BoilerFaultCodes 6C:0 to 6C:100 Medium
Boiler Fault Code 6C:0 to 6C:100
Also written as 6C0TO6C100 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code 6C:0 to 6C:100 appears across 1 boiler brand and 5 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your boiler's internal pump or fan is reporting an incorrect speed setting, which is usually a technical communication error between the internal computer and the parts that move water or air. (As reported on Viessmann Vitodens 200)
Pick your boiler brand for the 6C:0 to 6C:100 fix
Source
Information for the 6C:0 to 6C: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 27 April 2026