Viessmann · Vitodens 100-W Boiler
This fault indicates that the burner is in a fault state, likely due to a ground fault with the ignition electrode or a problem with the burner control unit (BCU). The boiler will not operate correctly.
Click steps to track your progress.
Check the ignition electrode for any signs of a ground fault or damage.
Reset the boiler by briefly turning off and on its power supply.
If the fault persists, contact a qualified heating engineer, as the BCU burner control unit may need to be replaced.