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FanSystemModel preventing Air Loops Detail in openstudio_results from running

asked 2025-10-29 16:55:36 -0600

jdlouhy's avatar

updated 2025-10-30 09:16:08 -0600

Hey all,

I replaced my Fan Constant Volume and Fan Variable Volume air loop fans with the Fan System Model fans from the OpenStudio library. When doing so the Air Loops Detail section portion of the OpenStudio Results will no longer run. The error that is output is:

Air Loops Detail section failed and was skipped because: undefined local variable or method `designMaximumFlowRate' for #. Detail on error is in Measure Warnings section, if enabled at the bottom of this report.

Later in the report it elaborates,

Air Loops Detail section failed and was skipped because: undefined local variable or method `designMaximumFlowRate' for #. Detail on error follows:
  C:/Users/[omitted]/AppData/Local/Temp/osmodel-948a-f4c2-5dbf-66c7-1761772272-0/resources/measures/openstudio_results/resources/Siz.FanSystemModel.rb:8:in `maxAirFlowRate'
  C:/Users/[omitted]/AppData/Local/Temp/osmodel-948a-f4c2-5dbf-66c7-1761772272-0/resources/measures/openstudio_results/resources/Siz.HVACComponent.rb:33:in `maxAirFlowRate'

I trouble shot a handful of potential issues but in the end if I had this component in the model the Air Loops Detail section would not run and if I had my original fan models (the Fan Constant/Variable Volume) it would run. I'm thinking this is an issue with the Siz.HVACComponent.rb file that won't recognize the FanSystemModel fan.

Does anyone know a workaround for this? I'd like to use the FanSystemModel so I can hardset the Design Electric Power Consumption values to match my calculations from 90.1 Appendix G.

Thanks for your help

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answered 2025-11-03 10:38:36 -0600

This is a bug in the reporting measure. In the /resources/Siz.FanSystemModel.rb file, all instances of designMaximumFlowRate should be replaced with designMaximumAirFlowRate (and similarly, autosizedDesignMaximumFlowRate replaced with autosizedDesignMaximumAirFlowRate).

You can make the changes in your local measure instance and the report should run. I'll try to get a PR to the measure gem source this week.

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Asked: 2025-10-29 16:55:36 -0600

Seen: 114 times

Last updated: Nov 03