Question-and-Answer Resource for the Building Energy Modeling Community
Get started with the Help page
Ask Your Question

Is there a way to simulate AC on dry mode?

asked 2024-03-04 01:39:08 -0500

syauqi's avatar

updated 2024-03-06 09:17:01 -0500

I want to simulate AC running on dry mode in openstudio or energyplus, and make it controlled by humidistat. But whenever I remove thermostat, the simulation always resulting in severe error.

This is quite a common issue in hotel project in area where humidity is high, so they need to control it by running the AC to prevent furniture damage by molds. So some management make it running all the time whenever the room is unoccupied, but since standard indoor AC doesn't have humidistat, they can't control it more efficiently. Its just an open loop control. Many room management system specialist propose additional humidistat for the AC, so the AC only run whenever humidity is above 70%.

I want to simulate this conditions, to predict how efficient this operation is.

Please help, thank you!

edit retag flag offensive close merge delete


@syauqi what simulation tool are you using? Please mention it in the title or body of your post, as well as add a tag so that others can provide better help.

Also, can you upload your model to Google Drive, Dropbox, etc. and then share a URL for others to download? That would help others provide better solutions.

Aaron Boranian's avatar Aaron Boranian  ( 2024-03-05 08:01:22 -0500 )edit

1 Answer

Sort by ยป oldest newest most voted

answered 2024-03-05 23:35:37 -0500

bentan's avatar

updated 2024-03-05 23:41:13 -0500

You will need minimum one thermostat object, for the hvac simulation to run. What HVAC system did you used for the simulation?

Keep in mind that a humidistat object only set up a humidity control point for the zone, some DX cooling-only system dont take care of the moisture properly; depends on your model, you will need a proper system for that. eg : you can add some object like ZoneHVAC:Dehumidifier:DX with reheat coil to take care of the excess moisture.

edit flag offensive delete link more


I tried using VRF system, but its just crashing. I don't want to use thermostat object, since in actual operation, it won't use thermostat to control the AC, but its a room controller with humidistat reading that will turn off the AC when RH value achieved.

So then i try to made air loop with DX cooling single stage in openstudio, it doesn't show severe errors but the result, the unit just not running at all throughout the year.

I don't intent to add dehumidifier in the model, since the actual that occurs in the field also doesn't use additional dehumidifier.

syauqi's avatar syauqi  ( 2024-03-06 02:43:27 -0500 )edit

@syauqi if you don't want temperature control, then apply very high cooling thermostat temperatures (say, 100C) and very low heating thermostat temperatures (say, -100C). If your humidistat controls are defined correctly, and your HVAC system has dehumidification potential (dehumidifier, DX coil with overcool-reheat, etc.), the HVAC should then only turn on when humidity control is needed. The single speed DX coil you're using doesn't have dehumidification.

Aaron Boranian's avatar Aaron Boranian  ( 2024-03-06 09:21:41 -0500 )edit


so my understanding is that you are trying to control the AC operation, when to turn the AC on or off with humidistat?

this is just pure guess but maybe you can try using EMS object. the sensors can be room humidity level (eg var Zone Air Relative Humidity) which then will actuate the thermostat setpoint value to turn the AC on/off based on the detected humidity level in the room.

bentan's avatar bentan  ( 2024-03-07 22:29:26 -0500 )edit


Yes indeed. Haven't try EMS feature in Energy Plus Yet. I'll try it. Thank you for your suggestion!!

I'll post an update if its successful.

syauqi's avatar syauqi  ( 2024-03-08 00:58:32 -0500 )edit

Your Answer

Please start posting anonymously - your entry will be published after you log in or create a new account.

Add Answer

Training Workshops


Question Tools

1 follower


Asked: 2024-03-04 01:39:08 -0500

Seen: 50 times

Last updated: Mar 05