High
LED 4: 0 on Ferroli Optima 201

Your boiler has detected an issue with the sensor that monitors hot water temperature, which often means the water is getting too hot or the sensor has stopped working.

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

D.H.W. sensor (42) not connected or D.H.W. temperature too high

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

LED 2View →LED 3View →

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