best way to evaluate plant sizing results in optimization process

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I want to optimize chilled water loop sizing and configuration to meet the cooling load of a building. I have a detailed model that includes thermal zones and AHUs but I don't want to change them during the optimization process.

My concern is choosing a variable as the constraint for thermal comfort. I need this to evaluated whether my plant loop can meet the demand or not. I tried Unmet hours but I got weird results and I cannot work with that.

Is there any variable in energyplus that I can ensure it can evaluate my plant sizing results?

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Update: I'm using "Time Setpoint Not Met During Occupied Cooling" with 1 C tolerance. I get about 52 hours of unmet cooling hours. I don't the standard value but it seems a lot to me:

By the way in this case I'm using two chillers with a sizing factor of 0.55 for each one.