How would you model multiple different-size variable speed pumps (VSP)?

[Shawn Huang]

There are two variable speed pumps (VSP) in a wastewater lifting station. One is a small VSP, which will be turned on when the flow is small and turned off when the flow is large. The other is a large VSP, which will be turned on when the flow is large and turned off when the flow is small.

One way to model this situation is to use Rule-Based controls and VSP controls within InfoWater. Rule-based controls will determine a pump is on or off from the system flow, while VSP controls will determine the running VSP's speed when the pump is on.

Rule-based controls apply only at the very beginning of each EPS step. Note that Rule-based controls do nothing in a Steady State run. In order to accurately simulate how the pump changes speed, the EPS time step should be small.