UnitarySystem No Load Supply Air Flow Rate

[grahamjlinn]

Hi IronBug folks, I think I’ve found an issue. I’m trying to set up a DOAS AirLoop using a UnitarySystem so I can have integrated geo source heat pump coils.

I’ve stumbled on a configuration thing - it seems in order to use SetPoint control type for a UnitarySystem (rather than set a control zone which doesn’t make sense for DOAS) you have to then also specify the fields related to No Load Supply Air Flow Rate. (I confimed this separately debugging with OpenStudio) However I am seeing errors trying to force these settings in IronBug

When I try to set the “method” for No Load Supply Air Flow rate I get error at Air Loop level:

When I instead try to Autosize the flow rate I get error at ObjParam level:

It only works when I hard set the flow rate to a number:

Also attached .gh and model input hbjson

MS_DD_02.hbjson (422.7 KB)

MS_hvac_01.gh (257.4 KB)

Thanks!

[MingboPeng]

Hi @grahamjlinn

Thanks for documenting this. Acturally, this is by design in OpenStudioSDK, you don’t need to set the “method” specifically. Just go set the “SupplyAirFlowRateWhenNoCoolingorHeating” directly for the “SupplyAirFlowRate” option, the method will be adjusted based on what value you used.

If a parameter is “autosize-able”, you can see this in its description: use -9999 for autosize.

In your screenshot, you are picking the wrong parameter to set the “SupplyAirFlowRate”, see my screenshot below: