BoilerFaultCodes F.540 High
Boiler Fault Code F.540
Also written as F540 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code F.540 appears across 1 boiler brand and 4 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 water formed during the heating process is blocked and cannot drain away, which prevents the boiler from operating safely. (As reported on Viessmann Vitodens 100-W WB1A)
Pick your boiler brand for the F.540 fix
Source
Information for the F.540 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