High Lockout
E00-720 on Worcester Bosch 24/28CDi II RSF

Your boiler has detected a fault with the burner unit, meaning it cannot safely ignite or maintain a flame to provide heat or hot water.

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

Burner – Natural Gas Aeromatic, Ref. AACC 2233//0055 33558842

What causes this fault?

This fault occurs when the boiler's internal computer detects that the burner is not firing correctly or the flame signal is too weak to operate safely. It is usually caused by a failure in the gas delivery system or worn-out ignition components that can no longer create a spark. Over time, carbon buildup on the burner or a faulty gas valve prevents the steady flow of fuel needed to maintain heat.

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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