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Old 03-19-2008, 02:00 AM   #1
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Default Grounding metal boxes

At work we install a wet location deep metal 2-gang box loaded with 20A GFCI & regular 20A receptacle (off of the GFI). The box and (metal) cover is supposed to be grounded, right?

If yes / yes I have a follow up...

-thanx

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Old 03-19-2008, 08:19 AM   #2
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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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Old 03-19-2008, 08:22 AM   #3
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Default Grounding metal boxes

Is this a trick question? I'm curious to hear the follow-up question.
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Old 03-19-2008, 08:44 AM   #4
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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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Old 03-19-2008, 08:53 AM   #5
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Other than having metal screws into the devices and boxes for the covers, how else would you ground the plates?
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Old 03-19-2008, 08:56 AM   #6
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Quote:
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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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Old 03-19-2008, 09:07 AM   #7
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Quote:
Originally Posted by Speedy Petey View Post
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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Old 03-19-2008, 05:05 PM   #8
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To ground a metal box is easy:


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

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Old 03-19-2008, 05:29 PM   #9
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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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Old 03-21-2008, 06:53 PM   #10
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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.

---

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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Old 03-21-2008, 06:57 PM   #11
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Pix of box / cover in question...





^that exact setup and 2-gang as well depending on the truck.
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Old 03-21-2008, 07:10 PM   #12
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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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Old 03-21-2008, 09:29 PM   #13
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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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Old 03-21-2008, 09:38 PM   #14
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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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Old 03-21-2008, 09:38 PM   #15
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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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Old 03-21-2008, 10:44 PM   #16
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Quote:
Originally Posted by rlc3854 View Post
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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Old 03-21-2008, 11:36 PM   #17
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Quote:
Originally Posted by rlc3854 View Post
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?
Quote:
Originally Posted by gilbequick View Post
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...

---

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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