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Sizing Design Day when "Sizing:Zone" object is not used

asked 2022-08-08 03:21:32 -0600

updated 2022-08-08 09:30:41 -0600

Hi, I usually run my cooling sizing simulations without the Sizing:Zone object because I assume that EnergyPlus will automatically use the SizingPeriod:DesignDay that I entered, but my colleague argued that I have to create the Sizing:Zone object to properly assign the Design Days to the simulation and results in the correct sizing of the AC System.

My question is, if I do not create the Sizing:Zone object and I do not assign the DesignDay into the Cooling Design Air Flow Method, what day or which Design Day will EnergyPlus use as reference?

Thank you! Best regards, Hanif

IDF File

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answered 2022-08-12 15:28:47 -0600

updated 2022-08-12 15:29:26 -0600

You used the unitary system template (HVACTemplate:Zone:Unitary) which, when expanded (see the *.expidf), creates a Sizing:Zone object for zone name listed (first field of the template). The Sizing:Zone has DesignDay as the Cooling Design Air Flow Method, but you could select other inputs for this field.

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Hi Eric, thank you so much for the really helpful answer, my follow up question is, how does the object decide which DesignDay is used to calculate out of all the many DesignDay objects I have in the idf?

kirakatsui's avatar kirakatsui  ( 2022-08-14 23:06:40 -0600 )edit

You only need to specify one heating design day and one cooling design day, but if you specify more than one, loads are calculated for each of the SizingPeriod:DesignDays, and equipment is sized to meet the greatest load.

ericmartinpe's avatar ericmartinpe  ( 2022-08-15 12:56:06 -0600 )edit

Ahh I see, thank you so much for the answers Eric, cheers!

kirakatsui's avatar kirakatsui  ( 2022-09-05 05:39:32 -0600 )edit

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Asked: 2022-08-08 03:21:32 -0600

Seen: 152 times

Last updated: Sep 05 '22