adding a new 3-way switch to existing circuit


  #1  
Old 12-02-03, 03:57 PM
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adding a new 3-way switch to existing circuit

We have a set of lights in our hallway that are controlled in several locations through 3-way and 4-way switches.
I would like to add one more location (put a switch at another doorway). The nearest switch is about 20 feet away and is a 4-way switch.
Is there a way to add another switch to this circuit? Would this switch be a 3-way if I ran a wire to the existing 4-way, or am I asking for trouble?
I believe there are currently 5 switching locations for these lights, so i would like to add a sixth.
Thanks.
Dave
 
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Old 12-02-03, 04:10 PM
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You need to add a four way switch. For two or more switches the first two are three-way switches and the others are all four-way switches. Electrically, the three way switches are at the start and end of the chain of switches, and the four way switches are in between.

To add a new four way switch near an eisting four way switch you will need to have four wires (plus ground) running from the existing four way switch to the new four way switch. You can buy a piece of 14-4 or 12-4, along with the appropriate box and the switch at most of the big box stores.

Connecting the new switch involves removing two of the wires from the existing switch and wirenutting them to two of the wires in your new cable. The other two wires go onto the existing switch. At the new switch all four of the wires go to the switch. The trick is to know which wires to connect and where to connect them. Hopefully this will be obvious to you. It may help to draw yourself a picture.

I have left out the ground wire on purpose. Your new wire will have a solid bare ground wire. This si connected to the ground wires at the existing switch and to the switch itself at the new switch. If the new junction box is metal then the wire must also connect to the junction box.
 
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Old 12-02-03, 05:09 PM
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Thanks, Bob.
We have Leviton Decora 4 way switches. Which of the 2 wires on the existing switch should be removed? I have read about traveler wires and common wires.
Also, on the switch, some of the scres are different colors.
 
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Old 12-02-03, 05:38 PM
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The wires to be removed on the existing switch most likely are in the same cable assembly. They will either most likely be black and white, or black and red if the return goes through the box. They should be going to screws of the same color.

If the return does go through existing switch junction box then leave it alone. This will be two white wires wire-nutted together.
 
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Old 12-02-03, 06:11 PM
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I undertand what you mean by in the same bundle because those are the traveller wires that go between the different switches.
What do you mean by "return wires" ? You said that there might be white wires connected together.
 
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Old 12-02-03, 06:31 PM
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Sometimes nearest isn't best. This project is a bit easier if you run a 12/3 or 14/3 to your new box from one of the 3-way switch boxes. Then you can replace the 3-way with a 4-way, and reinstall the 3-way in your new box. If you like this option, post back with the details of the wiring in the existing 3-way box, and I'll provide the connection information. Also tell us if this is a 15-amp or 20-amp circuit (i.e., is this 12-gauge or 14-gauge wire).
 
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Old 12-02-03, 07:26 PM
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John,
At the base of the stairs i found a 3 way switch. It is Leviton. On one side, there is a single brass screw with a red wire.
On the other side, there is a brass screw with a black wire and another screw which is a black color. To this black screw is attached another black wire.
The wire is 14 gauge.
Thanks.
Dave
 
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Old 12-02-03, 07:29 PM
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Electricity needs a path back to the source. For a 110 circuit, this path back to the source is provided by the return. In normal residential wiring this return is a white wire.

If the circuit is wired from the source through each of the switches and then to the light then the return wire will be wired through each switch box. This will show up as the white wire, and it will be wire-nutted to the the white wire going to the next switch. (Only the hot wire is switched, return wires should not be switched.)

However, if the circuit is wired from the power source to the light fixture, then the hot will be sent off to the first switch, where it will start the switches. In this case the extra wire present at the switches will not be a return, but will be a hot wire.

In either case, you should have 12-3 or 14-3 going into and out of the switch box containing the four way switch you want to tap into. Two of the wires from each cable will attach to the switch, the other wires will be wire nutted together. The wiring directions are the same regardless of which they are, so it's not a big deal.

John does present an alternative, which may or may not be easier for you. His alternative is electrically easier to wire, and perhaps easier to understand, but may or may not be easier to implement.

Take a look at the location where you want the new switch, and determine which existing junction box will be easiest to run a new wire to from that location. If one stands out as the easiest then go with that one. However, if two or more seem about the same then you can choose which one to use, in which case routing to a three way switch will be easier to implement.

As John said, let us know what you find and how you think you want to proceed. With a detailed description of the wireing at the switch you choose we can help you sort out the wiring.
 
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Old 12-02-03, 07:40 PM
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If you choose the option I have presented:[list=1][*]Run a 14/3 cable from the 3-way switch box to the location of your new box.[*]Remove the black wire from the 3-way switch black screw. Connect this black wire to the black wire from your new 14/3 cable.[*]Remove the other two wires from the 3-way switch and attach them to the two "input" screws on the new 4-way switch (sometimes the screws are labeled "input" and other times they are merely two screws of the same color).[*]Connect the red and white wires of your new 14/3 to the "output" (or other two screws) on the 4-way switch.[*]Take the 3-way switch you removed to the new box. Connect the 14/3 black wire to the black screw on the 3-way switch.[*]Connect the red and white wires of your new 14/3 to the other two screws on the 3-way switch which has been relocated to the new box.[*]Interconnect all grounding wires and green grounding screws.[/list=1]That's it.
 
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Old 12-03-03, 06:18 AM
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Well Guys,
I went in the basement and looked under the area where the existing 3-way switch is, and it is completely inaccessible (svereal heating ducts, etc underneath). I guess that means I will be going to the junction box with the existing 4-way switch and adding to that one. (the other 3-way switch is on the second floor).
I just want to get this straight now....I will take 2 wires that are probably from the same romex cable from the existing 4-way switch and connect them to the 2 wires that will be going to the new 4-way switch. Would these wires be on the "input side" or the "output side" of the existing 4-way switch?
Then to which screws would I attach these on the new switch.... the same screws I removed them from on the existing one?
I understand the other wires from the 14-4 wire will go from the existing switch to the new one. Thanks again.
Dave
 
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Old 12-03-03, 06:22 AM
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You will need 4 wires going to you new 4 way switch. 2 out of the box to the new 4 way and 2 into the box from the new 4way. I believe they need to be in the same cable. I don't think you can run 2 14/2 cables between the same box and be code compliant.
 
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Old 12-03-03, 06:45 AM
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I understand I will be using 14-4 romex...I'm just not 100% sure which 2 wires to remove from the existing switch and which to leave on it (2 wires from existing switch will need to be wire-nutted to 2 wires from the 14-4 cable going to the new switch.
 
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Old 12-03-03, 06:50 AM
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Dave,

The terms input and output don't really apply to a switch, at least not in this case. It sounds like you have the right idea.

You need to run a single 14-4 cable from the existing 4 way switch box to the new 4 way switch box. The reason for 14-4 (as opposed to two pieces of 14-2) is that the current going in each directions within the cable should be the same. With a piece of 14-4 this will always be the case, but with two pieces of 14-2 this will only be the case some of the time, depending on the position of this switch and the other switches.

In this new cable you should re-identify the white wire to be a hot wire. You can do this with a permanent marker, on the white insulation just below where it ends.

At the existing switch remove two of the four wires that are connected to the switch. These need to be two from the same cable, and they should be connected to similar colored screws on the switch. At this box, connect two of the new 14-4 wires to the switch where you just removed the other wires, and connect the other two wires with wire nuts to the wires you just removed.

At the new switch connect the four wires to the switch. Connect the two from the other switch to one set of screw terminals, and connect the two from the other wires to the other set of screw terminals.

Also connect the ground on each end. This should complete your circuit.

Please post back and let us know how this goes.
 
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Old 12-03-03, 07:43 AM
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Although the terms "input" and "output" are not particulary approrpiate for a switch, many 4-way switches do indeed have screws marked with those words. There is no polarity however, and input and output are symmetrical. The only purpose of the labeling is to arrange the four screws into two groups of two. That part is important. Other 4-way switch manufacturers do it with different color screws rather than using the terms input and output.
 
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Old 12-04-03, 05:28 AM
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OK, I bought a 4-way switch yesterday. It has 2 brass screws on the left side that say "in" next to them and 2 black screws on the right that say "out". When I use an ohmmeter, each set of screws (one in and out pair) will have continuity when the switch is on.
My question is: which wires do i remove from the existing 4-way (one in and out pair or 2 ins or 2 outs)? and does it matter where on the new switch I put them (top or bottom)? Thanks.
 
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Old 12-04-03, 05:38 AM
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On your existing switch remove either the two "ins" or the two "outs", it makes no difference which ones.

Whatever wires you connect to the existing switch, connect the same wires to either the "ins" or the "outs" on the new switch. Electrically it makes no difference which in or chich out you connect to.

Let me try to explain it this way. Starting with one of the three way switches, you have a pair of wires going out of the three-way and into the first four-way. You then have a pair of wires going out of the first four-way and into the second four-way. Then out of the second four-way and into the third four-way. Eventually you have a pair of wires out of the last four way and into the last switch, a three-way. To complete the description, at the beginning and end of the switches you have a single wire into the first three-way and a single wire out of the last three way.
 
  #17  
Old 12-06-03, 11:19 AM
ricciuto
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Are there any good wire diagrams to do what you are trying to accomplish? Showing the wires, connections and type of switches. I learn much better with pictures and diagrams. This is of interest to me as I have a similar situation.
 
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Old 12-06-03, 01:38 PM
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Choose your wiring method from one of these.

http://www.homewiringandmore.com/swi...let/index.html
 
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Old 12-07-03, 09:00 AM
ricciuto
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Great web page for the diagrams. Thanks. These diagrams are as basic and simple as it gets.


 
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Old 12-15-03, 02:36 PM
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I just wanted to update you guys....I ended up being able to snake a wire to the existing 3-way switch and then was able to convert it to a 4-way and added another 3-way in the desired location. It works like a charm!!! No more stubbed toes. Thanks again John and Bob.....You're the best!
Dave
 
 

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