BoilerFaultCodes 20, 21, 22, 23, 24 High
Boiler Fault Code 20, 21, 22, 23, 24
Also written as 2021222324 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code 20, 21, 22, 23, 24 appears across 2 boiler brands 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 has temporarily stopped working because it is getting incorrect temperature readings from one of its internal sensors. (As reported on Atmos Intersystem HE40 C)
Pick your boiler brand for the 20, 21, 22, 23, 24 fix
Source
Information for the 20, 21, 22, 23, 24 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 31 August 2026