How to model timed pump starts, such as a certain on-and-off cycles per hour

  Product(s): SewerCAD, WaterGEMS, WaterCAD
  Version(s): CONNECT Edition, V8i
  Area: Modeling

Problem

Is it possible to model a pump so that it cycles on and off over a certain time span? The time starts and stops do not tend to vary, and could be something like cycling 8 times in an hour.

Solution

With WaterGEMS, WaterCAD, and SewerCAD, you can also set up logical controls based on Clock Time or Simulation Time. The controls for this are found under Components > Controls. Note that if you are using SewerCAD with this type of control, you would need to set the pump property "Ignore On and Off Elevations" to True. Otherwise the program will use the "Elevation (Off)" and "Elevation (On)" properties in the pump.

However, this might not be the best solution. Instead, you may want to apply a control that turns the pump on and off based on the tank water level or elevation. This is a more typical control for pumps, and most like the pumps in the field operate based on the level of a tank. 

To get the pump to cycle the number of times you require may take a little trial-and-error. Set up the control so that the pump turns on at a certain tank elevation and turns off at another elevation. Then compute the model and see how often the pump cycles on and off. If the number of times is too small or too large, adjust the tank control elevations and compute again. 

The advantage to this workflow is that you need to model a change in demand (for WaterGEMS or WaterCAD) or load (for SewerCAD) the pumps will operate according to the changes in the tank that would occur rather than a hardcoded control based only on time.

See Also

Creating Controls - Conditions, Actions, and Control Sets

Creating a timer control to execute after a specific time period has elapsed

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