BoilerFaultCodes 30 (ll) High
Boiler Fault Code 30 (ll)
Also written as 30LL — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code 30 (ll) appears across 1 boiler brand and 4 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your boiler's internal computer is having trouble talking to its main control board, which has caused it to shut down to prevent incorrect operation. (As reported on Ariston Clas HE 24)
Pick your boiler brand for the 30 (ll) fix
Source
Information for the 30 (ll) 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