Wire Shelly 1PM behind UK light switch

  • Hi all

    I recently purchased 4 Shelly 1PMs And would like to wire them behind my actual light switch if possible.

    I have live neutral and ground behind each 1 gang switch. I can’t seem to find a wiring diagram in order to achieve this :(

    Hopefully someone could draw me a diagram to explain how this could be achieved!:/

    Thank you:)

    Edited once, last by Murray ().

  • Maybe you could post a pic of what it looks like behind your wall switch?

    In general your live goes to L (take it from „before“ the switch so the Shelly had permanent power), your neutral goes to N and the switched live goes to SW and the switched load goes to O.

    Hope that helps,


  • Thanks for you reply.

    Attached is an image from the switches' documentation that I have in all of the places where I wish to use the 1PMs.


    • IMG_2246.jpeg

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  • Okay so the above mentioned stands. The switch doesn’t need neutral but you wrote you have it behind the switch, right?

    Are you good with the information you have now, or do you have further questions?



  • Ok so it looks like I may have made a mistake and should be wiring it into the ceiling rose.

    I have drawn a diagram of all of my ceiling roses:


    Blue and brown goes to the light itself.
    The other wires come from the ceiling.

    There is also Earthing available but not shown in diagram.

    If someone could please show me how this should be wired I would appreciate it.

  • This looks different from what I’ve seen but there’s so much in that category I’m not even surprised.

    If I interpret your picture correctly and there are three clamps that connect the respective wires screwed into it and the rightmost clamp is the switched live one that only actually is live if the switch is on. I’m hoping the middle clamp has permanent live. If you don’t have permanently available live wires up there it won’t be easy to install the Shelly so that it fully functions...

    So again, assuming that middle clamp with the red wires is live:

    Blue to N and lamp

    Live (middle clamp I hope) to L

    Switched live (rightmost clamp I hope) to SW and

    Other wire from lamp to O

    I hope you have the tools to measure what’s going on in those roses. Otherwise make sure you get al electrician to have a look and safely install at least one of them so you know how it’s done.



  • Georg, the pictures as given show the "normal" way of running a light string in the UK to minimise cable use.

    UK lights are wired out from the distribution board as single cable strings, one per zone, so often one for upper floor, one for ground floor and additional ones as required.

    The strings go from ceiling rose to ceiling rose (sometimes a separate junction box). A separate single cable is dropped to the switch and is connected to the live and the return to a separate block in the rose to supply switched live to the light.

    Confusingly for householders the return is normally through what appears to be a neutral line and the convention is to sleeve the return line to indicate that it too could be live but that's not always done, especially in older properties and DIY houses.

    In the pictures the colours for the internal wiring are red and black so this is an older property wired before the point at which the UK only used harmonised wire colours with Europe (2004). If the earth sleeving is yellow/green then it is after 1977 likely be 1980 onwards. If solid green then certainly before 1977, maybe a few years after depending on who actually wired it and what sleeving they had.

    The light as you surmised is the blue/brown cabling as the flex often gets replaced with the light fittings.

    If the diagrams are accurate then the supply string will be the double cables screwed in one hole and the two singles with black going to the connecting block with brown lamp lead will be the switch cable. This is of course not guaranteed! and as you suggested always worth double checking before starting.

  • Thank you for the background, very interesting.

    I remember there were times where it was prohibited to install a socket in a bathroom, or at least I was told so... I suppose that has changed in the meantime, too, but it goes to show how big the differences were and still are between countries...