BoilerFaultCodesTechnical description
Temperature differential inverted
What causes this fault?
This fault occurs when the boiler's sensors detect that the return pipe is hotter than the flow pipe, which is the opposite of how it should function. The most common reasons are a pump failure that prevents water from circulating or a blockage in the heat exchanger that forces the heat to back up. It can also be caused by temperature sensors that have become faulty and are sending incorrect readings to the control board.
This issue often appears when the heating is first turned on after summer, as circulation pumps can seize up during long periods of inactivity.
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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