User Notification: "Different target heads for the same control node are not allowed."

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

Problem

When attempting to compute a model with variable speed pumps in parallel, it fails and the following User Notification appears:

"Different target heads for the same control node are not allowed."

Solution

This notification refers to the "Target Head Type" field in the properties of a pump that is set as a VSP ("Is Variable Speed Pump?" set to "True"). As noted in the "Criteria for parallel VSPs" section of this article, VSPs in parallel must all have the same target node and target head.

First, click the Validate button to get a complete list of impacted pumps. Then, check the properties of the pumps identified in the User Notifications and ensure that any VSPs in parallel refer to the same "target node", that they have the same "Target Head Type", and that either the Target Pressure or Target Hydraulic Grade are set exactly the same. In case the issue is with display precision, try re-typing the values or click the field and press CTRL+V to paste in the same value to all parallel VSPs.

Next, open the Pump FlexTable, add the necessary fields and ensure that there are no other pumps elsewhere in the model referring to the same control.

Next, try compacting the database via File > Database Utilities > Compact Database.

If this does not work are you using version 10.03.05.05 or earlier, you may have encountered a known issue related to the use of the Target Pressure Target Head Type. When parallel VSPs are set to use target pressure instead of target hydraulic grade, Validation may be incorrectly checking the target hydraulic grade field that is no longer exposed. If you had entered a target head value and then changed the type to target pressure, this can cause the issue in question. Try changing all parallel VSPs back to using "Hydraulic Grade" as the "Target Head Type", set all the target hydraulic grade values to zero, then switch the type back to Pressure. This known issue will be fixed in a future version - reference # 501653

See Also

Modeling variable speed pumps (VSP’s) in parallel

"Cannot solve network hydraulic equations" or other failure when using parallel variable speed pumps or VSPB

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