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Zone Multiplier and Airflow Rates

asked 2016-07-22 03:23:37 -0600

updated 2016-07-22 03:29:29 -0600

Similar to this question, I'm adding a number of objects to zones that have a multiplier attached to them. These objects are either Fan:ZoneExhaust and ZoneVentilation:DesignFlowRate as well as ZoneMixing (transfer air).

I basically want to model exhaust of $200 \ CFM$ in a trash room, with make up coming from the adjacent corridor. I have a floor that gets multiplied by two: I added a Zone Multiplier of 2 for all zones on this floor.

Should I enter $200 \ CFM$ or $ 2 \times 200 = 400 \ CFM$ for the aforementioned objects?

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answered 2016-07-22 11:19:36 -0600

updated 2016-07-22 11:35:04 -0600

The 'FanCoil_HybridVent_VentSch.idf' example file is a good one to use to test whether ZoneVentilation:DesignFlowRate and ZoneMixing are affected by zone multipliers, since it is set up with both those objects (and output variables). Let's science this:

Hypothesis: ZoneVentilation:DesignFlowRate and ZoneMixing object inputs are unaffected by zone multipliers.


  • Run unmodified example file
  • Change the multiplier for 'North Zone' in the example file, run modified file.
  • Verify that the zone design loads were affected as expected.
  • Check if the output variables 'NORTH ZONE:Zone Ventilation Standard Density Volume Flow Rate' and 'NORTH ZONE:Zone Mixing Total Heat Gain Energy' remained unchanged.

Conclusion: Hypothesis verified. ZoneVentilation:DesignFlowRate and ZoneMixing object inputs are unaffected by zone multipliers, and should be adjusted accordingly.

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answered 2016-07-22 08:20:52 -0600

For Fan:ZoneExhaust, to get the appropriate electricity consumption at least, you should multiply the airflow rate of a single zone by the multiplier. In the example I gave, that means inputing $400 \ CFM$.

Source: I've tested this by assigning a unique End-Use Subcategory and checking the html versus calculating the fan electricity consumption manually.

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This is obviously still a partial answer!

Julien Marrec gravatar image Julien Marrec  ( 2016-07-22 10:46:28 -0600 )edit

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Asked: 2016-07-22 03:23:37 -0600

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Last updated: Jul 22 '16