Using a 3-wire PIR motion detector with 2 wires

Discussion in 'Electricians' Talk' started by FlyingTuga, Dec 19, 2020.

  1. FlyingTuga

    FlyingTuga New Member


    I am trying to setup a motion detector at my place that has 2 light switches. Unfortunately, I can only find a 3-wire PIR motion detector that fits on the frame, but I only have 2 wires.

    Is there any way that I can make it work the 3-wire PIR motion detector with only 2 wires?

    This is the picture of the device.

  2. rogerk101

    rogerk101 Screwfix Select

    You only need a permanent line and neutral supply to the PIR detector. The detector then switches power to the switched line terminal which you then connect to the load (e.g. a light). The load also needs a neutral but that is a shared neutral with the permanent on that is supplying the detector.

    • twin and earth cable supplying the PIR detector with permanent line and neutral.
    • twin and earth cable supplying the load from the PIR detector with switched line and (permanent) neutral
    Pretty much exactly what they've shown in their pin-out diagram, but hopefully easier to understand. :)
  3. Philip Hyde

    Philip Hyde Screwfix Select

    You can change a light switch for this PIR unless your switch has a neutral wire. If your switch only has 2 wires it won't have a neutral.
  4. sinewave

    sinewave Screwfix Select

    Badly worded questions lead to others miss-interpreting what you're trying to achieve!

    I assume you mean you'd like to fit the above in place of an existing wall mounted light switch?

    If so you need 3 cores (wires) at the switch, L, N & switched L/Load

    You also state you have 2 light switches?
    I'll assume that's 2 way then?
    This raises further issues also!
  5. FlyingTuga

    FlyingTuga New Member

    @sinewave , you are absolutely right, I am a non-native English (living in a foreign country too), with basic electricity knowledge.

    So, I want to replace a light switch with this sensor. Though the switch has a "another box" next to it for a different light. So, I need a motion detector that fits into a double frame, and this 3-way was the one I could find. The other switch (toggle switch ?!) controls a corridor light that has 3 wires, but my understanding is that none of these are/would work as a (N)eutral either (picture below). I hope this makes it clearer.

    WhatsApp Image 2020-12-19 at 23.36.41.jpeg WhatsApp Image 2020-12-19 at 23.36.41.jpeg

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