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Old 06-21-2011, 08:09 AM   #1
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Upgrading 2 prong(ungrounded) outlets to 3 prong(grounded)


My daughter recently bought a 1950's ranch and the electrical is in need of a little attention. There is a 100 amp service panel and most of the wiring is with BX cable. There has been some new Romex cable installed over the years also. We recently removed an older 2 prong outlet in the garage and installed a GFCI outlet. At the same time we ran 2 new plugs for the garage door openers. I understand that the 2 wire BX cable is grounded by the BX cable and metal boxes. We used metal boxes to continue the look in the garage. My question is on grounding the 3 prong outlets?? We hitched the 12-2 romex ground wire to the existing plug, which we changed to GFCI, as we extended the circuit to the garage door opener. We kept throwing the GFCI breaker on the plug? After some testing, we realized that the ground wire as it hit the metal box, would throw the GFCI breaker. We removed the ground wire from the GFCI and it works fine. We tested the plug, as well as the 2 new plugs, and they are wired correctly, including ground. We are a little confused by the ground. I assumed that the ground wire from the new circuit would need to be connected to the GFCI plug to continue ground? Looks like the BX cable grounds the GFCI outlet, which is hitched to the metal box through the screw, and grounds the remainder of the circuit as well? My question is the safety of the grounding. The 3 outlets work fine and are on a 20 amp breaker at the main panel, 12-2 wire, and 20 amp outlets. Any info would be helpful. Thanks in advance.

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Old 06-21-2011, 11:27 AM   #2
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Upgrading 2 prong(ungrounded) outlets to 3 prong(grounded)


Note that the ground wire may not be connected to a neutral or white terminal of the GFCI unit. Connect the ground wire to the green terminal (if any). Also connect together all ground wires coming into the box.

If two or more wires might want to go under one screw, connect just a short, say 6 inch, jumper wire (12 gauge for 20 amp circuits) to that screw. Connect the other wires to the other end of the jumper aka pigtail.

Do not use a jumper and connect together neutral wires connected to the line (feed) side neutral and wires connected to the load (continuation) side neutral.

Metal boxes must be explicitly grounded. If necessary use a (or another) pigtail or use a clip for that purpose (and sold separately) squashed between the receptacle tab (yoke end) and the box.

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Old 06-21-2011, 12:52 PM   #3
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Upgrading 2 prong(ungrounded) outlets to 3 prong(grounded)


Thanks. The ground was connected to the green screw on the GFCI. It sounds like I will need the extra piece that you talked about that goes under the yoke and is squashed between the tab and metal box. That will get pigtailed to the ground and thus continue the ground circuit.

Another question that has come up? There seems to be some receptacles that have the white and black wires hitched to the screws differently. The receptacle has 2 brass screws and 2 silver screws. For an end of run receptacle with 1 wire coming into the box the black wire is hitched to the top brass screw and the white wire is hitched to the bottom silver screw. In a middle of run receptacle there is the black feed wire hitched to the top brass screw and the white feed wire hitched to the bottom silver screw. The wire that feeds the next receptacle has the black wire hitched to the bottom brass screw and the white hitched to the top silver screw. This appears to crossed? I have also seen the black wire hitched to the top brass screw and the white to the top silver screw for end of run. In middle of run, the feed black is hitched to the top brass and white to the top silver screws. The out wire is hitched to the bottom for both. Not sure if this even matters? Looks like the connceting tab connects the screws, silver or brass, together on each side, unless broken? Any info would help. Thanks
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Old 06-21-2011, 02:16 PM   #4
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Upgrading 2 prong(ungrounded) outlets to 3 prong(grounded)


On a receptical all that matters (with respect to these tabs) is brass is your hot wire (black) and silver your neutral (white). the two screws are connected unless the tab is broken like you mentioned. Attention should be given though on a GFCI. There is the line side and load side. The wires feeding that receptical need to be connected to line and anything feeding off of it (down the line) will be connected to load and will also be protected by the GFCI.
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Old 06-21-2011, 06:00 PM   #5
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Upgrading 2 prong(ungrounded) outlets to 3 prong(grounded)


Check the GFCI and the receptacles after it for ground wires touching a bare spot on the neutral wires or screws. That can trip a GFI.
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Old 06-21-2011, 08:21 PM   #6
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Upgrading 2 prong(ungrounded) outlets to 3 prong(grounded)


Thanks for the info. On the GFCI that kept throwing the GFCI breaker on the outlet, we replaced the old 2 plug receptacle with a GFCI. We wired it in respect to the Load and Line sides of it. The outlet worked UNTIL we pushed it back into the metal box. Pull it out and turn the power on and it was fine. After some research carefully, we realized that as soon as the bare ground wire touched the metal box, it threw the breaker at the GFCI. It is wired with a BX cable to the plug and we ran new 12-2 NM cable to the new receptacles for the garage door openers. I realize the BX with a metal box with the GFCI attached by a screw to the metal box is grounded. We connected the ground wire on the GFCI to the green screw and it threw the breaker at the GFCI. I assume that if I use the clip that was mentioned above, a Halex Ground Clip, I will connect the clip to the side of the metal box, run the ground through the clip, pigtail the ground to the green ground screw on the GFCI to ground the receptacle. The BX will be grounded, the metal box will be grounded and the new NM 12-2 will be grounded with the ground clip? Sorry for the questions, but want to be sure. Not sure if I mentioned but once we removed the ground from the GFCI on the NM cable, the 3 plugs were tested and wired correctly with the tester. Including being grounded. Confused me. Again, any info is very helpful.
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Old 06-21-2011, 08:44 PM   #7
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Upgrading 2 prong(ungrounded) outlets to 3 prong(grounded)


Check the receptacles after the GFI for ground wires touching a bare spot on the neutral wires or screws.
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Old 06-22-2011, 01:05 PM   #8
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Will take a closer look at the 2 receptacles after the GFCI for the ground wire touching a screw or bare white wire. It is wired with new 12-2 NM cable and carefully put in the metal boxes, however, it is possible. Question....would the GFCI and 2 next regular receptacles work if the ground was touching a screw or bare spot? As long as the ground wire is NOT attached at the GFCI, all 3 receptacles work and the tester reads a correct wire and grounded? The ground read confuses me because the ground is off at the GFCI that feeds the next 2 receptacles. When we hitch the ground to the GFCI, the 3 receptacles still work UNTIL you touch the bare ground to the metal box in the GFCI, which throws the GFCI breaker?? We will double check our work and let you know. At this point, the ground is NOT attached to the GFCI and that and the next 2 receptacles are working correctly? Thanks once again, I appreciate the support. As a reminder, a BX cable feeds the GFCI metal box.
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Old 06-22-2011, 01:27 PM   #9
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Upgrading 2 prong(ungrounded) outlets to 3 prong(grounded)


Are there other three prong (grounded) outlets upstream (same circuit) of this new GFCI? It sounds like you may have a bootleg ground... jumper connected between neutral and ground... on an upstream receptacle or you may have a neutral wire in contact with the BX. Also note, old BX without a bonding wire is NOT considered to be a grounding conductor.
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Old 06-22-2011, 01:44 PM   #10
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Is upstream towards the main service panel? I will assume so. There is another 2 prong receptacle on the porch before the new GFCI, we will check that one also for a possible bare spot on the white contacting the ground. Not sure what a bonding wire is to ground the old BX? We started by replacing this GFCI outlet a few weeks ago and it worked fine and was grounded, according to the tester I plug in. Once we installed the 2 new receptacles, downstream, the ground became an issue. As I said, as long as the ground is not attached to the GFCI or touching the metal box while attached to the GFCI, the circuit runs fine. We will test the upstream receptacles and proceed from there. Confusing Thanks.
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Old 06-22-2011, 01:49 PM   #11
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Upgrading 2 prong(ungrounded) outlets to 3 prong(grounded)


Toward the panel, yes. It would have worked fine as long as nothing was connected to the load side of the GFCI.
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Old 06-22-2011, 04:47 PM   #12
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Upgrading 2 prong(ungrounded) outlets to 3 prong(grounded)


So as long as I only had the GFCI hitched to the Line side, which I did, it worked. Once I extended the circuit through the Load side, I started having the ground issue. That is exactly what is happening. So I should check the upstream side for correct wiring? That makes sense because the downstream is all new and correct, I believe. I assume that I should follow the feed line from the panel to each plug in the circuit and I should find my problem with the ground? Is this circuit safe?? Thanks!!
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Old 06-22-2011, 06:35 PM   #13
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Upgrading 2 prong(ungrounded) outlets to 3 prong(grounded)


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Originally Posted by AdamsBurr View Post
So as long as I only had the GFCI hitched to the Line side, which I did, it worked. Once I extended the circuit through the Load side, I started having the ground issue.
Then either the GFI is bad, or the wiring after it has an issue. The GFI is not protecting things that come before it...bootlegged ground or not. It is only protecting itself and things after it. Try switching it out with another one...if you have another in the bath, basement or kitchen that you know works, pull it out and use it as a test.
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Old 06-22-2011, 08:31 PM   #14
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Upgrading 2 prong(ungrounded) outlets to 3 prong(grounded)


Thanks. When we switched the current GFCI from an older 2 prong receptacle to the new GFCI, the receptacle checked out as wired correctly. After we added the new NM 12-2 cable and ran 2 more receptacles overhead for the garage door openers did the issue start. The black and white wires hitched to the GFCI works all 3 plugs. Once we try and hitch the ground from the new NM 12-2 that feeds the overhead receptacles to the GFCI we have issues. It does work until the bare ground wire comes in contact with the metal box. If we keep the receptacle out of the metal box, we are good at all 3 plugs, once we push the GFCI into the metal box, the GFCI breaker throws at the receptacle. Right now the ground has been removed at the new GFCI and the 3 receptacles are working. When we test them, the tester reads that they are correct and grounded. Sounds like the issue is downstream the GFCI? We will check the new wiring, 2 receptacles, to make sure the ground is not hitting a screw. We will also check the GFCI. I also plan to install a larger metal box, deeper, at the GFCI to allow more space. Although I assume that it is ok for the ground to touch the metal box? After all, it is hitched to it. Maybe we should use the ground clip to the metal box, run the ground to the new line to it, then also hitch to the GFCI green screw? It was only hitched to the green screw, not the metal box. Thanks again for all this knowledge. I assume this circuit is safe?
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Old 06-24-2011, 09:13 AM   #15
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Upgrading 2 prong(ungrounded) outlets to 3 prong(grounded)


Thanks and more thanks. Just checked the receptacles downstream and found that the last receptacle added had an issue. The silver screw that was not attached to a white wire because it was the end of run, was touching the metal box. My error. We moved the receptacle in the center of the box to make sure it was not touching the box. Checked the middle receptacle, which was fine. At the GFCI we attached the ground. Thanks also for the info on the grounding clip. Attached the grounding clip to the side of the metal box with a short bare ground wire pinched between. Used a short bare ground wire to pigtail the incoming ground to the next receptacle ground wire and attached this pigtail to the green screw on the GFCI. It worked!! Also checked the 2 receptacles upstream from the GFCI and they are fine also. At this point the circuit, including the new GFCI and 2 new receptacles for the garage door openers, work fine. We also checked for correct wiring and they all test as wired correctly. Thanks to everyone that responded, I appreciate it. Now back to my own wiring project to run the 100 amp sub panel in my barn. I will keep you all posted.

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