High
LED 4 (CH) on Ferroli Optima 201

Your boiler has detected an issue with its internal temperature sensing, meaning it cannot accurately judge how much to heat your radiators.

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

Central heating sensor (34) not connected or boiler temperature too high or boiler thermostat (61) below CH temperature.

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

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