High
F11 on Ferroli Optimax

Your boiler has detected an issue with the sensor that monitors the temperature of the water returning to the unit, causing it to stop running as a safety precaution.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description

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

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Related fault codes

F10View →F14View →A06View →

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