High Lockout
F20 on Glow-worm Flexicom sx

Your boiler has reached an unsafe temperature and has automatically shut down to prevent damage or safety issues.

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

Overheating

What causes this fault?

This fault occurs when the water inside the boiler gets too hot, triggering a safety sensor to cut the power. The most common reasons are a pump failure that stops water from moving or a blockage in the system that prevents heat from escaping the boiler's internal components.

This issue is more frequent during the first cold spell of autumn when pumps that have been idle all summer can seize up or struggle to circulate water.

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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