Applies To Product(s): Bentley WaterGEMS, Bentley HAMMER, Bentley WaterCAD Version(s): 08.11.XX.XX Original Author: Mark Pachlhofer, Bentley Technical Support Group Problem How do I model parallel fixed head (target head) variable speed pumps that are controlled by flow in a downstream pipe? OR How do I resolve the user notification, "Variable speed pumps not in parallel cannot be controlled by the same control node"? Background Parallel variable speed pumps have special rules that apply and unless you make some specific changes to your model to workaround these rules your pumps will not work as you'd like them to. In the screen shot below the following model was originally set up where all the pumps had a single downstream junction, the black one immediately downstream of the colored junctions, which functioned as the single node the VSPs were controlled based on. The controls used for the model below are as follows: IF P-131 Flow = 25.000 L/s And P-131 Flow 50.000 L/s THEN P102C Pump Status = On Solution 1) Add 5 junctions between your pumps and the downstream control node. The software then interprets each of these VSPs separately, which is why we have step two. If we didn't have step two then the software would generate a red user notification that would prevent you from running the model. The user notification reads, "Not parallel variable speed pumps cannot be controlled by the same control node". 2) The fifth junction (green, blue, and pink all each line) that you place will be the new control node for the upstream pump, so make sure to set it appropriately in the pump properties for the control node.
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