Very promising.
The official cables aren’t that expensive on ebay and if we have a HA integration and a small board that can be easily purchased (maybe even with the openv self made optolink interface) This will be a lot more useful than vicare.
Yes, I noticed that too, but I don’t think it’s an issue as I found out that e.g. GitHub - arthurrump/esphome-opentherm: Create your own smart modulating thermostat using the OpenTherm component for ESPHome enables to implement it in my own way, basically.
So, for others who are interested, I plan to do this:
- buy Master OpenTherm Shield - DIYLESS Electronics - I really just need to control the boiler and don’t plan to combine it with an indoor thermostat. I am now using outside temperature to control the heating (via setting the heating curve). But extending it by an additional indoor temperature seems trivial, you have to just buy another 7$ device above (the thermostat shield)
- I will use some ESP8266 device (I prefer nodemcuv2 over Wemos as they use in the examples, but that is irrelevant, both should work just fine) to connect it with those few wires, specifically this way, and then connect the shield to the
Dconnectors on the boiler
- Then I will switch the settings on the boiler from whatever there is now to this mode 14: OpenTherm
- Will use GitHub - arthurrump/esphome-opentherm: Create your own smart modulating thermostat using the OpenTherm component for ESPHome (by tunning PID sensir) to get something like a heating curve I have now based on outside temperature sensors (which I have) and somehow tweaking it properly (I am not sure on this one)
- integrating it simply via ESPHome to home assistant and building a thermostat
It seems that it should support the two circuits: one for heating and one for domestic hot water by default. So we’ll see. If this works, it could mean that one could get rid of vicare without voiding the warranty and for under like 40$, and hopefully not that much time - it seems that I wouldn’t have to write any new code, but mainly just discover what OT interface on my does 100-W provides and then figuring out the good parameters for the heating curve/setpoint.
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The circuit is so simple that it is an overkill to buy a ready to use one 
I’ve made it a bit more sturdy with esp32 goldpin connectors and usb connection to the optolink plug. All soldered to make sure connections are sturdy. Total cost is less than 10 USD/EUR, including the esp32 board. You can also have a 3D printed plug in case you don’t have the original cable.
I have no idea how this works, so not an overkill for me .
I was referring to @M92718 for the optolink case. 2 resistors and 2 diodes only Indeed the opentherm is more complicated.
Not everyone is good at fiddling that together and find the proper combination of software components.
I think at least on the second part there is still some room for improvements.
Thanks Hans! Where did you get your optolink addresses from?
I have a Vitodens 111-W B1LF, with an integrated 46l boiler.
- ViCare is terrible, fully agree.
- Tested it with 2 solutions:
2.1 Drayton (Schneider) Wiser, both on Floating switching contact connection and OpenTherm. It works very well. Changed it to Tado because my Wiser was only for heating, no control on DHW. Pretty sure the right version of Wiser would have worked very well.
2.2 Tado V3+ Wirelles kit on OpenTherm. It works well.
However, when connecting on OpenTherm, you have no microcontrol on, for instance, the heating pemperature. It goes to 80 degrees (Celsius), and it stays there no matter what. I would have liked to keep it on, say, 55, and then adapting the timings as such.
ViCare still works, but you can’ really modify anything anymore with it.
In a nutshell, I think having individual TRV’s installed on each radiator, connected for instance on ZigBee or Matter, being piloted by HA which in return connects to the boiler via OpenTherm (ESPHome, since solutions already available) would replace Wiser/Tado and give us full control on the way it works. A bit more works, but full control.
At your disposal, guys, to test further more, if needed.
Basically from this repo:
It is mostly in German but google translate is good enough to find what you need.
Btw, have you managed to make a local integration for you heater? Mine is already 16 years old and might fail severely at some point…
@adorobis : sadly, I’m using the Vicare Integration to automate.
As long as my heater is in warranty period, I’m not prepared to be experimenting on the device.
Certainly not if no one has gotten this working on this specific 222-w model.
Ironically, my 222-w replaced a 12yo heater, which did have Optolink 
Thanks for info.
Well, I also give a bit of understanding to Viessmann, all new heaters have wifi built-in, so there is no need for optolink anymore.
Also all new ones can be controlled via opentherm controller. But as far as I know there are some limitations to it, e.g. it replaces some built in functionality e.g. it becomes a fixed temperature heating and the heating curve control has to be done by the opentherm controller. Not 100% sure on this though.
I fully agree. My comment wasn’t meant in a cynical way.
Just that, for tinkerers, the Optolink interface was more accessible.
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Indeed, the optolink is also great that you keep full functionality of the built-in controller and just monitor/adjust parameters that you want. That is probably not possible neither via opentherm or other local controls.
Anyway thinking ahead, are there any other heaters that have a good local integration or e.g. KNX integration that does not cost a fortune?
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Have a Viessmann Vitodens 050 here. Have been able to set max boiler temperature without difficulty.
Arthur Rump hasn’t made any updates to his code for two years, so I’ve been using this fork - GitHub - FreeBear-nc/esphome-opentherm: Create your own smart modulating thermostat using the OpenTherm component for ESPHome - A little more active, and there is a sample yaml for the Vitodens 050W.
Great job Adorobis.
Q1: can you send an instantaneous ON request to the heater from HA now ? Dont’ see this option in your pics.Or in another term, if you feel too cold, how can you rapidly tell the heater to turn ON ? via the party function ?
Q2: the room temp. (RT) sensor where it is located in your case (I suppose not directly to the heater but somewhere far away in a different room )? can you use this RT sensor + set bar in HA as a thermostat (i.e. the heater is heating until the set RT is reached–> 22°C in your pic ?)
Q3: can you program the RT on different days as it can be done on the heater onboard control ?
thanks a lot, Alex
Q1: there is no such feature, to just start heating. If the boiler is in the reduced temp mode (e.g. at night) you can turn on party mode and it will start heating if the room temperature is below the set one. One option could be to set the party mode target temperature at higher value so it would start heating.
Q2: RT is in the room controller (Vitotrol 300) which I have here. It duplicates most of the controls from the controller on the boiler (but not all of them). And yes, it acts as a thermostat and turns off heating on the circuit that it is assigned to (in case you have more than one circuit)
Q3: Yes - the programming is exactly the same as in the onboard controller.
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thanks !
to Q2: setting RT via HA is updating to Vitotrol300 display too ? Which Vitotrol300 model do you have, the old A type wired via BUS-KM or the new E wireless Vitotrol300 E ?
Q4: I was wondering why viessmann heaters came with an onboard chronothermostat if one usually needs an external (chrono)thermostat to control them? from the manual I see the onboard menu allows programming one or more heating circuits based on a RT input (or external sensor). So, would it be possible to control the heater through a RT probe directly connected to the heater control unit (without purchasing an external thermostat)?
Yes, this one. My heater is 16 years old and has the KM-Bus
Well, you don’t need the room controller, the on board one is enough, especially if you have floor heating and properly set heating curve. Actually since a few years now I never reach the temp set on my room controller.
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Can you please share details on how you connected the USB Optolink Adpater to the ESP32? Thanks.