When does deadheading occur in a hydronic pump?

Deadheading occurs when a hydronic pump's outlet is closed while the pump is still operating. In this situation, the pump continues to generate pressure but cannot move the fluid out of the system, leading to a buildup of pressure within the pump. Continuous operation under these conditions can cause overheating and potential damage to the pump, as it is not designed to operate without fluid movement.

The other scenarios do not accurately represent deadheading. If the pump is turned off, there is no fluid movement or pressure buildup, therefore deadheading does not occur. A blocked inlet would affect the pump's ability to draw fluid but is not specifically classified as deadheading, which involves the outlet being closed. Lastly, while exceeding the pressure limit can cause problems, it's more of a symptom or consequence of deadheading rather than a defining characteristic.