Medium
F11 on Ferroli Optimax HE 31 C

Your boiler is struggling to detect the temperature of the water for your taps and shower, which means the hot water may be inconsistent or not working at all.

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

Return sensor fault (Sensor damaged or wiring shorted / Sensor damaged or wiring broken)

From this model's manual
Verified against the Ferroli/Ferroli Optimax He 31 C 4726742 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.

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Related fault codes

F05View →F10View →

All 32 fault codes on the Optimax HE 31 C

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

A01A02A03A04A05A06A41F04F05F07F10F12F13F14F15F20F21F24F34F35F37F39F40F41F42F43F47F50F51Low system pressureNo burner ignition

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