High
LED 4 (D.H.W.) on Ferroli Optima 201

Your boiler has stopped producing hot water because it has lost contact with or is misreading the temperature sensor that monitors your hot water supply.

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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