Safety thermostat lock out High

Biasi Safety thermostat lock out Fault Code

Also written as SAFETYTHERMOSTATLOCKOUT — same fault.

The Biasi Safety thermostat lock out fault code means: your boiler has overheated, causing it to shut down automatically for safety.. It appears on 1 Biasi model in our database.

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: Safety thermostat lock out
Typical repair cost £100-250 (including labour)

DIY fix possible

Check that all radiator valves are open to ensure water can flow properly.Wait for the boiler to cool down for at least 20 minutes.Rotate the selector switch to the reset position 'R' for a few seconds and then back to the desired setting.

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Biasi models that show the Safety thermostat lock out fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Biasi Safety thermostat lock out fault code information on this page is sourced and cross-checked against the official Biasi service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026