Nonmetallic switch box & MC...

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1793

1793

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Location
Louisville, Kentucky
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Inspector
I was looking over Art. 314 in my 2008 Handbook and I saw something early in the section about plastic, nonmetallic, boxes and the use of MC.

Can we install MC in a nonmetallic box like this and be code compliant?
Zipbox.jpg
 
Just a question...

Just a question...

This is more of a question. I don't have any situation at this point that would require this. I'm just throwing this out to see if I'm reading the part of that Art. dealing with nonmetallic boxes correctly.

I don't have my book with me right now so I cannot reference the correct wording that started me thinking about this.
 
This must be it

314.3 Nonmetallic Boxes.
Nonmetallic boxes shall be permitted only with open wiring on insulators, concealed knob-and-tube wiring, cabled wiring methods with entirely nonmetallic sheaths, flexible cords, and nonmetallic raceways.
Exception No. 1: Where internal bonding means are provided between all entries, nonmetallic boxes shall be permitted to be used with metal raceways or metal-armored cables.
Exception No. 2: Where integral bonding means with a provision for attaching an equipment bonding jumper inside the box are provided between all threaded entries in nonmetallic boxes listed for the purpose, nonmetallic boxes shall be permitted to be used with metal raceways or metal-armored cables.
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I still say "NO"
 
1793 said:
I don't see where exception 2 comes into play here. Do I have to comply with both exceptions?
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No , my mistake but you would have to comply with one except. How would that box satisfy excep. 1. Where are the internal bonding means between the entries
 
That section of code is written backwards.

Rather than _prohibiting_ the use of plastic boxes with metallic wiring methods, it _permits_ plastic boxes, but only for non-metallic wiring methods.

Then the exceptions extend the permission to metallic wiring methods if the box has bonding means.

My understanding of NEC 'style' is that the paragraph is supposed to _prohibit_ something, and then the exception is supposed to eliminate that prohibition in specific cases.

So as I read the code section, you are prohibited from using plastic boxes with metallic wiring methods, with the exception that plastic boxes which provide suitable bonding between entries may be used with metallic wiring methods.

-Jon
 
It doesn't bond the jacket of the MC cable.
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Maybe they should have said that instead of "entries". It is logical to want the jackets bonded but they call for internal bonding.

I'm pretty sure they are just trying to confuse me.:-?
 
The only way you are going to attach an MC cable to the Carlon box shown is to drill a hole in it. I believe you violate its listing as soon as you do this.
 
The only way to get anything into a plastic JBs is to drill them. But I really don't see much room on that device box to put in a 1/2" KO.

As far as the bonding, put a bonding bushing on the MC connector to satisfy the exception. In 20 something years I can only remember having to bring MC into a PVC junction box one time.
 
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