Adding GFCI outlets


Old 12-28-04, 08:16 PM
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Adding GFCI outlets

My house was built in 1961 and additional wiring was added at an unknown later date. The original wiring does not include a bare ground wire, so the original duplex outlets only accept two-prong plugs. In order to accomodate grounded plugs, I decided to replace the upstream receptacle in each circuit with a GFCI unit and replace each of the remaining receptacles with new three-hole duplex receptacles. When I pulled several outlets from their boxes in an effort to determine the wiring sequence in a circuit, I discovered several boxes with three sets of wires per box, and several boxes with only one set. I infer from this that there are several tees (to use a plumbing term) in the circuit. The instructions that came with the GFCI outlet describe how to wire the outlet to one set of wires or two sets of wires, but don't explain how to proceed if there are more than two sets of wires in a box. Can anyone help me? Thanks.
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Old 12-28-04, 11:58 PM
Join Date: Aug 2004
Location: USA
Posts: 539
Not an electrical expert, but there are quite a few

things that could be going on.

1) Are any of these outlets controlled by a wall switch? A "switch loop" would explain some extra wires.

2) The box was used to continue power to other receptacles or light circuits. What else loses power when you throw the breaker/fuse for those outlets?

How many wires, what colors are they and where are they connected to which color screws on the old outlets? That may help us figure out what's going on. Also how many cables are in the box. (ie, 2 cables, 2 white wires connected connected to the silver screws, 2 black wires connected to brass screws, etc)

I hope this helped some, please post back with more info!
Old 12-29-04, 06:39 AM
Join Date: Jan 2002
Location: Chicago
Posts: 1,915
It is best to map out the circuit first and find out exactly what is controlled by that breaker. Not only to help you this time, but in the future it may save your life by knowing exactly what is controlled by what breaker.

Find out everything that is controlled by this breaker. Also, I'm pretty sure you can't just use one GCFI outlet and then simply replace the downstream outlets with 3 prongs. I believe you have to replace every one of them with GCFIs, but I could be wrong. Somebody else will probably clarify this point.

GCFIs don't add a ground in the true sense. In fact there is a sticker you need to add that says no ground present. It just adds a layer of protection to the circuit.
Old 12-29-04, 08:57 AM
Join Date: Sep 2003
Location: Central New York State
Posts: 13,973
You can use a GFCI to protect downstream receptacles and then install a three prong receptacle for those downstream receptacles. However, those downstream receptacles MUST be marked as "No Equipment Ground"

Keep in mind that there will be no ground. This means that computer and other electronics that want a good ground won't have one and may not behave properly.

In general, I recommend against what you want to do. instead, I suggest that you install a GFCI exactly where you need it, and only where you need it. Perhaps this means one per room, or one in the living room only, or whatever. This will remind you that you don't really have a grounded circuit.
Old 01-03-05, 06:27 PM
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Additional Information

Thanks to each of you who took the time to respond to my question about installing GFCI outlets. I stayed up late the next night answering your questions at considerable length, but managed to lose the whole response into thin air. Here goes again.

First, I agree with those who say I need to map the entire circuit (haven't had the time yet). It is highly likely that one or more light fixtures and outlets in the room directly below were added to the circuit when the basement area was finished some time after the house was built. The wiring in the duplex outlet boxes that I examined appeared very professional, but unusual. When there were two cables in a box, they did not use separate screws for the "line" and "load" wires. Instead, the bare end of the first white wire, for example, is wrapped around a bare spot several inches from the end of the second white wire and this connection is soldered and covered with tape. The bare end of the second white wire is then wrapped around one of the white terminal screws on the duplex outlet. The same procedure was followed for black wires except that they ultimately connect with a gold screw, rather than a white one. In other words, instead of line and load wires connecting via the duplex outlet, they are connected directly to each other before reaching the outlet.

For those outlet boxes which have three cables in them, the same general approach is followed except that two wires wrap together around the third wire, which in turn connects to the appropriate terminal screw on the duplex outlet. Boxes with three cables are the equivalent of a plumbing tee and are apparently used to create branch circuits.

I know that a GFCI outlet protects all downstream outlets on the same circuit when those outlets are wired sequentially. What I would like to know is, How will my branch circuits (as currently wired) affect GFCI protection? If the first outlet box in the circuit turns out to be one of those which contains three cables (i.e. if it is a point where a circuit branches in two directions), how should I wire in a GFCI outlet to achieve downstream protection? And a further question: Regarding the required warning labels to indicate that a receptacle is not grounded, where can I get such labels?

If you are confused by my explanations and questions, please tell me so I can try to find a better combination of words to explain myself. As you can tell, I need all the help I can get. Thanks to all who are trying to help me.
Gary (deskdriver)

Last edited by deskdriver; 01-03-05 at 06:39 PM. Reason: Clarity

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