What is the best way to stage/control cooling tower fans with vfd's?
Have a project to install vfd's on a cooling tower with 3 fans and a bypass valve. Plan on enabling fans only after bypass valve is 100% over the top of the tower. Then would you stage the fans with a deadband between start/stop of the fans based on water temperature, or speed of the operating fan/fans? Or, would it be best to start all fans and just let them ramp up together? Don't have any sequence of operation to work off of. Currently staging the 3 fans based on increase/decrease in temp.
The fans are gear box driven, so need to find out minimum speed fans can run.
Any thoughts or best practices would be appreciated.