Romex sheath

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I believe that if you check the NM manufacturer's website they will say that it may be repaired with tape, but I'm not really sure since I am going by memory. ;)
 
infinity said:
I believe that if you check the NM manufacturer's website they will say that it may be repaired with tape, but I'm not really sure since I am going by memory. ;)
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I agree with infinity here.....and if you would like to wait for a month or so, I'm sure I could dig up the reference :D
 
I think the closest thing we have is minutes from an old IAEI meeting, in which a Southwire rep says that if the sheathing was snagged open, but the conductors were not damaged, the jacket did its job. It only needs to last long enough to get the cable installed. The tape, at that point, would only be applied for beauty's sake.
 
I dug this up. I think it dates from 2002.

See what Gill Moniz of NEMA and Dave Mercier of SouthWire Corporation had to say about it during an IAEI meeting:
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When Gil visited us previously, he made a splash by noting that the transparent nylon covering THHN/THWN, while arguably making them sexy compared to THW, is not required to maintain the conductor's dielectric properties. Therefore, if in the course of installation the nylon suffers the odd nick, or unsightly run, or even is scraped off, the conductor is fine so long as the insulation underneath remains intact. Learning this much, we had to have Dave over for more of the story.

Unless conductors are exposed to gasoline or oil, or submerged for an extended period we're talking many months--the nylon covering offers strictly a mechanical protection, Dave explained, with the underlying PVC supplying the dielectric properties as Gil had told us. The nylon actually is stripped away for the UL acceptance test. Therefore, if the nylon is scraped off, but the plastic underneath is intact, an appropriate response usually is "Good; it's done its job," and a green tag.

It's not just the nylon covering on THHN/THWN, we learned, but the sheaths on cable assemblies also often are optional. A cable installer nicked the sheath of a nonmetallic cable installed in a dry indoor location, and responded in a curious way: he turned the cable so the nick faced toward the wall. Not a bad response, Dave opined (while not wholeheartedly endorsing); this way, people glancing at it in passing wouldn't be unnecessarily concerned.


You may detect from this that Dave is quite an engaging speaker; moreover he's one with 19 years' product and Code experience under his belt to give plenty of clout to the information.

Damage is not necessarily limited solely to cable sheaths, of course. If a cable appears damaged, Dave recommends cutting a window in the sheath so you can examine the conductor insulation beneath. If that's good, you can "reinstall the window."

What should you do when you do want to, or need to, repair a cable sheath? Vinyl tape does just fine, Dave said, except in a wet location, and self-sealing mastic tape does even better. Best is a layer of self-fusing tape covered by a layer of vinyl. It even can be used outdoors on UF or SE cable, so long as it is not buried. For that, you need the sealing coverings that come with a Listed underground splice kit.

Art asked whether NM or SE cable repaired in this way still meets the UL standard. Dave commented that it is tough to say. There needs to be a dialogue between the manufacturer, AHJ, and installer. A qualified installer of repair materials should be able to make a repair acceptable to the AHJ, and Southwire's warranty will remain in effect. "Qualified?" Jim Wooten asked. "Someone who has received certified training in using the material, either in an apprenticeship class, or continuing education such as is offered by tape manufacturers." Even damaged Medium Voltage cable remains warrantied, so long as the shielded jacket, which is there for mechanical protection like that of MC, is fixed using a Listed repair kit installed by a qualified person.

We hope to co-sponsor such a class with 3M or Raychem or some such organization.
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I too am only worried about insulation damage on the conductors themselves. As long as the damage to the outer sheathing is not excessive, I would allow an electrical tape repair...
 
Just how much damage are we talking about and will the repaired spot be covered over with drywall? A small 1 inch long tear with no other damage other than jacket probably will be fine. But if your asking and inspector to put his name on it you have a long wait. Best you simply repull it or hide it from view. Keep in mind that you are now liable for it for next 100 years. Its now damaged and you know it. Unlikely but if ever a fire and they can point at you as knowing ---------------- think this out
 
Jim W in Tampa said:
Keep in mind that you are now liable for it for next 100 years. Its now damaged and you know it. Unlikely but if ever a fire and they can point at you as knowing ---------------- think this out
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I'd sign my name on the damaged jacket and own it for the next million years. What, pray tell, do you think a pristine jacket is going to do to enhance the safety of the installation in the event of a fire or fault.? How is the safety of the installation compromised by having a gash in the jacket? An answer that includes the words, "...an attorney...", doesn't count. We have both a manufacturer's trade association and a manufacturer on record saying that a gash and tape repair are fine.
 
If my memory serves me, the requirement for NM-B was because of excessive heat in some attics. The relaxing of the requirement in 334.80 that states, "90?C (194?F) rating shall be permitted to be used for ampacity derating purposes." was ignoring the NM-B jacket because it has no rating. Since the conductors contained inside were rated at 90?C, it was OK to make this change in 334.80. :)
 
Jim W in Tampa said:
Just how much damage are we talking about and will the repaired spot be covered over with drywall? A small 1 inch long tear with no other damage other than jacket probably will be fine. But if your asking and inspector to put his name on it you have a long wait. Best you simply repull it or hide it from view. Keep in mind that you are now liable for it for next 100 years. Its now damaged and you know it. Unlikely but if ever a fire and they can point at you as knowing ---------------- think this out
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I just thought this out and it took me under 2 seconds to think about it. Knob and tube is an NEC recognized wiring method. It does not have an overall jacket like NM cable does.
 
peter d said:
I just thought this out and it took me under 2 seconds to think about it. Knob and tube is an NEC recognized wiring method. It does not have an overall jacket like NM cable does.
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I didn't think K&T was still a recognized method per NEC. Anyways I've never been tagged on taping little minor dings and nicks on romex.
 
Just use the correct color tape on your repair, white for 14, yellow for 12, and orange for 10. That way it looks like you never even nicked it to start with. :smile:
 
charlie said:
The relaxing of the requirement in 334.80 that states, "90?C (194?F) rating shall be permitted to be used for ampacity derating purposes." was ignoring the NM-B jacket because it has no rating.
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That's also why jacket markings are irrelevant when it comes to stripped NM, and why the jacket has nothing to do with its indoors-only limitations.

In other words, stripping the jacket from NM doesn't change the properties of the conductors within. They're still not rated for wet locations.
 
sparkchaser1961 said:
I didn't think K&T was still a recognized method per NEC. Anyways I've never been tagged on taping little minor dings and nicks on romex.
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wbalsam1 said:
  • 1956 Art 324
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I don't know where i got the idea K and T was not approved anymore. Looks like you gotta have special permission to wire with it unless your repairing something.
 
I just went through this on the volunteer house I wired. I had a piece of romex that I didnt notice had a nick in the insulation. It was existing wire and I think thats why I overlooked it. One of the few areas with drywall left on the front side. My first question to the boss on the job who had spoken to the inspector was can I just tape it? Her response was that was the one thing he had mentioned I couldnt use. So drywall came down and I repulled that piece. Oh well now I know I had a leg to stand on with the tape idea.
 
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