High Lockout
AL40 on Vokera Unica 24HE

Your boiler has detected that the water pressure in the central heating system is too low to operate safely and has shut down.

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

Insufficient system water pressure appliance operation

What causes this fault?

This fault occurs when the internal sensor detects that there isn't enough water pressure to safely circulate heat around your home. The most common reason is a slow leak somewhere in the radiator network or a drop in pressure following the bleeding of your radiators. In some cases, a component inside the boiler like the expansion vessel may have lost its charge, leaving the system unable to maintain steady levels.

This code is frequently seen at the start of autumn when homeowners turn their heating back on for the first time after summer, or after bleeding radiators for the winter months.

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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