I'm looking to add an occupancy sensor switch in a staircase that has a pair of 3way switches.

The power source comes in at the light, then goes to the switches, see Diagram:

http://www.howtowirealightswitch.com/wp-content/uploads/2014/09/two-lights-between-3-way-switches-power-via-light.jpg

The main issue I've been running into is that all occupancy switches I can find needs either a Neutral or a Grounding conductor, both of which are not in my switch boxes (and not in the budget to be added).

Reading up on the post below I noticed UMS-OPS6M-DV that says it only needs a 25w load to run.

Is there a motion sensor light switch that does not need ground?

What does this mean exactly? My LED lights run a Load of 18w total...

1) Will 18w work, if not I can increase the bulbs 2) Does this minimum load mean there is always (let's say) 25w being always used to just power the switch? Or why does this minimum exist?

  • Do you want to put in one occupancy sensor or two? If one, where do you want it to go -- at the top or the bottom of the steps? – ThreePhaseEel Sep 2 '16 at 22:27
  • 2
    A motion sensor with a legacy 3-way comes up a lot... What do people expect? If the motion sensor has the light off and someone throws the other 3-way... When does it turn off? If the motion sensor already has the light on and someone throws the 3-way, then what? If the 3-way has the light on, and the motion sensor sees motion, does it turn it off? It would have to be a carefully engineered product and would need all the wires plus hot and neutral, better to use a matched product as the remote. – Harper Sep 2 '16 at 22:49
up vote 1 down vote accepted

It's going to be a little tough, mainly in the search for appropriate products. Stack Exchange is not a shopping-assistance site.

A motion-sensor switch needs energy to function. The old way was to place the switch in series with the bulb, which depended absolutely on an incandescent bulb - that won't work in your case. The other way is to power it conventionally by bringing always-hot and neutral to the switch. You need this method.

First, you already have 3 wires between the power supply/lamp and each switch. Redesignate them as follows:

  • Actual Neutral (must be white or gray)
  • Always-hot
  • Switched-hot (which controls the lamp)

Then search for a matched set of smart switches (which are made to work together) which do what you want, and are compatible with that wiring.

For instance, two modern motion sensors (which take hot and neutral) may be able to work, each of them switching the switched-hot line.

Often, they are engineered products where one is a "master" and the other is a "remote". Either you need the type which communicates wirelessly, in which case switched-hot is only used by the master. Or, you need a "controller" up at the lamp, with two "remotes" at the switch locations, in which case the "switched-hot" is used for a communication wire instead.


To add to this answer... if you are obliged to rewire, then given the low overall power requirement of the lamps, I would consider doing all this in low-voltage lighting. The wiring is a lot easier to work with.

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