BoilerFaultCodes i4 Low
Boiler Fault Code i4
Also written as I4 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code i4 appears across 1 boiler brand and 1 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning This code is not actually an error; it is simply showing you the current maximum heating power level for your hot water production. (As reported on Worcester Bosch Greenstar Heatslave II)
Pick your boiler brand for the i4 fix
Source
Information for the i4 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