2-wire and 3-wire

Nearly all my lights here in the UK use 2 wires. Is it more 3 wire in the US? Struggling to find sensible modules. I can use dimmers, but they need bypasses which are a PITA.



Are you talking about to the fixture or to the switch box?

Switch box, but likely the same at the fitting. No idea where the common grounds are!


Catman i am a UK electrcian, This all depends how your house was wired.

What do you want to do?

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Just add modules (or even better integrated switches to some of my ceiling lights.

Our house was built in the late 90s and it seems pretty much all the wall switches are two wire. This (seems) to massively limit the choice of modules. AFAICT Vesternet (who I tend to buy from normally) don’t stick a single 2 wire module.

I get it, the thing needs to be powered but makes you wonder why they even make them?

Cheers for any advice or thoughts.


You can put switch insert in light fittings, then change old switches to monentary.

How to do this all depends on the light fitting

Your ideas interest me and I wish to subscribe to your newsletter…

Can you point me at a wiring diagram? Struggling to see how you’d get the contacts at the switch connected to the inputs on the module? Also, surely flicking the wall switch would cut power to the module?

Clearly I’m missing something crucial :slight_smile:


A very rough wiring diagram with THREE PLATE METHOD (i.e a standard ceiling rose, use a rose dry linning box to hide device https://www.ebay.co.uk/itm/5-x-Click-Round-Circular-Ceiling-Dry-Lining-Box-34mm-Deep-WA108P/173889495146?epid=1066049054&hash=item287c9f206a:g:gL4AAOSwkx5XEQwS )

depending on the module, I.e. dimmer you will need to change switch to monentary. I use click scudamore , as they have a great range form standard white to stainless etc, and they are resonable priced

My house is new, so I made it wired accordingly. My situation is very similar, but my modules are in a central box. The schematic is similar: momentary button linked to the module.

Usually here in Italy two wires design is more common if you don’t ask anything else specifically.

With all my new installations i give the customer the choice of running 3 core to all light switchs and install deeper boxes. Most decline.

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That’s awesome. I think!



OK sorry, still not getting it :frowning:


I only have one wire going from the switch to the light fitting. How do I get the other one?

Sorry :frowning:

OH! Unless that COM live routes back through the fitting!

Have I got it?


Catman, yes thats it, all the wires are at the fitting if your house is 3 plated, most uk homes are

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My thanks

I guess I can identify the correct ones, should I have an issue, by turning off the power (duh) and testing for continuity with a meter?

Thanks again!


All you need to identify is the switch wires going down to the switch, then disconnect them. Ensure all other lights are still working and test that the switch wire is independent and now isolated from the power. Sometimes electricians will use one wire to feed 2 switches.If in doubt post photos before you disconnect

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My thanks!

Be a while before anything I order from Aliexpress turns up :slight_smile:


I live in Sweden. All our wires go in 16mm pipes so you Always put in more wires. ( you just turn off power, Connect the new ones to old and use your mussles and draw out the old and the new ones go in.

How are your cabels mounted in the wall ? Is this an option maybe?
/ Mattias

Oh if only we did sensible things like that :slight_smile:

They’re just in the walls. Normally cemented in by the time the house is a few years old


Hi @Catman, below are some diagrams I did a while ago for integrating a Fibaro Single switch 2 into UK ceiling rose wiring. I chose this device as it not only will respond to impulse switches, but it also can be set to be used with normal on-off switches - it changes state when the switch changes state. It occasionally misses a switch but generally switches when the switch changes state. I did some mods to the wiring to enable the module to be removed easily in the future and revert to the original manual switch only. I used the Wago 224-112 connectors as the two wires that are side by side are push to connect and so they tend to stay put when you connect the third wire. The third wire can be released easily by pushing on a lever.

Sorry that the diagram is in the old UK wiring colours but hopefully it is still clear how the connections are done.

In addition to the recessed round boxes mentioned by @ElCid above you can also get surface mounting round boxes which are just a bit smaller in diameter than the normal ceiling rose. These may be easier to use if, as is often the case, the ceiling rose is mounted below a joist with the cables coming in from the side.

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Thanks! This is really helpful, all


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