100 Low

Boiler Fault Code 100

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed

Fault code 100 appears across 9 boiler brands and 14 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 at its absolute maximum power setting, which is usually a temporary state during a manual test or a specific system calibration process rather than a broken part. (As reported on Main Combi 24)

Pick your boiler brand for the 100 fix

Baxi 100 4 models British Gas 100 1 model ECA 100 1 model Ideal 100 1 model Main 100 2 models Navien 100 1 model Sime 100 1 model Viessmann 100 1 model Worcester Bosch 100 2 models

Source

Information for the 100 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