Your boiler is simply performing a routine preparation step by running its internal pump before ignition to ensure safe water flow.

pump pre-run

What causes this fault?

This status occurs when the boiler detects a demand for heat and starts the internal pump to move water through the heat exchanger. It is a vital safety check designed to ensure there is sufficient water flow before the burner ignites to prevent the system from overheating. Once the electronics confirm the water is circulating correctly, the boiler will proceed to the ignition stage.