Boiler Fault Code ALL 30

Also written as ALL30 — same fault.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026

Fault code ALL 30 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 has lost the ability to accurately measure the temperature of the water returning to it, so it has shut down as a precaution to prevent overheating. (As reported on Sime Brava Slim HE System)