BoilerFaultCodes Slow flash (unspecified rate) Emergency
Boiler Fault Code Slow flash (unspecified rate)
Also written as SLOWFLASHUNSPECIFIEDRATE — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code Slow flash (unspecified rate) 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 that it cannot safely get rid of exhaust gases, so it has stopped working to prevent a buildup of dangerous fumes. (As reported on Worcester Bosch Greenstar 12Ri)
Pick your boiler brand for the Slow flash (unspecified rate) fix
Source
Information for the Slow flash (unspecified rate) 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