Black (oxidized ?) copper wires

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  #1  
Old 11-30-04, 04:52 PM
Daytripper
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Question Black (oxidized ?) copper wires

My wife and I have just moved into a new (8 year old) home and in the process of doing some painting, I've pulled duplex recepticle and switch plates.

What I've noticed (and it's a first for me) is that both of the copper wires appear to be "blackened". There are many instances of this.

Oxidation ? or something else ? Cause for concern ?

Any help would be appreciated.

Daytripper
 
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  #2  
Old 11-30-04, 05:29 PM
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I doubt that it's a problem. Copper oxidizes black originally. Give it another 50 years and it'll turn green.
 
  #3  
Old 12-01-04, 11:34 AM
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One concern from experience: Are your switches and receptacles "push-in" connections, in the back, or are they connected with side screws? Push-in connections are notorious for loose connections, and loose connections naturally turn black from arcing, which is not good. If they are screw connections and everything works fine at present, they should be fine.

Juice
 
  #4  
Old 12-01-04, 11:45 AM
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Although after I posted before, I began to wonder why this copper was oxidizing so quickly. I've seen copper roofs exposed to the elements that turn black within six months. But I would expect that 8-year-old copper wire in electrical boxes not exposed to the elements would still be fairly bright copper.
 
  #5  
Old 12-01-04, 12:10 PM
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John, that's what I thought. In a clean, dry environment I would not expect, nor have I seen much of, copper oxidation unless arcing were present.
 
  #6  
Old 12-03-04, 05:05 PM
Daytripper
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Thumbs up Only with the help of the informed . . .

Thanks guys.

Push-in connections it is. Now starts the monumental task of correcting the problem.

Much appreciated.

Ron
 
  #7  
Old 12-03-04, 07:25 PM
SkyKing
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It is possible, not likely, but possible that during construction the lines were exposed to weather. In the cable industry the first 1/2" of copper can be blackened due to exposure to weather over the course of just 4 months.

I would assume John and the other's who believe it is due to arcing are correct!

My 2 cents.
 
  #8  
Old 12-06-04, 11:28 AM
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Push in connections are notorious for failure. They are poor connections, and degrade over time. Then they are loose connections. Loose connections cause arcing, where the juice tries to jump from the wire over to the other side of the conection in your receptacle. This would make the wires darken.

My advice, and that of many other veteran participants in this Forum over the years, is to land all your wiring on screw terminals only. Black wire goes on the brass colored screws, white wire on the silver colored screws.

With the power off, I would also recommend cleaning up all the bare ends of your wires with very fine sandpaper or emery cloth to get rid of the black and make nice, bright shiny copper prior to re-connecting to the recep. Wire with carbon covering it makes a poor connection as you are not exactly metal on metal.

juice
 
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