Adding a 4-way to a pair of 3-ways

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  #1  
Old 01-01-06, 06:11 PM
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Adding a 4-way to a pair of 3-ways

I want to add another switch to an existing circuit which has two 3-ways on it now. I can fish to eihther of the two exisitng 3 way locations, however would prefer to fish to just the location that feeds the load (lights). That location is a lot easier to get to than the other one.

I have not bought the switch yet, and the diagram that comes with it would probalby help, but I was running wire today (other areas) and trying to plan this out in my head. I could not find any diagrams on the internet to help with this. Your help is appreciated.

Thanks Mike
 
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  #2  
Old 01-01-06, 06:17 PM
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Run a black/red/white/bare cable from the location of your new switch to either of the two 3-way switch boxes. It makes no difference which one. Either will do just fine. After carefully recording which wire goes to each screw on the 3-way (especially noting which wire goes to the black screw), remove the 3-way from the box. You will move this 3-way to the new location, and install the 4-way in the box that you removed the 3-way from.

If all this sounds good, I can provide connection details. I need no more information from you, since this project is so easy you don't even need to understand how it is currently wired.
 
  #3  
Old 01-01-06, 09:43 PM
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John,

Thanks for the quick reply. I was going to take a stab at it here, (on paper) without looking it up in some diagram. However after thinking it through, began to second guess myself.

Please outline for me what goes where for the re-positioned 3way and the new 4way that is in the old 3 way spot.
You already know this, but the black screw is the outbound black to the light.

Heres my guess
On the repositioned 3way:- Red & Black remain on the gold screws. White gets re-labeled to black and goes on Black screw.

On the 4-way: Reds will remain my travelers staying on the gold screws. Blacks from other 3ways also go on the other gold screws (i think there are two other golds on a 4way, remember I still don't have that yet). re-labled white gets wirenuted to the outbound black to the light.

Is that it? If I did not want to re-label then I would have to run 2 - 14/2's or a 14/4. FYI, I will use a 14/3 since I still have lots left over from my spool. Let me know. Thanks
 
  #4  
Old 01-02-06, 06:04 AM
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No Mike, you're a little mixed up.

On the repositioned three way you have the right idea, but the wrong wires. Since one of the wires will become the switched hot wire, it should be the black wire. Connect the black wire to the odd colored screw on the three way, and connect the red and white to the same color screws. re-identify the white wire as hot with black or blue marker on both ends.

At the new four way switch these three wires get connected as follows: The black wire gets connected to the wire that was connected to the odd screw, the wire that takes power to the light. The red and white wires get connected to the four way switch. It does not matter which color screws they get connected to, as long as they get connected to same color screws. The other two wires that were connected to the three way switch get connected to the other two screws on the four way switch.

All grounds get connected to the metal boxes, the switches and each other.

I hope this makes sense.
 
  #5  
Old 01-02-06, 06:17 AM
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It would have worked just fine the way you want to do. It is just better(might be code) to use the black as the switched wire instead of a traveler.
 
  #6  
Old 01-02-06, 08:44 AM
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I didn't take the time to read what Bob and Joe said, but they're probably correct. They always are. I'll just say it one more way, just to give you more to read.

I won't mention the grounding wires or screws below, but interconnect them all in each box.

At the 3-way box (which is becoming the 4-way box):
  • Take the wire off the black screw on the 3-way. Use a wire nut to connect it to the (reidentified) white wire of your new cable.
  • Take the other two wires off the 3-way. Connect them to two screws of the same color on the 4-way. Sometimes these two screws are marked "input" or "output" (it doesn't make any difference which pair you use).
  • Connect the red and black wires of your new cable to the remaining two screws on the 4-way.
At the new box (to where you are relocating the 3-way):
  • Connect the (reidentified) white wire to the black screw.
  • Connect the red and black wires to the other two screws.
That's all there is to it.
 
  #7  
Old 01-02-06, 09:33 AM
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Guys, thanks for all of your help in this. I understand all of the connections now. However I have one problem - Box Fill.

That box now will have 2 - 14/3's and 1 - 14/2, plus the switch. My count would therefore be 8 conductors, 1 ground, 1 switch. Correct me if I am wrong, but that adds up to a value of 22 cu in. My box is 20.5 cu in, and I have not seen any single gang boxes any bigger. I also cannot re-route any wires. Is there some exception in the codes to allow for more wires in a box if they are all to service a single load / switch? What do I do now?
 
  #8  
Old 01-02-06, 02:11 PM
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Replace the box with a larger one. If the walls are closed, you'll probably want an "old-work" box. You can find one larger than your current 20.5. 22.5 is a common size and should do the trick for you.
 
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