High Lockout
F.22 on Vaillant ecoMAX

Your boiler has detected that there is not enough water pressure inside the system to operate safely, causing it to shut down to prevent overheating.

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

Dry fire

What causes this fault?

This fault occurs when the boiler's internal sensors detect a lack of water, meaning there isn't enough pressure to safely transfer heat away from the burner. The most common reason is a slow leak somewhere in your radiator system or a component inside the boiler, such as the air vent, letting water escape over time.

This issue often surfaces in autumn when the heating is turned back on after summer, as the change in temperature can cause weakened seals to leak or air pockets to move through the pipes.

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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