High Lockout
NEON5 on Glow-worm Hideaway 40B

Your boiler has switched itself off because it has detected that the water inside has become dangerously hot.

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.

Technical description

SAFETY TEMPERATURE LIMITER

What causes this fault?

This fault occurs when the internal temperature of the boiler exceeds safe limits, triggering a safety shut-off to protect the system. The most common reason is a lack of water flow, often caused by a failing circulation pump or a blockage in the heat exchanger preventing heat from being carried away. In some cases, it can also be triggered by a faulty sensor giving an incorrect high-temperature reading.

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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Related fault codes

NEON 1View →NEON 4View →

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