BoilerFaultCodes x[[ Low
Boiler Fault Code x[[
Also written as X — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code x[[ 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 currently performing a standard task, such as heating your radiators or hot water, and is operating exactly as it should. (As reported on Remeha Quinta 85)
Pick your boiler brand for the x[[ fix
Source
Information for the x[[ 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