GFCI Installation Woes

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  #1  
Old 12-20-09, 01:03 PM
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GFCI Installation Woes

I have an outlet in a bathroom that is not GFCI. Beyond bthat, the outlet has a screw in one of the grounding holes. So yesterday I decided to replace it with a GFCI. The outlet without a screw in it tested as correctly grounded with an outlet tester. When I removed the box I noticed two things which I felt were out of place. First of all, the box was about 1.5-2 inches back into the wall. Between the box and the surface was plaster and tile. Secondly, the outlet did not have a ground wire connected to it, but there were bare copper wires (presumably ground wires) connected to a screw in the back of the box.

A picture of what I found as I was removing the old outlet:



I posted a few weeks ago about a situation with an exterior outlet that tested as correctly grounded using a home tester when it was a non-GFCI outlet and tested correctly after my GFCI installation, but there was no ground wire connected to either outlet. The discussion pretty much concluded the box must be grounded somehow. I have since replaced normal outlets and they do have a ground wire. So although I found the situation very odd, I continued assuming it would work out just as the exterior outlet did.

I installed the GFCI, turned the power back on, and the GFCI tripped. I could not get it to reset and stop being tripped. I turned the power off, ensured the wires were connected, and tried again. Nothing. The four wires (this outlet is in the middle of a wiring path) were connected exactly as they were on the outlet with a screw in it and according to the GFCI instructions.

I gave up after this and put the outlet with screw back in. I turned the power back on, the outlet showed as grounded, and all outlets downstream of it showed correctly grounded as they had before.

Any idea what is going on with my outlet? Should I be connecting a ground wire from the box to the GFCI? I did test this with a different GFCI outlet (I had a multi-pack) and it's giving the same results. In this configuration, the only thing connecting the outlet to the box is a screw (there is tile and plaster between the rest of the outlet metal and the box) vs. the exterior outlet where I believe it screwed right onto the box.
 

Last edited by DIYnewbie9; 12-20-09 at 01:33 PM.
  #2  
Old 12-20-09, 01:36 PM
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A GFCI can be grounded or ungrounded and still be code compliant, at least in certain regions of the country.

Grounding is not what is causing your problem. Likely you had the line and load wires are backwards.

Regular outlets can be wired without regard to line and load. There is no wired backwards. GFCI's however "know" what is the hot and neutral wire, and was is the line wires and load wires.

Shut off the breaker to this circuit and take a test meter and identify the one and only hot wire.(To tell, test each wire to that ground wire). That hot wire goes on the hot LINE connection. (GFCI's mark on the back what all 4 terminal screws are for.) The other wire in the same Romex? cable would go to the LINE neutral connection.

If you have 2 other wires from the old outlet, then install the darkest color wire on the LOAD hot side and the lightest color wire on the LOAD neutral side.

Now reset your test button and you should be okay to go. If, for some reason it pops, reverse the 2 load wires, in case someone did those backwards.
 

Last edited by pcboss; 12-20-09 at 05:06 PM. Reason: technical correction re connections
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Old 12-20-09, 02:22 PM
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Success! Thanks! The line and load were wired upside down on the original outlet. I switched them around on the GFI and GFI along with the downstream outlets are working. The GFI is not showing any problems with the outlet tester either so it must be another weird situation like the exterior outlet where the box is grounded.

Since it happened once, I'm sure it can happen again. Is there a way to tell on outlets downstream (which I'll eventually be replacing due to color) or on outlets elsewhere which set of wires are the load and which are line?
 
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Old 12-20-09, 04:07 PM
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Some thoughts:
1) Does the tester that you are using have 3 lights, i.e., "O", "K", and "X" or "Bad" (or something)? It should show a light showing voltage between Hot and Neutral, Hot and Ground, and no voltage (difference) between Neutral and Ground ("X").

2) From your picture, it looks like the (bare) ground wire(s) are wrapped around the cable clamp screw. Aside that it may be against code, I do not like to do that. You can't really crank down on the screw to get a great air-tight electrical connection because it would clamp the Romex wires too much. Often there is a tapped hole at the back of the box between the clamps for a green Ground Screw -- one that specifically for this purpose. I live near the coast and I am concerned with corrosion getting into the electrical connections. So, when I have a situation such as yours, I remove the ground wire, add a short third wire, and wirenut the three together. Then I wrap the new third wire around the Ground Screw (or the unused clamp screw if there is no Ground Screw hole). Now I have a good air-tight, corrosion -resistant connection. (I also do not use push-in connections for the same reason.)

3) The ground connection on an outlet is connected to the metal tabs that the screws go through to fasten it to the box. If the box is grounded, the screws (should) provide a connection to ground. However, if the screws are loose or get corroded, there goes your ground connection. So, what you could do is attach that third wire (Ref: #2 above) to the outlet Ground terminal instead, and let the screws provide the ground connection to the box instead of the other way around. It is more important that the outlet be grounded than the box, in my opinion.

4) A GFCI internally monitors the current going going through the Hot wire and the current going through the Neutral wire. It the two currents aren't equal (because some of the current is returning through a path other than the Neutral), the GFCI trips.

I hope this helps.
 
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Old 12-20-09, 05:20 PM
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Originally Posted by DirtySox View Post
2) From your picture, it looks like the (bare) ground wire(s) are wrapped around the cable clamp screw. Aside that it may be against code, I do not like to do that. You can't really crank down on the screw to get a great air-tight electrical connection because it would clamp the Romex wires too much There is no reason to have the clamp screw connection so that it crushes the cable. The sheath just need to be snug. Air-tight connections are not needed when doing ordinary electrical connections. Often there is a tapped hole at the back of the box between the clamps for a green Ground Screw -- one that specifically for this purpose. I live near the coast and I am concerned with corrosion getting into the electrical connections. So, when I have a situation such as yours, I remove the ground wire, add a short third wire, and wirenut the three together. Then I wrap the new third wire around the Ground Screw (or remove the unused clamp and screw and install the ground screw if there is no dedicated Ground Screw hole). Now I have a good connection. (I also do not use push-in connections for the same reason.)

3) The ground connection on an outlet must be connected to the metal box. If the box is grounded, the screws (should) provide a connection to ground. However, this is not a Code compliant method unless the box is surface mounted. If the screws are loose or get corroded, there goes your ground connection. So, what you could do is attach that third wire (Ref: #2 above) to the outlet Ground terminal instead, and let the screws provide the ground connection to the box instead of the other way around. It is more important that the outlet be grounded than the box, in my opinion. Both need to be grounded.

4) A GFCI internally monitors the current going going through the Hot wire and the current going through the Neutral wire. It the two currents aren't equal (because some of the current is returning through a path other than the Neutral), the GFCI trips.

I hope this helps.
I have made some technical corrections in blue to the post.

Grounding connections like described in #2 were commonly done in the early generation of NM cable. The correct method is to use a dedicated ground screw in a tapped hole in the box. This is easily changed. All grounds should be connected together and to metallic boxes.
 
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Old 12-20-09, 06:07 PM
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I might add that it is important that wires be "tight" against what they are connecting to. This makes a good connection.

Thus the reason for using a drilled hole in the back of the box with a self tapping screw. You can tighten down the wire tight to make a good connection.

A poor connection would sort of be like a water hose connected to another hose with just one turn of the connector. If you placed your thumb on the end of the hose to spray the water, you would not have any "pressure". It would mostly leak out the poor "connection".

And also connect a "pigtail" or short length of wire to the ground connection on the GFCI outlet as well.

Like this...
http://www.move.com/home-garden/Imag...tcm12-1558.gif
 
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Old 12-20-09, 06:19 PM
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Originally Posted by pcboss View Post
There is no reason to have the clamp screw connection so that it crushes the cable. The sheath just need to be snug. Air-tight connections are not needed when doing ordinary electrical connections.
Thank you for your corrections, PCBoss.

If the connection allows corrosion in, then the connection becomes less than good. A simple, loose twist of any wires (as I believe is shown in his picture) is fertile for a bad connection. I'd rather use a tight screw or a wirenut.

Originally Posted by pcboss View Post
Both need to be grounded.
Both would be grounded, but which method would be more fail-safe?

We could use two pigtails.
 
 

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