Opentherm for 2 zone heating and Nest thermostats control

Hi, I wonder if I can get some advice. I'm trying to find the way of convneting my 2 zone heating controlled by 2 nest thermostats via heatlink connected to viesmann vitodends 100 system boiler. Everything is working well so far, but I would like to knwo whether it is possible to use opentherm feature for 2 zone system. My boiler has got opentherm feature as well as heatlinks, but boiler ha sonly got one opentherm output and I got two heatlinks, so I don't knwo if this will even work?
I got feedback from my friend who use this feature and their gas usage has dropped significanlty. May I have any advice on this please?


  • FreeBear
    FreeBear Posts: 14,268
    First Anniversary First Post Name Dropper Photogenic
    You can only have one device connected to the boiler using the OpenTherm interface. So to use two thermostats, you'd need to link them to a single heatlink device (if that is possible) and use that to control the boiler. I'm not familiar with Nest or heatlink. However, I do use OpenTherm to control my boiler (a Viessmann 050). Heating and scheduling is managed by Home Assistant, and an ESP32 plus shield to interface to the boiler.
    Early days with the Viessmann, but I'm not sure that there are any huge savings to be had with OpenTherm. Reducing the thermostat set point, smarter use of schedules, and optimising flow temperatures is working for me. May be, when winter really kicks in with sub zero temperatures, I can play a bit more with the OpenTherm settings. In the meantime, being able to interrogate the boiler and record the data is the biggest appeal of using OpenTherm.
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