Low
F21 on Ferroli HiTech RRT 24C

Your boiler has detected that the water pressure inside the system is a little higher than ideal, though it is currently just an advisory warning.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

What the manual says

Manufacturer manual

System pressure slightly high (visible only in the Alarm menu)

From this model's manual
Verified against the Ferroli/Ferroli Bluehelix Hitech Rrt installation & service manual.
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 the filling loop valves beneath your boiler.Carefully bleed one or two of your radiators to let out a little water and reduce the pressure.Keep an eye on the boiler's pressure gauge until it drops back into the green zone (usually between 1.0 and 1.5 bar).

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Related fault codes

F34View →F35View →

All 36 fault codes on the HiTech RRT 24C

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

A06A08A09A11A14A23-A24-F51A26A44A80A88A98A99F05F09F10F11F12F13F15 - A07F19F34F35F37F39F40F47F50F50 - F53F51F53F62F64F96F99Fh

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