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Discussion Starter · #1 ·
With glowing connections being (IMO) the greatest fire hazard, above and beyond any arcs, this is a good case for using metal boxes and AC or MC cable..
Or at least just metal JB's.
A glowing connection will melt through the loose wirenut and short on the metal box, thus kicking the breaker.
With a plastic box it will keep burning:

 

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This video makes a good case to make your connections solid.

That is more to the tune of it, not the box material. Knock it off with the loose wiring connections. (toss those yellow wire nuts in the trash where they belong.....) Tan Twisters and strong fingers solve most problems but overstuffing wire nuts with conductors is asking for trouble.

I remember explaining ''bridge splices'' on one of the electrical forums several years ago and you would not believe the resistance of some of the other posters to such a simple problem as too many wires in a single splice. Just use the same size wire to split one big splice into two smaller count splices and keep the conductor counts below the not to exceed limits on the package.
 

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I have indeed seen connections burnt up like this.

In the video, I suspect that the overcurrent protection (breaker/fuse) has been upsize to permit the flow of excessive current.

But your point has been made, and I agree, non-combustible enclosures for electrical connection.....especially where twisting/spicing the copper wire and wire nuts (Marrettes) are not tight enough.
 

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I cut a bridge splice once, in a neutral, we thought all the power was off but missed two pass through at the bottom of three extension rings. I swear every light on the floor started strobing

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I have indeed seen connections burnt up like this.

In the video, I suspect that the overcurrent protection (breaker/fuse) has been upsize to permit the flow of excessive current.

But your point has been made, and I agree, non-combustible enclosures for electrical connection.....especially where twisting/spicing the copper wire and wire nuts (Marrettes) are not tight enough.
It does not require improperly sized OCP for a high resistance connection to overheat.

You cannot protect John Q Public from HACK ELECTRIC WORK. BE a professional.



If metal boxes really made a difference it would be code after all isn't the NEC all for safe installations:laughing::laughing::laughing::laughing:. Oh wait a better solution was AFCI
 

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With glowing connections being (IMO) the greatest fire hazard, above and beyond any arcs, this is a good case for using metal boxes and AC or MC cable..
Or at least just metal JB's.
A glowing connection will melt through the loose wirenut and short on the metal box, thus kicking the breaker.
With a plastic box it will keep burning:

https://www.youtube.com/watch?v=_2HyTRxzwXs
Why stop there and get rid of Romex and use MC for residential?
 

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The reality is unless you used industrial covers, all boxes metal or plastic have a plastic cover over the device.

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Discussion Starter · #13 ·
But, in a different scenario, a plastic box wont cause a short and create a fire to begin with.
In this video, the cause of the fire was not a short.
A dead short will [hopefully] trip the breaker
In this case it was a high-resistance "glowing" connection.
 

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In this video, the cause of the fire was not a short.
A dead short will [hopefully] trip the breaker
In this case it was a high-resistance "glowing" connection.
That's why I said "in another scenario".

A short to a grounded metal box wouldn't necessarily trip the breaker. It could just make enough contact to, well...., start a fire.

Metal boxes + NM = evil.
 

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Discussion Starter · #15 ·
That's why I said "in another scenario".

A short to a grounded metal box wouldn't necessarily trip the breaker. It could just make enough contact to, well...., start a fire.

Metal boxes + NM = evil.
How would a near-zero resistance connection made between an ungrounded conductor and a grounded box (aka a short) not trip a properly working breaker?
A high-resistance, poorly made connection will glow and burn, while more or less safely contained within a metal JB, and once the wirenut's sheath burns off, the metal spring inside will eventually oxidize and the will glowing stop. Or, if the connection was was pressing against the wall of the JB, hopefully it will short and trip the breaker (Well, AFCI's ground fault detection would help here too).
What other scenario is there?
 

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A short to a grounded metal box wouldn't necessarily trip the breaker. It could just make enough contact to, well...., start a fire.
That sounds like it should be true.

Also, it is true, I have seen it happen.

Ran for the breaker (40 dp ge), ran back and smothered before fire got beyond sawdust
 

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Even if you had a metal box, with a metal cover... the box itself would heat past 451F ... so the materials around it would ignite i would think.

As others have said ... make a proper connection to begin with .. problem solved.
 
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im sure some of you have seen ceramic wirenuts. that would keep the plastic from starting the fire!:rolleyes:
 
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