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First box has 14/2 from panel, 14/2 to outlet, 14/3 to the other switch

Second box has 14/3 from the first switch and 14/2 to the light.. how can I wire these up for 3 way switch.

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    Props to you for clearly labeling what each wire is – Machavity Oct 2 '18 at 17:27
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Here's the headache. Cables are color-coded to distinguish wires from each other. They're not color-coded by function, which makes 3-ways super confusing. We're gonna fix that. Get a common 5-pack of colored electrical tape.

There is only one /3 cable. On both ends of that cable, tape both the red and black wires yellow. Yes, really; both wires get marked yellow. They are travelers, and they are interchangeable.

Over in the second box, with the cable to the lamp, tape its black wire red.

Now your wiring looks a lot like this

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Buy about couple feet of /3 cable that same size (or #12 if you don't know the size). From this we will make pigtails. You can also just buy 8" lengths of black, red and green #12 solid THHN if you'd rather.

On one 3-way switch, identify the black screw and put a black pigtail on it. On the other 3-way, also on the black screw, put a red pigtail on that. You could use another color and mark it with red tape.

Oh, almost forgot the grounds (safety earthing). I tend to ignore them, even though it is vital to hook them up, and do them first. So -- also, put bare or green pigtails on the ground screw of each switch. Either color is fine, they are equivalent but the green is less likely to short against stuff because it's insulated.

The 3-way switch with the black pigtail goes in the first box (with supply). This will be obvious in a moment.

In both boxes, the yellow wires go onto the brass screws on the 3-way switches. Join all the bare and green wires with one wire-nut and shove em into the back of the box. Join all the white wires to each other with one wire-nut, and shove em into the back of the box. Then do all the black wires similarly, then all the reds. And you're done.

  • For those working in the UK, the "red", "yellow", and "black" tapes above should be replaced by the colours allowed for phase (live) lines: Brown, Black, Grey. Don't know what one would do in Germany (where domestic like my house have a three-phase supply, so using the "wrong" phase colour could be confusing.) – Martin Bonner Oct 3 '18 at 16:51
  • @MartinBonner Surely the EU must have more colors acceptable for hots than the phase colors you named. That is simply too constrictive when you are working on conduit with 3-4 circuits possibly with switched-hots also. I have boxes with 8 colors in them, most getting spliced. Practical conduit capacity in the US is 9 hots + 3 neutrals in 3-phase wye. – Harper Oct 3 '18 at 17:03
  • @Harper : No, I don't think so. allaboutcircuits.com/textbook/reference/chpt-2/… lists just three phase colours for IEC, but it appears that US allows anything other than white/grey or bare/green/green+yellow for phase wires. – Martin Bonner Oct 3 '18 at 17:11
  • @MartinBonner yes, aside from those six in the link, we can also use purple and pink. I suppose robin's egg blue would be another option, but honestly we need another neutral color more badly than another hot, so I'd make that one a neutral. As a colorist (granted a male one) I kinda feel we've run the gamut. Literally. – Harper Oct 3 '18 at 17:52
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Box 1

  • Nut all three white wires together
  • Nut the bare wires together with a cut piece to attach to the switch
  • Cut a short black wire and then nut the hot and outlet black wires together with this cut wire (leave the 14/3 switch black out)
  • Attach the cut black wire to the black screw of your three-way, then attach the black wire of your switch wire(14/3) to the left screw, and the red wire to the right

Box 2

  • Nut the bare wires together with a cut piece to attach to the switch
  • Nut the white wires together
  • Attach the fixture(14/2) black wire to the black screw of the switch
  • Attach the black wire of your switch wire(14/3) to the left screw, and the red wire to the right
  • On 3-way switches therre is no consistency whatsoever to the location of black and brass screws. They are different on every switch, or so it seems. – Harper Oct 2 '18 at 17:48

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