Wiring 3-Way Switch with 3 Light Fixtures??

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  #1  
Old 08-22-05, 12:16 PM
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Question Wiring 3-Way Switch with 3 Light Fixtures??

I'm in the process of rewiring my entire house and am doing so up-to-code (inspector will be coming). In one area, I added 3-way switches and 3 ceiling lights. The set up is as follows:

Supply line -> 3-way switch -> light -> light -> light -> 3-way switch

Before I started working on it, I just assumed that 3-way cable would be sufficient. Then, when I was following the wiring diagram I have for doing 1 light with 3-way switches, I seemed to be short a "hot" line to run to the next light. My guess is that I need to buy 4-way wire for runs between each light. Then, I would nut the 2 travelers and all nuetrals together at each box except the first and last lights. Then I would use the 4th wire as the "hot" for each light.

Its pretty hard for me to explain but I'm sure you guys get the jist of what I'm talking about. Does this seem correct and legal? If not, how do I set this up? And please note, its a little late to make changes for the switch locations because the walls are finished. It is a drop ceiling though so that part is correctable. In other words, the lights need to stay between the 2 switches at this point.

Any help is greatly appreciated!

Thanks!
 
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  #2  
Old 08-22-05, 12:32 PM
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Your analysis is all correct. Many people make the same mistake you did, trying to extrapolate a diagram with one light to handle multiple lights. It doesn't extrapolate very well.

Your proposed solution, although it would work, is my least favorite. Why run the travelers through the three light boxes when it isn't needed in any of them? Why crowd the boxes and create a tangled mess of wires in the light fixture boxes for no good reason?

Let "-" mean 14/2 cable, "=" mean 14/3 cable, and "#" mean 14/2/2 (or two runs of 14/2).

Here are the main possibilities, in order from my highest recommendation to my lowest recommendation:
  1. Power-S1=S2-L1-L2-L3.
  2. Power-S1=L1=S2, and L1-L2-L3.
  3. Power-S1=L1#L2#L3=S2.
The first solution is by far the simplest and most straightforward.
 
  #3  
Old 08-22-05, 12:34 PM
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The way that you described (using '4-way' cable between the lights) is a correct method. You use the 4 conductor plus ground cable to carry the neutral, the switched hot, and the two travelers between the fixtures.

Many people find it simpler to wire standard '3-way' cabling to a _single_ light fixture, and then run standard 2 conductor cable from fixture to fixture to provide the power to the additional fixtures.

-Jon
 
  #4  
Old 08-22-05, 12:39 PM
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Yes, you will need four conductor cable for this, if indeed you must have all the lights between the switches.

I think you will find this diagram handy.

You will probably have to go to an electrical supply place to get 12-4 wg (or what they call 12-2-2) as the big box stores won't have it.
 
  #5  
Old 08-22-05, 12:48 PM
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Just finished wiring 6 lights on two - 3-way switches (why do they call them 3-way when there are only two of them?) .... Used 14/3 between the switches and 14/2 between the lights..... simple and easy.... if that's what you're looking for. In essence, you're putting one light between switches - and running a couple more lights off the first one (14/2 wire)

Look at Lowe's web site for three different wiring diagrams for this application..... one of them will work for you. 1. light before switches 2. lights between switches 3. lights after switches...
 
  #6  
Old 08-22-05, 12:54 PM
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Originally Posted by thezster
(why do they call them 3-way when there are only two of them?)

Don't think of the number of switches, think of the number of wires that connect to them (not counting the ground).

A 2-way switch (standard single switch) has 2 wires. A 3-way switch has 3 wires. A 4-way switch (used between 3-way switches when 3 or more switches are required) has four wires.

That might not be why they named them that way, but it keeps them straight.
 
  #7  
Old 08-22-05, 01:05 PM
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Thanks guys, there are some great recommendations in there. I didn't really think that it would be up to code to run the 3-way cabling in the typical fashion to 1 light, and then run the others off that light (John Nelson's example 2, and winnie & thezster's recomendation). That would be great except for one problem. The walls are already finished and the wire I have in the switch box (1) is enough to reach light (1) and switch (2) has enough wire to reach light (3). I don't have enough length of wire to reach from both switches to the same light.

With that in mind, do you think it would be cleaner (what would an inspector prefer) to add a junction box to extend the wire or do you think I should use the 4-way wiring method? I guess its just a matter of opinion at this point but you guys have been doing this longer than me

And a side question, chirkware mentioned 12-2-2 cable. I thought lighting circuits were fine on 14 gage cable?? I sure hope so because 14-3 is what goes to my switches!
 
  #8  
Old 08-22-05, 01:12 PM
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14-gauge wire is fine if the circuit is protected by a 15-amp breaker. Most of the time, including this time, the poster doesn't say what the breaker size is, so we just fill in the wire gauge with a guess, since "14/3" or "12/3" is less confusing than "xx/3".

Use any solution that works. If my #1 is impossible for you, then use #2. If my #2 is impossible, then use #3. If #3 is impossible, then remove some wallboard. The junction box is okay as long as it remains permanently accessible and that is cosmetically okay with you (and probably more importantly, with your spouse). Remember, drywall is easy and cheap, so get what you want, even if it means drywall damage.

If you stay with solution #3, make sure you do the box fill calculations. Also, if the boxes are metal, and if you use two 14/2 cables between the lights, make sure both cables enter through the same knockout. Most inspectors would find solution #3 goofy.
 
  #9  
Old 08-22-05, 01:25 PM
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That's exactly what I don't want, the inspector to think what I did is odd or goofy. That means he'll be more likely to scrutinize the rest of my work.

Solution 2 will work fine for me and will be cheaper (don't have to buy 14-4 cable and I think 2 14-2s would look bad). Although like you said, drywall is cheap, but my arms still hurt from sanding it! I really don't want to do that again!

It is considered "permanently accessible" if its under a drop ceiling, correct?
 
  #10  
Old 08-22-05, 01:53 PM
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Yes, mounted on the joists above a drop ceiling panel is okay. Put a blank cover plate on the box.
 
  #11  
Old 08-22-05, 02:06 PM
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Originally Posted by Pete112
And a side question, chirkware mentioned 12-2-2 cable. I thought lighting circuits were fine on 14 gage cable?? I sure hope so because 14-3 is what goes to my switches!

Sorry for the confusion...I tend to overkill, so I always think in terms of 12 guage wire and 20A circuits (I have no 15A circuits in my house). Most people do probably use 14 guage, 15A circuits for lights.
 
  #12  
Old 08-23-05, 08:02 AM
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Originally Posted by Pete112
Thanks guys, there are some great recommendations in there. I didn't really think that it would be up to code to run the 3-way cabling in the typical fashion to 1 light, and then run the others off that light (John Nelson's example 2, and winnie & thezster's recomendation). That would be great except for one problem. The walls are already finished and the wire I have in the switch box (1) is enough to reach light (1) and switch (2) has enough wire to reach light (3). I don't have enough length of wire to reach from both switches to the same light.

With that in mind, do you think it would be cleaner (what would an inspector prefer) to add a junction box to extend the wire or do you think I should use the 4-way wiring method? I guess its just a matter of opinion at this point but you guys have been doing this longer than me

And a side question, chirkware mentioned 12-2-2 cable. I thought lighting circuits were fine on 14 gage cable?? I sure hope so because 14-3 is what goes to my switches!
Don't know about your inspectors - but ours accept running additional lights off the first one with no problems...
 
  #13  
Old 08-25-05, 06:02 AM
Bi_Polar
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Although the question has been answered, here is another good link to 3-way switch diagrams (in color) that may help you or others out. I know it has helped me!

3-way switch diagrams and instructions
 
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