Rewiring of old outlets to GFCIs

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Old 10-14-16, 05:19 AM
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Rewiring of old outlets to GFCIs

I'm replacing an old outlet with a GFCI in my kitchen. Upon disconnecting the old, I've found that there are 3 black wires and 1 white. Using a voltmeter I've determined which of the 3 black was hot, and that was connected to the brass screw terminal. The other two were backstabbed into the two points on the back of the outlet to run downstream and supply the rest of the kitchen.

The GFCI I am installing only allows for rear screw clamp connections and screw terminal connections. After trying to figure this out for a few hours last night, I'm lost as to what the equivalent wiring is to the new GFCI.

I've tried pigtailing the two black wires that were backstabbed and attaching them to the load screw terminal, and the hot to the screw terminal, but the GFCI wasn't giving power to the face or downstream. Is it the wiring or is the GFCI potentially a dud?

The old outlet:

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Last edited by kkamin; 10-14-16 at 05:34 AM.
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Old 10-14-16, 05:31 AM
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I note you are in Chicago. Is the wiring in conduit? House or apartment?
I've determined which of the 3 black was hot
How? Did you use a multimeter? (A non contact tester can't be used.) Was the white wire connected to the silver side of the old receptacle?
 
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Old 10-14-16, 05:56 AM
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It's a condo and the wiring is in conduit. I used a multimeter to find which was the line source. The white wire was connected to the load / silver backstab of the old terminal, not the screw.

Here is a better idea of how the previous outlet was wired

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Last edited by kkamin; 10-14-16 at 06:15 AM.
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Old 10-14-16, 06:15 AM
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Connedt all three black wires to a pigtail and connect the latter to the line side hot screw of the GFCI unit. Connect the white wire to the line side neutral screw of the GFCI unit.

In the old receptacle (or any replacement non-GFCI duplex) each screw and the backstab hole nearest it and the prong slot blade on the other side nearest them are all joined together inside. In addition a tab between the two gold screws joins the two gold groups and same for the tab between the two silver screws. The tabs can be bent back and forth and broken off for certain wiring arrangements that I do not think you are using here.

Either the upper gold group or the lower gold group can be used for feed or continuation respectively (if the tab is not broken off) but for a GFCI receptacle the feed has to go on the line terminals and (with some restrictions) the continuation may go on the load terminals. We suggest not using the backstab holes at all but rather connect multiple wires to each other and to a pigtail if you do not have enough screws.
 
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Old 10-14-16, 06:20 AM
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I have tried that and had no success. Is it possible it stems from a outlet problem downstream maybe?
 
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Old 10-14-16, 06:33 AM
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Yes, an outlet problem upstream could be the cause.

Was the receptacle in question working OK immediately before you started working on it?

Could there be a GFCI unit upstream that you might never have seen before (and if so would make the new GFCI you are installing unnecessary).
 
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Old 10-14-16, 06:38 AM
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Thank you Allan, I have another GFCI but it is downstream from this one. The one I have been initially referring to is able to get power by testing with a voltmeter, (just not put it to the face or other outlets on the circuit), even if I disconnect the other one, that's how I'm deducing which one is up and downstream. I will have to take another look at the other GFCI to make sure it is wired properly, and then try again on the silver line terminal with this one. Perhaps my thoughts of up and down stream aren't correct here and that's the issue I'm not seeing.
 
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Old 10-14-16, 06:55 AM
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The receptacle would need two white wires to feed another receptacle. With only one white you have power in but no power out. The prior connections don't really make sense. Are you sure there isn't a missed wire in the back of the box?
 
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Old 10-14-16, 06:58 AM
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That's what I thought! There's no wire for a line out! But there's only the 4 wires in there. I've checked and rechecked it. Is it possible that one of those black ones was actually supposed to be white? Maybe I'll check that with a multimeter and see if a current will flow across any of the black / black connections..
 
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Old 10-14-16, 08:31 AM
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I almost suggested you measure each black to each black but you said all three were on the brass side and the tab wasn't removed. No harm doing it just to eliminate the possibility.

Are you sure that receptacle feeds another receptacle.
 
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Old 10-14-16, 08:44 AM
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Well I'm assuming it does because in a certain configuration I can get power to the other two outlets on the circuit, but if I disconnect this outlet, then I get nothing on the other outlets.

Maybe I'll go under the assumption that this doesn't feed any other outlet and is the last outlet on the circuit that goes back to the breaker.. maybe that will help me and explain the lone white wire.. but does that make sense then to have 3 black wires going to it if it's the last on the circuit?
 

Last edited by kkamin; 10-14-16 at 09:34 AM.
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Old 10-14-16, 11:48 AM
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but does that make sense then to have 3 black wires going to it if it's the last on the circuit
The only configuration I can think of is a switch loop. Hot comes in on black "A" and is connected to black "B" that goes to the switch and comes back to the receptacle on black "C". It could be at some point the switch failed or was removed and some wana-be electrician didn't know that only black "A" needs to be connected to the receptacle.

Now here's where it gets screwy if that power another receptacle. that receptacle could be getting power at the switch from "B" but that leaves the question of where the second receptacle gets its neutral.

I hope you could follow that.
 
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Old 10-14-16, 11:58 AM
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I follow most of it. Let me ask this, on the back of the outlet, since the tab is in place on the brass side, are the screw terminal and the two backstabbed areas essentially the same thing, regardless of the upper or lower position on the backstab? They're all one function piece that will accept and power the outlet? Or do they operate the same as the terminals, where the bottom backstab will need to get power from the upper backstab and then that's transmitted out?
 
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Old 10-14-16, 12:09 PM
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The tab intact means all the blacks were connected together and that is the real puzzle. I give my guess less than 50%. Even less if only one conduit.

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Old 10-14-16, 06:18 PM
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Do you have any switches in the room that appear to do nothing?

Normally the neutral must accompany the hot wire along all parts of the circuit except for switch loops. Without accompanying neutrals, the other two black wires are not correctly continuations to other receptacles or lights.

So perhaps the original receptacle in this location had the gold side tab broken off. The live hot and the white were the feed. The other two black wires were a switch loop to control one half of the receptacle unit. The original receptacle was replaced and the one there last, with the tab still in place, caused the other half of said receptacle to be always live and the switch to do nothing.

(The above is just a guess so you will want to trace all of the black wires.)
 
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