Outlet grounded on back of box

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Old 01-01-21, 06:25 PM
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Outlet grounded on back of box

Hi folks,

So every time I go to do something simple in the house like replace this outlet, I always find something new lol. This outlet pictured below is installed in a metal box. The white neutral wires and the black hot wires are wired just fine to the silver and gold screws on the outlet respectively. But the two bare ground wires are coupled together and then go out the hole in the back of the box and are wrapped around the aft end of the screw on the back of the box. It's the screw for the metal clamp that holds the cables in place that are coming into the box. Except in this case, this particular "clamp" isn't being used because the wires are coming in the other side of the box.

So my question is if this is ok to leave the outlet grounded this way? Or should I run a wire from the outlet's green/ground screw to the other ground wires, and then ground them to a "new" screw on the box (instead of the back of the box).

Thanks!


 
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Old 01-01-21, 06:48 PM
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What should be done is the two ground wires should be brought back into the box. The spare clamp should be removed and the screw put back in. Add a piece of ground wire to the splice, wrap it around the screw and bring it out to the receptacle.

The do have green ground screws that will go in the screw hole instead of the clamp screw.
Those can be used but are not imperative.
 
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Old 01-02-21, 04:27 AM
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In particular, wrapping the loose ends of wires around the aft end of a screw sticking through the box is not a good or sufficient connection (bonding).

OT: Also, just twisting the ground wire ends together is no longer good or sufficient; a wire nut or crimp ring is needed. A (wood) screw that relies on wood behind the box to screw into is not good or sufficient for connecting wires to the back of a metal box
 
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Old 01-02-21, 08:04 AM
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In particular, wrapping the loose ends of wires around the aft end of a screw sticking through the box is not a good or sufficient connection (bonding).

OT: Also, just twisting the ground wire ends together is no longer good or sufficient; a wire nut or crimp ring is needed. A (wood) screw that relies on wood behind the box to screw into is not good or sufficient for connecting wires to the back of a metal box
Thanks. I've seen AC cable into a metal box on one end. Then someone spliced Romex and then bonded the ground of the Romex to the metal box. I'm guessing this isn't permitted.

My understanding is that AC cable doesn't have a dedicated ground wire and relies on a bonding strip and the armor as a ground path. If my understanding is correct, how does one add a branch circuit without directly connecting to the ground?
 
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Old 01-02-21, 08:44 AM
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For metal spiral flexible armor cable and metal outlet boxes, the bonding strip required for grounding does not have to extend into outlet boxes let alone be wire nutted to other ground wires. When metal conduit including spiral armored cable is properly attached to metal outlet boxes and to properly grounded panel boxes the various outlet boxes are considered grounded and Romex cable continuing downstream from those boxes may have ground wires attached to the box (not just wrapped around an unnutted screw shank) as described higher up in this thread.
 
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Old 01-02-21, 10:23 AM
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Yes, I didn't pay attention to the picture that shows the grounds just wrapped around that screw and not clamped down with a nut.

But thank you for answer a question that has been bugging me. I always verified the continuity between the ground on branch romex and the cable/box but thought it might be against the code because it was a continuous wire back to the panel

The first time I saw armored cable I was so confused. I thought everything was ungrounded and the ground on the receptacles were just attached to the metal outlet box for show.
 
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Old 01-02-21, 04:03 PM
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The metal spiral armor does not count as a ground wire if there is no bonding strip or wire running the full length inside, outside of any paper lining.
 
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Old 01-02-21, 04:54 PM
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Hmm. I can't find any ground wire (inside or outside) or bonding strips. All I see are 2 wires and a metal clamp that connects the AC to the metal box. There is continuity between the nearby subpanel and the receptacle box but is the impedence possibly too high if there is a fault?

This is pretty much what I see if I were to remove the AC from the box (without the clamp):

 
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Old 01-02-21, 06:27 PM
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Check if bonding wire has been cut or broken. It is pretty thin bare wire. Your cable doesn't look old enough to not have bonding wire.
If it doesn't have bonding wire, you may not get a good ground connection and even if you do have good ground connection now, once some corrosion takes place, it will have high resistance in ground, which is not good.

Bad ground path can be worse than no ground path. If you have hot wire shorted to bad ground, breaker may not trip since you would get less than breaker's rated load and this will overheat the wire and cause fire.
 
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Old 01-03-21, 11:26 AM
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Donít want to nitpick or go off on a tangent, and maybe this was just done somehow for the picture, or maybe you are already aware of it, but that bottom neutral on the receptacle in the picture isnít connected properly.
 
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Old 01-03-21, 11:41 AM
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Please feel free to nitpick, itís what helps me learn and keeps us safe 👍

I can see in the picture it looks like the wire isnít wrapped around the screw properly, is that what youíre referring to? I think itís just the angle of the picture because it is in fact wrapped around the screw. Let me know if youíre talking about something else.
 
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Old 01-03-21, 12:04 PM
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Hi John Ė

Yep, it looked to me (and my eyes are not great Ėlol) that the wire is hardly wrapped at all around the screw. I believe they are supposed to be wrapped 3/4 around the screw Ė and thatís the way the top neutral looks to me.

But now looking more carefully at the picture I can see where itís just an illusion and it fooled me.

My bad. So never mind lol Ė and good luck!
 
 

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