Duty point

The duty point is at the intersection between the Q-H curve and the system characteristics.

In order to choose a pump for a heating system, it is necessary to know both the system characteristics and the pump curve. The pump is dimensioned so it can provide an adequate performance at the maximum system load.

  • The pump performance curve is a diagram showing the connection between flow (Q) and generated head (H) or pressure.
  • The system’s characteristics show the pressure loss in the system as a function of the flow.  
  • The duty point is the intersection between the pump performance curve and the system’s characteristics.

The maximal load is reached during only during a portion of the annual operating hours. This means that the pump system may be too large for the remainder of the operating hours, unless a pump system that can be regulated is employed.