High Lockout
LC4 on Ideal HP290

Your boiler has detected an internal electrical communication problem with the system that controls the pump and fan, meaning the unit cannot run safely.

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

Inverter Error

What causes this fault?

This fault occurs when the boiler's main brain loses its connection with the high-voltage component that powers the internal pump and fan. The most common reason is an electronic failure within the inverter board itself or a loose wiring connection preventing these two vital parts from talking to each other. Because the boiler cannot confirm the pump is moving water or the fan is clearing gases, it shuts down as a safety precaution.

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

LC1View →LC2View →LC3View →

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