High Lockout
L46 on Ideal HP290

Your heat pump's internal computer system has detected a communication or electrical issue with the power supply that controls the compressor.

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 there is a breakdown in communication between the heat pump's brains and the power system that drives the compressor. It is usually caused by an electrical failure on the inverter circuit board or a loose connection in the high-voltage wiring that prevents the system from regulating power safely.

This fault is more common during summer heatwaves or extreme winter cold, as the inverter components are pushed to their thermal limits while trying to maintain indoor comfort.

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

L45View →

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