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250.148 #220855 06/23/20 10:43 PM
Joined: Mar 2005
Posts: 236
watersparkfalls Offline OP
Member
I have a concrete box without means to connect a screw to it...It was installed in a block wall and the core is filled with concrete. It is for a GFI receptacle, no splices, wires in EMT go directly to the GFI, without claiming it is a Isolated grounding conductor...Is the EMT a good EGC for the metal box?

Thanks in advance,
H2O

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Re: 250.148 [Re: watersparkfalls] #220856 06/23/20 11:53 PM
Joined: Jul 2004
Posts: 9,512
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gfretwell Online Content
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A properly made up EMT run is a grounding path. Did they also include a grounding conductor in the bundle coming in? If you really want a connection to the box and the installer wasn't polite enough to put a screw in the tapped hole you should be able to chip a little concrete out next to the box and use a clip. When I set the concrete boxes in my walls I ran a #10 screw a little longer than a typical "green ground screw" and put a dab of duct seal on the outside so I had a good void to install my ground screws.


Greg Fretwell
Re: 250.148 [Re: gfretwell] #220857 06/24/20 08:49 AM
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Posts: 236
watersparkfalls Offline OP
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Yes, I have a black/white/green with no way to bond box, other than the EMT right now. If I just feed the GFI with the conductors and have EMT to ground jbox, would that be code compliant or would I need to at the very least use a grounding clip?

Thanks again,
H20

Re: 250.148 [Re: watersparkfalls] #220859 06/24/20 03:20 PM
Joined: Apr 2002
Posts: 7,191
HotLine1 Offline
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The box would be bonded via the EMT, however the presence of the green conductor would require that to be bonded to the box,

I would follow Greg and do the clip trick.


John
Re: 250.148 [Re: watersparkfalls] #220860 06/24/20 07:34 PM
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Posts: 9,512
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gfretwell Online Content
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They also make "self grounding" GFCIs with the little brass tab on the yoke and a spring on the screw that I suppose would be legal.


Greg Fretwell
Re: 250.148 [Re: watersparkfalls] #220864 06/25/20 07:33 AM
Joined: Apr 2002
Posts: 7,191
HotLine1 Offline
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Greg:

I had the same thought on the self grounding, but that would be dependent on the device to box mounting.

ie: 4" sq raised cover. Some AHJs may not 'like' that.


John
Re: 250.148 [Re: watersparkfalls] #220865 06/25/20 12:46 PM
Joined: Jul 2004
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gfretwell Online Content
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We are supposed to trust that a properly made up metallic raceway grounds the box so this would be supplemental grounding but I do think the clip might be a better solution if it could be done in a non destructive way. I suppose a more elegant solution would be using a small diamond wheel in a rotary tool to eat out the concrete but most guys are not going to have that in their bag.


Greg Fretwell

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