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Thread: ground electrical boxes

  1. #1

    Default ground electrical boxes

    hi

    I have 12/2 romex cable coming into a metal electrical box, I was wondering if I need to ground the metal box?

    If so, should i use 12 gauge to ground the box (or any gauge wire) and do they sell the screws to attach to the metal box so I can ground it? Or can I use any screws I see in the metal box?

  2. #2
    Plumber Cass's Avatar
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    If the ground wire will not reach to the threads where the ground screw goes then pig tail with yellow wire nut and a peice of #12 bare wire to it.
    Ground screws are avaliable at hardware stores and big box stores. They are green in color. As far as I know any screw with that thread is OK to use as long as it is green.

  3. #3
    Licensed Electrical Contractor Speedy Petey's Avatar
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    The screw does not need to be green, but it does have to be a machine thread. Sheet metal and drywall type screws are NOT allowed.

    And yes, the box MUST be grounded first and foremost.

  4. #4
    Aspiring Old Fart, EE, computer & networking geek Mikey's Avatar
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    The Equipment Grounding Conductor, the box, and any device attached to the box must all be bonded together. In addition to the guidance Speedy Petey gave you, the screw used for gounding/bonding can be used "for no other purpose", so you can't use a Romex cable-clamp screw (but if you aren't using the clamp, throw it away and you can then use the screw for grounding). Somewhere else on this forum there's a nice cutaway picture showing a neat way to accomplish that: the ECG is wrapped around the screw in the box, and carries on to the screw on the device; neat, clean, with no wirenut cluttering up the works.
    Last edited by Mikey; 01-27-2008 at 04:49 PM.

  5. #5

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    Get some panel screws. They are easy to wrap around the wire around and continue it over to the ground terminal.

  6. #6
    Licensed Electrical Contractor Speedy Petey's Avatar
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    Quote Originally Posted by iminaquagmire View Post
    Get some panel screws. They are easy to wrap around the wire around and continue it over to the ground terminal.
    This isn't the best advice.
    There are about 10 different types of panel screws, and very few have actual machine threads.
    If you are going to go get anything, get real ground screws. I'd bet they are also ten times cheaper than panel screws as well.

  7. #7
    Aspiring Old Fart, EE, computer & networking geek Mikey's Avatar
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    Quote Originally Posted by Speedy Petey View Post
    This isn't the best advice.
    There are about 10 different types of panel screws, and very few have actual machine threads.
    If you are going to go get anything, get real ground screws. I'd bet they are also ten times cheaper than panel screws as well.
    Took the words right out of my fingers...

  8. #8
    DIY Senior Member BrianJohn's Avatar
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    Is this 12-2 with a ground or are you in an older house and want to run an equipment grounding conductor to each box?

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