A nn Low

Boiler Fault Code A nn

Also written as ANN — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed

Fault code A nn 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 is currently recalibrating its internal settings and should return to normal operation automatically after a short period. (As reported on Keston C90 / C110)

Pick your boiler brand for the A nn fix

Keston A nn 1 model

Source

Information for the A nn 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