BoilerFaultCodesTechnical description
No water flow is detected for 60 secs and the temperature is less than 40ºC. Check system water levels, isolation valves, pump, and water flow sensor.
What causes this fault?
This fault occurs when the boiler's internal computer tries to start the heating process but cannot detect any movement of water through the system. The most common reasons are a pump that has seized up or failed, air being trapped within the unit, or a physical blockage that is preventing the water from circulating correctly.
This issue is more frequent in autumn when the heating is turned back on for the first time after summer, as the internal pump can often stick during long 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.