BoilerFaultCodesYour boiler has detected that heat is flowing in the wrong direction or the sensors are reading temperatures incorrectly, causing the system to shut down for safety.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Temperature differential inverted (return sensor temperature higher than thermistors flowsensor temperature)
What causes this fault?
This fault occurs when the boiler's internal sensors detect that the return pipe is hotter than the flow pipe, which is the opposite of how a heating system should function. The most common reasons are sensors that have shifted out of calibration, a faulty pump that isn't circulating water correctly, or a blockage in the heat exchanger.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
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