BoilerFaultCodesFerroli F21 Fault Code
The Ferroli F21 fault code means: your boiler has detected that the water pressure in your heating system is too high, which can put unnecessary strain on the internal components.. It appears on 6 Ferroli models in our database.
Technical description: Incorrect system water pressure (The pressure is reaching the maximum value)
DIY fix possible
Locate a radiator in your home that is easily accessibleSlowly open the radiator bleed valve using a radiator key to release a small amount of waterMonitor the pressure gauge on the front of the boiler until the needle drops into the green zone (usually between 1.0 and 1.5 bar)Close the bleed valve once the pressure is correct
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Ferroli models that show the F21 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Ferroli F21 fault code information on this page is sourced and cross-checked against the official Ferroli service / installation manuals for each affected model.
- Ferroli Bluehelix HiTech RRT manual (PDF)
- Ferroli Bluehelix Pro RRT manual (PDF)
- Ferroli Bluehelix Tech manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026