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Old 07-25-2008, 08:32 PM   #1
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Listed for grounding or not


For sometime I have been unable to document which metal box covers are listed for grounding. Any of you guys know what the latest is...?

I'm told there is something in the new 2008 about this . I am being informed that the flat cornered covers ( see images below) are listed for grounding and the round ones are not. Being retired but having installed many of these covers we were never red tagged for not grounding the metal yolks of devices as long as they were attached to the covers with at least 2 screws.


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Old 07-25-2008, 08:47 PM   #2
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Listed for grounding or not


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Originally Posted by Stubbie View Post
For sometime I have been unable to document which metal box covers are listed for grounding. Any of you guys know what the latest is...?

I'm told there is something in the new 2008 about this . I am being informed that the flat cornered covers ( see images below) are listed for grounding and the round ones are not. Being retired but having installed many of these covers we were never red tagged for not grounding the metal yolks of devices as long as they were attached to the covers with at least 2 screws.

Stub-

I didn't think that either were listed for this purpose since if you remove the screws, the device yoke is no longer bonded. Another problem is if corrosion develops on the screws, that could cause the lid to become electrically isolated if not in good contact with the box. Whether or not it is required (I never did bother to look), I always bond the device to the rear of the box via the devices' grounding screws. Always seemed like the smart way to complete the install.
Just me, 'tis all,
Jimmy

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Old 07-25-2008, 08:53 PM   #3
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Listed for grounding or not


your asking if you can not ground the switches themselves if you use an industrial raised cover? I'm not sure if technically can get away with it, but i always ground my devices just cuz i think its kinda cheesy not to
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Old 07-25-2008, 09:41 PM   #4
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Listed for grounding or not


Jim thanks for your opinion ... jimmy21 yes thats what I'm asking.

For surface mounted boxes 406.4(c) says for devices mounted to covers a connection must be made to the metal yokes grounding screw unless the box and cover are listed as making continuity for the box and receptacle the below image is what I'm talking about. This is how I thought it should be done but the exception says if listed to provide the grounding for the receptacle you do not have to connect to the ground screw of the device. How the heck do I know whether it is listed or not? I only know of two kinds the round ones and the flat cornered ones. Logic says the flats would be listed but where is the documentation from the manufacturer? I can't find a thing on raco or steel city.


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Old 07-25-2008, 09:56 PM   #5
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And wouldn't the grounding be under the UL listing the cover is given?
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Old 07-25-2008, 10:09 PM   #6
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Thanks Chris

That is exactly what I'm looking for,...yeah you would think the UL white book would have it but I can't find it.
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Old 07-25-2008, 10:26 PM   #7
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Thanks Chris

That is exactly what I'm looking for,...yeah you would think the UL white book would have it but I can't find it.

I wouldn't loose any sleep over it... You could always just try email to the cover manufacture for the listing.
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Old 07-25-2008, 11:40 PM   #8
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I wouldn't loose any sleep over it... You could always just try email to the cover manufacture for the listing.
Amen. That's what I was going to recommend myself. Still, I keep wondering...If the recepts are "grounding type" due to the inclusion of that copper strap that grips the screw, what is there on the blister cover that guarantees the same? Nothing!

Not arguing with you Stub, just that I have always felt, as an engineer, that they should be bonded explicitly, i.e. with 6" of ground wire. That way, there is never a question.

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Old 07-25-2008, 11:52 PM   #9
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And BTW Stub and Chris-I don't care what the code says about this! I will continue to do what I feel is responsible, if it is above the code requirements (i.e. not required by the NEC but in my mind a good idea). My big engineer brain sometimes sees a good reason for things, often based on my field experiences!

Take care you guys. Lot's of respect as usual,
Jimmy
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Old 07-25-2008, 11:53 PM   #10
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No way I can argue that point Jim.... I think we always have to remember that the NEC is really minimum safety standards. Just for some backround I asked this very question on the Mike Holt Forum a few years back and none of those guys could tell me what a listed cover would be at that time. And as you know there are a lot of credentials that hang out over there. I see now (thanks to Chris) that they (the cmp for art. 250) finally decided a little clarification was in order. Our inspectors never never tagged us cause there are only two primary manufactured device covers for metal squares, not counting mud rings. They didn't know either!! Sooooo....
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Old 07-26-2008, 12:22 AM   #11
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And BTW Stub and Chris-I don't care what the code says about this! I will continue to do what I feel is responsible, if it is above the code requirements (i.e. not required by the NEC but in my mind a good idea). My big engineer brain sometimes sees a good reason for things, often based on my field experiences!

Take care you guys. Lot's of respect as usual,
Jimmy
Even if you install emt with no grounding conductor?
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Old 07-26-2008, 01:08 AM   #12
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Leave it to you to bring that up...
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Old 07-26-2008, 08:39 AM   #13
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Leave it to you to bring that up...
Just wondering what the answer would be....
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Old 07-26-2008, 11:59 AM   #14
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Listed for grounding or not


I bet BigJimmy would pull a EGC in the EMT run anyway, just like I would.
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Old 07-26-2008, 12:24 PM   #15
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Listed for grounding or not


Well I would agree with that except in a residence you don't face the issues of a commercial environment. If the emt is installed correctly it makes for one heck of a equipment ground.

In many commercial buildings and agricultural they spec that a insulated egc be ran even though the installation is in emt. But this is because equipment like riding jacks and fork lifts and other equipment are prone to damage runs of emt and open the fault path. Animals are also tough on conduit runs.

In a residence I just don't see the problem, other than incorrect installation.

I won't argue with the ground wire being ran anyway but if I installed the emt in a residence I probably would not run the redundant egc.

Does anybody know if it is required to do so in the Chicago area where metal conduit is common in residences?

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