BoilerFaultCodes E783 High
Boiler Fault Code E783
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code E783 appears across 1 boiler brand and 3 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your boiler is having trouble communicating with your wall-mounted thermostat or smart control system, which prevents it from knowing when to turn on your heating. (As reported on Navien NCB H)
Pick your boiler brand for the E783 fix
Source
Information for the E783 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 7 July 2026