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-   -   Evaluating a kinked cable (http://www.diychatroom.com/f18/evaluating-kinked-cable-70735/)

dave11 05-07-2010 01:35 PM

Evaluating a kinked cable
 
I took a close look for the first time at a cable running through the joists in my basement, which runs from the main to a garage subpanel. It's a 6/3 NM cable, length about forty feet. It's secure up in the joists, but I noticed one area that looks like it had been pretty badly kinked, then straightened. I assume it happened either before or during installation, because the cable doesn't have enough slack or play to have kinked after the install.

It's the only area like that. My question is what, if anything, to do about it. The cable sheath is intact, but the wire bundle underneath has a ridge in it that can be seen and felt.

The breaker on the main for this cable is 50 amp. Now, I never come close to that amperage in the garage. I have a large compressor, but wired for 240 it draws I think 18 amps. The lights when all on draw 3 amps. The receptacles can carry 20 amp, but they're not in use most of the time. The prior owner had a welder, which must have needed the extra amperage.

Given that my expected ampacity in the garage is way below the cables rating, am I being goofy by wondering about the kink in the cable?

And would simply touching the cable at the kinked area, after its under full load for say an hour, be a decent way to test if there's a problem? Obviously, if it warmer there, then there's a problem, but if it's the same temp, is there no problem?

I suppose the alternative is to cut out the kink and splice the ends, but I don't want to if it's not necessary.

Thanks for any input.

Scuba_Dave 05-07-2010 02:07 PM

Can you post a pic ?

codeone 05-07-2010 02:16 PM

The only real way to evaluate the cable, if there are no obivious cuts or breaks, is to get someone with a megger (meg ohm meter) and do an insulation and resistance test on the cable.

dave11 05-07-2010 03:26 PM

I can try getting a decent pic, but the cable is solid black, and against the dark wood background, I think all you'll be able to see is a bump in the edge of the cable. I didn't get concerned about it till I ran my hand over it, and felt the ridge in the wire bundle.

It sounds though like maybe I'm not being obsessive and paranoid about this?

Yoyizit 05-07-2010 03:30 PM

If copper wire work-hardens then repeated small-radius bending at this location will cause a break sooner than in cable areas that have not been kinked.
http://en.wikipedia.org/wiki/Work_hardening

J. V. 05-09-2010 10:20 AM

Straight is always better. But NM cable while being installed does kink. The installer should have corrected this during the initial run (installation). You should have no concern as its on the correct size breaker.


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