BoilerFaultCodesTechnical description
Temperature differential exceeded
What causes this fault?
This fault occurs when the boiler's internal sensors detect that the water temperature is rising too fast or there is too much of a difference between the flow and return pipes. The most common reason is a blockage in the system or a failing pump that prevents the hot water from moving away from the heat exchanger quickly enough. It can also be caused by air trapped in the boiler or sensors that have become faulty and are giving incorrect readings.
This issue often appears when the heating is first turned on after summer, as the pump can seize or debris can settle in the pipes during the months 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.