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Thread: Ground Wire

  1. #1
    Join Date
    Feb 2009
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    Default Ground Wire

    I have recently replaced a few receptacles (plugs) in my home, I have the older metal boxes and armored cable. There is no ground wire attached to the old receptacles. Should I attach a new ground wire between the new receptacles I am installing and the metal box? Advice appreciated, thank you.

  2. #2
    Join Date
    Jan 2009
    Location
    Needham, MA
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    559

    Default Re: Ground Wire

    yes, that's exactly what you should do. the ground goes from the outlet to the box which is in turn grounded by the armored cable.

  3. #3
    Join Date
    Feb 2009
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    Default Re: Ground Wire

    Thank you very much..

  4. #4
    Join Date
    Feb 2009
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    Default Re: Ground Wire

    A little late on the reply but would like to add a couple thoughts.

    The armored cable and connectors were never intended to be a grounded conductor or carry fault current.

    Also, to meet the requirements of the NEC you would need to drill and tap the back of the box to a 10-32 screw size and use a listed green grounding screw.

    If you wanted to use three wire grounded receptacles as replacements on your two wire system the NEC allows it as long as you protect the circuit with GFCI protection and don’t connect the ground terminal on the receptacle to anything including the box. Then, identify the receptacles per NEC requirements.

    The part I like the least about what you propose is that modern, correctly grounded receptacles give the “ground” an alternate path back to the grounded conductor, the neutral wire. I doubt very much that your service has the neutral electrically bonded to the metal parts of the system. (The armored cable or panel.)

    What this means is that should you have a fault from hot to “ground” all you are going to do is energize your armored cable sheath and the metal parts of the system. You will not blow a fuse or trip a breaker. In essence you are creating a hazard for yourself.

  5. #5
    Join Date
    Sep 2009
    Location
    jersey
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    174

    Default Re: Ground Wire

    Quote Originally Posted by NEC View Post
    A little late on the reply but would like to add a couple thoughts.

    The armored cable and connectors were never intended to be a grounded conductor or carry fault current.

    Also, to meet the requirements of the NEC you would need to drill and tap the back of the box to a 10-32 screw size and use a listed green grounding screw.

    If you wanted to use three wire grounded receptacles as replacements on your two wire system the NEC allows it as long as you protect the circuit with GFCI protection and don’t connect the ground terminal on the receptacle to anything including the box. Then, identify the receptacles per NEC requirements.

    The part I like the least about what you propose is that modern, correctly grounded receptacles give the “ground” an alternate path back to the grounded conductor, the neutral wire. I doubt very much that your service has the neutral electrically bonded to the metal parts of the system. (The armored cable or panel.)

    What this means is that should you have a fault from hot to “ground” all you are going to do is energize your armored cable sheath and the metal parts of the system. You will not blow a fuse or trip a breaker. In essence you are creating a hazard for yourself.
    I been looking for post like these, bx sheathing being used as an eguipment ground is soooo common and seriously dangerous. The resistance of that outer jacket is so high that a fault current on it will cause it to actually heat up cherry red like an element in a stove. If it doesnt have an equipment ground in it you can not install a 3 prong outlet (without a gfi as NEC said)
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