Sunday afternoon Call,,,,,Chicago Guys will love this one..

LEO2854

Esteemed Member
Location
Ma
Client calls;

"My TV Buzzed out it was loud!, Then I heard a crackling sound and more Buzzing on the other side of the room next to the sliding door to the back porch, there is a switch-box there and the wall is burning hot with a melted plastic smell.....

Okay, go to your basement and shut off the main breaker and I'll be there in an hour.

So I look at the switch box, it looks fine and the wall is cool now, no smoke marks around the box are showing so I open it up to have a look it stunk of electrical burning,but nothing is showing in the box itself, but there is no power there either( I turned on all the breakers when I got there),,,Hmmm:blink: Okay so I open the receptacle below in, nothing showing there either, this box had 2 14/3's feed through red leg switched,that still had power from the red leg, but that's coming from a 4 way switch near the front door. So I open some of the other receptacles just to make sure they're ok, then I open the panel (ITE) everything checks out.

So there is only one thing left to do,,,,That's Right Cut open the wall around the switch, the last thing I want to do because now the grand total will jump big on the client, so I told him there really is no choice and your insurance will cover it, I started out with a 4" hole saw and sure enough the paper on the insulation was black from flames, so out to the truck for the sawzall, let the fun begin...:laughing:

Here is the inside of the switch-box..



This is the inside of the wall....:eek:



As you can see on this one is that if the outside-wall was not so tight it would have had more oxygen and this four family condo would have gone up in flames, but I suspect that there was not enough oxygen to feed it so some of the paper burnt itself out.



All the wiring was good here, the problem was the siders were using long nails in their nail gun about 15 years ago when this place was built, these outside-walls are 2x6 construction so you would think that there would be enough room for the wires,,,,Nope...

 

LEO2854

Esteemed Member
Location
Ma
This is the top of the switch-box...



So I pulled that off of the stud because the problem was behind the box, as I was doing so I got more sparks but the breaker held, so they are probably "NO-BLOW-BREAKERS":lol:




These two are in love....:D



Gotta love those nail guns...:eek::lol:

 
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I'm not sure todays MC cable would stop those nails, however EMT would laugh at those nails:lol:
Oh, I hear you, I just meant that with MC a nail would be likely to make the hot short out to the armor and kick the breaker, or if hit off-center, maybe to move the cable aside.
NM stands no chance there in either one of those two scenarios..
 

LEO2854

Esteemed Member
Location
Ma
Oh, I hear you, I just meant that with MC a nail would be likely to make the hot short out to the armor, or if hit off-center, maybe to move the cable aside.
NM stands no chance there in either one of those two scenarios..

The one thing the original electrician did wrong was he drove those staples home and right where the nail went through the wire there were staples snug as can be.

I'll bet the older MC cable that was heavy until the 1990's would have been fine.
 

LEO2854

Esteemed Member
Location
Ma
Wow, that is a incredible find. Makes me wonder how many "electrical fires" are caused by others vs. install error.

That's just it,,,,,:blink: They always say faulty wiring, but the electrician did not do that, it was whoever was doing the siding or the framing for the sliding door that is 3" to the left....
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
If AFCI were required at that time, the failure wouldn't have gotten that far.
Often times damage like this acts like a poor or glowing connection, and that is something an AFCI cannot directly detect. It probably would have tripped based on its ground fault protective circuit, but not all of the new AFCIs have a GFP circuit. In my opinion the GFP is, by far, the most important part of the AFCI, but it is not required by the standards and at least one manufacturer no longer has GFP in their AFCIs.
 

kwired

Electron manager
Location
NE Nebraska
If AFCI were required at that time, the failure wouldn't have gotten that far.
Maybe so, But this ITE breaker did not even trip when I was pulling the box out causing it to spark up again.:eek:
don already covered most of what I was going to say.

Just for curiosity I would have liked to install an AFCI on that circuit just to see what it would do, as well as a try a GFCI, because chances are there was enough leakage to ground at some point that a GFCI would have tripped.
 

LEO2854

Esteemed Member
Location
Ma
don already covered most of what I was going to say.

Just for curiosity I would have liked to install an AFCI on that circuit just to see what it would do, as well as a try a GFCI, because chances are there was enough leakage to ground at some point that a GFCI would have tripped.
That would have been fun to mess with but I don't think the HO would like it...:lol:

I bet the GFCI would have tripped.

One of the cables the conductors were melted bare and looked very close together.
 

LEO2854

Esteemed Member
Location
Ma
Even with 2x6 framing, I probably wouldn't have run NM behind the outlet box. Did it have it's required depth from the edge of the framing?

Yes the wires were close to the center of the stud, we only need 3/4" here


2014 mass code

334.17. Revise to read as follows:
334.17 Through or Parallel to Framing Members and Furring Strips. Types NM, NMC, or NMS cable shall comply with 300.4 where installed through studs, joists, rafters, and similar members. Grommets or bushings shall be used in metal studs as required in 300.4(B)(1), shall remain in place during the wall finishing process, shall cover the complete opening, and shall be listed for the purpose of cable protection.
In both exposed and concealed locations, where the cable is installed parallel to framing members, such as joists, rafters, or studs, or is installed parallel to furring strips, the cable shall be secured so that the nearest outside surface of the cable is not less than 19 mm (3/4 in.) from the nearest edge of the framing member or furring strip where nails or screws are likely to penetrate. Where this distance cannot be maintained, the cable shall be protected from penetration by nails or screws by a steel plate, sleeve, or equivalent at least 1.6 mm (1/16 in.) thick. A listed and marked steel plate less than 1.6 mm (1/16 in.) thick that provides equal or better protection against nail or screw penetration shall be permitted for this purpose.
 

junkhound

Senior Member
Location
Renton, WA
I'm not sure todays MC cable would stop those nails, however EMT would laugh at those nails:lol:
Those look like 8d air gun driven nails. Apparently the wiring was done before the sheathing put on?

An 8d like that goes thru EMT easily --- have used scraps of 1/2" emt for temporary bracing, nail guns will tack up emt right nice.
Now, sched 40 would 'laugh at' the nails.
 

mgookin

Senior Member
Location
Fort Myers, FL
The insurance company would rather pay for the electrician to open the wall than have the fire dept ventilate through the roof!

I see two different size nails in the pictures. I see siding nails and I see framing nails. Even the siding nails are longer than necessary (1/2" through the backside is sufficient). I'm guessing there's something out on the other side of the wall that the carpenter was attempting to connect to that stud with framing nails. Is there something out there?
 
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