FIRE
So im repairing ¾ of the homeruns in this apartment where a fire happened. I found the problem ( short answer is someone replaced a double pole 20 amp breaker with a 30 amp one plus some more but that can be it's own topic. ) the wire that started the fire has me scratching my head on why the wire looks the way it does. The third picture shows the wire that went across the attic and where the nm cable looks good is where it turned down the wall and went the box. The second picture is the other side of that wire and once more going down the wall it is good. I think it is insulation around the wire cooked it but that dont hold true as we're the wire went down to the switch ( the third picture) it was not cooked. My question is why didn't the in the walls get cooked as well and not just the run across the attic space. The other homeruns that got cooked near the fire spot was only damaged at that spot. Any thoughts on this would be nice, it is stuff like this that is never teached so if I can use this as a training moment im going to.
Greetings Rob. Thanks for sharing the images and your experience. In many cases the reason cables aren't damaged down the wall is lack of adequate oxygen to fuel the fire and simple isolation. In these cases it's hard to pin down causes but attics will always have higher potential of issue.
In attics, the risk of cable damage is much higher but also in many cases ambient heat is higher and that ambient heat becomes cumulative on an already damaged or overloaded cable. Fact is overloading and under protection by an adequate OCPD can indeed cause thermal breakdown.
As someone who has investigated these things before it's very hard to "diagnose" without being there and "Touching" it so I won't be able to speculate beyond that sadly.
I have actually seen a very similar example in a converted "Grow House" where cables in an attic were bundled and buried in the insulation. Heat couldn't dissipate and ultimately melted down the cable and of course the rest was history. So, maybe not your case but it can happen.
Paul Abernathy Thanks for the knowledge paul!
Yikes! Could have been much worse, I imagine! Thanks for sharing and explaining, Rob! Keep up the good work out there!