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overheated conductor


John Dirks Jr
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Take a look at this wire. Does the discoloration look like evidence of overheating? It felt kind of brittle in that area. It's a 10/3 serving a 30amp clothes dryer circuit. It's fed from a FP Stab-Lock nonetheless.

There were 3 spots on this wire that looked like this. All were within 18 to 24 inches of each other.

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Originally posted by SonOfSwamp

Originally posted by John Dirks Jr

Anyone got a PDF about FP Stab-Locks? I want to host it at my site and link it in my reports.

I missed the solid conductor wiring. Sparkys comming out anyway. Is it the second 240 from the top right where you see the solid AL? I'm pretty sure the rest of the solid was copper.

I suggest that you Google up an appropriate document. Shouldn't take more than 10 minutes. Include the word, "Hansen."

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And/or Friedman.

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Originally posted by Brian G

The excellent article by Douglas Hansen, in pdf.

http://www.codecheck.com/cc/pdf/electri ... ov2003.pdf

Dan Friedman's FPE webpage

http://www.inspect-ny.com/fpe/fpepanel.htm

Brian G.

Load Them Bullets & Fire At Will [:-thumbu]

I searched before you posted these Brian. This one that you posted >> http://www.inspect-ny.com/fpe/fpepanel.htm is the one I used.

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Originally posted by Neal Lewis

Originally posted by John Dirks Jr

Is it the second 240 from the top right where you see the solid AL? I'm pretty sure the rest of the solid was copper.

The wiring for that breaker is old tinned copper with the cloth insulation. I don't see the AL wiring.

Agreed,

Blow it waaaay up and you'll be able to clearly see that it's old rubber and cloth-wrapped tin-coated copper.

ONE TEAM - ONE FIGHT!!!

Mike

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Originally posted by John Dirks Jr

Take a look at this wire. Does the discoloration look like evidence of overheating? It felt kind of brittle in that area. It's a 10/3 serving a 30amp clothes dryer circuit. It's fed from a FP Stab-Lock nonetheless.

There were 3 spots on this wire that looked like this. All were within 18 to 24 inches of each other.

Those are some very interesting burn marks. I'm puzzled by them because I haven't been able to reproduce them.

My first thought was like Mark's. I figured that it was a plumber's errant torch. But when I took a propane torch to a section of NM cable, the sheathing first got really shiny and soft then, almost instantly, started to burn & blister. Your cables don't show any sign of the shininess or blistering.

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Then I thought, like Eric & Brian, that someone put something hot on the cables. So I heated up a piece of metal and touched it to the cable. The sheathing turned to taffy but it didn't really discolor.

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Then I thought, "Maybe it's radiant heat." So I laid a piece of romex across the top of my old-fashioned toaster. The heat rising from the slots made the sheathing drippy. Then I pre-heated the toaster and then put the cable across. This gave me something like the burn pattern in your pictures, but the sheathing all around the burns was shiny.

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Then I wondered what would happen if the wires inside got really hot. Not wanting to run that much current through them, I just stripped off the insulation from one end and held the wires over the gas range burner. The wires got cherry red and the insulation smoked like crazy and began to distort, but it never caused a burn pattern or any significant discoloration on the sheathing.

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My last thought is that someone might have placed a halogen work light over the cables. My work lights are all burnt out so I can't try them, but I suspect that they'll create the same shiny texture that the toaster did.

Of course, the romex that I'm working with is newer than yours and a different brand. Perhaps the outer sheathing behaves differently on your sample.

- Jim Katen, Oregon

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I came across similar discoloration today. It was on 10/3 non-metallic feeding the AC outside unit. The cable was attached to the basement wall with rubber lined clamps. The sheathing around every clamp was looked like it was burned.

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I removed one and found the discoloration was actually lighter where the rubber had been in direct contact with the sheathing.

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Could the rubber be out-gassing something that is interacting with the sheathing? I've always figured sheathing is pretty inert stuff.

This raises more questions than answers.

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Originally posted by Inspectorjoe

. . . Could the rubber be out-gassing something that is interacting with the sheathing? I've always figured sheathing is pretty inert stuff. . .

Wow. That sure looks to be the case. Either that or some kind of chemical reaction between the rubber and the white sheathing.

- Jim Katen, Oregon

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