Issue overview

The attached file uses a DesignSpecification:ZoneHVAC:Sizing to size the airflow of window air conditioners using a heating/cooling fraction of autosized heating/cooling supply air flow rate of 0.5.

The EIO shows that the maximum air flow rate for the window AC is 50% of the fan's:

 Component Sizing Information, Fan:OnOff, WINDOWACFAN_1, Design Size Maximum Flow Rate [m3/s], 0.67551
 Component Sizing Information, ZoneHVAC:WindowAirConditioner, WINDOWAC, User-Specified (scaled by fractional multiplier) Maximum Supply Air Flow Rate [m3/s], 0.33776

Simulation output shows that when the fan is running at the expected flow rate (0.33776 m3/s), the fan runtime fraction is 0.5 which seems to imply that actually for that reported timestep the flow is 0.33776 / 0.5 = 0.67551 m3/s. I don't think that this is the case (I switch to a Fan:ConstantVolume and saw the same airflow reported) and the 0.5 probably comes from the fact that the fan maximum flow rate is greater than the maximum flow rate from the window AC. If that the case, shouldn't the reported fan runtime fraction be 1?

Details

Some additional details for this issue (if relevant):

• Platform: Windows
• Version of EnergyPlus: Latest develop (24.2)

Checklist

Add to this list or remove from it as applicable. This is a simple templated set of guidelines.

• Defect file added: 4_WindowAC_Two_2.zip
• Ticket added to Energy
  Plus Defect Complexity (Github Project)
• Pull request created (the pull request will have additional tasks related to reviewing changes that fix this defect)