How much does it cost to fix boiler error code C20?

Typical repair cost for the boiler C20 fault is £120-200 including labour.

C20 High

Boiler Fault Code C20

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed 27 April 2026

Fault code C20 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 struggling to accurately measure the temperature of the water returning to it, so it has stopped operating to prevent potential overheating. (As reported on Atag Premier)

Pick your boiler brand for the C20 fix

Atag C20 1 model

Source

Information for the C20 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