BoilerFaultCodesTechnical description
Maximum acceptable flow temperature rise exceeded. The boiler will shut off for ten minutes, then restart. Should the flow temperature conditions remain the same after 5 attempts, this code will be recorded as a shut-down failure. Boiler will not lockout.
What causes this fault?
This fault occurs when the water inside the boiler heats up much faster than it can be moved away into your radiators or cylinder. The most common reasons are a failing pump that isn't pushing water fast enough, or a buildup of sludge and limescale that has partially blocked the narrow channels inside the heat exchanger.
This issue often comes to light in autumn when the heating is first turned on after summer, as internal pump components may have seized or debris settled during the period of inactivity.
DIY fix possible
Check that all radiator valves are fully openEnsure the central heating bypass valve is not closedCheck the system pressure gauge and top up to 1.5 bar if low