High Lockout
J46 on Ideal HP290

Your heat pump’s internal power control system has encountered a fault, meaning the outdoor unit cannot currently run to provide heating or hot water.

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 internal power management system, known as the inverter, stops communicating correctly with the main computer of the heat pump. The most common reason is an electrical failure within the inverter circuit board due to power surges or component wear, which prevents the unit from controlling the fan and compressor speed.

This fault can be more frequent during summer or extreme heatwaves, as high ambient temperatures put additional thermal stress on the electronic power components.

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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