High Lockout
L1 on Ideal Logic Combi ESP1

Your boiler has shut down because the water inside it has become too hot, usually due to a lack of water flow or a circulation problem.

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 Temp Overheat Lockout

What causes this fault?

This fault occurs when the water inside the boiler exceeds a safe temperature limit and cannot be cooled down quickly enough. The most common reasons are a pump failure preventing the water from moving or a blockage within the pipework that restricts flow. In some cases, it can also be triggered by a faulty sensor giving a false reading to the boiler's control board.

This fault is frequently seen at the start of autumn when heating systems are turned on for the first time after summer, often because the pump has seized due to 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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