BoilerFaultCodes Thermal fuse lockout High
Boiler Fault Code Thermal fuse lockout
Also written as THERMALFUSELOCKOUT — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code Thermal fuse lockout appears across 1 boiler brand and 7 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your boiler has overheated because a safety switch has tripped to protect the internal components, and it now needs to be manually restarted. (As reported on Ideal Compact HE)
Pick your boiler brand for the Thermal fuse lockout fix
Source
Information for the Thermal fuse lockout 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