Replacing 3 way switch (horizontal switch) 2 separate 3 ways in one box, each switch has its own power going to it. Top switch two travelers are hot common is not. it seems to work fine with the old switch attached, just curious as to why?

Top switch two travelers are hot.

Top common not hot

  • Can you post a pic? – BillWeckel Nov 13 '18 at 18:23
  • Can you post pictures of the old & new switch? It could be as simple as "screws for hot vs. common flipped old vs. new". Simple usual guide is that 2 screws will be one color and one a different color (brass vs. silver) - the 2 that are the same get travelers and the other one gets common. – manassehkatz-Moving 2 Codidact Nov 13 '18 at 18:24
  • The common, white wire, shouldn't be hot unless it's being used as part of the switch leg, in which case, it should've been marked hot with black or red tape... There are 3 or 4 different ways to wire a 3 way circuit... – BillWeckel Nov 13 '18 at 18:41
  • All three wires going to that switch are blue. – John Nov 13 '18 at 18:50
  • 2
    @BillWeckel because OP's installation is in conduit. In that case you get to use two actual, same colors for the travelers. Although I do find conduit work where someone used red, white for the travelers and black for the third, same as if they were in Romex because they cribbed off an Internet how-to diagram... And that's illegal, can't remark white to be a hot in conduit, you're to use the right color wire in the first place. Legal hot colors are anything but white, gray (neutral) or green. – Harper - Reinstate Monica Nov 13 '18 at 20:51

The usual reason is that the installer is moving the wires to the same position on the new switch, rather than looking at the screws' function -- because every 3-way has their screws in different places and the installer did not realize the screw colors are the important part. That's the usual reason.

This is one reason I make a point to positively identify the two travelers and mark them with yellow electrical tape. Yellow wires on yellow screws, there ya go. In a cabinet with two unrelated 3-ways working in close proximity, I use blue, purple or green for the second set of travelers. They sell a 5-pack of 5 colors of electrical tape for about $5 in most stores.

  • I also mark travelers or in conduit pull the same color makes it easy to figure out.+ – Ed Beal Nov 13 '18 at 20:06

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