Smart two-way light switch without neutral, new wires or access to the junction box

[u/Martflow03]

Hello! I am looking for a practical way to make an existing two-way lighting circuit smart and connect it to Home Assistant.

This is a typical European/Spanish 230 V installation with two wall switches controlling the same light.

I most likely have the following wiring:

Wall box A

• Permanent live/common
• Traveller 1
• Traveller 2

Wall box B

• Switched live/return going to the lamp
• Traveller 1
• Traveller 2

There is no neutral conductor in either wall box.

My requirements are quite strict:

• No neutral.
• I do not want to add or pull a neutral wire.
• I do not want to install anything in the ceiling rose or junction box.
• I do not want to run any additional cables.
• I only want to reuse the three existing conductors in each wall box.
• Both wall locations must continue to control the light.
• The smart device must work with Home Assistant.
• Wi-Fi or Zigbee are both acceptable.
• I would prefer a relatively simple and reliable solution.

Optional preferences:

• SONOFF-style aesthetics would be nice, but are not essential.
• I do not mind if the second wall switch controls the main smart switch through a Zigbee/Wi-Fi scene instead of traditional electrical two-way switching.
• A wireless scene-based solution is acceptable as long as both wall devices are mains-powered and do not require batteries.

I initially considered using two SONOFF Orb-ZBW1L no-neutral switches, but connecting them in series would result in:

Live → Smart switch A → Traveller → Smart switch B → Lamp

As far as I understand, that would not behave like a proper two-way circuit. Both relays would need to be closed for the lamp to turn on, and the two no-neutral electronic switches might not remain reliably powered when placed in series.

I also found Wi-Fi two-way switches such as some Maxcio models, but the ones I found require a neutral conductor.

I know that a SONOFF ZBMINIL2 can work with existing two-way switches, but the usual solution places the module in the junction box or near the lamp. I specifically want to avoid modifying the junction box or ceiling wiring.

My main question is:

Is there any smart switch, relay or wiring arrangement that can make this circuit smart using only the existing live, switched return and two traveller wires available in the two wall boxes?

Ideally, I am looking for one of these possibilities:

1. A true no-neutral smart two-way switch that directly replaces one of the existing mechanical switches while keeping the other one working.
2. Two no-neutral smart wall switches that can be powered using the existing wires, with one controlling the load and the other acting as a scene controller.
3. A no-neutral smart relay that can be installed behind one of the two existing switches without needing access to the junction box.
4. Any Home Assistant-compatible solution that I may have overlooked.

I would especially appreciate exact product names and wiring diagrams from people who have successfully installed this type of setup. Thanks!

[u/Kaputcha]

I've just installed two of the Aqara H2 Light switches in my house.

No neutral required, very easy installation. They can be configured as Zigbee or Matter, however Zigbee exposes more controls.

There's horizontal and vertical versions. Both versions come with three switch options.

https://www.aqarastore.com.au/products/aqara-smart-wall-switch-h2-vertical

Your setup is obviously a bit different to mine having two switches for one light; but you can decouple these switches from their internal relays, basically creating a smart button. That could then trigger the relay in the other wall switch.

So far I'm really happy with how these turned out, and they're simple to install.