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Yea, i understand, you can change operation mode in installer settings.   Under service menu = + OK 4sec Go to b.5 and OK It shows AP Hold = 3 sec Find C.7 1 - constant water temperature  or 4 - outdoor sensor then save with OK and exit with  =. ... Mehr anzeigen

How old is that Tado, if it is like 5 years, it may have internal power supply capacitors bad. Yea the room unit sure isnt rebooting but the box at the boiler?   Looks like you have substantial power backup, like some ecoflow or sth.   Interesting that you got update for boiler, my 100w is new from january and no updates yet.   I have bought DIYLESS opentherm tmermostat for 30€, for testing and i would say its the cheaoest opentherm thermostat, in case you would need replacing. For now it never dropped OT connection.   Yea but really without changing thermostat for testing it is hard to diagnose whats going bad. I hope that they didnt send you evil upgrade to the boiler😉   ... Mehr anzeigen

Great observation Andrei.   I was imagining that scenario, i would guess that Tado is rebooting or having bad power supply.   Its crazy tho that boiler even responds to such short error state with firing up to 60. Thats proof that software needs fixing in all those E3 platform boilers like vitodens 50 and 100.   I would call service guy to get thermostat bridge tested and replaced. I wish you get it resolved soon.       ... Mehr anzeigen

Hi Andrei   Welcome in my thread, it looks you have proof that Vieesmann needs to upgrade firmware to handle thermostat loss better without going crazy to 60°C.   Is your error 95 and intermitent or red error light is on all the time.   In your case its worth checking if Tado opentherm box at the boiler is still having all the lights on, and in the Tado app check for errors. You can send a picture.   It may be bad power supply in the Tado box, or just loose opentherm wires to the boiler maybe.   I would ask service guy that they test it out with diferent opentherm thermostat not just blame it, as under warenty.   As fast relief You can change the max limit temperature to 40 or 50 to keep the room temperature normal, until you get thermostat fixed.   Setting is under = + OK 4sec choose b2 OK -> .8 OK And set temperature limit to 45 for example. Save with OK. Then exit with 3 taps to =   Let me know how it went.   Cheers Matthew ... Mehr anzeigen

Oh so you have internal wiring problem i assume as the guy was moving down the front panel.   I think you can check if the connector has disconected for that 3 way walve for heating/hotwater.   Turn the power off and open the front cover. I drew a yelow circle around that valve, unplug connector and plug it back in the valve.   Also check that wiring bundle in the main board under black cover that it has not unpluged there, gently push on conectors to the board.   If nothing got broken during maintenace you should be back and running after this check.           ... Mehr anzeigen

Thanks Joey, So now we have 2 prooven cases for this fault.   Viessmann engineers have to give us an option to change that emergency heating to like 20 or 30°C.   Joey, can you try and issue a fault through your official maintenance firm so that we let VIESSMANN know we really need a solution ASAP.   Cheers ... Mehr anzeigen

Hi Fiddle   Thanks for the feedback.   There is a setting for plug 96 under C14 that appears only when OpenTherm is enabled. It is set to 0 - no function, or ia had it also as 4 - external demand, but nothing changes. And plug 96 is not bridged btw.   I've been reading manual some more and it looks like it is running some type of emergency heating, that is enabled when thermostat of any kind like Vitotrol or OpenTherm losses conention.   The intent is right but it is behaving stupidly going 60 C even when 25 outside, I also connected outdoor sensor to the boiler as I got it already, and I see outdoor temperature even on my thermostat now.   But the boiler could not care less, to do a check if heating is really needed at 25 outside with OpenTherm mode, when thermostat loses connection (this time i intentionally unplugged thermostat power).   The only hack I came up with today is that I can set water temperature limit via opentherm thermostat to like 22, the setting is stored in a boiler at b2-8 and it prevents the boiler form firing up it just starts the pump if there is the error 95.   It's essentially my summer lockout trick, but I would rather have the boiler check outside temperature or have like a setpoint of like 30°C water that is active only when thermostat fault occurs.   I know that at 30C water even at -20C nothing freezes indoors, I think developers need to import that if there is no such setting already that maintenance guy can set.   What do you recommend as a proper solution?   Cheers Mathew           ... Mehr anzeigen