No, the recirculating pumps supplied on EVAPCO closed circuit coolers are ON/OFF and require full flow to maintain system efficiency and prevent premature scaling of the coil. They are not designed to operate on a variable frequency drive (VFD).
Every fluid cooler pump is sized for a set flow rate to adequately wet the coil and provide 100% heat transfer via evaporation from the coil. If a recirculating pump is operated on a VFD at a lower speed and flow rate than required at 100%, not only will the system efficiency decrease, but premature scaling of the coil could occur from continuous wetting and drying of certain areas of the coil.
Please note that pump starters are not supplied by EVAPCO and must be provided by other manufacturers.