Hello, I have Vitodens 200-W B2HB 13 kW installed since 10/2017. It is connected only to one simple floor heating circuit (7 loops, 70 m2) with no 3-way valve, no aditional circulation pump, no regulation valves on loops. No aditional devices are installed (ie solar, hot water tank etc.). It worked good for 3 months with equitherm regulation. Burner modulated from 11 % and number of cycles was verry small. Last 14 days something become wrong. Boiler is not capable to run everytime on 11 % of power, it runs in 90 % causes on 33 % to 55 % as minimum, although measured water temperature is higher than set point. I've made this actions and test: - disable equitherm regulation (now it runs only on boiler water temperature setpoint - now 39 °C) and disconnect the outside probe. - reset all settings to factory default (from menu and also by coding addres 7C to value 42 as Viessman technician advised to me by phone). - check temperature sensors (hot water output, fluegas). - increase internal pump power from menu, increase flow through manifold by opening balance valve to bathroom towell heater, check magnetic filter separator (but water flow was OK everytime - when burner ignite, pipes are hot immediatelly). - check and softly clean ionisation probe. - force burner to run on the lowest power (by relay menu) - even it was forced to run on low power, the burner runs on 55 % (as I measured by natural gas consumption). I noticed, that the minimal burner power differs between starts - sometimes it is 33 %, sometimes 55 % and in very few cases it can run on 11 %. In attached photos you can see sceens demonstrating the problem - water temperature setpoint is 39 °C, burner power is 32 % although real boiler temperature is 46 °C. It isn't any transition state, it takes few minutes until the water reach aprox 49 °C and burner is shut off. The heat consumption of heating circuit is enough (return temperature is about 30 °C) No alarms are present. Could you please advice me, what to check? Thank you, Michal Hejsek
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