High Lockout
E131 on Potterton Promax

Your boiler has shut down because the exhaust gases have reached a dangerously high temperature, triggering a safety sensor to prevent damage.

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

Flue overheat lockout

What causes this fault?

This fault occurs when the internal temperature of the boiler rises significantly above safe operating limits, causing the safety sensor to trip. The most common reason is a buildup of limescale or debris inside the main heat exchanger, which prevents heat from being transferred to the water and forces it out through the exhaust instead.

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

E110View →E130View →E160View →

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