Your boiler's pump is running longer than it should to cool down the system after heating water, usually because a sensor has detected a temperature imbalance.

Pump over run (for loading warmstart) (ecoMAX 800)

What causes this fault?

This fault occurs when the boiler detects an unusual temperature difference between the water leaving the unit and the water coming back in. The most common cause is a faulty or drifting temperature sensor providing inaccurate readings, which trick the boiler into thinking it needs to run the pump longer than necessary to cool down. In some cases, it can also be a sign that water is not circulating as freely as it should through the heat exchanger.