High Lockout
neon1 on Glow-worm Space Saver

Your boiler is not receiving the correct electrical power, meaning it cannot start the ignition process to provide heating or hot water.

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

Is there 240V~ between 12 and 10 and between 11 and 10? Correct power supply problem.

What causes this fault?

This fault occurs when the boiler's internal controls detect that the main electrical power is either missing or interrupted before it can reach the ignition system. The most common reason is an external fuse that has blown or a loose connection in the wiring that prevents electricity from flowing correctly through the unit. Without this steady power supply, the boiler cannot safely trigger the spark needed to light the flame.

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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