BoilerFaultCodesViessmann F.450 Fault Code
Also written as F450 — same fault.
The Viessmann F.450 fault code means: your boiler's internal computer has encountered a software timing error, causing it to lose its place during its normal operating sequence.. It appears on 4 Viessmann models in our database.
Technical description: Error in scheduled program run monitoring
DIY fix possible
Press the Reset button on the control panel to clear the temporary software glitch.Turn the power supply to the boiler off at the fused spur switch, wait 30 seconds, and turn it back on.Check that the boiler display is not repeatedly cycling or 'freezing' after the restart.
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Viessmann models that show the F.450 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Viessmann F.450 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