BoilerFaultCodes 1.b Low
Boiler Fault Code 1.b
Also written as 1B — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code 1.b appears across 1 boiler brand and 1 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 maximum power level to provide hot water and this code is often just an operational status indicator rather than a breakdown. (As reported on Worcester Bosch Greenstar CDi Compact)
Pick your boiler brand for the 1.b fix
Source
Information for the 1.b 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