Page 207 - WaterSense at Work

October 2012
Optimizing Chiller Efficiency
To optimize chiller efficiency, consider the following:
Use controls to monitor the capacity of the chiller and turn chillers on or off as
necessary, depending upon the cooling demand of equipment connected to
each chiller.
The smaller the temperature difference between the chilled water and condenser
water loop, the higher the chiller efficiency. Therefore, raising the chilled water
temperature and lowering the condenser water temperature will improve ef-
ficiency. Such temperature adjustments can only be made within the constraints
of outside conditions. The chilled water temperature will be constrained by the
cooling load. A condenser water return temperature 5° to 7°F above the ambient
wet bulb temperature is optimal.
Apply variable speed control to circulation pump motors.
Inspect chillers regularly to remove any scale buildup, which can decrease the
heat-transfer efficiency of the chiller.
Reducing Demand on ChilledWater System
WaterSense at Work
includes a number of best management practices for technolo-
gies that might be connected to the chilled water loop. Optimizing these products or
systems can reduce the load on the chilled water system, which will, in turn, reduce
the load on the cooling tower.
Optimize Cooling Tower Efficiency
To optimize cooling tower efficiency, consider the following:
Refer to
Section 6.3: Cooling Towers
to ensure that the cooling tower is operating
most efficiently in order to deliver cooled condenser water to the chilled water
If the facility has multiple cooling towers that are plumbed in parallel, run con-
denser water over as many cooling towers as possible at the lowest possible fan
Retrofit Options
With proper preventative maintenance, chilled water systems have a typical life-
time of 20 years or longer. Therefore, it is often practical to retrofit individual system
components, rather than the whole system. However, the functioning of the overall
system should still be considered. The effect of an individual component retrofit on
Pacific Gas and Electric Company. January 2006.
High Performance Data Centers: A Design Guidelines Sourcebook
University of Massachusetts Amherst, CEERE, IAC,
op. cit
op. cit
Chilled Water Systems