No ground wire for outlet, but showing grounded

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Old 12-05-09, 07:25 PM
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No ground wire for outlet, but showing grounded

Today I decided to do my first electrical DIY job and install a GFCI outlet outside. It is under an overhang so the outlet previously was allowed to be a non-GFCI, but I wanted the additional protection. The outlet previously was a duplex 3-prong outlet that showed no issues on my 3-prong outlet tester (2 yellow lights on and no red). When I took the outlet out and went to install the GFCI, I realized that there was no ground wire. I was confused, but was honestly too excited from my first DIY electrical to stop. I hooked up the outlet, put it back in, and flipped the breaker. The outlet works fine, but it also is showing as correct on the outlet tester. I know the tester itself is working because it showed open ground on another outlet in the house.

The house is from the 50s, but with the exception of a few randomly located outlets (attached to the breaker box, high up the wall where a clock used to be, etc.) everything is three-prong and they all showed correct on the outlet tester except the one with open ground.

My question basically is how was the previous outlet and my new GFCI outlet showing correctly grounded when neither outlet has a ground wire directly attached to it? Is it somehow actually grounded in some way other than a direct wire attachment to the outlet?
 
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Old 12-05-09, 07:41 PM
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well, a couple questions:

is this in a metal box?

What type of cable feeds the box?
 
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Old 12-05-09, 07:42 PM
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Sorry nap beat me to it....
 
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Old 12-05-09, 07:44 PM
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Is it a metal electrical box the GFCI is installed in?

Is there a ground wire screwed to the back of the metal box?

Is the wiring run to the metal electrical box via metal conduit?
 
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Old 12-05-09, 10:48 PM
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do you have metal siding by chance
 
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Old 12-05-09, 11:23 PM
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It is a metal box.

The house is full brick construction with the exception of a couple overhangs which have metal siding.

I didn't take out the box to see if there was something screwed into it. The box is pretty solidly sunk into the brick and I just swapped the normal outlet for a GFCI.

I don't remember the wire that fed the box. It was only the white and black wires in the box.

Unless the conduit is withing the brick, I don't think it's using a conduit. It is an outdoor outlet, but is not external. It is in a metal box, in the brick, and flush with the brick.

My best guess is that it is running off the interior outlet directly behind it. It's on the same circuit as that outlet (as well as others) and there are no load wires running off the external outlet.
 
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Old 12-05-09, 11:59 PM
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Originally Posted by DIYnewbie9 View Post
It is a metal box.

The house is full brick construction with the exception of a couple overhangs which have metal siding.
I didn't take out the box to see if there was something screwed into it.
The box is pretty solidly sunk into the brick and I just swapped the normal outlet for a GFCI.
My best guess is that it is running off the interior outlet directly behind it. It's on the same circuit as that outlet (as well as others) and there are no load wires running off the external outlet.
If the tester shows a good ground then the installer of that box has something acting as a bond to effectively ground the outlet box.

Since you have gfci I wouldn't give it any more thought. Your gfci does not need the ground to function properly. This is a misconception by many people. So plug your lights in and enjoy the holidays....
 
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Old 12-06-09, 01:13 PM
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Originally Posted by Bruto View Post
So plug your lights in and enjoy the holidays....
Wow, you're good! That's exactly why I was doing this work now. Thanks for your help!
 
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