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It looks like this is just a matter of how -by default- OpenStudio translates the CoilSystem:Cooling:DX object to IDF. By default, the exported object doesn’t include the Dehumidification Control Type (and related fields).

What OpenStudio exports:

CoilSystem:Cooling:DX,
  Two Stage DX Coil With Humidity Control CoilSystem, !- Name
  Always On,                                          !- Availability Schedule Name
  Node 6,                                             !- DX Cooling Coil System Inlet Node Name
  Node 10,                                            !- DX Cooling Coil System Outlet Node Name
  Node 10,                                            !- DX Cooling Coil System Sensor Node Name
  Coil:Cooling:DX:TwoStageWithHumidityControlMode,    !- Cooling Coil Object Type
  Two Stage DX Coil With Humidity Control;            !- Cooling Coil Name

What it needs to be in IDF to enable dehumidification control:

CoilSystem:Cooling:DX,
  Two Stage DX Coil With Humidity Control CoilSystem, !- Name
  Always On,                                          !- Availability Schedule Name
  Node 6,                                             !- DX Cooling Coil System Inlet Node Name
  Node 10,                                            !- DX Cooling Coil System Outlet Node Name
  Node 10,                                            !- DX Cooling Coil System Sensor Node Name
  Coil:Cooling:DX:TwoStageWithHumidityControlMode,    !- Cooling Coil Object Type
  Two Stage DX Coil With Humidity Control,            !- Cooling Coil Name
  CoolReheat,                                         !- Dehumidification Control Type
  Yes,                                                !- Run on Sensible Load
  Yes,                                                !- Run on Latent Load
  No,                                                 !- Use DOAS DX Cooling Coil
  2.0;                                                !- DOAS DX Cooling Coil Leaving Minimum Air Temperature

After adding these fields, it’s “just” a matter of right-sizing capacities, configuring the outdoor air economizer, and setting supply/return airflows. With those tweaks, I’m getting good results using the Barcelona EPW (TMY) file.

It looks like this is just a matter of how -by default- OpenStudio translates the CoilSystem:Cooling:DX object to IDF. By default, the exported object doesn’t include the Dehumidification Control Type (and related fields).

What OpenStudio exports:

CoilSystem:Cooling:DX,
  Two Stage DX Coil With Humidity Control CoilSystem, !- Name
  Always On,                                          !- Availability Schedule Name
  Node 6,                                             !- DX Cooling Coil System Inlet Node Name
  Node 10,                                            !- DX Cooling Coil System Outlet Node Name
  Node 10,                                            !- DX Cooling Coil System Sensor Node Name
  Coil:Cooling:DX:TwoStageWithHumidityControlMode,    !- Cooling Coil Object Type
  Two Stage DX Coil With Humidity Control;            !- Cooling Coil Name

What it needs to be in IDF to enable dehumidification control:

CoilSystem:Cooling:DX,
  Two Stage DX Coil With Humidity Control CoilSystem, !- Name
  Always On,                                          !- Availability Schedule Name
  Node 6,                                             !- DX Cooling Coil System Inlet Node Name
  Node 10,                                            !- DX Cooling Coil System Outlet Node Name
  Node 10,                                            !- DX Cooling Coil System Sensor Node Name
  Coil:Cooling:DX:TwoStageWithHumidityControlMode,    !- Cooling Coil Object Type
  Two Stage DX Coil With Humidity Control,            !- Cooling Coil Name
  CoolReheat,                                         !- Dehumidification Control Type
  Yes,                                                !- Run on Sensible Load
  Yes,                                                !- Run on Latent Load
  No,                                                 !- Use DOAS DX Cooling Coil
  2.0;                                                !- DOAS DX Cooling Coil Leaving Minimum Air Temperature

After adding these fields, it’s “just” a matter of right-sizing capacities, configuring the outdoor air economizer, and setting supply/return airflows. With those tweaks, I’m getting good results (constant 45% RH) using the Barcelona EPW (TMY) file.