BoilerFaultCodesViessmann F.447 Fault Code
Also written as F447 — same fault.
The Viessmann F.447 fault code means: your boiler has detected an issue with the flame detection system, meaning it cannot safely confirm that the burner is lit, so it has shut down to prevent gas buildup.. It appears on 4 Viessmann models in our database.
Technical description: Burner in a fault state | Deviation, ionisation voltage signal
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Viessmann models that show the F.447 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Viessmann F.447 fault code information on this page is sourced and cross-checked against the official Viessmann service / installation manuals for each affected model.
- Viessmann Vitodens 100-W WB1A manual (PDF)
- Viessmann Vitodens 200-W B2HF System manual (PDF)
- Viessmann Vitodens 200-W B2KF Combi manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026