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I was checking out the outlets in my house, that's when I discovered 1 outlet didn't have an ground wire attached to it. I looked inside the plastic junction box, I could see 2 ground wires twisted together then looped around the screw at the back of the box. Does it mean the outlet is already grounded?

If it's not grounded, can I just attach a copper wire to the ground terminal on the outlet and twist it around the ground wires?

Also, the previous owner attached a cable on the opposite wall of this outlet, but it only has 2 wires: Hot and Neutral

I'm going to install an additional outlet there, I already purchased a metal outlet box. Since there is no ground wire, will the outlet be grounded if I just attach a copper wire to the ground terminal and loop it around the screw on the metal box?

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    So this plastic box has a ground screw in the back of it? What country is this in? – JPhi1618 Aug 8 at 16:07
  • Can you post a photo of the inside of the box please? – ThreePhaseEel Aug 8 at 22:28
  • It's obvious he is grounding to the plastic box. He may know something about plastic I do not! – Harper Sep 7 at 21:12
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First off, verify the two wires twisted together are really grounded and not just some addition that hasn't been completed. If they are grounds, then yes, connect a copper wire to the two twisted together, use appropriate wire nuts, and the other end to the ground screw on the outlet.

The wire the previous owner attached, is it in conduit with a metal box? if so, it might be grounded, you'd have to check that. The metal box you're installing will not be grounded unless you connect to conduit that is grounded or to cable that has a ground wire. Just going from a metal box to the ground on an outlet will not ground it.

  • Should the ground wire that is looped around the screw at the back of the plastic junction box be removed then attach it to the ground screw on the outlet? or should I just leave it as is and just add an copper wire to it? what is the purpose of it have it looped around the screw at the back? the wire the previous owner attached it is connected to the hot and neurtral wires in the plastic junction box I just mentioned. so will it be grounded? – oliveoil10 Aug 8 at 16:46
  • I am not familiar with a plastic box with a ground screw. It might be a requirement where you live. to play it safe, twist two new copper wires to the existing two, then connect one to the box and the other to the outlet. – JACK Aug 8 at 16:54
  • There is no point to attempting to ground to the plastic box. The entire point of plastic is that it is a terrible conductor. When you have a metal junction box, the box can touch the mounting flange of the outlet, which should be connected to the ground prong socket, and that can make a ground path, assuming the rest of the circuit is grounded. – Valkor Aug 8 at 19:51
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Question one: is it grounded? No. Question two: can you complete the ground? Yes. Question three: will the new outlet be grounded? No.

For the purpose of this answer, I am assuming that your house has modern grounded wiring throughout, and this is the exception.

Your first outlet sounds like it was done by someone who had seen wiring installed in metal conduit and metal boxes. In those cases, the ground is bonded to the conduit in the junction boxes, as well as to the outlets. The mounting flange of an outlet can provide a ground path, but check your local code to see if that is acceptable. Direct wire connection is more reliable. The plastic box you have will not conduct electricity, and is not any part of your grounding system. Assuming the ground wires are properly connected everywhere else, connecting the ground wires to the ground screw on the outlet will provide the proper ground.

The second outlet is problematic. You say "attached on the wall", but that can mean a lot of things. If you have a two wire extension cord stapled to the wall, you definitely can't get a ground in your second box. If the second box is attached to a conduit with two conductors in it, you might have accidental grounding, but don't trust it. A conduit shouldn't be a conductor. There are too many pieces and connections along the way.

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