BoilerFaultCodesProtherm F0 Fault Code
The Protherm F0 fault code means: your boiler has stopped working because the water pressure inside the system has dropped too low to operate safely.. It appears on 1 Protherm model in our database.
Technical description: Loss of water (pressure in CH system is less than 0.7 bar)
DIY fix possible
Locate the filling loop (usually a silver flexible hose) underneath or near the boiler.Slowly open the tap or taps on the filling loop until you hear water flowing.Watch the pressure gauge until it reaches between 1.0 and 1.5 bar, then close the taps fully.
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Protherm models that show the F0 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Protherm F0 fault code information on this page is sourced and cross-checked against the official Protherm service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026