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I'm trying to replace one of the 3-way switches in a 4-way switch circuit with a 3-way occupancy sensor.

Here's my current wiring for the occupancy sensor:enter image description here

And here's the current wiring for the other 3-way switch enter image description here

I haven't touched the 4-way switch.

Before I changed any wiring, the black screw on both 3-way switches was connected to the black wire.

Here is the current behavior of the circuit:

When occupancy sensor is OFF:

  • 4-way switch does not function
  • If the 4-way switch is in the OFF position:
    • 3-way switch does nothing
  • If the 4-way switch is in the ON position:
    • 3-way switch works, but only if I switch it slowly. If I switch rapidly, it only works every other time the switch changes.

When occupancy sensor is ON:

  • 3-way switch works properly
  • When the 4-way switch is switched, the lights flicker off while the switch is in between positions.

Any thoughts on what I've screwed up with my wiring?

  • What make and model is the occupancy sensor? – ThreePhaseEel Dec 27 '16 at 2:23
  • Some of the occupancy sensors require the neutral. The 2nd switch only has 2 wires going to it is it a digital model that doesn't require the travelers? If this is the case you will need the same brand and model for the system to communicate to the other switches. – Ed Beal Dec 27 '16 at 2:34
  • @ThreePhaseEel it's a Lutron MS-OPS5MH-LA – Jonah H. Dec 27 '16 at 3:29
  • @EdBeal there are three wires in the second switch, I just have the one of the travellers and the hot wired together with the yellow wire, as instructed by the occupancy switch's installation directions. – Jonah H. Dec 27 '16 at 3:32
  • Can we have photos of the inside of the occupancy sensor box and the four-way box? – ThreePhaseEel Dec 27 '16 at 12:41
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You generally have 3 conductors in a 3/4-way switch loop, and you can't misuse ground as a conductor. That leaves Only two ways to do it (short of a relay and low-voltage wiring):

Smart switches in the auxiliary locations

Obtain smart switches designed to be "remotes" for the main motion sensor and interact with it electronically, either using 1 wire as a data line, or wireless via power-line signaling or radio.

Very lucky topology

This can only work, if

  • supply power comes in to the light, the switches are all one spur, and the motion sensor is in the first box.
  • supply power comes into the same switch box as the spur to the light, and the sensor is in that box.
  • the essential interconnections are in conduit, and you can pull more wires.

Otherwise you'll have a spot where you need 4 wires, and you only have 3 in the walls.

Your sensor needs three wires coming in: always-hot, switched-hot from the switch, and neutral for the light's current return. The sensor doesn't need neutral, but the light does, so inevitably neutral must come back this way.

http://www.lutron.com/TechnicalDocumentLibrary/369488.pdf

It does not support a 3-way switch. It supports a plain switch which switches between 'open' and always-hot or switched-hot. If it is placed in one position and the one other position was a 3-way switch, then they have you rewire the 3-way to be a plain switch.

Since you have two remaining positions with manual switches, those two positions must together emulate the behavior of a plain 1-way switch. They way you do that is the classical 3-way circuit. The 4-way switch needs to be swapped out for a 3-way. Which you happen to have spare. However, if supply to the light also travels the switch wires, you'll need 4 wires in that segment:

  • always-hot for the smart switch
  • messenger 1
  • messenger 2
  • neutral to return current from the light

This is one more than a traditional n-way, installed with the usual 14/3, and you can't retrofit a consuctor.

This does work if your topology is just right: the two remaining physical switches are on a spur. In that case you won't need to carry lighting power (i.e. The neutral) between switches and you'll have enough wires.

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  • I found this question which has an answer that seems to indicate via this document that this is in fact possible if I were to purchase two of these companion switches. Is that correct? – Jonah H. Dec 27 '16 at 7:40
  • Ha! I fell to the narrow thinking I am usually warning others about! Yes, if you go smart switxhes in all locations, you are sympatico. Then instead of 2 messengers you have just 1 comms wire (or 0 if it uses signal-over-power or wireless). – Harper - Reinstate Monica Dec 27 '16 at 14:52

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