High
Lockout (Red LED) on Potterton Housewarmer

Your boiler has stopped trying to light itself because the small starter flame failed to ignite within the safety time limit.

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.

What the manual says

Manufacturer manual

The pilot will attempt to light, if the pilot does not light within 60 seconds (due to air in the system) the boiler controls will go to 'Lockout' and the LED on the user controls will go Red.

From this model's manual
Verified against the Potterton Boiler Housewarmer installation & service manual.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

What causes this fault?

This fault occurs when the boiler's internal safety system detects that the small pilot flame hasn't lit correctly. The most common reasons are a build-up of debris on the ignition part or air trapped in the gas supply, which prevents the spark from catching. If the boiler cannot confirm a healthy flame within 60 seconds, it shuts down to prevent unburnt gas from escaping.

This issue is more frequent during the autumn when a boiler is turned back on after months of inactivity, as air or debris can settle in the pilot assembly during the summer.

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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