BoilerFaultCodesWhat the manual says
Manufacturer manualWater circulation fault. Possible pump failure
What causes this fault?
This fault occurs when the boiler detects a significant temperature difference between the water leaving the unit and the water returning to it, suggesting a blockage or pump failure. The most common reason is a seized or failing circulation pump that can no longer push water through the radiators and pipework. Additionally, a build-up of sludge or limescale within the heat exchanger can restrict flow enough to trigger this safety shutdown.
This fault is more common in autumn when heating is turned on for the first time after summer, as pumps are prone to seizing 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.
Avoid the next call-out bill
A cover plan would handle faults like F23: no call-out fees, no surprise bills.
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