CBECC-Com 2019 v1.2 Sizing

I saw this option of sizing the HVAC system capacities using energy plus in CBECC-Com 2019 v1.2. However, when i tried using the same and compared the sizing between what CBECC-Com does vs E+, i find not difference in the equipment sizes? Why is that so? I checked the following excel file - ap - HVACSecondary for each of the runs and the capacities are exactly the same. What does that option do- Auto size proposed HVAC capacities using Energy plus ? Can this be used to size the system for T24 compliance?

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Thanks

@Ranjani, this option, if checked, does not result in a valid compliance run.

It is available for research/early phase analysis, and it results in the E+ model capacity fields be specified as 'Autosize' instead of using the values that are defined in the CBECC-Com UI. Using a text diff tool and comparing idfs both w/ and w/o this option checked should show you the impact of this option clearly.

Checking this option does not result in the HVAC capacities of the model changed to match the autosized E+ capacities, it only impacts the E+ simulations. This is why the - ap - HVACSecondary.csv files are the same. Equipment efficiencies are preserved in the simulation when you select this option, so you should see in the idf that they are not changed.

The utility of this option is pretty limited to research purposes. If you are struggling with sizing, you can enable this option to see what E+ sizes systems, and use that to inform your design. However, there are many nuances to E+ sizing, and some shortcomings in what this option offers, so you may need to edit the idf file further to make it useful for your situation.