Rodentia

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electrofelon

electrofelon

Senior Member
Location
Cherry Valley NY, Seattle, WA
Occupation
Electrician
Went on a troubleshoot call today. I had never seen this before, but turns out mice had chewed completely through the hot wire on a piece of 14-2 NM, Certainly Ive seen them chew on insulation and make a big bare spot, zillions of times, but never seen a wire partially or completely chewed through. That thread in campfire I started where we got talking about wiring with MC or EMT? I think Im doing my house in MC now.....
 
electrofelon said:
Went on a troubleshoot call today. I had never seen this before, but turns out mice had chewed completely through the hot wire on a piece of 14-2 NM, Certainly Ive seen them chew on insulation and make a big bare spot, zillions of times, but never seen a wire partially or completely chewed through. That thread in campfire I started where we got talking about wiring with MC or EMT? I think Im doing my house in MC now.....
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I've seen squirrel damage a lot. Once I saw it chewed all the way through. Half dozen or so times I've seen major compromises in the copper, without being chewed through
 
Over the years when I've had trouble shooting calls for plugs or lights not working, I almost always figure it out, but there have been a couple times when I just couldn't for the life of me find what was going on. I always assumed just a buried failed junction somewhere. It was kind of good to see this because now I can say I have seen it.
 
If you find NM chewed through, do you replace it with NM? I can see where replacing it with MC or EMT would not be practical or cost effective, but replacement NM would likely be attacked again if the rodent problem continued. I guess the solution would be to get rid of the rodents.
 
Coppersmith said:
If you find NM chewed through, do you replace it with NM? I can see where replacing it with MC or EMT would not be practical or cost effective, but replacement NM would likely be attacked again if the rodent problem continued. I guess the solution would be to get rid of the rodents.
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Yeah I just replaced it with NM, but you have a good point. I think it is more likely to be damaged if it is right next to where they are nesting. In this case it was right in a corner and it was a nice little nook for them I think , in the dead space behind the corner framing.
 
Just wondering...Would a GFCI or an AFCI detected this??
 
Archer said:
Just wondering...Would a GFCI or an AFCI detected this??
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If they chewed off insulation but conductors remained in free air, no. Needs to be something else involved to make a ground fault or an arc fault before either of those would respond to anything.

These rodents apparently have well insulated teeth and apparently don't get their tongue or other parts involved in the process. I seen direct buried 277/480, maybe even 480 corner ground that had rodent damage, likely while energized, and never any dead rodent in the vicinity when you excavate it. About only time I have found dead rodents is in equipment where they are found laying across two terminals of different potential or something like that, contact was through their feet not the mouth/teeth.

I have never seen 14 or 12 solid chewed all the way through, have seen 16AWG and smaller control wires chewed all the way through a few times.

They don't "eat" the insulation, at least not as a general rule, they take it back to nesting areas and spit it out and use it for nesting material.
 
Thanks for the interesting replies. I particularly like kwired comment about 'well insulated teeth'. I've been following this forum for several years, but this is the first time asking a question. I've been industrial for the last 43 years (retiring in a few months) and have learned a lot from all of you, especially about residential which I haven't done since I started industrial...Keep up the good work!!
 
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