Finish Nail Hit Electrical Flex Conduit - Blew Fuse

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Old 05-09-20, 11:14 PM
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Finish Nail Hit Electrical Flex Conduit - Blew Fuse

I was installing baseboard in my basement with a 16 gauge finish nailer and must have hit a wire in some flex conduit in the wall - the breaker (newer arc fault type) blew. I removed the nail, reset the breaker and seems to be OK.

I know this isn't a good thing, but hoping my fears are wrong. Do I need to open up the wall and repair, or is there any chance this can be left alone. Again, this is Flex Conduit with a newer arc fault breaker type. If I do need to repair, what is the best way to handle it.

BTW: I know there will be questions how this could have happened. Previous owner installed romex in shallow walls near the bottom. I'm remodeling the basement, I decided to replace the romex with flex conduit because I thought it would protect against nails! Guess I was wrong!

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Last edited by JohnCec; 05-09-20 at 11:38 PM.
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Old 05-10-20, 05:10 AM
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I certainly would NOT just leave it. If there is enough extra wire available you could cut the conduit at the break, mount a single gang electrical box in the wall, cut the wire where the nail knicked the insulation, connect the wires with wire nuts, then cover the box with a blank cover plate. The connection must be accessible so your enclosure and connections must be in a box accessible from the room. If you don't have a foot of extra wire to do a splice then I would replace it.
 
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Old 05-10-20, 06:07 AM
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Since you have conduit you should pull in new conductors at a minimum.
 
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Old 05-10-20, 08:10 AM
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Thanks for the replies. I should be more clear on my question.

I understand it'll need to be repaired for peace of mind. There isn't enough conduit length to place a box or additional outlet in that spot. Never pulled wire through flex conduit before - but there are some tight bends in this run that most likely create a challenge. If I start that process and it fails, I'll be a mess.

Is there a way to open the wall in that spot, remove the conduit around the damage wire (without cutting the wire) , tape the damaged wire, then repair the conduit with some kind of Flex Conduit coupler/housing/cover or something? Otherwise I have to cut a large section of wall to replace the entire run! This will involve sheetrock repair, rigid Polyiso Continuous Insulation repair as well. Kind of a big job.
 
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Old 05-10-20, 08:19 AM
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The electricians can correct me if I'm wrong, but it's possible that this product could be used if it was protected by no nail plates anywhere the section of flex conduit has been removed.
 
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Old 05-10-20, 08:50 AM
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That splice is for NM cable, not flexible conduit. Pulling new conductors is the easiest and best solution.
 
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Old 05-10-20, 09:02 AM
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This is 3/8" flex conduit with some very tight bends (including a tightly bent corner). Is it fairly easy to pull wire through? Also, if a finish nail gun punctured the metal conduit, would that create a sharp spot inside the conduit?

Hoping something like this for 3/8" electrical flex conduit (although I know this particular product is not for this purpose)
https://www.zoro.com/zoro-select-rep...E&gclsrc=aw.ds
 

Last edited by JohnCec; 05-10-20 at 09:28 AM.
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Old 05-10-20, 09:40 AM
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Based on the size it sounds like AC or MC cable ,not conduit. If so your choice is to open the wall, and replace the cable.
 
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Old 05-10-20, 10:07 AM
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Unfortunately, this will be a big project. A good amount of sheetrock will need to be removed along the entire wall and around a corner - and a built in cabinet will need to be removed. Just want to make sure there is no other way to resolve this. Pulling new wire through 3/8" flex MC according to your post sounds like it's not possible. Is there an acceptable way I can open and remove a section the 3/8" flex MC without cutting the wires, tape the damaged insulation (as long as the conductor in the wire is not damaged) and place some kind of metal housing clamp over it?
 
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Old 05-10-20, 10:18 AM
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If it's 3/8" it's either AC or MC..... some type of spiral metal clad cable. There is no way to repair in the middle of it. The spiral will break apart if you try to open it and make some type of repair. Unfortunately there the wires are usually tight inside it and won't pull out either except for very short runs.

Putting a patch over the cable is of no help. When the cable is hit the metal punches in to the wires. It's this sharp point inside the metal jacket that is the problem.

No basement or attic to work thru ?
 
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Old 05-10-20, 11:36 AM
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I decided to replace the romex with flex conduit because I thought it would protect against nails! Guess I was wrong!
Nail plates are the better solution for cables less than 1 1/4" from the face of the stud. Also not using 2 1/2" nails.

MC and AC cable only has an aluminum jacket and will not stop a nail.

Cut the drywall about 12" from the bottom. Cut the cable where the damage is and install a box to the left and right of that spot about 4'-8' apart and install a receptacle at each location. (one can always use more receptacles) Run a new cable between the new boxes to complete the repair. Boxes will be metal remodel boxes that only attach to the drywall.
 
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Old 05-10-20, 11:36 AM
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I did open the wall and removed about 1" of the MC around the nail hole and inspected the wires. The White wire insulation was nicked, but the conductor looks OK. The Black and Green wire looks OK. I did place tape around the White wire (and Black wire to be safe). I placed a couple of antishock bushings on both sides - now just trying to see if I can customize a way to cover it with some sort of metal clamp housing.

I know this is not by the book, but I don't think the book covers every scenario. I trying to find a reasonable and balanced repair and is SAFE - since the wires looks OK except for a nick in the insulation it seems worth a shot..
 
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Old 05-10-20, 11:43 AM
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"Cut the drywall about 12" from the bottom. Cut the cable where the damage is and install a box to the left and right of that spot about 4'-8' apart and install a receptacle at each location. (one can always use more receptacles) Run a new cable between the new boxes to complete the repair. Boxes will be metal remodel boxes that only attach to the drywall. "

I'm still considering something like this. There's not enough cabling to just install a box at normal level for an outlet, so I'll have to mount the box to the left of it, then remove the sheetrock all the way to the next outlet to rerun new Flex MC. I know this is probably the best and preferred method for my problem - a small nick in the insulation of the white wire! Wish a simpler solution was available!
 
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Old 05-10-20, 12:11 PM
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a small nick in the insulation of the white wire!
That will trip an AFCI breaker when it arcs to ground. Nails hitting cables is one of the reasons why AFCI devices were invented.
 
 

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