Column The performance gap Results So what does all this mean and how could it impact the project? To summarize, the default eQUEST partload performance curve significantly underpredicts the energy performance of even a minimally compliant chiller according to ASHRAE Standard 90.1-2010. This gap gets worse when higher performing chillers are selected. The error created by using a generic curve can be inadvertently masked or amplified by seemingly innocuous adjustments to the chillers' simulated minimum operating threshold. www.info.hotims.com/44639-10 62 ASHRAE JouRnAl ashrae.org D ecem ber 2013 Figure 3 Lead chiller bin data. 1,200 1,000 800 run hours realistic minimum part-load operating threshold. The default eQUEST input for this variable is 10%, significantly below the intended range specified by this particular manufacturer and well into the arena of poor performance. Table 2 provides another comparative snapshot indicating that the actual installed chiller is 54% more efficient than the default curve would indicate. 600 400 200 0 10 20 30 40 50 60 70 80 90 100 Part-Load range (%) The simulation exercise for this project limited the minimum operating threshold to 20%. At a 20% partload limit, the actually selected chillers outperformed a fictitious chiller baseline (eQUEST) by more than $41,000 www.info.hotims.com/44639-4