Boiler Fault Code F.694

Also written as F694 — same fault.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026

Fault code F.694 appears across 1 boiler brand and 1 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning 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. (As reported on Viessmann Vitodens 222-F B2TF)