# Grounding metal boxes



## Speedy Petey (Jan 10, 2007)

The box MUST be grounded first and foremost. Then the devices and in turn covers. 
There are rare exceptions to grounding devices, but never metallic boxes.


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## georgiasparky (Jan 22, 2008)

Is this a trick question? I'm curious to hear the follow-up question.


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## Speedy Petey (Jan 10, 2007)

Actually, on re-reading this I think he knows the box must be grounded but is asking if the plate is required to be. 
Am I correct?

Is so then as I said, the plate is grounded via the devices, or direct attachment to the box


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## randomkiller (Sep 28, 2007)

Other than having metal screws into the devices and boxes for the covers, how else would you ground the plates?


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## Speedy Petey (Jan 10, 2007)

randomkiller said:


> Other than having metal screws into the devices and boxes for the covers, how else would you ground the plates?


That's what I meant.

I'm thinkin' there is a trick question here somewhere.


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## randomkiller (Sep 28, 2007)

Speedy Petey said:


> That's what I meant.
> 
> I'm thinkin' there is a trick question here somewhere.


Or a poorly educated inspector. (One of the if you can't do type guys)


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## 480sparky (Sep 20, 2007)

To ground a metal box is easy:







 
I assumed the OP was asking how to ground covers like this:


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## Podagrower (Mar 16, 2008)

We used some metal "in use" covers on a job recently. Box grounded, obviously, device grounded, no problem. The metal cover attached to the device is "kind of grounded" thru the 6/32 screw heads only.
Here is where it got wierd--a piece of 14 gauge green wire runs from the hinged cover of the plate to a connector you were supposed to put the 6/32 screw thru. 
No solid connection of the ground to the plate.


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## Mackie (Mar 16, 2008)

Sorry, I'm back...

Ok, y'all affirmed what I thought. Here's the thing, though, - wet location boxes are supposed to have some kind of sealant (silicone, etc) around all the 'seams' PLUS, there's a foam gasket which sits between the faceplate and the box or wall behind it (which is my case - these are mounted in work trucks, - interior of vehicle > box > vehicle wall > faceplate > outside). 

Hmmm... now that I think about it, the box is installed so that the *large wireless phone company* guys will have an outlet outside the truck. The box is mounted up against the _aluminum _wall of the truck. That should serve as a ground (EGC). 

I guess the only way for the metal cover to be grounded is via the 6-32's.

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Just wondering 'cause in studying I saw the NEC say ~'all metal receptacle face plates shall be grounded...' I'll post some pix soon.



-thanx


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## Mackie (Mar 16, 2008)

Pix of box / cover in question...



















^that exact setup and 2-gang as well depending on the truck.


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## 480sparky (Sep 20, 2007)

The box should have a ground screw included, as well as a spot in the back/bottom for it to go to.

The cover is grounded by the screws that attach it to the device.


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## goose134 (Nov 12, 2007)

What's the problem? 480 said it and I agree. Bell box should have ground terminal screw and the device screws bond the yoke.


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## 480sparky (Sep 20, 2007)

goose134 said:


> What's the problem? 480 said it and I agree. Bell box should have ground terminal screw and the device screws bond the yoke.


I just noticed that the photo is missing the ground screw.... it shows the two mounting straps & screws as well as the KO plugs... Unless it's pre-installed?


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## rlc3854 (Dec 30, 2007)

Mackie, are the trucks you build using a generator mounted in the truck to power these these "AC" outlets? If so is the genrator's bonding/grounding isolated from the trucks "DC" system?


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## gilbequick (Oct 6, 2007)

rlc3854 said:


> Mackie, are the trucks you build using a generator mounted in the truck to power these these "AC" outlets? If so is the genrator's bonding/grounding isolated from the trucks "DC" system?


If you've got a vehicle mounted generator producing AC power and you're installing AC receptacles into the side of the truck (in the metal), how would you isolate the grounds?


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## Mackie (Mar 16, 2008)

rlc3854 said:


> Mackie, are the trucks you build using a generator mounted in the truck to power these these "AC" outlets? If so is the genrator's bonding/grounding isolated from the trucks "DC" system?





gilbequick said:


> If you've got a vehicle mounted generator producing AC power and you're installing AC receptacles into the side of the truck (in the metal), how would you isolate the grounds?


These are very good questions that will have to wait until Monday as I only deal with the feeder conductors off of the generator down... I'll ask the boss.

Not only is the box connected to the aluminum shell of the truck, but the breaker box, the generator, the air module, the overhead fluorescent lights (luminaires, that is...), and pretty much everything else! Hmmm...

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In the pic of the box, the ground screw comes in the little baggie with all of that other hardware shown.


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