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# severe error about illegal value for convection coefficients on partition holes, when using calculated natural ventilation

I am modelling a building with natural ventilation, where the window openings for one of the floors are controlled by an EMS script depending on CO2 and temperature. In order to apply the script, I need to have calculated natural ventilation.

I am able to get reasonable results and no errors when running the simulation on Design Builder. However, after exporting it to an IDF file to run the simulation directly on Energy Plus (I need to do that to see the resulting CO2 concentration output), I get severe errors on the convection coefficients for the partition holes in the floor where I am applying the script:

** Severe  ** GetUserConvectionCoefficients: SurfaceProperty:ConvectionCoefficients, illegal value for Surface Name=2ND:T10_PARTITION_8_0_0_0_0_0_HOLE


Here is the extract from the IDF file, where it is specified the convection coefficient for that hole. I have not written it manually, so it has the fields and values given by Design Builder:

  SurfaceProperty:ConvectionCoefficients,
2nd:T10_Partition_8_0_0_0_0_0_Hole,  !- Surface Name
Outside,                 !- Convection Coefficient 1 Location
Value,                   !- Convection Coefficient 1 Type
.1,                      !- Convection Coefficient 1 {W/m2-K}
,                        !- Convection Coefficient 1 Schedule Name
,                        !- Convection Coefficient 1 User Curve Name
Inside,                  !- Convection Coefficient 2 Location
Value,                   !- Convection Coefficient 2 Type
.1,                      !- Convection Coefficient 2 {W/m2-K}
,                        !- Convection Coefficient 2 Schedule Name
;                        !- Convection Coefficient 2 User Curve Name

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We've done a quick test exporting the IDF to run in the same EnergyPlus version used by DesignBuilder and weren't able to reproduce the problem. We did, however, get the same problem when trying to use the converted IDF in E+ v9.1 (not yet supported by DesignBuilder). I would suggest that you import the IDF into the same version of EnergyPlus as you have in the version of DesignBuilder that you're using. If that doesn't fix the problem you should ask DesignBuilder's support team to review your model, assuming you have a licence.

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I did not manage to open the IDF file produced by DesignBuilder v5 for EnergyPlus v8.6 since this version of E+ has been purged from the web due to some vulnerability issues.

This meant that I had to update DesignBuilder to v6, which uses EnergyPlus v8.9.

Thankfully, my model worked both on the new DesignBuilder and on EnergyPlus v8.9 and v9.1 without further changes.

( 2019-09-12 07:08:19 -0500 )edit