High Lockout
L1 on Ideal Logic Max System

Your boiler has switched itself off because the internal water temperature has become too hot, usually caused by a lack of water flow through the system.

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

Flow Temperature Overheat Lockout

What causes this fault?

This fault occurs when the water inside the boiler exceeds a safe temperature, causing the system to shut down for safety. The most common reasons are a pump failure preventing water from moving through the system or a blockage caused by a build-up of sludge and debris. It can also be triggered by a faulty sensor that is incorrectly reporting the water temperature to the control board.

This fault is more common in autumn when homeowners turn their heating back on after a long summer break, as the internal pump can often become seized or stuck during 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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Related fault codes

L2View →F1View →

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