BoilerFaultCodes P33 Low
Boiler Fault Code P33
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code P33 appears across 1 boiler brand and 2 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your boiler has detected that the external conditions are cold enough to risk freezing, so it is running a safety protection mode to keep its internal components from icing up. (As reported on Alpha Pro Tec Plus)
Pick your boiler brand for the P33 fix
Source
Information for the P33 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