0C
Viessmann fault code
Viessmann 0C: mains voltage too low
Engineer only
Viessmann says the boiler is blocked because the mains voltage reaching it is too low. The power supply needs checking.
What you can safely do
There is nothing you can safely do yourself with this one. Leave the boiler off and book an engineer.
Call a Gas Safe engineer if
- Have the power supply to the boiler checked by an electrician or engineer.
Find a Gas Safe engineer near you
Opens the official Gas Safe Register search.
Applies to: Vitodens 100-W (B1HC/B1KC). Codes can differ between models, so check your manual.