vfd speed controlled by a thermistor

Does the drive have PID capability?

For a cooling tower application, shouldn't you be using the water temperature as the feedback? You would also like to monitor/calculate the outdoor air wetbulb temperature to bound your setpoint.

A cooling tower can be used to cool the water to perhaps 5-7degrees higher than ambient wetbulb temperature, but not lower. SO if the ambient wetbulb is 78F, you should be able to cool the water to ~83F. If the wetbulb is 85F, you will not be able to cool the water to 85F no matter how hard the fans run.

The vfd does have PID capability.

I am not the engineer on this job and I am not familiar with all the details on cooling towers. I am basically making sure they have the hardware to do what they want to do.

But thanks for your suggestions. I may be able to suggest improvements to them along the way.

Also. This motor is only a 3hp so I believe it is some auxiliary motor and not used for the main cooling action