Using Controls to change pump speed

  Applies To 
  Product(s): WaterCAD, WaterGEMS, HAMMER, SewerCAD
  Version(s): V8 XM, V8i, CONNECT Edition
  Area:  Modeling
  Original Author: Jesse Dringoli, Bentley Technical Support Group

 

Problem

How can I use controls to set / change the speed of my pump based on some logic?

Solution

This can be accomplished in the Controls feature by using the pump Action "setting" instead of "Status". The "Setting" represents the relative speed factor of the pump, where 0.7 for example means 70% of full speed (where full speed means the pump characteristic curve as you have entered it in the pump definition).

Troubleshooting

If you speed-based controls are not working, first make sure that they are added to the control set used by your current scenario (operational alternative)

If using logical (as opposed to simple) controls to control the speed of a pump and if the pump is initially off, ensure that the initial relative speed setting is 0.0. The reason is because a logical control does not change the setting of a pump if that pump's setting is already the same, (within a tolerance) even if it's status is 'off'. For example, if the initial relative speed factor of an initially off pump is 0.875 and you define logical controls to turn the pump on by setting the relative speed factor to 0.875, it will not turn the pump back on, since the new relative speed is the same as the speed that the pump is already using.

Also note that when using controls to turn a pump "on", do not use a composite action that both turns the status of the pump to On and changes the relative speed to some value. This causes a conflict since changing the speed will automatically turn it on and changing the status to ON would automatically set the speed to 1.00. The last control in the action sequence prevails, so you may end up with an unexpected result. If you are turning on a pump at a certain relative speed factor, make sure the control's action only changes the relative speed factor.

Note that logical/simple controls in HAMMER are only used during the initial conditions simulation.

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