BoilerFaultCodesYour heat pump has stopped working because water is not flowing through the system quickly enough to prevent it from getting too cold.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: High Flow/Return Differential 3 times in succession and Flow Temperature <7°C Error
What causes this fault?
This fault occurs when the water inside the system isn't moving fast enough to carry heat away, causing a sharp temperature difference that triggers a safety shutdown. The most common reasons are a blockage in the pipework, a buildup of debris in the system filter, or a pump that has failed and is no longer circulating the water correctly.
This issue often surfaces during the first cold snap of autumn when the heating is turned back on after being idle all summer, allowing settled debris to block the flow.
DIY fix possible
Check that at least two or three radiators have their valves turned to the maximum settingEnsure any external valves on the pipework leading to the unit are fully openCheck your central heating controller to ensure the pump is being told to run
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A boiler cover plan would cover faults like High Flow/Return Differential Error — no call-out fees, no surprises.
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