Multi Pump Cascade Pump Control – Single VFD running multiple pumps
Problem: Secondary pump was started manually to provide make up water in filling application. Occasionally operator forgot to turn off pump when completed as this involved re-entering pump house building to switch off. Secondary pump was “dead heading” and wasting energy.
Solution: Installation of the OptiDrive Eco Series VFD, contactor and Dwyer pressure transmitter to detect pressure drop when external water value is opened.
Basic application overview using a OptiDrive ECO Series VFD by Invertek.
A single Variable Frequency Drive (VFD) has the ability to run multiple pumps in a closed loop system. This describes the use of a relay to control multiple pumps. We will cover multiple VFD’s in another post. The configured VFD controls the Master pump with a feedback sensor signal and runs a separate fixed speed pump. This set-up requires a contactor and an analog or digital signal such as flow, pressure or temperature from a transducer.
Feedback is signaled to the VFD via a transducer (flow, pressure, temperature) to maintain a setpoint. If the setpoint cannot be met by the primary pump, the VFD signals to a relay and starts the secondary pump. The secondary pump can be DOL, Stat/Delta or on a Soft Starter. Once the set point is met, the Primary (Master) pump will vary speed and maintain this set point or until it reaches a stop speed and will shut down the secondary (follower) pump. If there are multiple pumps, the VFD will bring on additional pumps in sequence to assist the Master pump. If selected, the VFD can also turn off the longest running pump and switch to the shortest running pump.
A North Fringe employee would we pleased to discuss with you simple and effective solutions to pump automation.
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