What causes these burn marks?


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Old 02-29-16, 05:43 PM
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What causes these burn marks?

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I have 2 wires that have marks from the wires getting hot?
These are not the marks made by pulling the cable, as I have seen that in other places, and this occurred along 10 feet towards the outlets and not near the breakers.

I did have one breaker that suspicious. Is it normal for you to see part red on a Square-D breaker? (see photo). Did I have bad breakers?

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I replaced that breaker and have cut the power to the lines with burn marks.

The yellow line goes to 1 outlet. The white line goes to an outlet, then switch to a light above it. I checked the outlet on the 12 gauge line and all connections were tight and looked normal.

Extra info:The yellow line tripped the breaker when installed. It was grounded by accident and immediately tripped, the short by the plug was fixed and the plug worked with various appliances for a week or two. I am quite sure the burn marks were not present then, but figured I should mention all details.

I checked connections in the panel, all grounds, neutrals and hot lines were tight. Since 2 lines did this, did it happen through the panel??

Could there be a staple to tight, very likely. Not going to do that again! What is your recommendation for installing staples.


Thank you for all suggestions and tips!


 
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Old 02-29-16, 06:03 PM
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Can you give us a closeup of the marks? The cable would have to get really hot to cause a burn mark.
 
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Old 02-29-16, 06:14 PM
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Photos

1. Yellow Wire
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2. Wire to the light.
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I think this one is a wear mark, from moving the cable around the staple.




3. More Marks:
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4.
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5. Close up
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Old 02-29-16, 06:32 PM
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I can guarantee that they are not burn marks. If you scrape the jacket lightly with a knife edge you will find it comes off. I have seen it many times.

I think your staples are fine, but I personally like the plastic GB brand staples. The staple should be driven to secure the cable.

Yes, it is normal to see red from an angle on QO breakers.
 
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Old 02-29-16, 07:04 PM
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I too am sure those are not burn marks. Looks like asphalt or tar. Probably got there by rubbing against old wire or asphalt shingle? Roofing tar?
 
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Old 03-01-16, 07:36 AM
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Those are scuff marks from installation of the cable. They were probably pulled against an old tar impregnated cable or through a hole where a tar impregnated cable had been run in the past. The small brown marks just occur when you pull the romex through bored holes in the wood. Given that you have T&G subfloor, I'm assuming this is an old house with various generations of wiring.

This type of old cable leaves black streaks on everything it touches. It is coated in tar and silver flaky stuff:
 
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Old 03-02-16, 07:18 PM
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Thank you for clearing it up!
 
 

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