2 lights and 2 switches, but want it 3-way.

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  #1  
Old 11-05-06, 10:37 PM
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2 lights and 2 switches, but want it 3-way.

My kitchen currently has two lights-- one on each end of the room. Each light is controlled by its own switch, also with one on each end of the room. I would like to use 3-way switches to make these lights turn on and off together.

I purchased two 3-way switches and 50 ft of 12/3 wire. I ripped out all the old cloth insulated wiring, and installed the new 3-way switches. Here is how I've run the wire (S for switch, L for light):

Breaker to L1 (12/2)
S1 to L1 (12/3)
S2 to L2 (12/3)
L1 to L2 (12/2)

But now, I can't figure out how to connect these lights together. Can someone explain to me which connections go where?
 
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  #2  
Old 11-06-06, 02:45 AM
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You need to run the 12/3 from S1 directly to S2 or run 12/4 from L1 to L2.
 
  #3  
Old 11-06-06, 04:22 AM
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As you have (almost) figured out, you cannot wire it to work properly the way you have run the cables. You either need 12-4 between the lights, or you need to run from S1 to S2 and remove the cable between the lights.

I always recommend that any cable runs you are unsure of should be drawn out on paper first. If it won't work on paper, it won't work when you run the cables. It's cheaper and less time to do the work on paper than it is to do the work with cable.
 
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Old 11-06-06, 05:22 AM
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Can I use two 12/2 cables between the two lights rather than 12/4?
 
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Old 11-06-06, 05:28 AM
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The quick answer is no.

You COULD use a run of 12-2 and a run of 12-3, but that would be, in my opinion, ludicrous. You would need to be very careful how you wired this to get it right.

Do the right thing. Admit your mistake. Replace the wire from S1 to L1 with 12-3 from S1 to S2.
 
  #6  
Old 11-06-06, 05:42 AM
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I have no problems admitting my mistake, and I want to fix it the right way, which is why I am here!

Let me make sure I am understanding you:

breaker to L1 (12/2)
L1 to L2 (12/3)
L2 to S2 (12/2)
S2 to S1 (12/3)

Can you also explain the connections? Thank you for your help!
 
  #7  
Old 11-06-06, 06:14 AM
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Instead of going from s1 to s2 you could run both of the 12/3 switch runs to the same light fixture and a 12/2 between the lights. Use L1 where the power feed is.
you would have this setup with an addition 12/2 cable going to the second light.

http://www.selfhelpandmore.com/switchoutlet/3way/3waypwfxthrufx.jpg
 
  #8  
Old 11-06-06, 06:40 AM
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There are many, many ways to wire a setup that has two three way switches. The method that uses the least wire may not be the easiest to understand. There are pictures in books (and you should go buy at least one), and there are pictures on the Internet.

Please make a drawing on paper before you do anything. While this is not difficult to understand, you NEED to completely understand this before you attempt to wire it.

The easiest connection to wire and understand is as follows:

Breaker to S1 with 12-2
S1 to S2 with 12-3
S2 to L1 with 12-2
L1 to L2 with 12-2

This is connected as follows:

At S1 connect the power black to the common of the switch.
At S1 connect the two white wires together.
At S1 connect the red and black to S2 to the traveler terminals of the switch.

At S2 connect the two whites together.
At S2 connect the red and black from S1 to the traveler terminals of the switch.
At S2 connect the black to L1 to the common switch terminal.

At L1 connect the blacks together and to the hot wire of the light.
At L1 connect the white together and to the neutral wire of the light.

At L2 connect the black wire to the hot wire of the light and the white wire to the neutral wire of the light.
 
  #9  
Old 11-08-06, 08:02 AM
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Guys,

Thanks so much for helping me out on this one. I ended up following this diagram:

http://www.the-home-improvement-web.com/information/how-to/three-way-switch-option8.htm

This is how I originally had it wired, except for the 2nd wire between the two fixtures. I realize, as racraft pointed out, that there are many ways to wire a 3-way switch, but this diagram seemed appropriate as my power was delivered to a light, not the switch. I took it one step further, and wrapped the black switch wire between the two lights in red electrical tape so if I ever open up these boxes I won't get lost.

I also picked up a copy of Wiring Simplified (41st edition) for entertaining late night reading. It was only $12.
 
  #10  
Old 11-09-06, 07:55 AM
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Using two 12/2 cables side by side like that is problematic. Not necessarily wrong, but often wrong. The site that you linked to should have had suitable warnings.

Did you use romex or some sort of metal clad cable?

Are your junction boxes metal or plastic?

-Jon
 
  #11  
Old 11-09-06, 08:07 AM
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You can, of course, eliminate any potential problems with the wiring diagram linked to by using one section of 3 three conductor cable and one of 2 conductor cable, instead of the to runs of 2 conductor cable shown.
 
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