Hard size the flow rate in the pump or set maximum flow limit to the condenserloop
a good rule of thumb in 3 gpm condenser flow per ton of cooling provided
I have found that the condenser loop sizes too large such that the cooling tower fan rarely turns on and the condenser loop meets the load through the free convection portion of the tower. Also size the tower so that the free convection capacity is appropriate. I would suggest using a setpoint manager of the type FollowOutdoorAirTemperature