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User notification: Constant flow VSPs (or VSPBs) and fixed head VSPs (or VSPBs) are not both allowed in the same scenario

Product(s): WaterGEMS, WaterCAD
Version(s): 10.00.xx.xx, 08.11.xx.xx
Area: Modeling
Original Author: Scott Kampa, Bentley Technical Support

Problem

When validating a model, the following user notification is generated:

Constant flow VSPs (or VSPBs) and fixed head VSPs (or VSPBs) are not both allowed in the same scenario.

Problem ID#: 81585

Solution

The inclusion of both fixed head and fixed flow variable speed pumps can have adverse effects on the model calculation. For this reason, the use of both methods in the same scenario is not allowed. As a workaround, either try to correlate the fixed flow value to a head value or use the Pattern-Based VSP type.

A fixed head is correlated through a trial-and-error process. The pattern for pattern-based VSP can be set up as time from the start of the simulation going to 24 hours with the multiplier that will control the relative speed factor for the pump. If you know your pump at a relative speed factor of 1.0 at a certain flow you should be able to figure out what relative speed factor the pump will need to be set to in order to run at whatever flow settings you need.

See Also

How to I model parallel fixed head (target head) variable speed pumps that are controlled by flow in a downstream pipe

  • Created by Bentley Colleague
  • When: Wed, Aug 26 2015 10:32 AM
  • Last revision by Bentley Colleague
  • When: Wed, May 24 2017 1:18 PM
  • Revisions: 2
  • Comments: 0
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