BoilerFaultCodesTechnical description
The temperature recorded by the flow temperature sensor or the safety sensor is rising too quickly
What causes this fault?
This fault occurs when the heat inside the boiler cannot be carried away quickly enough, causing the internal temperature to spike dangerously fast. The most common reasons are a failed pump that isn't pushing water through the pipes or a blockage, such as sludge or limescale, that is restricting the flow. Essentially, the boiler is generating heat but has nowhere to send it, so it shuts down to prevent damage.
This issue often appears at the start of autumn when the heating is turned back on after a long summer break, as internal 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.