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If I replace one switch in a 3-way circuit with an occupancy switch, would this cause the occupancy switch to work in reverse (or not at all) if the regular switch was toggled?

If so, would the best solution be to remove the second switch from the circuit, or just put two occupancy switches in? The switches are nearby enough that only one is necessary for proper operation.

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up vote 2 down vote accepted

DMoore is spot on about using the 3-way occupancy sensor, but off a bit about needing to replace both switches with occupancy sensors. The occupancy sensor installation instructions should show how to connect the device to a 3-way circuit, without replacing the other switch.

Here is an example wiring diagram from the Lutron Maestro Occupancy Sensing Switch installation guide.

3-way wiring diagram

However, occupancy sensors only work if they can see you. So if the switch locations are not within line of sight, you may have to replace both switches depending on your operating preferences.

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Our switches are definitely within line of sight of each other - one of them is actually in line of sight with an other occupancy switch on a different circuit, which is the one I wouldn't want to replace/cap off. – Crazydog May 1 '13 at 15:21

Wouldn't it be easier to just replace it with a 3-way occupancy switch

You can take out one of the switches but this would keep you from having to cap a box or redoing your wiring and give future flexibility.

So you will need 2 3-way occupancy switches since if you just replaced one you could possibly be turning it off.

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