BoilerFaultCodes 5 1 High
Boiler Fault Code 5 1
Also written as 51 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code 5 1 appears across 2 boiler brands 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 failing to light the burner despite several attempts, meaning you currently have no heating or hot water. (As reported on Atmos Interopen HE22)
Pick your boiler brand for the 5 1 fix
Source
Information for the 5 1 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