BoilerFaultCodes 257 b7 High
Boiler Fault Code 257 b7
Also written as 257B7 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code 257 b7 appears across 1 boiler brand and 2 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your boiler's main computer has encountered an internal fault and is unable to operate safely, meaning you currently have no heating or hot water. (As reported on Worcester Bosch Greenstar CDi Compact)
Pick your boiler brand for the 257 b7 fix
Source
Information for the 257 b7 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