BoilerFaultCodesTechnical description
The flow temperature sensor is not detecting a rise in temperature following a burner start
What causes this fault?
This fault occurs when the boiler fires up but the internal sensors don't see the water temperature increasing as expected. The most common reason is that water isn't moving through the system quickly enough, often due to a seized pump or a blockage in the heat exchanger. Because the heat has nowhere to go, the boiler shuts down immediately to protect its internal components from overheating.
This issue often surfaces in autumn when the heating is turned back on after a long summer break, as pump components can seize up during 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.