The behavior of the VSP is set under the VSP tab within the pump dialog box. There are two ways to control a variable speed pump. One is to provide a Pattern of pump relative speeds. This is best used for cases where you are trying to model some past event where the pump speeds are known exactly or where the pump is not being controlled by some target head. This would be the case where human operators set speed based on a combination of time of day, weather and other factors.

The second type of control is Fixed Head control, where the pump speed is adjusted to maintain a head somewhere in the system. For water distribution pumping into a pressure zone with no storage, this is usually some pressure sensor on the downstream side of the pump. For wastewater pumping, the pump may be operated to maintain a constant wet well level on the suction side (i.e., flow matching).

To indicate that a pump is behaving as a VSP, first check the box next to Variable Speed Pump? at the top of the VSP tab. This will change the remaining boxes on the tab from gray to white.