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Old 07-04-2012, 01:11 AM   #1
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So, our house just suffered an electrical fire...


...and now we're putting all the pieces of the puzzle together, working backwards to determine a root cause. This is a pretty good example of what you should never work on electrical by yourself without knowing exactly what you're doing. I could use some help in identifying some issues from the pros here.









Met with the Fire Inspector today, who was extremely knowledgable. He focused on one junction in particular with at least two circuits feeding through it and some serious code violations. I know that nothing learned here will have bearing on the report he submits to the insurance company. However, I'd like to know if there are major code violations here or if I'm just overreacting as a result of the accident. Take a look:









In the junction box, I noted that there's no cover. Cellulose insulation is a factor, as the box was completely covered over, and insulation has worked it way down into the box. Box fill limits appear to have been exceeded. Connections appear to be made questionably, but can't say for sure without touching.

A 220v 600v romex line exits the junction, but I can't identify a 220v line entering. Is it possible they took a two 110v lines from different legs, joined the neutrals, and hacked it together?

Three separately insulated black 12g lines exit the box (the ones that are twisted), piled up in a rats next on top of the drywall, then proceed down into the fiberglass and cellulose to somewhere we can't identify without digging in. Fire investigator has never seen this before. Obviously not K&T, as this house is 30-40 years too modern and this conversion is probably 20 years newer than that. What could this be?

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Last edited by Thadius856; 07-04-2012 at 01:33 AM.
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Old 07-04-2012, 04:01 AM   #2
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So, our house just suffered an electrical fire...


Bad connection. That is why you cannot cover junction boxes over.

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Old 07-04-2012, 07:00 AM   #3
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So, our house just suffered an electrical fire...


Boy are you lucky, especially being right there at that framed hole!! Were you home at the time? Did the fire go out by itself?

Last edited by zappa; 07-04-2012 at 07:25 AM.
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Old 07-04-2012, 07:11 AM   #4
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So, our house just suffered an electrical fire...


Whenever I see tape on wirenuts, You know something is amiss...
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Old 07-04-2012, 07:17 AM   #5
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So, our house just suffered an electrical fire...


Quote:
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Whenever I see tape on wirenuts, You know something is amiss...
And that's just the start of that mess.

This is kind a rare occurrence, but it does happen often enough. Especially considering how many messes like that I encounter...and that's just lil' old me.
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Old 07-04-2012, 07:17 AM   #6
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So, our house just suffered an electrical fire...


If there were two separate 120 circuits entering a metal box at different knockouts and the two hots were used as a 240 circuit, there would be inductive heating of the box.

There is no limit as to how hot it can get, inductive furnaces melt iron using this principal.

The insulation makes this scenario even worse; the heat has nowhere to go.

Could be the cause, maybe not.

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Old 07-04-2012, 07:20 AM   #7
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So, our house just suffered an electrical fire...


To me, it doesn't look like the JBox was the cause. I'm not a fire investigator, but I would expect the wires in the box to be much more damaged if the fire started there. If I were to guess by looking at the pictures, I would say that the fire started somewhere under that access hole. Maybe the wire was damaged there when stapling or rodents chewing, then the wire arced and lit the insulation. Again, the same could be said about the J-Box, but I wouldn't expect the wood under the JBox to look as bad as it does and the wire look as good as it does.
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Old 07-04-2012, 07:24 AM   #8
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So, our house just suffered an electrical fire...


Quote:
if there were two separate 120 circuits entering a metal box at different knockouts and the two hots were used as a 240 circuit, there would be inductive heating of the box.
huh??
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Old 07-04-2012, 07:37 AM   #9
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So, our house just suffered an electrical fire...


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To me, it doesn't look like the JBox was the cause. I'm not a fire investigator, but I would expect the wires in the box to be much more damaged if the fire started there. If I were to guess by looking at the pictures, I would say that the fire started somewhere under that access hole. Maybe the wire was damaged there when stapling or rodents chewing, then the wire arced and lit the insulation. Again, the same could be said about the J-Box, but I wouldn't expect the wood under the JBox to look as bad as it does and the wire look as good as it does.
I tend to agree with this but would like to see a picture of the inside of the jbox. The visible connections are not the cause as they not even burnt up.

There is no problem with a junction box being buried in insulation but it must have cover like all junction boxes.
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Old 07-04-2012, 07:48 AM   #10
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So, our house just suffered an electrical fire...


Does that J-box appear to be missing clamps? My guess would be slowly expanding/contracting wires that eventually wore out the insulation on the wire by rubbing against the sharp edges of a clampless entry into the box.
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Old 07-04-2012, 08:06 AM   #11
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So, our house just suffered an electrical fire...


No maybe not, the wires would be burned bare. The area immediately surrounding the box looks like the point of origin for the fire though.
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Old 07-04-2012, 08:28 AM   #12
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So, our house just suffered an electrical fire...


I do have an above shot, but it's taken with an iPhone which makes uploading it without a PC difficult. Regardless, the wire nuts are not melted.

Investigator didn't find signs of arcing, but finds the three twisted separately insulated 12g wires suspicious. They are bare where they enter/exit the box. He used the term pyratic... something (sorry). Also looks like its not the first time the beam has been burnt!

If the insurance company accepts his preliminary, the story ends here, we engineer a new beam solution, and start repairs. If they think they can recover from somebody (previous owner, inspector, electrician, manufacturer?) then they'll bring in an electrical engineer to check it out a bit more.

Yes, I was home (used a day off). Around 2am. I smelled it, then found the paint blistering off the ceiling. We even did most of the extinguishing. Nobody hurt, thankfully.
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Old 07-04-2012, 08:33 AM   #13
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So, our house just suffered an electrical fire...


Where the joist has been burned away is where the highest heat/longest burning was but that may not be the exact point of origin. With so much damage it's hard to tell what started the fire. But you can eliminate areas by looking for intact insulation on the wires.

One code violation I see is 2x4 joists and rafters. If they skimped there, there's no telling where else they skimped.

Is your panel fuses or breakers? If they are fuses, you don't by any chance have one of those fuse panels with all 30A fuses in it, do you?
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Old 07-04-2012, 08:44 AM   #14
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So, our house just suffered an electrical fire...


Beakers on 100A service, mostly 20A and a few 15A. No AFCIs or GFCIs in the panel. None of them tripped.
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Old 07-04-2012, 09:15 AM   #15
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So, our house just suffered an electrical fire...


Quote:
Originally Posted by stickboy1375 View Post
Whenever I see tape on wirenuts, You know something is amiss...
Why is that?

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