BoilerFaultCodes H 3 Medium
Boiler Fault Code H 3
Also written as H3 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code H 3 appears across 1 boiler brand and 3 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your boiler is struggling to accurately detect the temperature of your hot water, which means it may fail to provide a consistent supply or stop heating your water altogether. (As reported on Ideal Isar HE)
Pick your boiler brand for the H 3 fix
Source
Information for the H 3 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