Grounding a Metal Gang Box ?

[Robert11]

Hello:

In a series of posts a while back, it was generally agreed that one should, to be code compliant, use a "dedicated" grounding screw to fasten the green wire to a metal gang switch/outlet box.

Also, that using the screw that held the box against a wooden stud was not acceptable.

Can't find any metal boxes in my local hardware store that comes with a dedicated grounding screw, or does there seem to be a threaded hole for.

Would like to do it correctly.

The boxes I have seen have 2 screws for fastening a clamp against the NM wire where it enters the box on one end, and 2 more for a clamp on the other end.

Does it satisfy the code to use one of the screws that is Not holding any NM wire in place as the "grounding screw" ?

B.

[Doug Miller]

Yes.

Note, also, that the Code _specifically_prohibits_ using a screw that *is* holding NM cable in place, for any other purpose.

-- Regards, Doug Miller (alphageek at milmac dot com)

Nobody ever left footprints in the sands of time by sitting on his butt. And who wants to leave buttprints in the sands of time?

[The Real Tom]

imho:

When looking at the back of a metal box, you should see one hole that has threads. It might look smaller than the other holes.

Next time you are in the store ask someone there to show you one.

BTW, if you still can't figure out how to ground a box, then get a nonmetalic one.

hth,

tom @

[Paul Franklin]

Often the hole isn't threaded. When you buy the green grounding pigtail with one end already wrapped around a screw, the screw is self-tapping and will make it's own threads. Often you will see 3 or

4 holes in the box and one or two will be slightly smaller. These are the ones that the screw will fit.

HTH,

Paul

[Paul]

I just noticed the other day looking at metal boxes in Home Depot, some now have a raised "bubble" with a threaded grounding screw hole, so you can mount the box flush on a hard surface and fasten the grounding screw without interference from the material behind the box.

-- Paul

[The Real Tom]

Oh yeah, when mounting a handy box, I now look for that bubble. Life is good!

later,

tom @