Cooling Tower Relief is an optimization strategy for chiller plants that compliments the optimization strategy Condenser Water Temperature Reset. Before evaluating this strategy one should first understand CW Reset (short of Condenser Water Temperature Reset).
The Chiller Plant Optimizer(TM) implements this strategy independently from CW Reset except that CW temperature is not allowed to exceed chiller design temperature as long as the cooling tower has the required capacity.
On the other hand Cooling Tower Relief is not implemented unless CW Reset has been implemented.
With CW Reset there is the potential for operation of the chiller at part load with a high outside wet bulb temperature which can result with the cooling tower operating at maximum output without being able to lower the condenser water temperature. With many plant configurations this point of operation can cause the cooling tower to expend more energy than the chiller energy savings. Cooling Tower Relief prevents and eliminates this condition. Therefore the overall energy savings is balanced for optimum efficiency.