BoilerFaultCodes C1 54 High
Boiler Fault Code C1 54
Also written as C154 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code C1 54 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 is heating up too quickly or flowing in the wrong direction, often because something is blocking the circulation of water through the system. (As reported on Atag Sov.)
Pick your boiler brand for the C1 54 fix
Source
Information for the C1 54 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