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Plastic Versus Metal Junction Box

 
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Old 10-03-2018, 07:13 AM   #21
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Re: Plastic Versus Metal Junction Box


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Originally Posted by John Valdes View Post
I take a very simple approach to this.


If you are using metal conduit or metal cable, metal boxes are the way to go.
I have seen some plastic boxes with KO's in them, but its far from an everyday item.


Romex/NM/UG - I use plastic.
Since is nm will go plastic or bakelite/equivalent.
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Old 10-03-2018, 11:43 AM   #22
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Re: Plastic Versus Metal Junction Box


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Since is nm will go plastic or bakelite/equivalent.
Good. Not saying you cannot use a metal box, but plastic is less money and you will not need a connector.
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Old 10-05-2018, 03:14 PM   #23
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Re: Plastic Versus Metal Junction Box


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Originally Posted by 480sparky View Post
You need three things to start a fire.
1. Fuel
2. Oxygen
3. Source of ignition
By agent, I meant fuel. The other two are a given. Oxygen exists in the structural atmosphere and ignition was described as live exposed electric.

In many cases, you may not be able to tell the makeup of certain materials, like aged insulation. Though I have heard "if it has fiber. technically it can burn". So are there "norms" to consider for possible fuel?

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Old 10-05-2018, 04:22 PM   #24
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Re: Plastic Versus Metal Junction Box


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By agent, I meant fuel. The other two are a given. Oxygen exists in the structural atmosphere and ignition was described as live exposed electric.

In many cases, you may not be able to tell the makeup of certain materials, like aged insulation. Though I have heard "if it has fiber. technically it can burn". So are there "norms" to consider for possible fuel?
live exposed electric is not ignition if so every bare conductor would be ablaze, ignition would be when that live conductor gets grounded or shorted to neutral. At that point the circuit breaker should trip.
Even the screws on outlets are exposed.

There are live exposed conductors in your main panel and that is not on fire
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Old 10-05-2018, 05:29 PM   #25
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Re: Plastic Versus Metal Junction Box


So who's house is going to burn down yours or your client's?
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Old 10-05-2018, 06:03 PM   #26
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Re: Plastic Versus Metal Junction Box


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Originally Posted by artinall View Post
By agent, I meant fuel. The other two are a given. Oxygen exists in the structural atmosphere and ignition was described as live exposed electric.

In many cases, you may not be able to tell the makeup of certain materials, like aged insulation. Though I have heard "if it has fiber. technically it can burn". So are there "norms" to consider for possible fuel?

"Live exposed electric" is NOT a source of ignition. If it were, every switch and outlet in your house would burst into flame due to the 'live exposed electric' terminals attached to the drives. Your panel would do the same, since the 'live electric terminals' are present.

What IS a source of ignition is an arc caused by the flow of current across a gap.
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Old 10-05-2018, 06:43 PM   #27
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Re: Plastic Versus Metal Junction Box


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Originally Posted by 480sparky View Post
"Live exposed electric" is NOT a source of ignition. If it were, every switch and outlet in your house would burst into flame due to the 'live exposed electric' terminals attached to the drives. Your panel would do the same, since the 'live electric terminals' are present.

What IS a source of ignition is an arc caused by the flow of current across a gap.
Alright, I misspoke...

So what specific type of thing/factor might cause a flow of current across a gap?

Last edited by artinall; 10-05-2018 at 06:58 PM.
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Old 10-05-2018, 06:50 PM   #28
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Re: Plastic Versus Metal Junction Box


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So who's house is going to burn down yours or your client's?
Neither, it was done right. Connections were placed in a sealed box with 3/8 romex connectors and grounded. Wire nuts taped shut. Not a chance of anything happening.

At this point, I'm trying to finish answering this practical question in my mind...

But thanks for your concern.
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Old 10-05-2018, 07:04 PM   #29
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Re: Plastic Versus Metal Junction Box


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Alright, I misspoke...

So what specific type of thing/factor might cause a flow of current across a gap?
Current has to flow to something that is at a voltage potential different from the voltage present.
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Old 10-05-2018, 07:16 PM   #30
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Re: Plastic Versus Metal Junction Box


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Current has to flow to something that is at a voltage potential different from the voltage present.
You say it has to flow to, but is it caused by the difference in voltage potentials in and of itself? What catalyzes the act of transference?

Last edited by artinall; 10-05-2018 at 07:20 PM.
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Old 10-05-2018, 08:06 PM   #31
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Re: Plastic Versus Metal Junction Box


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You say it has to flow to, but is it caused by the difference in voltage potentials in and of itself?
Of course. If there was no difference, no current would flow.

The potential for fire happens when current flows through a resistance. That causes heat. The resistance of a properly wire-nutted connection is negligible, so it would take an enormous amount of current to produce significant heat.

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