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Old 10-02-2007, 09:14 PM   #1
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Ground screw in 4" box


Hi;
I have a mix of NM and BX in a 4" J box.
The box does not have the standard 10-32 (or whatever the thread is) for the GND screw from the NM cable (because it is an older box that originally had only BX). There were some holes on the edges of the box, but none had any threads at all, so I opened one hole up and put in a 10-32 screw, nut, flat washer, and split lockwasher to secure the GND wire from the NM cable.
Is this code, or does the screw need to thread into the box?
If not, I will change the box.

Thanks

FW

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Old 10-02-2007, 11:23 PM   #2
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Ground screw in 4" box


It's not code compliant but on a scale of one to 10 I'd put it pretty low on that list. There is a item called a ground clip that clips to the side of the box and fastens the grounding wire.... that would have been fine and code compliant. Like this....



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Old 10-03-2007, 12:46 AM   #3
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Ground screw in 4" box


What stubbie provide the link and the photo of the grounding strap hook up this one of the common way to hook up with older boxes

btw some older box it do come in 10-24 screw pattern so watchout with this it will catch ya by suprise

Merci, marc
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Old 10-03-2007, 02:46 PM   #4
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Ground screw in 4" box


Stubbie's way is code compliant...your way isn't but it is very effective...which way will give you a better ground over the years??? who can tell. If I was the Authority Having Jurisdiction and inspecting this box i'd give you a pass.
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Old 10-03-2007, 08:32 PM   #5
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Ground screw in 4" box


I bought some of those ground clips.

This method seems a whole lot easier than dealing with screws and nuts, especially when I had to open up the hole first.

Before I started getting "strict" with myself about code, I sometimes used to use the cover plate with screw to attach the ground. But more often I used the threaded ground hole, a #10-32 screw, and always a flat washer.

I now realize that using the cover screw to connect the ground wires is a big NONO, as the ground is lost once the cover to the box is removed!
It's amazing how we change when we get a little older<g>

I bought a pack of the green ground screws, so I shouldn't need the washer anymore.
I also understand that I am not allowed to put more than one ground wire under this screw, and that all thru-grounds must be securely fastened, and a pigtail run to the box ground screw.

While on the subject of pigtail ground wires, let me run this by you:
I am wiring a GFCI receptacle in my kitchen to a 20A line which will use Romex (12/2) from the panel.
There is a BX cable (12/2) already in the box which goes to one more receptacle in the kitchen.

Can I run one continuous ground wire from the Romex cable around a green screw in the outlet box, then up to the GFCI outlet?
I would think this would be better than using a pigtail which would have two short ground wires coming off of the Romex ground; one for the box and one for the local receptacle.

FW
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Old 10-04-2007, 12:53 PM   #6
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Ground screw in 4" box


Look at 314.40-D

"Tapped hole or equivalent". Seems that "equivalent" would include the hex head 10/32 bolt and nut, would be compliant. Now, you cannot use a self tapping screws. Odd isn't it?


I like the clips too. But I use the ones with the conductor already attached.
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Old 10-04-2007, 07:34 PM   #7
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Ground screw in 4" box


I looked at my local HD for the ones with the conductor attached, but could not find any.

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Old 10-05-2007, 01:25 PM   #8
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Ground screw in 4" box


Fw.....You have to go to an electrical supply house. Price may be an issue, but not always.

I can buy wire from Graybar cheaper than Lowes or Home Depot. Even cut wire!
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Old 10-05-2007, 03:07 PM   #9
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Ground screw in 4" box


John

314.40 d is means provided by the manufacturer not the electrician.

It is not unusual however to tap your own hole using a greenleee tap drill and put in your own screw.

250.8 is the applicable code for listed grounding hardware

FWIW... in 2008... 250.8 has been completely rewritten and will include a machine bolt and nut as a compliant grounding means. This is why I said that it wasn't code compliant (yet) but I would put it very low on my list of things to worry about. Heck there is nothing in the code that says you can't use a wood or drywall screw...you just can't use a sheet metal screw. Go figure....

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