Boiler Fault Code ER 20

Also written as ER20 — same fault.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026

Fault code ER 20 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's internal temperature sensor is failing to provide a reading, meaning the unit cannot safely manage its water temperature and has shut down to prevent damage. (As reported on Johnson Starley Warmcair DW)