High
Reset LED is lit on Glow-worm Micron 50FF

Your boiler has sensed it is getting too hot and has shut itself down as a safety precaution.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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

Check water system for overheating. Reset by turning temperature control knob off and on.

From this model's manual
Verified against the Glow Worm Micron 50ff 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 water inside the heat exchanger reaches a dangerously high temperature, triggering a safety sensor to cut the power. The most common reasons are a failed pump that isn't moving the water away fast enough, or a blockage such as air or sludge trapped within the pipework.

This issue often appears when the heating is first turned on after summer, as pump components can seize up during long periods of inactivity.

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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