You are currently reviewing an older revision of this page.
What is the difference between the "Is variable speed drive?" check box in the "motor" tab of a pump definition, and the "Is variable speed pump?" property of a pump node element?Problem ID#: 44136
The "variable speed drive" check box in the pump properties is used to for energy cost analysis only. With a constant speed pump (Non-VSP) the motor speed, and thus the motor efficiency, is constant. However with a VSP, the motor speed changes, so the user must account for the different motor efficiency for various motor speeds. So, this check box allows you to enter a table of speed (relative speed factor) and motor efficiency. For a pump that is a VSP, that check box should be checked, since the speed (relative speed factor) will very likely not be constant (1.00).The "is variable speed pump" option in the pump properties allows you to choose if the pump can actually operate as a variable speed pump, where the motor speed can change over the course of the simulation.
http://communities.bentley.com/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/20094.modeling-variable-speed-pumps-in-parallel-with-different-pump-curves-solution-500000100851
http://communities.bentley.com/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/27039.benefits-of-using-variable-speed-pump-batteries-vspb-element-and-how-it-works