BoilerFaultCodes i15 Low
Boiler Fault Code i15
Also written as I15 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code i15 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 Your boiler is simply displaying the current outdoor temperature because a weather sensor is connected, which is a normal status reading rather than a fault. (As reported on Worcester Bosch Greenstar Heatslave II)
Pick your boiler brand for the i15 fix
Source
Information for the i15 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