BoilerFaultCodesTechnical description
Anti-cycle flow temperature differential
What causes this fault?
This fault occurs when the boiler detects that the water inside the heat exchanger is getting hot much faster than it can be moved around your radiators. The most common reason is a blockage or a failing pump that is preventing the water from circulating properly, causing the heat to build up to unsafe levels within the unit. It can also be caused by air trapped in the system or closed radiator valves stopping the flow of water.
This issue often appears when you first turn the heating back on in autumn, as internal pump parts can seize or sludge can settle during the summer months of inactivity.
DIY fix possible
Check that all radiator valves are fully openEnsure your system pressure is between 1 and 1.5 bar on the gaugeBleed all radiators to remove trapped air