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OpenStudio Design Day Conditions

asked 2021-04-07 18:16:31 -0500

Draza gravatar image

updated 2021-04-13 19:31:02 -0500

Can I change the design day to 1% annual cumulative frequency dry-bulb and wet-bulb temperatures for cooling conditions? When I import a .ddy file the default cooling design day conditions are set to .4%. Is there a way to change this? or does the temperature, humidity, wind solar, etc. data for the 1% design condition have to be entered manually in a custom design day?

My workaround was to just make a custom design day based on the weather file, however there was some confusion on what to enter for the "Humidity Indicating Conditions At Maximum Dry Bulb" for the Enthalpy "Humidity Indicating Type" design day. The weather file has the value in J/kg. When I looked up the conversion for IP units it says that it should be in BTU/lb (as expected), but the autocalculated values in this field are not calculated using the J/kg to BTU/lb conversion factor found in the Eplus documentation

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answered 2021-04-13 18:29:07 -0500

OpenStudio automatically selects the most stringent available design days in the DDY. There is an existing feature request to allow selecting which design days are available.

In the meantime, one option is to create a copy of the DDY file, open it up in a text editor, and delete all the .4% (and 99.6%) EnergyPlus objects. Then OpenStudio will choose the next most stringent objects (e.g., 1% and 99%).

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Thanks for the information! My workaround was to just make a custom design day based on the weather file, however there was some confusion on what to enter for the "Humidity Indicating Conditions At Maximum Dry Bulb" for the Enthalpy "Humidity Indicating Type" design day. The weather file has the value in J/kg. When I looked up the conversion for IP units it says that it should be in BTU/lb (as expected), but the autocalculated values in this field are not calculated using the J/kg to BTU/lb conversion factor found in the Eplus documentation. I edited the original post to include screenshots

Draza gravatar image Draza  ( 2021-04-13 19:29:51 -0500 )edit

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Asked: 2021-04-07 18:16:31 -0500

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Last updated: Apr 13