BoilerFaultCodes Overheat thermostat lockout High
Boiler Fault Code Overheat thermostat lockout
Also written as OVERHEATTHERMOSTATLOCKOUT — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code Overheat thermostat lockout appears across 1 boiler brand and 6 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your boiler has detected that it got too hot and has automatically shut itself down to prevent internal damage. (As reported on Ideal Mini HE)
Pick your boiler brand for the Overheat thermostat lockout fix
Source
Information for the Overheat thermostat 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 7 July 2026