BoilerFaultCodes F11 – A11 High
Boiler Fault Code F11 – A11
Also written as F11A11 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code F11 – A11 appears across 1 boiler brand and 3 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 an issue with the sensor that monitors the temperature of the water coming back into the system, causing the boiler to stop working for safety. (As reported on Ferroli iBoiler 28)
Pick your boiler brand for the F11 – A11 fix
Source
Information for the F11 – A11 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 27 April 2026