Question-and-Answer Resource for the Building Energy Modeling Community
Get started with the Help page
Ask Your Question
1

Supplemental Heating Coil Not Responding to Load Request

asked 2026-01-25 21:46:20 -0600

Abir Ahsan's avatar

updated 2026-01-26 09:10:09 -0600

Hello,

I am using a Coil:Heating:DX:SingleSpeed to simulate a heat pump conditioned building. The building is a IECC 2006 prototype building model. The building model has been modified to remove all domestic hot water distribution loop. Special modification is done on the Supplemental Heating Coil to make it a hot water based one using the Coil:Heating:Water object. A plant loop has been created to supply hot water to the supplemental coil to respond to any supplemental heating demand request. However, when I run the simulation, the supplemental coil is not responding. Zone temperature (LIVING_UNIT1) is falling abruptly when heat pump is unable to satisfy load. I am uploading the .idf file here. I will appreciate any expert opinion on this. Thanks.

-Abir Ahsan

edit retag flag offensive close merge delete

Comments

@Abir Ahsan have you tried an alternative where the supplemental heating is electric or combustion? This would isolate the supplemental heating coil and/or unitary system inputs to troubleshoot rather than the hot water plant.

Aaron Boranian's avatar Aaron Boranian  ( 2026-01-26 09:11:43 -0600 )edit

@Aaron Boranian Thanks for your comments. Already checked that, the system is able to work when the supplemental heating coil is modeled using the Coil:Heating:Fuel object.

Abir Ahsan's avatar Abir Ahsan  ( 2026-01-26 09:52:50 -0600 )edit

1 Answer

Sort by ยป oldest newest most voted
1

answered 2026-01-26 11:51:02 -0600

I was able to get the supplemental water coil to turn on but only by changing the software. I am not sure what is happening here. The fact that there is only 1 HW coil on the demand side of the loop should not be an issue. The plant is simply setting the water flow rate to the coil to 0 so the coil does not turn on. If I trick the software the coil does turn on. So this will take more investigation to figure out what is wrong. i.e., something in the input file (I don't see anything) or something in the software. I see that there was a fix for supplemental water coils used in AirLoopHVAC:UnitarySystem for 24.1 here so maybe you could try using that parent object?

image description

edit flag offensive delete link more

Comments

@rraustad I replaced the current object with the parent object AirLoopHVAC:UnitarySystem. Still supplemental water coil is not turning on. Could you tell me the work around that you followed?

Abir Ahsan's avatar Abir Ahsan  ( 2026-01-26 12:29:43 -0600 )edit

@Abir Ahsan that makes me think the issue has something to do with the plant setup. I just don't see what that might be. It could also be a fundamental issue with a plant with only 1 component but I can't find that either. My work around was a code change so it will not help you. Thanks for testing the UnitarySystem, that's another clue to what's happening here.

rraustad's avatar rraustad  ( 2026-01-26 12:54:36 -0600 )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

2 followers

Stats

Asked: 2026-01-25 21:46:20 -0600

Seen: 58 times

Last updated: 2 days ago