017 at 15:27
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    @Kris me neither, yet another thing made for speed of instalation. At least not as bad as backstabs! Mar 5, 2017 at 20:13

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