VSP Controlled by Suction Side Tank

Similar to the function of a VSP controlled by a discharge side tank, a vsp can also be controlled by a tank at the upstream of pump, that is the suction side of a pump. This is the typical use case for a sewer forcemain sub-system, where a wet well (essentially a tank) is usually located at the suction side of a pump. In this case, the control target is to maintain a fixed water level at the wet well. When a VSP is installed at the downstream side of a wet well to pump the flow out of the well and also to maintain a fixed wet well water level, WaterGEMS CONNECT can be used to model the control scenario.

Unlike the vsp controlled by discharge side tank, when the wet well level is below the target level, suction side controlled vsp will slow down in speed to allow the water level to increase to the target level. When the wet well water level is above the target level, a vsp will speed up to move the flow out of well in order to reduce the water level at the wet well.

The workflow is the same as the VSP controlled by a discharge side tank, except that the user needs to set the attribute of Is Suction Side Variable Speed Pump to True in the property grid.

Note: When the target level is missed due to either too high demand or too much inflow into the wet well, the VSP will be operating at the fixed speed until the target level can be reestablished, however, the reestablished target level may not be exactly the same as the initial target head. This is because the VSP is forced back by using the given time step, the pump is operated as a fixed speed pump to move the amount of water within one time step, so that the level cannot be exact unless the time step is small enough to ensure the exact amount of water is moved out the tank to maintain the exact target. The smaller the time step, the closer it will be to returning to the target.