mc in plastic boxes

[peter d]

But this makes me wonder, is an MC connector connected to a metal box which is grounded an approved method for bonding?

Yes, that would be an approved method for bonding the armor. However, it would not be an approved EGC.

 

[steelersman]

Yes, that would be an approved method for bonding the armor. However, it would not be an approved EGC.

right on. That's what the green ground would be for.

 

[LarryFine]

why? the armor isn't a ground.

Similar to the way we must bond to the metal water piping system whether or not it's an electrode.

 

[LarryFine]

But this makes me wonder, is an MC connector connected to a metal box which is grounded an approved method for bonding?

Yep, which is why I use a metal box when MC/AC/BX meets up with NM or an outlet box.

 

[LarryFine]

right on. That's what the green ground would be for.

Which, of course, AC/BX doesn't usually have.

 

[steelersman]

Which, of course, AC/BX doesn't usually have.

true but we were talking about MC which does. AC or BX is not in this discussion.

 

[iwire]

But this makes me wonder, is an MC connector connected to a metal box which is grounded an approved method for bonding?

Yes, an MC connector is listed for grounding.

The outer armor of MC is required to be grounded just like any metal raceway or metal enclosure.This is regardless of the fact there is a green EGC inside the MC.

 

[M. D.]

I've never used MC in Plastic boxes for one.

Which is a good thing,... as they are not listed for such use.

 

[iwire]

I doubt,after my discussion with Brian at Arlington that you will find a plastic single gang device box listed for use with M.C. cable

I keep thinking plastic junction box not device box.

 

[mthead]

mc in plastic boxes

P.D. must be pullin' our legs to see how long this can go on!
There are acceptable methods allowing a transition from one cable/wireing method to another-that would easily be NEC compliant and make sense.
If you attempt to try a silly method-and I do mean MC into plastic is pretty silly other than as an academic exercise-I'd say you stand a good chance of being EASILY shot down-and wether you like it or not the easy way to squash an argument like this will involve the infamous "Listing" requirements of everything involved in this hypothetical --and I hope that is all it stays as -situation.
If comon sense and what we know can work was all it took -well then mad max installations would be beautiful-but we do have to follow the rules-even when we might think we know better--
I've seen people try to stick a piece of mc into 1 side of a plastic nail on and tie into a piece of RX coming out of the same nail-on--
AND THEY SOLVE THE DILEMA BY CUTTING AWAY ALL THE GROUNDS!!!!
It's been a rough day-Find a wire manufacturer who'll go along with this,a connector manufacturer who'll go along with this,a wire nut ...etc... and maybe you'll be able to do it the way you describe.
You won't be able to get them to say its ok because their lawyers will not allow it-no matter if you think you know better.

 

[peter d]

P.D. must be pullin' our legs to see how long this can go on!

Not at all. Show me the code(s) that say it can't be done. And yes, this is an "academic exercise" to get people to actually see what the code says and apply it correctly, rather than just blindly following some mantra like "That doesn't seem right to me" or "It can't possibly be legal" etc etc.

 

[M. D.]

110.3(b) it is not installed in accorrdance with it's listing(Talking about the box that Marc had posted)

 

[RJohnsonMasterElectrician]

250.96?
I'll find out for sure

 

[peter d]

110.3(b) it is not installed in accorrdance with it's listing(Talking about the box that Marc had posted)

Yes, the OneBox..that has been established. But not the PVC junction box that has also been discussed.

 

[M. D.]

I'm thinking that the only way to connect to the box Bob posted is with a junction box adapter and by that I don't mean a terminal adaptor ,.. seems I looked into this and terminal adaptors are for threaded hubs and metal boxes ,..I highly doubt that listed M.C. connectors would be listed for connection to a PVC junction box. I'll see what I can find:roll:

 

[M. D.]

Well ... I did not find anything that says MC connectors are limited to metal boxes nor did I see a limitation to their use in K.Os ,.. so if ,.. and I doubt there would be , given the thickness of the type of box Bob posted,.. there were enough threads left for a bonding bushing ,..The language does allow for it ....

 

[iwire]

.. so if ,.. and I doubt there would be , given the thickness of the type of box Bob posted,.. there were enough threads left for a bonding bushing ,....

Leave the locknut out of the equation.


That said, it is not something I have run into more then one or two times. :smile:

 

[RJohnsonMasterElectrician]

I beleive the grounding bushing takes place of the lock nut?

 

[LarryFine]

I beleive the grounding bushing takes place of the lock nut?

It does if it's a metal bushing, but a locknut might still be needed, either inside or outside, to tighten the connector fully.

 

[steelersman]

It does if it's a metal bushing, but a locknut might still be needed, either inside or outside, to tighten the connector fully.

I've never seen a plastic bonding bushing?