mc in plastic boxes

Status
Not open for further replies.
I've read through this entire post and followed all the links, etc. It's been a good post to get one reading carefully to determine the "intent" of the language at 314.3.



My understanding is this:
  • The main provision is intended to limit the use of non-metallic boxes
  • "shall be permitted only" is mandatory
  • Exception 1 clearly uses the word "internal" meaning 'having to do with the inside, being situated inside'. This clarifies that if a bonding method is contained within the inner dimensions of the box (such as two bushings with bonding lugs) it is permissible ('shall be permitted' is not mandatory, it's permissive language) to bond together (assure mechanical and electrical continuity) two or more metallic cable entries.
  • Exception 2 clearly uses the word "integral" which means 'complete or whole' indicating the box was manufactured this way so as to provide a means to mechanically and electrically continue a bonding path.
  • Therefore, I agree with iwire and mdshunk
 
peter d said:
Do boxes have listings that say what types of wiring methods can and can't be used with them? I know that a plastic nail-on box does. A PVC junction box? Maybe it does. Regardless, if I bond the metallic raceways or wiring methods then I am code compliant.
Click to expand...



I agree that thinking out of the box does help with the creativity leading to a good installation.

I do not agree that thinking out of the box and not following the code leads to a good installation.

314.3 is a direct code requirement (there is no mention of listing in this section), that does not say creativity is permitted to "go around" this section.

It is quite obvious that there are some who do not care to change their installation methods if the change is too difficult for them to wrap their heads around the concept.
I am not posting to convince those, I post because there are so many others who also read the posts and they can make up their minds based on what they read. In the end we control nothing and all will install as they may. ;):cool:
 
wbalsam1 said:
Therefore, I agree with iwire and mdshunk
Click to expand...
yes, it does feel good to be on the winning team.

I might ask Pierre what hazard exists, in his opinion, when an installer dead ends an MC cable in a non-metallic box? I offer that not only does no hazard exist, but the overall safety of the installation is actually enhanced.
 
680.23(F)(1) allows MC cable on the supply side of a plastic J-box for a pool underwater luminaire in a building. 680.24 sets out the requirements for the integral grounding terminals in the J-box.

In this instance the bonding conductor for the underwater fixture is connected in parallel to the egc going to the fixture, and they are both connected to the integral terminal strip in the J-box. Presumably there would be a bonding bushing for the MC cable that would have a bonding jumper connected to the terminal bar. This would assure a continuous path back to the panel.

This is similar reasoning, IMHO, as the Exception 2 to 314.3 :smile:
 
Pierre C Belarge said:
I do not agree that thinking out of the box and not following the code leads to a good installation.

314.3 is a direct code requirement (there is no mention of listing in this section), that does not say creativity is permitted to "go around" this section.
Click to expand...

And this is where we diverge. Nowhere did I suggest that the code should be violated...in fact throughout this thread I have stressed the importance of code compliance with respect to bonding.

As for your take on 314.3, that is a non-starter. Exception #1 to the rule specifically allows non-metallic boxes with metallic wiring methods and with proper bonding, whether the bonding is integral or internal. No creativity is required unless you consider a bonding bushing to be creative wiring.
 
Pierre C Belarge said:
Chapters 1-4 apply generally, Chapters 5, 6, and 7 supplement or modify the general rules.
The above reference you provided is very specific in nature and has no bearing on the requirements of 314.3.
Click to expand...

Obviously, forget I mentioned it. I was just pointing out a place in the NEC that requires a box with integral bonding provisions.

There is still nothing in Exception 1 of 314.3 that requires a special box. All that exception requires is bonding, how that is done is up to the installer.
 
George Stolz said:
The grounding accessory is not required by the NEC, IMO. It is provided in case the luminaire installed does not have a grounding tail.

celtic said:
I know [at least hope :wink:] those aren't "your" words George ~ that is one of the silliest things I have ever heard.:grin:


George Stolz said:
Well, I can't think of another reason for it to be there - can you offer one? :)
Click to expand...
Click to expand...
Click to expand...


There is no reason for it to be there.
What is wrong with a wire nut and a tail?


Why don't device boxes have them?
Devices usually don't come w/grounding tails.
 
peter d said:
And this is where we diverge. Nowhere did I suggest that the code should be violated...in fact throughout this thread I have stressed the importance of code compliance with respect to bonding.

As for your take on 314.3, that is a non-starter. Exception #1 to the rule specifically allows non-metallic boxes with metallic wiring methods and with proper bonding, whether the bonding is integral or internal. No creativity is required unless you consider a bonding bushing to be creative wiring.
Click to expand...



Did I mention your name?
 
I have emailed the manufacturer with some questions about plastic boxes and MC cable, I hope for an answer in the next couple of days.







While visiting the website, I came across this information. It is from Carlon's website.

"
The SuperBlue Boxes I am using are just about 3.5". Is this too big for a
2X4 wall stud and only used for 2X6 walls? I am tempted to not use the
entrance/exit knockouts in the back and just drill some holes nearer the
center of the stud but it would take too much time.
It is acceptable for the NM Cable to enter the outlet box through its knockouts even though it comes close to the drywall. The NEC is concerned with damage to the cable from nails or screws. Outlet boxes are usually located low to the floor or above counter spaces. Also switches will be found near door opens and a little above the waist. It is unlikely that a picture would be hung in these areas.​

Section 300.4(B)(2) does state that "if" it is likely that a screw or nail would penetrate the cable than a steel plate needs to be used.​

Finally, if you drilled a hole in the box than you would void the listing of the product and would get tagged by the inspector.
(I highlighted and changed the italics and size of the font)​


Last year we sold over 500 million boxes with knockouts without a problem pertaining to the NM Cable entering the knockouts."​
 
Pierre C Belarge said:
Finally, if you drilled a hole in the box than you would void the listing of the product and would get tagged by the inspector
Click to expand...

And that is certainly false statement by Carlon.

Here is a PVC box covered by 314.3, it happens to be a cantex.

Is adding a KO to this box a UL violation?

8450938_Detail.jpg


Or was the above box manufactured not to be used?

Or are the rules different for smaller boxes and if so where is that explained?

314.3 applies to all non-metallic boxes not just single gang device boxes. :smile:
 
iwire that exact box was install by myself today - pvc underground to an 8x8 x6 carlon - on a steel hollow beam that will house the mc for the lighting - its a prefab polygon structure(picnic shelter), mc will be out of the weather so after reading all this i said woopee i can do this and not feel bad in the morning - wrong!mc connector does not fit through the damn thing - i had to use a rigid coupling and a nipple to even make it work - good thing its inside a beam were noone can see it -
 
nolabama said:
iwire that exact box was install by myself today - pvc underground to an 8x8 x6 carlon - on a steel hollow beam that will house the mc for the lighting - its a prefab polygon structure(picnic shelter), mc will be out of the weather so after reading all this i said woopee i can do this and not feel bad in the morning - wrong!mc connector does not fit through the damn thing - i had to use a rigid coupling and a nipple to even make it work - good thing its inside a beam were noone can see it -
Click to expand...

I was just thinking the same thing. The pvc in that box is probabbly 1/4 " thick making it difficult to find a connector that has threads long enough to reach the other side of the connector.
 
nolabama said:
iwire that exact box was install by myself today - pvc underground to an 8x8 x6 carlon - on a steel hollow beam that will house the mc for the lighting - its a prefab polygon structure(picnic shelter), mc will be out of the weather so after reading all this i said woopee i can do this and not feel bad in the morning - wrong!mc connector does not fit through the damn thing - i had to use a rigid coupling and a nipple to even make it work - good thing its inside a beam were noone can see it -
Click to expand...

Would 330.40 affect this?:-?:smile:
 
Status
Not open for further replies.
Top