BoilerFaultCodesTechnical description
Maximum temperature rise slope
What causes this fault?
This fault occurs when the boiler's internal sensors detect that the water temperature is rising much faster than it should. The most common reason is that water isn't moving through the system quickly enough, often due to a failing pump or a buildup of debris and sludge that creates a blockage. Because the heat cannot be carried away to your radiators, the boiler shuts down to prevent itself from overheating and becoming damaged.
This issue often surfaces in autumn when the central heating is switched back on after a summer of inactivity, which can cause internal pump components to seize.
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.