Rats/Mice

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jmellc

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Durham, NC
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Facility Maintenance Tech. Licensed Electrician
How capable are rats & mice of chewing through copper cable? I know they can get into the walls and ceilings of a house or apartment. Looking at the possibility in an apartment.
 
In a former life I wired fire alarm systems in barns, on occasion. We always ran the cable in EMT. For some reason, the local rodents had a prodigious fondness for FPLP.
 
jmellc said:
How capable are rats & mice of chewing through copper cable? I know they can get into the walls and ceilings of a house or apartment. Looking at the possibility in an apartment.
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Rodents can and will destroy NM cable by gnawing on the insulation. In severe infestations, they have even been known to destroy pvc water pipes and conduit.

There are 2 fixes for this- tougher wiring methods, MC Cable/emt/rmc etc- or an exterminator needs to be hired if this is, or could be, a problem.

I don't know if its true, but I have heard that rodents are part of the reason why some cities like Chicago and a few places on the east coast don't allow NM.
 
jmellc said:
How capable are rats & mice of chewing through copper cable? I know they can get into the walls and ceilings of a house or apartment. Looking at the possibility in an apartment.
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They definitely will chew off insulation, usually leave the remaining bare copper intact though.

I don't know that they ingest it, or very much of it, I do know they chew on things pack it in their cheeks and take to nesting spot and spit it back out to use for nesting material.

If you want to see how they do this get a hamster and put some paper in it's cage.
 
kwired said:
They definitely will chew off insulation, usually leave the remaining bare copper intact though.

I don't know that they ingest it, or very much of it, I do know they chew on things pack it in their cheeks and take to nesting spot and spit it back out to use for nesting material.
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^^^^^^^
Saw some K&T once where they did that. It was like they had literally picked the wire clean in spots!

The removed cloth/RW, along with whatever else they could scrounge up for a home, was found at varying spots at the bottom of the stud bays on the first floor.
 
Rodents need to chew because their front teeth never stop growing, so they are compelled to chew on hard things to keep them worn down. Usually that would be nut shells, bones, small grit in their grain seeds etc., but when they dine on our nicely prepared and soft leavings, they don't encounter that enough and have to find other things to chew on. They like wire because it is stiff on the inside, soft on the outside, kind of like roots. Once they do get to the copper they will usually keep chewing (if they don't get shocked or electrocuted), just not for the purpose of actually injesting it.
 
I would be good if they did chew through the copper. At least you know there is a problem, not just bare copper conductors waiting for something to move them so they short out. But I guess AFCI breakers will solve that problem...

-Hal
 
For some reason, the rodents don't seem to like UF like they do NM. I know it's probably happened, but I have never seen UF chewed through. It's run under mobile homes with no problems I am aware of. I did see NM chewed through under a mobile home that was installed by the owner.
 
About 20 years ago when I was working at a wastewater plant, the AC went down. We had the doors to the building open. I come back one hour, only to find my sample refrigerator and DI (deionized) water dead. I check the breaker, it's good. I pull the sample frig away from the wall, and there's a muskrat looking at me all squint eyed. No idea how long he'd been in the building, but in one hour he popped himself twice with 120V and took out 2 pieces of my lab equipment. Not having access to any electrical tools at the time (nor being an electrician), I took my leatherman tool, stripped back the wiring, twisted the strands back together, and taped it up with scotch tape until morning time.

I caught him with a fishing net and took him back outside.

I've seen squirrel damaged wiring too in attics, eaves, soffits. Mice got my coffee pot and fry daddy wiring a few years ago. They love wire, even when (or perhaps especially?) when it runs a billion dollar particle accelerator:

http://www.cnn.com/2016/04/29/tech/cern-weasel-irpt/index.html

and ofc most of us have seen or heard the results of a squirrel chewing on a pole xfmr primary...

eta: they are capable of chewing thru stranded wire anyway, guess it's thin enough and their teeth sharp and hard enough to bust those little wires. Never seen one eat 14ga or bigger, just the surrounding insulation. I've heard that electromagnetic fields attract rodents, hence their like for energized wiring, but cant confirm it.
 
JFletcher said:
and ofc most of us have seen or heard the results of a squirrel chewing on a pole xfmr primary...
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POW! ... and fried squirrel shrapnel all over the place. It happened near my house in '85 or so.
 
Fortunately, this turned out to be another issue. Kitchen receptacles were fed from an unlikely other receptacle I found when I returned. It had gone bad.
 
Several times a summer squirrels seem to like to chew on the primary taps of a nearby transformer on a utility pole near my house. 11K volts and he's welded to the terminal.:happyyes:
 
I was rewiring a remodel finding extensive mice damage -- the owner did not want to replace all of the wiring -- I found Mickey in the ceiling frozen in time as he made it through a live nm cable - with the owner present I tapped dead Mickey with a stick causing sparks to fly -- owner changed his mind immediately
 
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