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I replaced the panel yesterday, and as I was removing the old panel, the hot and ground wires from a damaged cable broke off. I stripped the hot and that looks good above the damage. The neutral seems to have the insulation scorched only.

So now I'm looking to extend the cable into the new panel because I only have about one inch of wire (hot and ground) inside the panel. I'm looking at a metal box, located above the panel on the inside of the wall (see picture pls). The picture shows an open knockout hole. This is where the box will attach.

Optionally, I can move the brown cable to the empty knockout and put the box closer to the stud. I think a regular 1 gang metal box may fit there. I'm wondering if I can use a conduit box? instead of the 1 gang box. The conduit box looks smaller/narrower. Either box would be fitted to a 1/2 in nipple and threaded to the panel (and the box). Then the cable would come into the box from the top with a wire clamp. I'll add an foot or so of cable to extend it into the panel and make the connections.

I will be fixing the dry wall so no access will be possible in the future, unless I cut the drywall again. So I want the cable connection to be rock solid. I would rather solder the wires before adding the wire nuts, probably a no-no? Any better options? Thanks

short cable panel top metal boxes

  • You cannot cover that box with drywall. That would be illegal. It must remain exposed so that access is possible in the future. – Craig Sep 16 '18 at 19:28
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    You have an additional investigation to determine just that caused that charred jacket on the neutral wire. There was some type of thing that caused high heat to be created in that area and it should be understood before just cutting it out and waving it away. – Michael Karas Sep 16 '18 at 20:20
  • True, which is another good practical reason to not hide a junction box inside a wall (and is obviously part of the reasoning for the legal rule). – Craig Sep 16 '18 at 20:22
  • You can see the original picture here. It looks like the hot arced to ground and at some point in the very distant past even caught fire. – Rodo Sep 16 '18 at 22:12
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Those conduit boxes have to be left exposed so that they are accessible.

You're going to need to either pull new cable from the nearest outlet/junction box on that circuit, which will not be easy since this is obviously NM cable, presumably stapled (as it should be) to studs along the way, or you're going to need to install an accessible junction box near the panel.

You cannot legally cover any boxes like you're talking about doing. You cannot legally have any hidden connections. Any electrical connections must be in a box that has a cover permitting access any time in the future.

You could potentially use an approved in-wall splice, although I'm going to leave it up to other folks who have real experience with them to recommend them (or not). But this is what I'm talking about.

You should find a spot in the wall to cut a new hole for a new junction box, where you know you will be able to fish this cable out undamaged. Use an "old work" box that you can clamp onto the drywall. Fish the wire into the box, strip the sheathing and cut the wires so that about 6" of wire is sticking out of the box. Then fish your new cable from the box into the panel.

  • Well ...there goes my bad idea. Leaving the box exposed is ok but the picture I show is from the inside of a linen closet. Is it ok if the box is in the inside of a closet/cabinet that is built-in between two walls? – Rodo Sep 16 '18 at 20:19
  • Yes, that would be okay. The box will be exposed, but covered with a blank faceplate. @Edbeal also makes a good point that there might be enough wire left to go ahead and make a splice inside the panel, which would be fine. – Craig Sep 16 '18 at 20:21
  • I like the in-wall splice better but I could only find the 2 wire version in my local home depot. Can the ground wire be by itself? – Rodo Sep 16 '18 at 20:25
  • You should really check your local code. But if the ground wires are bonded well enough (clamped and maybe soldered for good measure) then I'd imagine it would be fine. Exposed ground wires are not abnormal, but I'd probably use high quality electrical tape around the splice for good measure. If there is a wiring mistake that energizes the ground (it is there as a failsafe, not for conducting current under normal circumstances), it could be shock or even a fire hazard. – Craig Sep 16 '18 at 20:38
  • I'm going with the "Romex Splice Kit 2 Wire". I found it a the local homedepot/lowes. This is for 3 wires (hot, neutral and hot). The instructions say that I can use it for 14/2 (15A) or 12/2 (20A). I'm reading the NEC 300.15 and 334.40 before I do. – Rodo Sep 17 '18 at 1:48
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Based on what you say you want to do, your only option is the Tyco type "inside the drywall" boxless splices now on the market. That is the only code-legal way to make a splice without without a junction box that remains accessible. And even then, your inspector may not allow the Tyco method given the limited conditions under which it's allowed to be used, and the pre-existing cable damage to this cable.

Really this cable should be replaced.

Now we talk about the "box" solution.

I do this all the time.

Many of my installations have a junction box near the panel. It solves all sorts of problems. Not least, your panel does have a convenience receptacle for the Electrician right next to it, right? No? Why not put a receptacle on the face of this junction box? **

You just said that you intend to bury the box in drywall. No you won't. You can't do that. You are never allowed to bury boxes. Every junction box cover must be accessible without disassembling any part of the house.

Now, you'll be using a large size steel junction box because you'll be making potentially more than one splice in it. Junction boxes have cubic inch requirements for splices. With cable clamps entering the box, a handi-box is too small. Splicing is illegal in conduit bodies*.

I would use a 4-11/16 deep box, unless you're sure you'll only have 2 of these, then a 4" x 4" x 2-1/8" box will suffice.

EMT Conduit

This box will be attached via less than 2 feet of EMT conduit, at least 8" simply to avoid blocking other holes. Find the happy medium of the largest conduit size (1/2, 3/4, 1") that will fit both box and panel knockout, and figure out how to mount the box so it will ultimately be flush to the finish surface.

Noting that you have two drywalls there, use either one - whichever makes the best fit. It would seem to be more aesthetic to have the blank cover plate above the panel not on the shown wall.

If you want to get fancy with bending the EMT to make room for whatever, go for it - but keep total EMT length < 2 feet.

By doing steel and EMT conduit, we remove grounds from the picture. There's a ground screw hole in the junction box tapped #10-32; we take a pigtail off that, and the circuit grounds to that. We don't need to carry ground wires down the EMT conduit into the panel.

Attach and splice

Once the junction box is mounted finished, now bring that cable clamp into a knockout in the box. Like I say, the ground ends here: the metal EMT carries it the rest of the way to the panel. The two conductors (hot/neutral) you give yourself about 12" of length, and nut it to a couple feet of hot/neutral wire. Those go down into the panel.

Here you are at liberty to use "stranded THHN" if you prefer, it's much easier wire to work with. It'll work great on wire-nuts, breaker lugs and neutral lugs.

What if you have more than one circuit to splice like this? How many splices can you do inside one junction box? There's a formula for that. 2.0 cubic inches for #14, 2.25 cu.in. for #12 and 2.5 ci for #10. *Except all grounds together count as only 1 wire (the largest) and all cable clamps together count as 1 wire (the largest).* So in your case at #14, you'd be joining 2 wires to 2 wires, +1 for grounds +1 for cable clamps = 6 "wires" = 12 cubic inches. And this is why we need big boxes.

When you see the job done right, instead of horked together dirty, you'll be proud and you'll want to do work of this quality in the future.


* Disclaimer: for all conduit that is sensibly sized for its wires. Don't ask why I have to disclaim this.

** Typically the electrician's convenience receptacle is on a dedicated circuit. If you follow my box-and-EMT plan, you can easily add this to the box with 2 wires, a receptacle, a cover and a breaker.

  • Could you elaborate why "Really this cable should be replaced". It was working for 18 years without a problem until I jerked/pushed/pull on it. Replacing it would be a big undertaking. Would an AFCI breaker help prevent future arcing in this wire (after I install the splice)? – Rodo Sep 17 '18 at 1:54
  • Because it could have taken thermal damage down its entire length, which may hav broken down the insulation. When you cut it back, you'll know for sure. – Harper Sep 17 '18 at 4:25
  • That is not a bad point. – Craig Sep 17 '18 at 17:13
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It looks like there is enough good wire to make the splices inside the panel. This would be code compliant as long as you have 1/4" of the outer insulation inside the panel.

I use RACO insiders, which are a plastic snap in clamp that takes less room than screw clamps and these are installed from the inside of the panel. I have no connection to RACO/Hubble other than using many of these over the years. I usually keep a box on hand because they are great for both new installs, and are even better on remodels because you don't have to cut sheetrock to install them.

Just fish the cable through the knockout and snap the clamp in place. It will provide a little more slack than a 2 screw clamp and you can extend the wires to the breaker and busses, with no retaining nut required.

If the length is too short you can add a box but it must be accessible later on. Not a big deal; just make sure the cover plate can be removed so the splices can be accessed.

With the 2 cables in front of the existing knockout, Joliet will take a nipple that is several inches long and probably an offset nipple to bring the box forward if the wires are two short.

  • I'll try to pull some wire if I can and see if I can get that 1/4 in and add the splice inside the panel. Thanks. – Rodo Sep 16 '18 at 22:15
  • Ed, do you mean like these? amazon.com/Raco-4714-Cable-Connector-Sheathed/dp/B000R8147I – longneck Sep 16 '18 at 23:45
  • Yes those are great for new work and even better for remodels where you can fish a wire in. No need to cut sheetrock to install a old 2 screw clamp. – Ed Beal Sep 17 '18 at 13:09

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