Ground on PVC box

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  #1  
Old 03-26-14, 07:50 PM
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Ground on PVC box

I'm sure it's been answered a few times already but I cannot find a clear answer. I have a 12/2 BX cable that goes to a PVC box with a ground screw then to an outlet with a ground screw. What's the code on wiring ground for those boxes? I understand that if using a metal box you need to ground it but basically what are you grounding if it's made of PVC?


I have the exact same box. You can see the ground screw on the bottom left side.

Carlon | Outdoor Weatherproof PVC Single Gang FSC Device Box – 1/2 In | Home Depot Canada


And here's the outlet http://sigma.octopart.com/177881/ima...s-CR5252IG.jpg

I've pigtailed the ground but I'm just wondering what am I grounding sice everything is plastic even the outlet itself.
 
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  #2  
Old 03-26-14, 08:00 PM
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Had to approve your post... Spam O matic at work!!!!



The electricians should respond soon...
 
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Old 03-26-14, 08:30 PM
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Only metallic devices and enclosures can be bonded to ground and all metallic devices and enclosures must be bonded to ground. A ground screw on a PVC box is useless. Interestingly, I don't see any ground screw or any provision for one in the specifications for Carlon's PVC boxes.

The image you linked to is of an IG5252 isolated ground 15A commercial/industrial grade receptacle from Hubbell. It is not made of plastic. It is made from metal and, to be properly installed, must be connected to an isolated ground. Connecting it to a ground that contacts any portion of the enclosures and raceways between the direct path to ground and the device is a violation of the manufacturer's specifications for that receptacle. You do NOT pigtail the ground to one of those unless you are assembling a quad outlet that will house two of them in the same enclosure.

Note, BTW, that one of the unique features of an IG receptacle is that the mounting yoke is isolated from the grounding connection and the grounding slots in the device.
 

Last edited by Nashkat1; 03-27-14 at 05:54 AM.
  #4  
Old 03-27-14, 04:44 AM
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Are you using type AC or MC cable? With the AC cable you are going to need a bonding locknut to continue the ground to the device.
 
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Old 03-27-14, 04:49 AM
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So what I could of done is just bypass the grounding on the box and go straight with the ground wire to the outlet? Should I re do it or leave it as it is? As it is now the ground wire goes through the ground of the PVC box and then to the ground's outlet
 
  #6  
Old 03-27-14, 05:17 AM
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It's AC type the ground is exposed inside What do you mean by a locking nut?
 
  #7  
Old 03-27-14, 08:43 AM
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You linked to an Isolated Ground receptacle. For that receptacle to function as it was designed to, the grounding terminal on it must be connected to a "clean" ground. That requires a conductor that connects to the ground on the receptacle on on end and directly to earth ground on the other. Armorlite® Type MC Isolated Ground is one example of a cable assembly that contains two grounding conductors, to enable that to be done.

Is that what you need where you're planning to install this receptacle?
 
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Old 03-27-14, 09:45 AM
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Type AC cable uses the sheath and bond strip as a ground. There is no grounding conductor to connect the the device. A bond locknut with a jumper would need to be used to ground the device.
 
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Old 03-27-14, 02:40 PM
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A bond locknut with a jumper would need to be used to ground the device.
And doing that means that there is no isolated or "clean" ground available. That's why Type AC isn't used to feed IG receptacles. It's a mismatch in technologies.
 
  #10  
Old 03-27-14, 03:01 PM
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Even in commercial setting it seems like IG receptacle usage is down. I can't think of a reason to use one in a residential setting.
 
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Old 03-27-14, 07:40 PM
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Even in commercial setting it seems like IG receptacle usage is down.
I'll bet you saw that one coming. I know we did. They were a total PITA and a major expense to install, and we couldn't see anything they added that proper bonding of the EGC and isolation of the neutrals wouldn't provide. We had an ongoing bet on whether the double-Es and the IT geeks really believed what they thought their overly-precise $500 meters were telling them or they were just using it to fool the customers.

I can't think of a reason to use one in a residential setting.
Nope. I can't either.
 
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Old 03-27-14, 08:23 PM
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Guys.... I'm a little lost here. I.G. receptacle aside... the OP asked about using a plastic box with AC cable. I don't see it mentioned that a metal box needs to be used and plastic can't be.... did I miss it ?
 
  #13  
Old 03-28-14, 05:29 PM
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I changed the outlet to a regular one I have another question Not related to that project. When running AC through a wall can I use that spiral cable wrap Spiral Wrap | Cable Wrap | Abrasion Protection for Wires and Cables | CableTiesAndMore to protect the cable? Or I really have to use BX cable? I'd be jumping from an electrical box to another one that's about 3 feet apart
 
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Old 03-28-14, 06:34 PM
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That spiral wrap cannot be used in a wall. The wiring needs to be a recognized method to be in wall. Use AC or MC cable.
 
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Old 03-28-14, 08:12 PM
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Why can't you use Type NM in the wall?

BTW, PJ made an important point earlier: You can't run any metal-jacketed cable or any metal conduit to a non-metallic box.
 
  #16  
Old 03-29-14, 01:42 PM
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I asked the guy at home depot and told me as long as the pvc box is for indoor use. What could be the problem using bx to a pvc box?
 
  #17  
Old 03-29-14, 02:03 PM
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The grounding gets interrupted by the PVC box and you would need to use bonding locknuts.
 
  #18  
Old 03-29-14, 02:28 PM
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PJ, there is an exception that allows plastic boxes with metallic methods if bond locknuts are used. Article 314.3
 
  #19  
Old 03-29-14, 07:00 PM
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I don't think the box the OP linked to in his post #1 should ever be used with any type armored cable, it's a PVC conduit FS box.
 
  #20  
Old 03-29-14, 07:18 PM
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PJ, there is an exception that allows plastic boxes with metallic methods if bond locknuts are used. Article 314.3
A plastic weatherproof box has molded plastic hubs.... how could you possibly use a bonding locknut ??

I understand bond locknuts with plastic splice boxes..... however that isn't what we are dealing with here.
 
  #21  
Old 03-30-14, 01:22 AM
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Agreed that the box shown cannot be used with the AC cable.
 
  #22  
Old 03-30-14, 05:04 PM
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The ground get loop through with the green screw on the PVC box I think they put those ground screws just as a strain relief or so you can jump your ground from one box to another
 
  #23  
Old 03-30-14, 05:13 PM
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I guess I'll go with a metal box!! Another question can the red wire on a 12-3 cable be used as ground as well as the copper one? Instead of using marrettes to pigtail all the grounds can I use the ground copper wire to ground an outlet and the red to ground another outlet if it's labeled properly? Kind of hard to explain but one of the box I'm working on has no more room for pigtails I went to Home Depot and all they had was 12-3 and no 12-2 so I thought to make that red cable useful. Basically it would be copper to ground- red to ground(I can label it and put green etape on it) black to Hot and white to neutral. Is that acceptable?
 
  #24  
Old 03-30-14, 05:25 PM
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Technically the green cannot be reidentified as a ground under the NEC. I would think the CEC would be similar.
 
  #25  
Old 03-30-14, 05:41 PM
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But in reality could that be an issue to have 2 ground on the same cable? it's for a generator that would power up some tools in a shed I highly doubt anybody will ever open that box if so it would be to recuperate the box when they tear down the shed. It's an inlet that cost me around $65 so it would be worth salvaging http://www.hillarysboatshop.com.au/i.../114918-01.jpg
 
  #26  
Old 03-30-14, 08:56 PM
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can the red wire on a 12-3 cable be used as ground as well as the copper one?
No. All branch circuit grounding conductors must be either bare or green insulated. See 120/240V Wiring Color Code Interpretation.

I thought to make that red cable useful.
It isn't a red cable. It's a red conductor or red wire.

That said, what utility would using that red conductor as a grounding conductor provide you? What would you gain? One low-impedance path to ground in a box should be all you need.
 
  #27  
Old 03-30-14, 09:02 PM
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What's the difference between a green jacket and a red one? black white red or green it's all from the same material
 
  #28  
Old 03-30-14, 09:37 PM
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The insulation colors mean nothing to the electricity. They exist to provide information to dumb humans. That information is life-safety critical, and that's why they can only be redesignated in certain limited conditions and be compliant with code requirements.

Did you read 120/240V Wiring Color Code Interpretation yet? Also,
Originally Posted by Nashkat1
what utility would using that red conductor as a grounding conductor provide you? What would you gain? One low-impedance path to ground in a box should be all you need.
 
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