# Metalic wiring system in plastic box



## RIVETER (Sep 26, 2009)

*Metal system...plastic boxes*

To my way of thinking, if you have a continuous mechanical ground, properly connected throughout the system, you are probably safe...But I don't think it is legal. I don't believe that you can EXTEND an existing circuit with other than the original type of system. Eg. conduit changing over to NM. I don't know all the reasons but it probably has to do with the conductibility of the conduit verses the mechanical ground of the NM.


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## TOOL_5150 (Aug 27, 2007)

I believe those carlon boxes are intended to be used with their "carflex" - smurftube - fnmc.

~Matt


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## wildleg (Apr 12, 2009)

RIVETER said:


> To my way of thinking, if you have a continuous mechanical ground, properly connected throughout the system, you are probably safe...But I don't think it is legal. I don't believe that you can EXTEND an existing circuit with other than the original type of system. Eg. conduit changing over to NM. I don't know all the reasons but it probably has to do with the conductibility of the conduit verses the mechanical ground of the NM.


nothing personal dude, but this is gibberish. where does it say this in the NEC ? as long as you comply with the given article for the given wiring method, and you comply with the associated articles for 250 bonding, whatever chapter/articles that apply to what you are doing, don't violate the listings for the associated equipment/enclosures/etc, there is no violation in terminating multiple wiring methods in a common enclosure.


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## Mr. Sparkle (Jan 27, 2009)

Yeah, you mean to tell me you have never transitioned from....lets say EMT to MC? :confused1:


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## ECB (Nov 25, 2009)

RIVETER said:


> I don't believe that you can EXTEND an existing circuit with other than the original type of system.


Well of course this is wrong. But I've heard electrician's tell this to customers to sell more expensive remodels, etc. As a result of this sales trick, this has become urban legend.


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## TOOL_5150 (Aug 27, 2007)

Mr. Sparkle said:


> Yeah, you mean to tell me you have never transitioned from....lets say EMT to MC? :confused1:


I honestly do not get your point. I personally would do that transition with a Jbox, but thats just me. EMT can be used as a GEC, so the sheath of the MC isnt isolated, its grounded by the EMT. Just as long as your green in the MC is hooked to the GEC as well, I dont see an issue with it.

~Matt


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## crazymurph (Aug 19, 2009)

IMO, plastic boxes are for NM and smurftube. If you are using any metalic raceway or fitting you need a metal box.


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## JohnJ0906 (Jan 22, 2007)

Take a look at 314.3, and the 2 exceptions.

IMO, exception 1 would allow the use of MC or EMT, as long as bonding bushings were installed.


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## Speedy Petey (Jan 10, 2007)

JohnJ0906 said:


> Take a look at 314.3, and the 2 exceptions.
> 
> IMO, exception 1 would allow the use of MC or EMT, as long as bonding bushings were installed.


Completely agree. It IS legal if all conditions are met. 

Question though....WHY in the world would you?????


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## Speedy Petey (Jan 10, 2007)

RIVETER said:


> I don't believe that you can EXTEND an existing circuit with other than the original type of system.





ECB said:


> Well of course this is wrong. But I've heard electrician's tell this to customers to sell more expensive remodels, etc. As a result of this sales trick, this has become urban legend.


Funny, I have never ever heard anyone say or suggest this. 
Must be a regional legend. :laughing:

Of course, this statement is completely false.


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## Bob Badger (Apr 19, 2009)

JohnJ0906 said:


> Take a look at 314.3, and the 2 exceptions.
> 
> IMO, exception 1 would allow the use of MC or EMT, as long as bonding bushings were installed.





Speedy Petey said:


> Completely agree. It IS legal if all conditions are met.


Until very recently I would have agreed with both of you. Recently I saw some documents that seemed to say that the box would have to be designed with the bonding means included, a field installed bonding bushing would be a violation. (Even though I am sure it would work fine).

I am trying to find the post with the info and will post it here if I can find it.


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## Speedy Petey (Jan 10, 2007)

Wasn't there something to the effect that if a bonding means was present on the box it must be used?


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## Bob Badger (Apr 19, 2009)

Speedy Petey said:


> Wasn't there something to the effect that if a bonding means was present on the box it must be used?



No, it was more like the bonding means had to be provided by the box manufacturer.

The only enclosure I can remember seeing something like that is on "System Sensor" Duct smokes, they place a piece of metal in front of the plastic KOs so metal raceway bonding is maintained and gives a place to put a EGC onto this metal.


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## Speedy Petey (Jan 10, 2007)

Many of the PVC FS type boxes I use have this. The have a bonding lug off a brass ferrule where the device mounts.


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## JohnJ0906 (Jan 22, 2007)

314.3, exception 1 "Where internal means are provided between all entries, nonmetallic boxes shall be permitted to be used with metal raceways or metal-armored cables"

This doesn't specify how the means are provided, or who provides them. 

Now if the box or box instructions state that it is to be used with non-metallic cable or raceways, then IMO it would be a violation.


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## Bob Badger (Apr 19, 2009)

JohnJ0906 said:


> 314.3, exception 1 "Where internal means are provided between all entries, nonmetallic boxes shall be permitted to be used with metal raceways or metal-armored cables"
> 
> This doesn't specify how the means are provided, or who provides them.


John, I know what it says, and have argued this very point myself many times. I am still hunting for the paper work I saw that change my view.


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## Mr. Sparkle (Jan 27, 2009)

TOOL_5150 said:


> I honestly do not get your point. I personally would do that transition with a Jbox, but thats just me. EMT can be used as a GEC, so the sheath of the MC isnt isolated, its grounded by the EMT. Just as long as your green in the MC is hooked to the GEC as well, I dont see an issue with it.
> 
> ~Matt


There is a misunderstanding here, of course I would use a J-box and all that. I was referring to Riviters comment about it not being legal to switch the type of wiring method in the middle of a run:



RIVETER said:


> I don't believe that you can EXTEND an existing circuit with other than the original type of system...



as in if the run leaves the panel in EMT it has to be in EMT all the way to it's destination....unless I am misunderstanding him. I mean as long as it's allowed in the location and installed as listed geez you could transition 10 times with 10 wiring methods if you had to.

Bob, is that avatar the printout from that Supermarket Panel that lost the B phase?


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## JohnJ0906 (Jan 22, 2007)

Bob Badger said:


> John, I know what it says, and have argued this very point myself many times. I am still hunting for the paper work I saw that change my view.


I certainly would be interested in seeing it.


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## pjmurph2002 (Sep 18, 2009)

JohnJ0906 said:


> 314.3, exception 1 "Where internal means are provided between all entries, nonmetallic boxes shall be permitted to be used with metal raceways or metal-armored cables"
> 
> This doesn't specify how the means are provided, or who provides them.
> 
> Now if the box or box instructions state that it is to be used with non-metallic cable or raceways, then IMO it would be a violation.


 
I would agree with John in that, if the manufacturer stipulates that the box is not to be used with a metallic raceway, you can not use it with a metallic raceway. As installers, we required to follow the manufacturers instructions. The manufacturer has received a UL stamp of approval for this product based upon the statement that this box is not to be used with a metallic raceway system.

IMO


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