Your heat pump's internal motor controller has encountered an electrical problem and has stopped working to protect the system.
Book a Gas Safe engineer within 24–48 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 inverter, which acts as the 'brain' controlling the speed of the pump's motor, detects an electrical irregularity or a direct hardware failure. The most common reason is a malfunction within the internal circuit board or the compressor itself, which causes the system to shut down to prevent further electrical damage.
This fault can be more prevalent during extreme summer or winter temperatures when the compressor is under the highest operational load and the inverter components are prone to overheating.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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A boiler cover plan would cover faults like LBC — no call-out fees, no surprises.
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Could it be time for a new boiler?
If repair costs are adding up, a new energy-efficient boiler could be the smarter long-term choice.
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