A20 Emergency

Boiler Fault Code A20

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed

Fault code A20 appears across 3 boiler brands 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 detecting a flame at the wrong time, suggesting that gas might be leaking into the burner when it should be shut off. (As reported on Potterton Powermax HE)

Pick your boiler brand for the A20 fix

Ariston A20 3 models Potterton A20 1 model Vokera A20 1 model

Source

Information for the A20 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