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I’ve got a 3-way switch setup with 2 x switches and multiple light fixtures. It appears that the light fixtures are getting power from the panel and then has an always hot line coming into switch #1 with maybe a switched hot? Switch #2 then has two travelers and an always hot?

Is the white capped line a neutral and the black (always hot) and red (switched hot) in switch #1?

enter image description here

I’m just trying to understand as I’m wanting to replace this wiring with a Lutron Caseta Switch + Mechanical Switch. Is the following the correct way to re-wire to match the schematic provided by Lutron understanding that the line goes to the fixture and has both switches downstream of the fixture and line? Any need for me to use a jumper as depicted in their schematic?

EDIT: PROPOSED WIRING CHANGE for Caseta PD-5ANS + Mechanical Switch: enter image description here enter image description here

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  • Wow, that is one weird wiring diagram (image #34). It seems to be not correct, since if the mechanical switch shunts switched-hot to the datacomm line, the switch position could not be detected when the lamp is off. Your drawing actually looks more correct lol. However note that they are saying to leave one 3-way switch terminal vacant (a traveler), so they are using it as a 1-way switch.
    – Harper - Reinstate Monica
    Jul 28, 2022 at 18:52
  • @Harper-ReinstateMonica I agree that 34 looks a bit wacky. (OP's diagram, by the way, is wrong - it shunts full incoming power into the blue wire when switched on, and I'm sure that's not the intent of Lutron, and it definitely doesn't match diagram 34, though given the poor color coding chosen by Lutron, it is totally understandable how OP got there). In any case, if fixture is already on thanks to "smart on", then blue wire would be a simple detector of switch 2 status - therefore flip switch 2 and smart switch knows user flipped the switch and can turn fixture off.
    – manassehkatz-Moving 2 Codidact
    Jul 28, 2022 at 19:00
  • But when fixture is off, blue sees nothing in any position. My hunch is that when the fixture is off, the smart switch sends a low voltage pulse of some sort. That would be enough to detect/not detect in the blue wire but not enough to affect the fixture. Would have to be low voltage though - send regular 120V for even a fraction of a second and a modern LED will blink annoyingly. Send 5V through for 1/60 second once a second and there should be nothing perceptible on the fixture but be reliable enough to detect status of the switch.
    – manassehkatz-Moving 2 Codidact
    Jul 28, 2022 at 19:02

1 Answer 1

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Your description sounds 100% correct. Just keep in mind a few things:

  • Red and white between the two switches are your travelers. Those are not magical colors, just what happens to be available in a standard cable. So wiring diagrams for the new switches may use other colors or refer to travelers or something else.
  • The capped white is your neutral, so if one of your new switches needs neutral and the other doesn't, you will have to place the one that needs neutral in box 1.
  • If your new switches have screw terminals, they may or may not match the layout of the existing switches. There is no standard screw configuration for 3-way switches. The new switches should be clear about what goes where, but if one of them is a simple switch and doesn't include directions, it should have two screws of one color and one screw of a different color, and the travelers would go to the two screws that are the same color.
  • The Caseta may use travelers to the other switch "as is" or may have a particular configuration - follow the directions carefully.
  • Colored tape is your friend. Since everything is black, white, red, marking specific wires based on function can help. The only requirement is neutral = white. Typical (but not required and not universal) is black for hot, red for switched hot, which you appear to already have. But traveler colors can vary depending on configuration. You can use, for example, blue or yellow tape to mark travelers or other particular wires. Always mark both ends the same way.

Update based on installation instructions

Old setup:

  • Incoming (from panel and fixture): Black = hot, red = switched hot, white = neutral
  • Switch 1/2 cable routes black from incoming hot to common of switch 2, red and white as travelers from switch 2 to switch 1
  • Common of switch 1 to switched hot

I believe the Caseta instructions are based on a few assumptions that don't apply in your case. In particular:

  • Incoming hot and neutral on a black ("tagged")/white cable
  • Switch 1/2 cable travelers black & red, neutral white
  • Outgoing switched hot and neutral from switch 2 to fixture black ("tagged")/white cable

You have a "medium" setup. You have neutral in one box (absolutely critical here) but you have white between the boxes as a traveler, not as neutral.

I definitely fault Lutron for using the "tagged" indication for both hot and switched hot. That confused me quite a bit until I realized they are two different, not connected, wires.

Based on the schematic (page 2, as posted at the moment as an image in the question), things are actually OK:

In the Switch 1 box:

  • Incoming hot black to Caseta black (disconnect it from Switch 1/2 black)
  • Incoming white neutral to Caseta white
  • Incoming switched hot red to Switch 1/2 black and Caseta red
  • Caseta blue to Switch 1/2 red.
  • Cap Switch 1/2 white for safety.

In the Switch 2 box:

  • Remove the white wire from the switch. Cap it with a wire nut for safety.

You won't need the yellow jumper.

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  • Thanks for the write-up. I added a schematic for the Lutron Switch + Mechanical 3-way. Would you mind taking a look and seeing if I got it right. There are no examples in their wiring diagrams where the line goes to the fixture and then has the switches down line.
    – Russ W.
    Jul 28, 2022 at 2:55
  • It doesn't matter that there are no examples of "line to fixture" because the old problem with that was lack of neutral, but you have neutral. I'll try to explain.
    – manassehkatz-Moving 2 Codidact
    Jul 28, 2022 at 3:53
  • 1
    Explanation made complete sense and your assessment has everything functioning as expected. Very much appreciate you taking the time to spell this out. I learned something and I’m greatly appreciative.
    – Russ W.
    Jul 28, 2022 at 23:26

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