Adding a 4-way to an existing 3-way circut.

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  #1  
Old 06-27-05, 02:00 PM
MJKc3
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Question Adding a 4-way to an existing 3-way circut.

I seem to have a unique 3-way circut installed for my basement lighting.
Instead of the (power/feed) coming from one end (at a switch) the power source enters to a junction box (in the basement) then the cable to the light fixtures (also in basement) and the 2 existing 3-way switches (upstairs) go out from there.

It works fine but I need to add a 4-way to control these lights from the basement as well. The problem is that all the diagrams show a flow which I do not have. I cannot figure how to add the 4-way as there is no (black/red) connected between the 3-ways to put the new switch into.

I ran 2 new romex runs giving me 4 wires to the new box and a new 4-way there. I then split the (white /red) which came from the 3-way switches in the junction box, accross the new switch. This seemed to work until I realized that when the 4-way was left off both 3-way switches had no power. (they each have telltale lights)

Any and all help would be greatly appreciated.

Marc
 
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  #2  
Old 06-27-05, 02:31 PM
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When working with three and four way switches, it helps to draw yourself a picture.

The easiest way to add a four way switch is to run 3 conductor wire (plus ground) from either existing 3-way switch to the new location. You then replace the 3-way switch with a 4-way switch, and wire the 3 way switch in at the new location.

I cannot tell from your post what the original wiring is. If you want to work from your existing wiring, try again to explain it. Be specific, include ALL junction boxes and all wiring. Describe each cable and the wires inside the cable by insulation color. Include all wires, even those not attached to the switch or light.

As for what you have done already, it is wrong. You should not have run two pieces of 2 conductor NM cable. You should have run one piece of 4 conductor NM cable. If either box is metal where these two cables connect then you will be creating an unsafe situation. An inspector would not generally allow this. With plastic boxes it is still wrong, but not unsafe. An inspector might allow this. However, this is a debatable issue.
 
  #3  
Old 06-27-05, 02:40 PM
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If you can do what Bob said (i.e., run a new 14/3 cable from one of the existing 3-ways to the location of your new switch), you don't need to understand anything at all about how it is currently wired. You can to this purely mechnically. The 3-way will move from the existing box to the new box, and the 4-way will go in the existing box.
  1. Remove the 3-way switch.
  2. Connect the wire which was formerly connected to the black screw (common) on the 3-way to the black wire of your new 14/3.
  3. Connect the other two wires that were connected to the 3-way to the two "input" screws on the 4-way.
  4. Connect the white and red of the new 14/3 to the two "output" screws on the 4-way.
  5. At the new box (the other end of the new 14/3), connect the black wire to the black screw (common) on the 3-way.
  6. Connect the red and white of the new 14/3 to the two remaining screws.
This algorithm works no matter which of the numerous different ways it might be wired now.

You can also do it with the two 14/2 cables you ran, but it wastes more wire. In this case, you leave the 3-way switch where it is and install the 4-way in the new box.:
  1. Remove just the two traveler wires from the existing 3-way (leave the wire attached to the common screw alone).
  2. Connect these two wires to one of your new black/white pairs.
  3. Connect the other black/white pair back to the two screws you just vacated on the 3-way.
  4. At the new box, connect one black/white pair to the two "input" screws on the 4-way and the other black/white pair to the two "output" screws on the 4-way.
This algorithm also works without having to figure out which of the many ways it is currently wired.
 
  #4  
Old 06-27-05, 03:03 PM
MJKc3
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Thanks for both replies...

I'm sorry if my description was lacking detail.
I returned all connections to the original configuration and works again as before, all connections described below.

I have:

(1) 14/3 from (front) 3-way switch upstairs to junction box in cellar.
(1) 14/3 from (rear) 3-way switch upstairs to junction box in cellar.
(1) 14/2 from panel to junction box.
(1) 14/2 out of junction box to (4) light fixtures in cellar.

All bare copper together and jumpered to box.
White from both front & rear switches joined together in junction box.
Black from panel/feed connected to black of front switch.
Black from fixtures connected to black of rear switch.
Red from both front & rear switches joined together in junction box.

Thanks, Marc
 
  #5  
Old 06-27-05, 06:20 PM
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Marc, I'm not sure why you gave us all that information. We don't really need it. Can you use either of the two solutions I presented in my last post?
 
  #6  
Old 06-28-05, 05:03 AM
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John,

Marc provided the information because I asked him to.

Marc,

Now I have a clear picture of the situation. You can connect your two pieces of 14/2 in the manner John described in the lower portion of his post. They get connected to the red and white wires that go to/come from both switches.

Take the red and white from one 3 way switch and connect to the black and white of one of your new 14-2 cables. Take the red and white from the other three way switch and connect to the black and white of your other new 14-2 cable. At the four way switch connect one black and white to the input screws and the other black and white to the output screws.

To minimize issues related to using two pieces of 14-2, run the cables side by side or on top of each other, and if possible through the same holes on the junction boxes. Use plastic boxes.

Keep in mind that the junction box in the basement where all these wires connect is going to be rather full. If it's a box in the open that you can easily replace, you might want to consider a larger box. Make it a plastic box.
 
  #7  
Old 06-28-05, 02:23 PM
MJKc3
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Oh well...

This morning before work I tore out those 2 new runs of 14/2, so looks like I'm on to plan B.

I plan to run the new 14/3 from one 3-way location upstairs to the new switch location in the basement. I just got home with some 14/3 and decided to check back here first.

Marc
 
  #8  
Old 06-29-05, 07:09 PM
MJKc3
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Thumbs up Finished !

THANK YOU to all... Especially Linesman !!!

New switch functions perfectly !

Hopefully I can assist someone in the future. This is a great resource.

Marc
 
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