Double gang and NEC

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  #1  
Old 09-09-06, 09:46 AM
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Double gang and NEC

I am planning on calling for my rough inspection next week and reading in "Wiring Simplified" that the NEC requires a cable clamp to the box for a double gang box. I have removed sheetrock where necessary to pull out the old (1968) single gang receptacles and in their place nailed in plastic double gang switch boxes.

Is "Wiring Simplified" correct? If so, could I use ENT plastic double gang boxes with metal cable clamps for my receptacles?
 
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  #2  
Old 09-09-06, 10:08 AM
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Tyger52, I do not have a copy of that book, so I not sure what you are talking about. Do you mean to hold the romex cable into the box, or to hold the rec into the box?

A box is a box, single gang, double gang etc. Your saying that you are replacing single gang rec boxes with double gang switch boxes. What do you mean. Are you putting in two recs where one was before or puttting switches in where recs where?

ENT is a type of wiring conduit where you would pull in seperate conductors like THHN instead of cable line romex. What is an ENT box?
 
  #3  
Old 09-09-06, 10:54 AM
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You do not need a cable clamp on every box. Some plastic boxes have built in cable clamps and/or you can properly attach the cable to the stud near the box.
 
  #4  
Old 09-09-06, 12:18 PM
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Thanks

Thanks for all the replies.

JWhite,

The book says that NEC allows no cable clamp on a single gang non metallic box. Other boxes, it says, require a cable clamp.

A single gang box I thought holds one switch or one receptacle. I thought a double gang can hold two. I would like to have more outlets, so the easiest way it seems is to replace the single gang with a double, that way I can get four outlets where there were only two before. Does that make sense?

The ENT box is one I found at Lowe's, it is meant for ENT I guess because it is marked as such. It is blue plastic and has knockouts like a metal box. The question is, can I use a metallic cable clamp on it since there is no other kind of clamp on this kind of box. I like this kind of box because of how it mounts, it is got the most cubic inches, and the clamping is more secure but I need to pass inspection and don't want to do anything wrong or dangerous.
 
  #5  
Old 09-09-06, 01:21 PM
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Now I got the picture. A metal clamp cannot be used on a non metalic box because if the wire shorted to the clamp, it would not be grounded and trip the breaker.

They make a snap in plastic bushing that will clamp the romex in place and serve the purpose.
 
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Old 09-10-06, 09:41 AM
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Originally Posted by jwhite
Now I got the picture. A metal clamp cannot be used on a non metalic box because if the wire shorted to the clamp, it would not be grounded and trip the breaker.

They make a snap in plastic bushing that will clamp the romex in place and serve the purpose.
jwhite...Have you got a code number that prohibits using a metal romex connector on a plastic box?
steve
 
  #7  
Old 09-10-06, 09:52 AM
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[QUOTE=Tyger52]Thanks for all the replies.

JWhite,

The book says that NEC allows no cable clamp on a single gang non metallic box. Other boxes, it says, require a cable clamp.

It doesn't say that a cable clamp is not allowed on a single gang non-metallic box, it says that is is not REQUIRED if the
non-metallic sheath cable (Romex) is secured within 8" of the box.
If you fish a wire and cannot secure the cable within 8", a cable clamp is required. This is why single gang "old work" boxes have a internal clamp built in. 2 gang boxes and above require a cable clamp. All 2 gang (and above) plastic handy boxes have a internal clamp built in.
steve
 
  #8  
Old 09-10-06, 10:40 AM
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Originally Posted by hillbilly ace
jwhite...Have you got a code number that prohibits using a metal romex connector on a plastic box?
steve
How about 250.4 unless you have found a way to bond the connector. It is made of metal, and part of the electrical system.
 
  #9  
Old 09-10-06, 03:45 PM
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QUOTE=hillbilly ace "jwhite...Have you got a code number that prohibits using a metal romex connector on a plastic box?
steve"

QUOTE by me "How about 250.4 unless you have found a way to bond the connector. It is made of metal, and part of the electrical system."

I stand corrected. I just got an email back from somone who I consider to be a code guru. He says you CAN use a metal romex connector in a plactic box.

I won't mention any names for my source, but some of you know his name from other web sites He is a nationally known inspector and educator in the electrical field and the NEC.
 
  #10  
Old 09-10-06, 05:34 PM
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Sure it's legal. All that is required is a bonding locknut or bushing be used and a ground wire attached.
 
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Old 09-11-06, 04:41 AM
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Smile

Originally Posted by itsunclebill
Sure it's legal. All that is required is a bonding locknut or bushing be used and a ground wire attached.
I beg to differ.
steve
 
  #12  
Old 09-11-06, 04:43 AM
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If you have the drywall out, just put a staple within 8" of the box. I believe this is all the NEC requires for cable support for non-metallic boxes.

If you have just enough drywall removed to put the new box in, then I do not believe any support would be necessary. Would be the same as fishing the cable through an existing wall, would it not?
 
  #13  
Old 09-11-06, 04:57 AM
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Howdy,

OK...no need for a clamp if you are running this to a plastic box as most have plastic built in retention methods, just be sure to support it within 8 inches in regards to the plastic boxes.

Remember the NEC also states you can "FISH" NM Cable within a wall as well with no supports on small sections so to be honest with you I would not sweat the box connection issue before your rough in.

I wire probably 100 homes a year and many over 1.5M and we use plenty of 2 gangs and 3 gangs and it is not a issue and I am sure it will not be for you as well.

BTW... I will assume you are refering to Section 314.17(C) and I would not worry about it nearly as much. Do what RAC suggested and you will be fine.
 
  #14  
Old 09-11-06, 09:38 AM
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I'd really like a code reference for exempting metal NM-B clamps from the definition of metal parts that may become energized needing to be bonded.

Plastic box, metal clamp, pinched hot wire, and adjacent water pipe or damp surface. Tell me how this doesn't add up to a code violation.
 
  #15  
Old 09-11-06, 11:11 AM
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Went with plastic

I found some plastic clamps that just pop right in the ENT box so I removed the metal ones and used the plastic. In some cases, I was able to staple the wire near the box, but in others, there just wasn't a way to swing anything at the staple.

I tried using a clamp in one place where there was limited room and that worked, but again, in some cases I would just have to remove a lot of sheetrock.

I am not real sure why metal is a problem anyway. If a metal clamp on a plastic box gets current, where is it going to go? Could current arc from the clamp to a damp surface or pipe? Like I said, I went plastic so now there is no worry at all.
 
  #16  
Old 09-11-06, 11:29 AM
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"I am not real sure why metal is a problem anyway. If a metal clamp on a plastic box gets current, where is it going to go? "

It could sit there and wait to be touched by some unsuspecting soul. Since the breaker would not trip, the connector would be hot.
 
  #17  
Old 09-11-06, 04:32 PM
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Now that you put it that way ...

I wasn't totally comfortable with the metal but then again, this particular box was behind drywall and will be again after rough inspection. It is in my garage but it was not too hard to replace the metal with plastic so I can sleep better at night.
 
  #18  
Old 09-12-06, 06:07 AM
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Smile

I've personally never had a reason to use a metal romex connector in a plastic box. I was just making the argument that the Electrical Code (NEC) wouldn't require me to bond it if I chose to.

250.86 Exception NO. 2 states "Short sections of metal enclosures or raceways used to provide support or protection of cable assemblies from physical damage shall not be required to be grounded".
steve
 
  #19  
Old 09-12-06, 07:09 AM
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Would it be Code-compliant to secure Type NM cable to non-metallic outlets boxes with Ty-Wraps?
 
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