Medium
F21 on Ferroli Extrema C

Your boiler has detected that the water pressure in your heating system is too high, which can put unnecessary strain on the internal components.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

What the manual says

Manufacturer manual

Incorrect system water pressure (The pressure is reaching the maximum value)

From this model's manual
Verified against the Ferroli/Ferroli Extrema C installation & service manual, page 27.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

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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Related fault codes

F37View →

All 25 fault codes on the Extrema C

Seeing a different code? Every code this model can display, in one place.

A01A02A03A04A06A15A26d1d2F07F10F12F13F14F15F20F34F35F37F39F40F42F47FH

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