Shelly's behind light switch - confusing existing wiring

  • Hello all- please could I get some advice before i install my Shelly's.


    I have have two use cases:

    1. Shelly 1 - behind a 1 gang, 1 way switch. That its, there is one switch on one faceplate to control one set of lights in one room (no other switches control the lights).
    2. Shelly 2.5 - behind a 2 gang, 1 way switch. That is, there are two switches on one faceplate to control two sets of lights in one room (no other switches control the lights).

    Problem statement:

    1. Shelly 1. I was not expecting so many wires in the back box. Specifically, I was not expecting two wires in the L1 terminal of the switch. How do I wire up the Shelly 1? I had expected two wires in the COM and one in L1 - not the other way around.
    2. Shelly 2.5. Same as 1 - how do I wire up the Shelly 2.5? Again id expected to see the two COM terminals bridged, not the L1's.

    Photos:


    1 gang, 1 way switch (for Shelly 1). What I expected to see (https://images.weserv.nl/url=w…47e0132a265c2cc238e5dbdae


    What I did see:

    72C64E39-A4A4-4A11-A610-DE2004E8FE9F.jpeg


    66BDEEFB-4A0C-40DA-98DF-55A2144FD45C.jpeg


    2 gang, 1 way switch (for Shelly 2.5). What I expected to see (https://www.diynot.com/wiki/3500bbae96569eee7ba0442d596d20aa).


    What I did see:

    AB628143-B890-4502-8C05-31596B9D944D.jpeg


    6C693F12-E852-4AC3-B0B1-A317CDA39372.jpeg


    Does anyone have any ideas please?


    One idea I had was to instead fit in light fittings - which are:


    In the 1 gang, 1 way switch room one set of LED spots, each with Neutral Blue and Brown Live In and Neutral Blue and Brown Live Out (plus Earth).

    In the 2 gang, 1 way switch two sets of LEDs spots, same config.


    Could I put 3 x Shelly 1s in (1 in 1 gang, 1 way and 2 in 2 gang, 1 way) - at the light fitting end?

  • It's hard to tell from the perspective of the pictures, but it doesn't look like there is a ton of space in those backing boxes, so it might be better to put the Shellies in the light fittings, as you suggest. Please do keep in mind that they're supposed to be in a backing box of some kind (i.e. not just in the ceiling space).


    That said, it's totally possible to wire them into the boxes you show (electrically - again not sure if they'll fit physically).


    Standard disclaimer here: If you aren't sure about what you are doing, it's best to hire an electrician. Fitting Shellies into the circuit you show is totally doable, but it's not without risk.


    Don't worry that the 'common' and 'L1' terminals are swapped vs the picture you have - this is not an issue at all - many of the lights in my house were wired like this, and it makes no difference at all (except being confusing in 3-way arrangements, but that's not an issue here). Regular light switches are not 'polarized' so it makes no difference which terminal is the source and the sink - in any case, it's AC electricity, so current is flowing both ways anyway!


    You can simply imagine that the L1 and C are swapped on the switch vs the diagram you provided, and act accordingly.


    Is swapping the backing boxes for deeper ones an option? I do think you may struggle to squeeze the Shellies in there! Even if you can manage as they are, if you ever change switches / etc, you will always be grateful for extra space!