BoilerFaultCodes 1500 mm Emergency
Boiler Fault Code 1500 mm
Also written as 1500MM — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code 1500 mm 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 flagging that the flue terminal is positioned too close to a window or opening, which can be dangerous as it may allow exhaust gases to enter your home. (As reported on Malvern TenTwenty)
Pick your boiler brand for the 1500 mm fix
Source
Information for the 1500 mm 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