Hello,
I’d like to install a Shelly Plus 1 on a 3-way switch and a single switch but I don’t really understand how to do it in my current installation :
On a room with two switch I have :
The switch are : Hager essensya WE001
I’m living in France and it seem the electrician who done the wiring ignored all color coding at my home…
Thanks in advance
I don’t understand. Can you explain in simple terms what those switches control and how.
They control my living room lights
If I understand correctly the system is called a “va-et-vient” in french :
And I imagine the second room is the same thing but with only one switch (don’t know how they wired this one tbh as in a “bipolaire” way they should only have two wire but I have 3).
Don’t really understand everything.
Ok you have two mechanical switches that are controlling one light.
I don’t use a smart relay behind a switch. I use smart switches.
As I know wiring for a smart switch and mechanical switch is different. Your wiring us made for a mechanical switch as I understand this.
Wiring is very likely the same for smart relay as it is for smart switch.
Wiring goes like this:
One switch is master and it has connected live, neutral and light wire.
Other is a slave and it has live and neutral for power.
It is turned off on by an automation.
Call electrician to rewire wires for this to work.
Two way:
Three Way:
Multi 4Way Switch:
Multi 5 Way:
Wiring is different for mechanical than for smart switches. Probably it’s the same with smart relays.
If I understand correctly those schemas, the “va-et-vient” is a 2-way system.
I’ve seen some folk in France using a Shelly 1L (without neutral) to wire a “va-et-vient”.
I ordered one to try, but from your message @ddaniel my wiring won’t allow me to do this I see.
i don’t think a smart switch will help in my case from a quick look at amazon as i see a 4 wire or some who use ground wire (don’t have them).
I’m a tenant so I probably won’t be able to do that rewiring, but my electrical installation is really unsafe, so I scheduled a talk with the building caretaker to have an electrician to come check in September.
Will probably “assault” him to install them. 
Thank you both for your time in answering my question.
I don’t use a smart relay so I’m not sure. But smart relay should have constant power to operate. When you turn of main switch it cuts the power on the other. So if you put a relay like this probably it will shut down the relay when you turn off the light. But I’m not sure.
As for smart switches goes you need one with a neutral wire. And just rewire wires in a way I wrote you. This is how I have and everything is working fine.
i see, well hopefully in september the electrician will also judge my installation unsafe and rewire them. (he should do some rewiring as half of my power outlet are not delivering power so i have some hope).
Thank you again.
Couple of things. First, a va-et-vient is what is called a 3-way switch in the US. A 2-way is just a single normal switch. The first two circuit images posted by @lordwizzard above are electrically identical. They’re both 3-way switches, ie. des va-et-vients.
Second, the ideal way of adding a smart relay to such a setup is to wire the output of the second switch (the one going to the lightbulb) to the switch input of the Shelly (or whatever other smart relay). The bulb then goes onto the relay output. The only problem with this setup is that you need both the switch output wire and a continuous line voltage supply wire (and a neutral) to power the relay. Those are not usually available at the switch or at the light fixture. Some installs have aggregation wall boxes (boites de dérivation) that have everything you need and dispatch it to the individual switches and fixtures. But older homes typically don’t have that. In that case, you need one more wire.
He also ignored all color coding legally required for rental properties… Some very old houses can have that, but this doesn’t look like a terribly old setup. Having the whole thing checked by a new electrician is probably a good idea. Who knows what other shortcuts the previous electrician took.
Usually what I do is whichever switch has neutral and live, that one gets a smart switch which controls the power, and the other (second) switch which does not get neutral + live, I simply defeat that part of the circuit, and in that box I install a Hue wall module (battery powered) which I then hook up with an automation to toggle the first switch. Effectively this turns the circuit into a regular circuit instead of va-et-vient, but it still works as a va-et-vient.
