Viessmann Vitodens 050-W (BPJC) does not work with any OpenTherm thermostat

[nyctomanica]

Hey folks,

I have been trying to replace the controls on my Viessmann Vitodens 050-W boiler (BPJC type, with the white front panel), switching from a Hive to a DIY OpenTherm thermostat (using ESPHome for those curious).
The goal is to implement load compensation, to adjust the CH flow temperature depending on how many (smart) radiators are calling for heat, and how much each room needs to be heated.

However, the boiler just will not connect to any OpenTherm stat, only working in on/off mode!
The ESPHome one would only show me errors, so I borrowed a spare Nest to test if it was my hardware or the boiler itself.

The Nest would not work either in OpenTherm mode, telling me it was not detected.
Out of curiosity, I then tested my DIY stat on my mate's Ideal boiler (who I borrowed the Nest from), and it worked perfectly!

I have checked the Installation and Service manual and double checked that I'd wired the stat to the correct terminals for OT, and even emailed Viessmann who rather unhelpfully just showed me the same page from the manual I'd been using.

Could there be some setting that needs to be changed on the boiler (not in the manual!), or is it just not working properly?
I'm at my wit's end here, so I'd appreciate if anyone could give me a hand!

Cheers!

also, here's the manual for anyone who wants a look

https://viessmanndirect.co.uk/files//8e0ea54e-2b22-4e73-822f-a9d1010d4f14/Vitodens%20050-W%20Installation%20and%20Service.pdf

 

[eset]

I have exactly the same problem after today installation. This damn thing is showing constantly error 95. I wrote here to Netatmo cuz I have modular Thermostat with Relay for OT from them https://helpcenter.netatmo.com/hc/e...rmostat-Modular-with-Viessmann-Vitodens-0-50W

Im confused what's going on. I saw other movies on YouTube where people were using OT with that Model using Google Nest. And worked, so what the ****?!

 

[nomacaron]

OP: can you send some pictures of your wiring for on both the thermostat end and the boiler end? I have the same boiler and was able to wire up an OT stat so may be able to help.