COLUMN ENGINEER'S NOTEBOOK Condenser Evaporator develop the same chilled water pipe FIGURE 4 Alternative recommended central plant makeup water system solution. air entrainment issues. The long-term solution selected by the owner for implementation was to provide a separate dedicated industrial makeup water line for the cooling towers, so extreme cooling tower makeup water demands will not influence the makeup water pressure on the campus CHW line. Figure CT Makeup ICW PRV Water Solenoid 3 (page 47) shows a sketch of this CHW Makeup ET Water Solenoid or ICW PRV arrangement. This solution has the Control Valve Pressure Center P Campus advantage of robust, immediate CHWS system refill response to losses of Campus CHWR water volume in the system, but Alternative Recommended Central Plant Makeup Water System 3 also comes with the potential issue of " feeding the flood " if there is a significant leak in the system. An alternative solution the author recommends automate leak detection, as described in a previous designers consider is to use a pressure sensor to expansion tank column by Steve Taylor.1 This design approach enables automated fault detection of system leaks through the pressure sensor. To build on the expansion tank piping scheme presented by Taylor,1 the ASHRAE eLearning The Complete HVAC&R Learning Experience author recommends designers consider adding a solenoid or full-port control valve in series with the pressure No Travel Required * Learn When Convenient reducing valve to automate system refill response, while Access When Needed * Track Performance maintaining the ability to limit the rate of system refill to avoid " feeding the flood " when a significant leak event CORPORATE PROGRAMS AVAILABLE occurs (Figure 4). Condenser Evaporator Condenser Evaporator Conclusion This case study illustrates that properly setting and maintaining a campus' chilled water system pressure is essential to keep critical campus operations functioning. Reliable operating pressure, in turn, depends on having independent piping connections that are not vulnerable to extraordinary demands from other interconnected sources. The author recommends that campus central plant designers consider decoupling makeup water lines for cooling tower condenser makeup water from the chilled water system makeup lines to achieve more reliable operation. For the complete course catalog visit ashrae.org/elearning or contact elearning@ashrae.org 48 ASHRAE JOURNAL ashrae.org MARCH 2021 References 1. Taylor, S. 2016. " The fundamentals of expansion tanks. " ASHRAE Journal 58(11). https://bit.ly/3o6Pw0R Rate this Columnhttp://www.ashrae.org/elearning https://www.bit.ly/3o6Pw0R http://ashrae.org