E51 High

Boiler Fault Code E51

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed

Fault code E51 appears across 2 boiler brands and 13 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 computer has detected that the air fan installed is not the correct type or is communicating incorrectly, causing the system to stop for safety. (As reported on Alpha Evoke 10 / 18)

Pick your boiler brand for the E51 fix

Alpha E51 7 models Navien E51 6 models

Source

Information for the E51 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