Switch loop and three way switches

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Old 12-22-13, 05:36 PM
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Switch loop and three way switches

I have a light that currently works on a regular, good old switch loop. Works absolutely fine. This is done with a piece of regular 14/2 romex running to the ceiling box, power also being fed into the that same ceiling junction box. Nothing to fancy going on there.

In the box that holds the switch for the switch loop are three additional wires: red, black, and yellow, which travel to another switch box. Currently these are not hooked up to anything, they were just placeholder wires.

Wiring a three way switch is well documented on the net, and I can do that just fine. However, the introduction of the switch loop into the situation makes it somewhat confusing for me. Does anyone have any helpful instructions on how to wire a three way switch that takes into account the fact that my switch runs on a switch loop? Or, perhaps a three way switch is not the solution to my situation?

TIA experts!
 
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Old 12-22-13, 05:43 PM
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You have an existing single pole switch on a two wire loop.

Now you want to convert the above switch and add a new switch to the red, black and yellow wires so that you have two 3 way switches.

Do I have that correct ?

The three wires to the remote location are ok but you'll need one more conductor to your existing two wire switch loop. You need three wires from each switch to the light location, which also contains the power.
 
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Old 12-22-13, 05:49 PM
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Correct, currently single pole switch on a two wire loop. Sounds like it would require another wire run, which would be more work that I am willing to do. Thanks for confirming.
 
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Old 12-22-13, 05:54 PM
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You're welcome...........
 
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Old 12-22-13, 06:18 PM
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You have enough wires.

At existing switch box:
  • Switch loop white to yellow.
  • Switch loop black to switch common terminal.
  • Other black and red to traveler terminals.
At new switch:
  • Yellow to common.
  • Black and red to traveler terminals.
 
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Old 12-22-13, 06:29 PM
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Posternine is absolutely correct. Thank you !

I thought I read the three colors went to the existing light whereas they are actually at the single pole location. You only need two 3 way switches and you are ready to go.
 
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Old 12-22-13, 07:07 PM
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Your yellow by the way is likely a dirty/stained white.
 
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Old 12-22-13, 08:41 PM
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Mr. Awesome wrote:
Your yellow by the way is likely a dirty/stained white.
I was puzzled why there was conduit between the two switch boxes but Romex for the switch loop. But that explains the mystery.
 
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Old 12-23-13, 06:21 AM
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The preferred method of converting a "regular" switch loop switch to 3 way is to run a 3 wire cable from the existing switch box to the new switch location. No changes are needed at the light box. In your case the cable (with the dirty white wire) is already strung.

For those eavesdropping who need to string the 3 wire cable, if the best route between switch boxes passes the light box then the new cable can go non-stop around the outside of the light box.
 
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Old 12-23-13, 12:46 PM
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In the box that holds the switch for the switch loop are three additional wires: red, black, and yellow, which travel to another switch box. Currently these are not hooked up to anything, they were just placeholder wires.


If I read the post correctly your three unused wires are in the box that contains the switch and not in the ceiling box with the power coming in correct?
Is this wired in conduit? The yellow wire is not normally found in a cable. If this is the proper gauge wire for the circuit then you could easily use what is there provided that the wires are all run within the same cable or conduit. Do these wires run to a box at the location where you would like the other three way switch? The switch loop should carry power on the white wire (recoded black) from the ceiling box down to the switch box (call this box A). Inside the switch box (box A) you connect this incoming hot (white recoded black) to the black wire of your three wire cable which goes out to box B. The black wire returning up to the ceiling box cable goes to the common screw of the three way switch (box A). The red and yellow are travelers and go to either one of the remaining two screws of the three way switch (box A). At the new location (box B) you will connect the black wire to the common screw and the remaining red and yellow to either of the other two traveler screws.
 
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Old 12-23-13, 01:09 PM
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Teamo, thanks for the input but if you notice it was answered and it was determined the yellow wire was probably a discolored white.
you connect this incoming hot (white recoded black) to the black wire of your three wire cable which goes out to box
To avoid confusion it is probably better to use the discolored white as common since white on the switch loop almost certainly carries unswitched power.
 
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Old 12-23-13, 01:49 PM
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I didn't notice the other posts as they were probably being written at the same time I was typing mine. As for the white being used as common, it seems that every time I open up a switch box that was wired by someone other than myself I find different methods of 3 way wiring. I like to use the black to the common and I always recode my white wires with black tape. Not sure if there was ever a standard that should be followed but I was taught that way so I continue to do it that way.
 
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Old 12-23-13, 02:13 PM
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I didn't notice the other posts as they were probably being written at the same time I was typing mine.
Wow, you must type even slower than i do.

As for the white being used as common, it seems that every time I open up a switch box that was wired by someone other than myself I find different methods of 3 way wiring. I like to use the black to the common and I always recode my white wires with black tape. Not sure if there was ever a standard that should be followed but I was taught that way so I continue to do it that way.
As you suggest, there isn't a requirement or a standard. Most professionals find it's a better practice, because it's generally less confusing, to use the re-designated white wire to carry the unswitched, ungrounded power to the second switch. It's the same concept as using the re-designated white wire to carry the unswitched, ungrounded power down to the switch in a switch loop. That was required prior to the 2011 cycle.

That's why Posternine said "it is probably better."
 
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Old 12-23-13, 02:25 PM
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Default on this board is the posts in reverse order of the time posted. If you haven't changed that to oldest first it can be confusing when you read the posts. Wouldn't have said anything but since your color scheme differed from mine I just wanted to be sure the O/P wasn't confused by the difference between mine yesterday and yours today.
 
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Old 12-23-13, 03:53 PM
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Nitpicking.

The wire bringing (switched) power back to the light fixture (connected to the light fixture black wire) may not be white, even when remarked.

If the raw power is connected to (the common screw of) the near switch (and switched power connected to the common screw of the far switch) then the wire connected to common of the far switch may not be white, even when remarked.
 
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Old 12-23-13, 04:15 PM
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If the raw power is connected to (the common screw of) the near switch (and switched power connected to the common screw of the far switch) then the wire connected to common of the far switch may not be white, even when remarked.
Really? That makes sense, but I haven't heard it before.

Do you have a code reference for it?
 
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Old 12-23-13, 04:42 PM
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I've never heard that either but in this instance I'd probably use red and white(dirty yellow) as travelers and black as the common return from the far end.

I never remark my white as black....it's always blue.
 
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