The key thing with the T500 is to discard the first 50ml of distillate as this contains your unwanted chemical or congeners.
Ideal cooling water outlet temperature should be between 55-65°C (131-149°F) to give you the best possible quality of alcohol. If you stick to the lower end of the range, alcohol output will slow down but will be as pure as is possible with the T500. If you move to the higher end of the range, alcohol output will increase at a lower quality.