BoilerFaultCodes F.668 Medium
Boiler Fault Code F.668
Also written as F668 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code F.668 appears across 1 boiler brand and 2 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your boiler is struggling to coordinate its hot water system because it has lost the signal from a sensor that monitors the heat coming from your solar panels. (As reported on Viessmann Vitodens 222-F B2TF)
Pick your boiler brand for the F.668 fix
Source
Information for the F.668 fault code is sourced from the official service / installation manual for each model that displays it. Read more about how we source fault codes →
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026