Smart dimmers under existing wall switches (UK hub, German home)


I have a couple of newbie questions. I have a few of wall switches that I want to keep and make smart. In one room I have 3 x 9 W LED bulbs connected to one wall switch (bistable). My understanding is that it is possible to control and dim the lights from my SmartThings and the wall switch itself independently, regardless of the actual state (correct me if I’m wroing). Will I need a bypass since my load is quite small?

Can’t seem to find these in the “works with SmartThings” list, do they work?

In another room I have two wall switches that control the same ceiling lamp. This means that either of the buttons will change the state of the lamp. Is there something similar which will work with that kind of setup?

Greatly appreciate the help.

@anon36505037 has done his entire house with Fibaro kit, he should be able to answer your questions. :sunglasses:

With regard to your second question, in the UK that is referred to as a “two-way setup” and it definitely should be doable, although it does depend on the details of your wiring. Again, Robin can probably say more. ( The same setup in the US would be referred to as a “three-way” in case you are reading other forum threads, just so you don’t get confused. The UK counts the number of switches, while the US counts the number of circuit branches.)

Yeah, 3way doesn’t really make any logical sense at all. There’s only 2 travellers, and only two switches. It’s not like a single switch is called a “2 way” switch, though it can be called a single throw switch. Technically a “3way” is just a paired set of double throw switches, so … 2 + 2 = 3?

In the US, it describes current flow. From Mike Holt’s electrical systems forum:

It is not a matter of how many positions the switch can have (i.e., up or down is only two positions). It is a matter of how many ways current can get to the switch, how many paths current can take on its way to the switch. Think of driving down a road, and coming to an intersection at which you have to take either the left fork or the right fork. That is commonly called a �3-way intersection.�

But, yes, in most other countries you just count the number of switches. :wink:

Yeah, that’d make sense if there was two way traffic (which I suppose there technically is because of alternating current flow) but from a block diagram perspective, it more closely resembles a fork and a merge.

If it was called a “3 wire switch” I’d be convinced. :wink:

What a great community, thank you for the replies guys!

After taking a look inside, I realized it might be hard to fit the dimmer behind the switch because of all the cables. Also seems to be a bit different from the cables in the chart. I have 1 cable of each color coming from the bottom, and 2 of each color going up. Only the brown cables are connected to the switch.

But since it’s probably a good idea to exchange the switch to one with a dimmer, I might as well get one with Z-Wave/ZigBee. Any specific (European) switch you could recommend?

Green/yellow is your ground wire. Blue is your “common” wire, and brown is your switched wire, most likely.

Hi, once again thank you for your replies. It would definitely be more convenient to have it under the switch, than the ceiling, in our case. But I might look for a smart switch, since we won’t be able to dim the lights with the current one anyway.

As for your question, I can’t recall adding UK to my title, but if I did then I must have been referring to the SmartThings Hub being from the UK (not that it matters). But this particular installation is actually in Germany, and it’s an old house from the early 1900’s, but I’m sure the electric installation has been changed at least once since then. If wires are used differently in the UK and in Germany then perhaps I should look for information regarding what the different wires are used for.


Hi @Qliver, I think the confusion lies in the topic title “Smart dimmers under existing wall switches (UK)” …might be leading readers to think you’re in the UK. :slight_smile:

1 Like

Yes, UK meaning UK frequency hub. The first post all had links to European Z wave devices. Sorry for any confusion. In the devices section we generally just divide between the two hub regions, US or UK, but I understand the wiring can be very different in different individual countries. :sunglasses:


I really can’t figure this out. Can I not use rotary dimmers together with the Fibaro dimmer? I guess the wall dimmer would always have dimming priority over the Fibaro? It would be nice to have one like this

because then it would also be possible to dim the lights from the wall. But like I said I don’t know if that’s even possible.

So far I’ve only been able to find one build-in wall dimmer with Zigbee/Z-Wave, also from Busch-Jaeger, but it was crazy expensive. Anyone got any tips?

Okay, so just a regular dumb momentary wall switch, doesn’t have to be anything special about it? Don’t understand why it’s so hard to find, the switches I find are either rotary or smart. Would be appreciated if you had a link to something for reference.

To be fair they are really not that common over here, took me some time to find any whatsoever. First found some info on Vesternet, and I think what you meant is something like this:

Must say they are quite pricey.

Does anybody know if the wall dimmer also has to work with LED light sources? If it is a LED dimmer like the one in my link, do I still need the Fibaro bypass? Or can I use any dimmer as long as I have a bypass?

No no, that’s just a dumb dimmer wall switch (momentary). I thought this was the type you meant. Underneath that I want to put my Fibaro dimmer. On top of it you can put whatever plastic button suits you (shape, color).

At the moment we have an on/off switch that I am looking to replace. The reason is to make it possible to control the lights without Z-Wave if we want to. The lamp consists of 3 x 8 W filament LED bulbs.

Right, now I get it. So the switch itself has no electronics, it just breaks and opes a circuit, and the Fibaro is the dimmer itself. Total novice here like I said. I’ll get a Fibaro dimmer and a bypass then :slight_smile:

I simply need a switch that has a spring so that it bounces back to the middle position. Thanks!

1 Like

“Retractive switch” is what you’re after :slight_smile: 1-way are like the switches you find on office exit doors and 2-way would be like a ‘normal’ light switch but ‘bounces back’ when either end is pressed.

Sorry, my incredibly poor description there! You’re absolutely right. I was trying to convey the single rocking motion vs the double rocking motion i.e. press the top and it ‘bounces back’ or press the bottom and the same happens.

1 Like

So I went and bought a retractive switch. Unfortunately the Fibaro dimmer won’t fit in the back box with it, as a matter of fact I had trouble fitting only the switch itself. So my idea was to do a ceiling mounting as you suggested. But as usual I’m pretty clueless how to do it. All I have coming from the ceiling are three wires, live, neutral and ground, nothing else as far as I can tell. I assume the live wire is switched, thus it would switch off the dimmer, right?

Yep, I am looking at it. In my case there’s brown, blue and green/yellow (only these 3 wires are visible).

I get that the brown one goes to Sx, and the blue one goes to S1. Then I make two new wires, from ~-> to the brown one in the lamp, N to the blue one in the lamp. But what about the wire you have marked as L?

The lamp, with only 3 wires.

So I’m pretty sure I won’t be able to connect the dimmer here and still be able to use the wall switch.

A quick sketch of the wires in the back box.

I don’t know how the wires are pulled through the walls, but there are 4 wall sockets in the room and one lamp switch. There is one socket near the floor right under the wall switch, and three more in one corner of the room each.
I’ll have to check tomorrow if I didn’t mix up the two top brown wires in my sketch, I’ve assembled the switch again.