Abstract: A precooling system for an evaporative cooler for a closed loop cooling fluid system includes a supplemental heat exchanging coil connected in the cooling fluid loop upstream of the main evaporative cooler coils and positioned in the outlet air flow through the evaporative cooler, but above or outside the path of the spray water. The supplemental heat exchanging coil provides enough additional cooling capacity to allow the spray water system to be completely shut off and the spray water sump drained during low outside ambient temperature operation. Freeze up of the sump and other parts of the spray water system are completely eliminated and a substantial saving in spray water consumption and energy for freeze prevention systems is realized.