BoilerFaultCodesTechnical description
flow temperature too high /flow sensor error (2nd CH)
What causes this fault?
This fault occurs when the boiler detects that water is not circulating through the heat exchanger, causing it to overheat rapidly. The most common reason is that the main pump has seized or failed, but it can also be caused by a blockage in the internal valves or a build-up of debris restricting the flow. Essentially, the boiler is generating heat but has no way to move that heat away into your radiators or hot water tank.
This issue often appears in autumn when the heating is turned back on for the first time, as the pump can seize up after sitting idle during the summer months.
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.