304 Low

Boiler Fault Code 304

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed

Fault code 304 appears across 3 boiler brands and 5 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 running a special testing or setup procedure designed for engineers, rather than operating in normal heating mode. (As reported on Baxi Assure)

Pick your boiler brand for the 304 fix

Atag 304 2 models Baxi 304 2 models Main 304 1 model

Source

Information for the 304 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