MC in plastic box

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george t. everett

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New York
I saw an installation today, where MC cable was run from the main panel up a wall to a plastic box to an outlet. At first I thought this was not code compliant, now I am not sure. The sheath is grounded at the panel.
What are your thoughts?
 
Since the sheathing/armor for typical MC cable is not listed as suitable for a grounding path, and the sheathing is bonded at the panel, the equipment ground conductor is terminated to the device... is this a violation???

lets say the MC is secured to the box by the plastic clamp provided with the box.
 
I believe 330.40 says it all. If the fitting is listed and identified for use then the grounding (bonding) is another issue. I have often wondered about 250.118(10). If do not have the types listed in 250.118(10) (which is generally the case) why bond the MC in the first place seeing as how it is not an effective ground-fault path? It seems to me then that if you had the approved fittings per 330.40 then you could go from nonmetallic to nonmetallic. If you have the type per 250.118(10) then you would need to bond at least one end. This is probably clear as mud and if so I apologize. :lol:
 
Pierre, I totally respect your knowledge and experience my question has to do with the sheathing that is not suitable as an effective ground-fault current path (according to Mikes' " Grounding versus Bonding" page 73 "Authors comment" after 250.118(10)). Isn't that why we bond to have an effective ground-fault path? If it isn't there why bond it? I may be a stirring the pot here and also a Devil's Advocate but hey isn't that what we are here for. :D
 
andrew said:
Isn't that why we bond to have an effective ground-fault path? If it isn't there why bond it? I may be a stirring the pot here and also a Devil's Advocate but hey isn't that what we are here for.
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We still must bond the jacket because it's metallic and conductive, and if we left it unbonded we would introduce a greater hazard. But we can't RELY on the MC cable jacket for the sole equipment bonding conductor, hence the copper EBC contained within.

Does that make sense?
 
Peter that makes perfect sense. Thank you for your reply. I call it that way. Was just looking for a little more ammunition for the ones who look at it the way I described but Pierres' and your answer is all there is and it is all that is needed.

Thank you both again
 
As many people as there are, there are ideas. That is one of the reasons why applying the NEC sometimes is such a challenge..


This is an example of one of many ideas. I would never think of installing MC to a plastic box... yet if all other things taken into consideration, is it a violation? What do the installation instructions say?
 
Sometimes "approved" is almost meaningless. The approval is by the AHJ.
So we bond the sheathing at the panel, and the cable enters the box and is secured by the plastic clamp (approved). Now is this a code compliant installation????
 
So we bond the sheathing at the panel, and the cable enters the box and is secured by the plastic clamp (approved). Now is this a code compliant installation????
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No. Violation of 314.3.
Don
 
But it approved for what type of wiring method :wink: NM yes MC will have to see what the manufacturer lists.Now go one step further than the OP use a old work cut in box and LNMC drill 1/2 in hole to enter.All of this inside of a kitchen island.This was an issue awhile back but was resolved with due dilligence and communication.The AHJ said the box is not listed to have holes drilled in it.Argument was it isn`t forbiden by the manufacturer either (VERY GRAY AREA )
AHJ wanted metal LC boxes and armored flex etc.....Argument was this is a sure fire way to cause stiches and injuries to young kids that always find there way into cabinets.Solution use the LNMC and PVC cut in boxes no problem with grounding and a cleaner install.
 
allenwayne said:
The AHJ said the box is not listed to have holes drilled in it.
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It's not listed 'not' to have holes made in it either. :)

I do not believe that you will find any box specifically listed for hole drilling.
 
Bob that is what I did argue and did win after having to take it to the top of the ladder.I would rather see LFNMC and a pvc cut in box rather than metal LC boxes & armored flex anyway.The higher ups did agree with this logic so that is the way we go now.Besides the cabinet installers don`t have a box they use to mark they use a template from a pvc cut in box and metal LC boxes almost fall in the opening and madison straps were the only way to secure them (Another hazard in a base cabinet filled with pots and pans ETC.)
 
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