installing GFCI in old house: a mystery story

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Old 03-07-06, 03:54 PM
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installing GFCI in old house: a mystery story

Everything is my old house seems funky and nonstandard....

I want to replace a three-prong receptacle in the middle of a circuit with a GFCI receptacle, so I disconnect the recept and find that sheathed cable comes in from two places (of course). Each cable has a red wire and these are connected in the box with a wire nut. Now if I position the black wires at 10 and 2 o'clock, and the white wires at 8 and 4 I find that touching EITHER black wire and the box makes my tester glow. And touching either black to the 8 o'clock white makes the tester glow. AND touching white to white makes the tester glow. What is going on here? And how do I connect the new GFCI?

Many thanks.
 
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Old 03-07-06, 04:59 PM
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If there is a load downstream on the red side current will be drawn through the test light to that load. The test light completes the circuit. The white wire that shows voltage to a black is the neutral from the box. The other white feeds the downstream loads. The GFI goes on the neutral from the box, the one that shows voltage to black. To work safely you must turn off both the breaker to the black and red.
 
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Old 03-07-06, 05:22 PM
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thanks but...

Thank you. Maybe I misunderstand but let me make clear the the red wires that enter the box are connected only to each other; not to the receptacle. Only black and white wires were connected to the old receptacle and they are as I first described. And if I connect the GFCI to the white that shows volatage to black, what do I do with the other white? You're dealing with a rookie here.
 
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Old 03-07-06, 05:22 PM
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To properly conduct the test you tried to do, you need to completely remove any downstream loads. This means any wired lights must be turned off (or remove the bulbs), and anything plugged in must be unplugged. Testing with any load will cause it to appear as if the neutral is charged.

To connect your GFCI, connect the white wires to the LINE neutral connection and the black wires to the LINE hot connection. Connect the ground to the back of the metal box with a ground wire. Do not use the LOAD side of the GFCI.
 
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Old 03-07-06, 07:24 PM
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Originally Posted by gulleyj
Thank you. Maybe I misunderstand but let me make clear the the red wires that enter the box are connected only to each other;.
Yes but based on your description both the red wire and the black wire use the same neutral. Therefore at some other point there is a load on the neutral you are seeing and the red wire.

One common use of both a red and black wire and one neutral in a case such as you describe is that at least one of the outlets is on a wall switch. There are other reason though. Bottom line though theymost likely share the same neutral. It is important to shut off both the red and black wires breaker. If not you could end up as part of the path to ground for the live one.

Follow the other poster's instructions though especially if they vary from mine. I'm not an electrician. This is just based on DIY learning.
 
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Old 03-07-06, 08:02 PM
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multiwire circuit

The red wire still uses the white neutral.

Therefore you cannot use the LOAD side of the GFCI unit.

Whatever is using the red circuit is putting current on the white wire, hence the voltage reading.
 
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Old 03-08-06, 06:30 PM
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HI Gullyj.
what we understand is that you only want the receptical in the middle to be GFCI protected. If this is correct then follow RACRAFTS direction.
You most likly have a switched ckt there and that explains the readings on your tester, don't mess with the red wire. You must understand that the only receptical that will be protected by GFI is the one in the middle. Also most of those testers are for referance only. The others will tell you aswell, DON"T trust your life to them, If you get serious about this, Invest the money for the real deal. Good luck and BE SAFE!!
 
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Old 03-08-06, 08:05 PM
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gratitude

MANY thanks to you all. Mission accomplished and I learned something. For some reason the logic of electrical wiring is foreign to the circuitry between my ears, so I'll be back with more questions eventually, I am sure. My best to you all.
 
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