BoilerFaultCodesViessmann F.694 Fault Code
Also written as F694 — same fault.
The Viessmann F.694 fault code means: your boiler has detected a safety concern with its exhaust system and has shut itself down to prevent any risk of overheating or unsafe operation.. It appears on 1 Viessmann model in our database.
Technical description: Burner in a fault state. Signal comparison, deviation, flue gas high limit safety cut-out.
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.694 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Viessmann F.694 fault code information on this page is sourced and cross-checked against the official Viessmann service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026