Emergency Lockout
D.(1) on Potterton Kingfisher 2 RS60, RS80, RS100

Your boiler is not turning off when the water gets hot enough, which runs the risk of the system overheating.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Act immediately

Turn off your boiler and stop using gas appliances. Call a Gas Safe engineer now. This fault can be dangerous if ignored.

Technical description

Main burner fails to shut down when water reaches pre-determined temperature - Thermostat out of calibration or faulty.

What causes this fault?

This fault occurs when the internal sensors fail to tell the boiler to stop firing once the water has reached its target temperature. The most common reason is that the control thermostat has lost its calibration or become stuck in the 'on' position, meaning the burner stays lit indefinitely. This creates a safety risk as the water inside the unit could potentially reach boiling point if the safety limits do not intervene.

Engineer required

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

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