ZoneHVAC:IdealLoadsAirSystem dehumification control type HUMIDISTAT

Issue overview

While preparing some examples to students and analyzing the results.
ZoneHVAC:IdealLoadsAirSystem
When Dehumidification control type is HUMIDISTAT, during cooling it seems that it is using the Minimum Cooling Supply Air HUmidity Ratio and keeps its value constant as if the option selected was ConstantSupplyHumidityRatio.

Enclosed find the example file.
Minimum Cooling Supply Air HUmidity Ratio is now at 0.01 since it keep the relative humidity around 50% which was the setpoint.
If 0.002 is tried then the relative humidity of the zones go down.
Best regards

p.s. I apologize beforehand if I am misunderstanding something.
I have reviewed the Engineering Reference ...without a clear response.

Details

• Windows 10
• EnergyPlus v8.9

Checklist

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

• Defect file added (list location of defect file here)
• Ticket added to Pivotal for defect (development team task)
• Pull request created (the pull request will have additional tasks related to reviewing changes that fix this defect)

ON_OFF_Hrel.zip

Start by reproducing the reported behavior with the attached ON_OFF_Hrel.zip example in EnergyPlus v8.9, focusing on ZoneHVAC:IdealLoadsAirSystem with HUMIDISTAT and the Minimum Cooling Supply Air Humidity Ratio. Compare the results with ConstantSupplyHumidityRatio and consult the Engineering Reference; done means HUMIDISTAT follows its documented control behavior.