High Lockout
35 on Viessmann Vitodens 111-W

Your boiler has failed to ignite or stay lit, meaning your heating and hot water have stopped working.

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

Boiler does not activate

What causes this fault?

This fault occurs when the boiler's control system cannot confirm that a flame has been successfully established after several attempts. The most common reasons are a worn-out component that senses the flame, a lack of gas reaching the burner, or a build-up of carbon deposits on the ignition parts.

This issue is more frequent during the first cold snap of autumn, as ignition components that have sat idle or were already weakened can fail when suddenly asked to work under higher demand.

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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