wiring 3-way circuit with fixture between boxes

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  #1  
Old 10-12-04, 01:42 PM
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wiring 3-way circuit with fixture between boxes

I would like to wire a ceiling fixture with a 3-way circuit.
The power enters at one of the switches.
Is there a way to run the power in a 3-way circuit from the one switch through the fixture and then to the far switch? How would I do this?
I normally run 14-3 between the 2 switches and then 14-2 to the fixture.
However, I am limited with how many wires I can put into the far box, so I was wondering if there is a way to run 14-3 from the first switch (switch with power) to the light, and then run 14-3 to the far switch.
Thanks.
Dave
 
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  #2  
Old 10-12-04, 02:05 PM
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From the first switch run the neutral to the fan on the white wire, and use the red and black for the two switch legs, as you normally would.

At the fan connect the white neutral to the fan. Connect the red and black switch legs from the first switch to the red and black that go to the second switch. Connect the white wire (marked with black marker) to the second switch to the black wire of the fan.

At the second switch connect the red and black wires to the terminals of the switch, as you normally would. Connect the white wire (reidentified with black marker) to the common terminal. This will carry switched power back to the fan.
 
  #3  
Old 10-12-04, 05:19 PM
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Bob's advice is almost correct, but it contains a code violation.

At the ceiling, connect red to red as Bob said. But connect the black coming from the first switch to the white going to the second switch. Then at the second switch, the red and white will be connected to the traveler screws, and the black will be connected to the second switch common.

Then back at the ceiling, it will be the black from the second switch which attaches to the black from the fixture.

Also, in Bob's first sentence, it would be more common terminology to refer to the red and black as "travelers" rather than "switch legs".
 
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Old 10-12-04, 05:35 PM
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Boy, and I was trying to make it easier on him.
 
  #5  
Old 10-12-04, 07:25 PM
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For what its worth:

Bob's advice may contain a code violation, but only in the color coding. NEC 200.7(C)(2) requires that when the white wire in a cable assembly is used in a switch loop, that it be re-coded with black marker or tape, and that the white wire be the hot supply wire to the switch. The benefit of this is that when all is said and done, the two wires left to connect the lamp are a white wire and a black wire.

_However_ this is such a minor safety issue as to compare (IMHO) to 'ground up or ground down'. In fact, my understanding is that the UK electrical code requires exactly the opposite use of coding, with the re-coded white wire being the switched wire going to the lamp. In addition, NEC 200.7.(C)(1) would seem to permit the white wire to be used for _any_ ungrounded conductor if properly re-colored.

Bob's way of doing it make the travelers between the switches much easier to identify, and I personally would be strongly tempted to bend code and follow his technique, if in fact his technique is not to code.

-Jon
 
  #6  
Old 10-12-04, 08:12 PM
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Okay,
This is what I have now....the electrician, when the house was built, prewired the switch box to potentially have a 3-way circuit. However, there was only a single pole switch there at the present time.
So, this is what I have in the first switch box....
There is a black line wire (hot)...another black wire which currently goes to the light on the single pole switch. There is also a red wire that is capped off. The neutral(white) is attached to the other white/neutral wires in the box (there is another switch in the box on the same circuit).
 
  #7  
Old 10-12-04, 08:17 PM
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Does not sound like it's prewired for a 3-way. More likely it's prewired for a ceiling fan. But you can use the wiring for a 3-way instead if you want to.
 
  #8  
Old 10-13-04, 04:52 AM
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What I started to do (and then changed my mind) was to have him picture this as the fan at the end of the circuit, rather than between the switches. I was suggesting he envision a 14/3 going to second switch carrying the neutral, and then a 14/2 coming back. I was then going to tell him to then eliminate the neutral, wiring direct at the fan. This would leave an unsed white wire in each cable, and only a black wire used in the 14/2, which could easily be moved to the unused white wire in the 14/3.

But I figured that might just as easily confuse someone rather than help them, so I left it out. I did stay with the concept of continuing the red and black travelers to the second switch.


Dave, as John said, you can put a three way switch in place of the regular switch. The capped red wire and the black wire become the travelers.
 
  #9  
Old 10-13-04, 06:35 AM
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Since the code is followed more often than it is violated, the code-compliant way of wiring this is much less likely to cause future confusion to any experienced person. When an electrically-experienced person sees a red and black connected to a red and white, he instantly knows exactly what is going on.
 
  #10  
Old 10-13-04, 10:17 AM
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Thanks a million, guys!!! It worked perfectly.
Dave
 
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