High Lockout
E40 on Keston C36

Your boiler has switched off because there is too much water pressure in the system, which can put unnecessary strain on the internal seals.

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

Water pressure too high - You have put too much water pressure in your system

What causes this fault?

This fault occurs when the water pressure inside your heating system exceeds safe operating limits. The most common reason is that the filling loop valve has been left slightly open or is leaking, allowing too much water to enter the system from the mains. Over time, this extra water pushes the pressure high enough that the boiler shuts down to protect its internal components.

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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