Boiler Fault Code A2:0

Also written as A20 — same fault.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026

Fault code A2:0 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 is currently ignoring the standard priority for hot water and is attempting to provide heating and hot water at the same time, which may result in lukewarm water or poor heating performance. (As reported on Viessmann Vitodens 200)