Old work boxes for MC

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electrofelon

electrofelon

Senior Member
Location
Cherry Valley NY, Seattle, WA
Ok if anyone want to make a million dollars, simply make a good old work box for MC. What are you guys using? I have always used 2x3 metal boxes with ears and mc clamps, and madison bars if installed in drywall. Two problems with this: #1 slow, have to ground the box and its a real pain to get to the back of the 3.5 inch deep ones. #2, Do northwest supply houses really not have boxes with MC clamps??????? The guy at stoneway said "nope dont have them, not even really sure what you are talking about.......

Here is how to make the million, I would do it but Im just too busy. The perfect box would have the following: be nonmetallic, have two ports that have an integral snap in fitting sort of like the arlington 38ast. this port would be in the back corner and/or low profile so that the box can be angled and inserted into the cutout easily. common with the fitting would be a ground screw and a bonding jumper to the device screw. The cutout would be rectangular. The box would have wings like your typical nm old work box but it would be able to accept wall material thicknesses up to 1.5 inches
 
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liquidtite

Senior Member
Location
Ny
You can't use a nonmetallic box with mc .i never had problem with supply houses not having the clamps inside
 
kwired

kwired

Electron manager
Location
NE Nebraska
buzzbar said:
Where in the NEC does it say you can't use a nonmetallic box with MC cable?
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I'll second that.

I have entered many enclosures that were non metallic with MC cable and never have seen anything that says you can't and never been cited for doing so either.

To the OP, I hear you. I have often thought there has to be a better way to install old work with MC cable.

ETA: If using MC where the sheath is the EGC, then you could have some issues, but using a grounding bushing or other equivalent device to connect an EGC to the MC sheath should be a way around this issue.
 
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electrofelon

electrofelon

Senior Member
Location
Cherry Valley NY, Seattle, WA
What's wrong with using these on a steel old work box?
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I have never seen those before, looks like they would work nicely

You can't use a nonmetallic box with mc
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reread my op - there would be a metallic clamp common with a ground screw and the device mounting screw.

I just think its interesting that there is very little "free market make a better product innovation" with electrical boxes. Go into big orange and all they have is those garbage blue boxes (I am starting to see some allied molded stuff in some stores). Even for NM I think the perfect remodel box has yet to be made. Are you readig this racketeers?
 
kwired

kwired

Electron manager
Location
NE Nebraska
electrofelon said:
I have never seen those before, looks like they would work nicely



reread my op - there would be a metallic clamp common with a ground screw and the device mounting screw.

I just think its interesting that there is very little "free market make a better product innovation" with electrical boxes. Go into big orange and all they have is those garbage blue boxes (I am starting to see some allied molded stuff in some stores). Even for NM I think the perfect remodel box has yet to be made. Are you readig this racketeers?
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Take your idea to Arlington industries, they seem to come up with all kinds of handy gadgets that work well. And they even have improved some nifty idea products even more over the years.
 
growler

growler

Senior Member
Location
Atlanta,GA
kwired said:
Most cases where I have entered a non metallic enclosure there was only one MC cable entry so bonding between all entries is pretty easy if there is only one entry.
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If there is only on cable entry (MC) I am assumming that it a receptacle or fixture junction box
so why would you be useing a non-metalic box?
 
kwired

kwired

Electron manager
Location
NE Nebraska
growler said:
If there is only on cable entry (MC) I am assumming that it a receptacle or fixture junction box
so why would you be useing a non-metalic box?
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A common application is emergency egress lighting. Many of these are designed so they can be supplied by a raceway or cable, get into a place of assembly and you will not be using non metallic wiring methods.
 
buzzbar

buzzbar

Senior Member
Location
Olympia, WA
Occupation
Electrical Contractor
kwired said:
There is this, but the exceptions still will allow use of MC cable if conditions of the exceptions are met.



Most cases where I have entered a non metallic enclosure there was only one MC cable entry so bonding between all entries is pretty easy if there is only one entry.
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Yeah, basically it says that you have to make sure you actually tie the ground wires together. Hmmm, what a novel concept. ;) That being said, I always use metal boxes with MC cable anyway. But it's good to know that you CAN use a plastic box if you'd like.
 
kwired

kwired

Electron manager
Location
NE Nebraska
iwire said:
Sorry I hit edit instead of quote and screwed up your post, it was not intentional and I apologize.
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For those following at home....:) the deleted portion was a quote of 314.3 and both exeptions that follow from 2011 NEC.

The exceptions basically allow metallic raceways or metal sheathed cables to enter non metallic boxes or enclosures where a means is present to allow for bonding the metallic raceways or metal sheathed cables together.

I will now stifle myself:ashamed1:
 
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hurk27

Senior Member
Location
Portage, Indiana NEC: 2008
buzzbar said:
Yeah, basically it says that you have to make sure you actually tie the ground wires together. Hmmm, what a novel concept. ;) That being said, I always use metal boxes with MC cable anyway. But it's good to know that you CAN use a plastic box if you'd like.
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Nope the grounding conductors in AC cable do not bond the metal sheathing which is what the NEC requires to be bonded together, grounding locknut's or bushings is the only two ways I can think of to bond the MC fitting, and inside of a deep box could be a challenge trying to reach into the back of the box

One time I found some box's that looked like full size masonry box's (2x4) without stud brackets but had adjustable ears like a GEM box (2x3), I was able to use F-straps on them, but never could find them again, if they would make them again they would be perfect for use as old work box's.

Most GEM box's listed for N/M are also listed for AC, MC with the clamp in the back of the box, just make sure you use the red hats in them, they have 4 K/O's in the angle of the back of the box but I would never try to use them as an old work box with more them one AC or MC cable.

Edited to add I was looking at Raco's 2"x3" and they are not listed for N/M and MC/AC as they are differant clamps so you do have to get them for either N/M or AC/MC, wonder the reason why as I have seen some that covered both?
 
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