# Plastic versus Metal Junction Box



## artinall (Aug 14, 2007)

John Valdes said:


> I take a very simple approach to this.
> 
> 
> If you are using metal conduit or metal cable, metal boxes are the way to go.
> ...


 Since is nm will go plastic or bakelite/equivalent.


----------



## John Valdes (Apr 14, 2010)

artinall said:


> 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.


----------



## artinall (Aug 14, 2007)

480sparky said:


> 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?


----------



## rrk (Apr 22, 2012)

artinall said:


> 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


----------



## avenge (Sep 25, 2008)

So who's house is going to burn down yours or your client's?


----------



## 480sparky (Feb 1, 2009)

artinall said:


> 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.


----------



## artinall (Aug 14, 2007)

480sparky said:


> "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?


----------



## artinall (Aug 14, 2007)

avenge said:


> 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.


----------



## 480sparky (Feb 1, 2009)

artinall said:


> 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.


----------



## artinall (Aug 14, 2007)

480sparky said:


> 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?


----------



## Tinstaafl (Jan 6, 2008)

artinall said:


> 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.


----------

