What is this third set of wires?

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  #1  
Old 03-06-13, 10:08 AM
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What is this third set of wires?

Hi Guys,

So I've replaced plenty of switched in my time but never came across this before. The switch controls two fluorescent light fixtures which stopped working so I replaced them but the new ones didnt work either so I figured it must be the switch, I wne to install the switch and took out the old one (wish I paid attention to how it was wired) and when I went to install the new one I noticed these two wires comming through the bottom. I'm pretty sure the green one was attached to the ground but I have no idea where that bottom whiteone went or what it even does.

Any thoughts?

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  #2  
Old 03-06-13, 10:39 AM
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Logic would say those three cables you have are:

Feed in
Feed out
To light.

So now, you are going to have to identify which is your feed in. It will have power on the black line.
The feed out probably goes to other receptacles or lights

Since you have all those connections open.... there should be something else dead in the near vicinity.

I would install the light.
Identify the hot cable.
Try connecting to one of the other cables to see what comes on or connect to either one until you find the light cable.

After that the connections are pretty much straightforward.
 
  #3  
Old 03-06-13, 10:51 AM
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Looking at the old switch I guess there is no ground on it, so I gotta pair the green with one of the blacks, other black to the otehr pole on the switch then all whites together?
 
  #4  
Old 03-06-13, 11:01 AM
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Do not splice the green to the blacks. Green is for grounding only. Black is an ungrounded or hot conductor.

Try splicing the whites together. Two blacks to the switch. Cap the black/white pair.
 
  #5  
Old 03-06-13, 11:10 AM
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But there's only two blacks, the ones coming out of the bottom are green and white, I just took apart the plug for the washer and its black and white so I have no idea where the green and white pair goes unless thats the main hot and the two top ones go to the washing maching and the lights. Also you can see a seperate copper ground comming up through where the green and white ones do so the green shouldnt be a ground I wouldnt think. Should I just try it? will it blow anything up? lol
 

Last edited by Dave3; 03-06-13 at 11:26 AM.
  #6  
Old 03-06-13, 11:35 AM
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Having dealt with creative wiring in the past year, there are two things I can think of;

Option A; Unlikely
1) Black-A from box to switch
2) Black-B from switch to one fixture
3) Black-C from switch to a different fixture
4) Whites B and C from fixtures to White-A (to breaker box)

EDIT. Now that I think about it; I had a horrible time fixing a switch panel for my parents because of this exact problem; two outside lights came separately into a single switch.

Option B; What PJmax said
1) Black-A from box to switch
2) Black-B from switch to one fixture
3) Black-C spliced into Black-A (directly with a pigtail, or by way of the light switch) to provide power to outlets or another room.
4) Whites B and C to White-A (to breaker box)


I can also conceive of a way that this could be used for a 3-way switch. But I have trouble believing someone would do it this way when the correct way would have the same amount of difficulty.
 
  #7  
Old 03-06-13, 11:38 AM
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Are you sure that it is "green" and not "old black"?

Have you tested which wire combinations are hot?
 
  #8  
Old 03-06-13, 11:43 AM
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My first thought was switch loop, like maybe the wires in the bottom are coming from the box where the power comes in and the top two are heading back to the two light fixtures.
 
  #9  
Old 03-06-13, 11:49 AM
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Not sure if anyone noticed...but it appears there is a bare copper coming in from the bottom and is screwed to the box. Also looks like there is bare copper coming from both top cables and also clamped to the box.

Does that make any difference?

Looks to me like (if the bottom is really green and white) that someone just used some sort of odd cable to do what they did.
 
  #10  
Old 03-06-13, 11:50 AM
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I can come up with a few more examples of bad wiring that would technically work, but it would involve some some strange splicing of wires with the switch that I think you would have found odd enough to remember.

But, for fun, you might want to take a look at the lights themselves (or the electrical box they connect to) to see what you have for wires up there.

But first, I'd leave the wires apart and see what other lights/outlets are not working. Most likely it's the power supply to those.
 
  #11  
Old 03-06-13, 11:51 AM
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I noticed these two wires comming through the bottom. I'm pretty sure the green one was attached to the ground but I have no idea where that bottom whiteone went or what it even does.
There should not be a cable with one green, one white and one bare wire in it. You need to investigate a little more. First of all, is the cable in your house MC or NM? Then,
  • Try loosening the clamp securing the bottom cable and pulling it into the box a little more to see if it has other wires that have been cut;
  • Open nearby receptacles and look for a cable with that green wire in it.
  • Open the light (again) and look there;
  • Look in the panel;
  • Separate all of the wires in this outlet and test each pair for 120V
  • Consider whether the "green" wire might be a discolored black.
 
  #12  
Old 03-06-13, 11:53 AM
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I saw the bottom one. Not sure if the others have bare copper, but you could be right.

I didn't really notice in the original post the first time I read it that we were talking about two light fixtures. Now I think we are just looking at one set of wires from the breaker box and one set each to the lights.
 
  #13  
Old 03-06-13, 12:06 PM
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Michael....
If you look carefully between the black and white on the uppers on both sides (as well as below the clamp) it appears there is a bare wire.
 
  #14  
Old 03-06-13, 12:15 PM
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Gunguy45.

I concede; there are three grounds. (anyone read that in Picard's voice?)

Because of that, I can come up with a way that the lights would have worked with the "green" (still convinced it's back) connected to ground. Since that is just a horrible idea, I will not share it.

I will also pose this option; since we are dealing with fluorescents, the ballasts might simply be bad. If possible, I would connect some other light instead of the fluorescent ones to do the troubleshooting.
 
  #15  
Old 03-06-13, 12:53 PM
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So I wired it up green(pretty sure its actually green but who knows) with left black and right black to other post, added a ground to the box and its working!

Thank you guys very much for the advice!
 
  #16  
Old 03-06-13, 04:50 PM
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Glad you got it, and thanks for letting us know.
 
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