Good morning, I installed a Viessmann VitoDens 200-W B2KB-26 boiler with climatic adjustment and Tado system for remote modulation and control.
The system includes 11 thermostatic valves, thermostat, bridge and extension kit.
I have a clarification to ask:
1 - When the system is at full speed and the rooms are at the required temperature, all the thermostatic valves on the radiators are in closed position and as there is no heat request the boiler switches off the burner leaving the water pump turned on for circulation. Since all the thermostatic valves are closed, the pump circulates the water only inside the boiler by-pass.
If, afterwards, there is a request for heat from one of the thermostatic valves on the radiators, the burner turns on, bringing the heating water to 65/70 ° C in a few seconds and also emitting a loud noise of water almost in boiling.
Then turn off for a few minutes and repeat this operation several times.
The boiler in 806 hours of operation carried out 12672 burner starts. Approximately 1 start every 4 minutes.
I tried to follow this operation and I saw that the burner, even with a minimum heat demand, brings its own combustion set to 60% by clearly boiling the little water available in the by-pass.
I tried to remove a thermostatic valve leaving therefore a radiator always free to receive water and the problem was greatly reduced.
But it is not a solution that I really like.
I also asked the technician who installed the boiler and he also suggested that I leave a couple of radiators free in order to always allow the circulation of water.
Do you have any suggestion in terms of boiler parameterization to mitigate this phenomenon?
Or should I provide for the installation of a differential by-pass valve between the flow / return manifolds?
Thank you
Federico Gamberini
