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Error Replacing Electric Heating Coil with Gas Heating Coil

asked 2014-12-17 12:11:36 -0500

DW gravatar image

updated 2015-01-09 12:36:06 -0500

I am using OpenStudio 1.5 and am modeling a VAV system. On my central air loop I have a TwoSpeed DX cooling coil and then a heating coil. The heating coil was initially modeled as electric, and the simulation ran just fine. I am now trying to replace that electric heating coil with a gas heating coil. The simulation always errors out after the sizing period, just after it says initializing simulation.

Is there a sizing object I need to add in OpenStudio? I'm not quite sure what it is that I'm missing. Any advice would be appreciated.

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What is the error message you are getting? My initial suspicion is that when you switched to the gas coil, you didn't give it an operating schedule.

Benjamin gravatar image Benjamin  ( 2014-12-17 13:44:57 -0500 )edit

The gas coil uses the same operation schedule as the electric coil "Always On Discrete"

The last line in the eplus.err file is as follows: * Warning * ManageSizing: For a plant sizing run, there must be at least 1 Sizing:Plant object input. SimulationControl Plant Sizing option ignored.

DW gravatar image DW  ( 2014-12-17 14:11:32 -0500 )edit

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answered 2014-12-17 15:55:40 -0500

updated 2014-12-17 16:16:46 -0500

Maybe you don't have any plants, but inadvertently turned on the plant sizing option shown in the screenshot. Normally OpenStudio leaves this option off in the model, and then turns it on when creating the idf file if there are plants.

image description

https://github.com/NREL/OpenStudio/bl...

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Unfortunately, turning off the plant sizing calculation does not help. In fact, it even crashes my working simulation (the one with the electric heat coil).

DW gravatar image DW  ( 2014-12-19 12:20:24 -0500 )edit

Can you upload your model to a dropbox or similar service and provide me a link? If this is a model that needs to be kept more private, then let me know and we can work something else out.

Kyle Benne gravatar image Kyle Benne  ( 2014-12-19 12:45:58 -0500 )edit

Let me know if this link works for you. Thank you for your responses and your help.

https://www.dropbox.com/sh/0ejva0rnt8...

DW gravatar image DW  ( 2014-12-19 13:07:14 -0500 )edit

I apologize for the delay, but I was able to download and inspect your model. I set the weather file and the simulation completed successfully right away. I did reproduce a warning about SizingPlant required for a plant sizing calculation. But the simulation continued successfully. Then I turned off "Do Plant Sizing Calculation" as suggested in my original response and the warning went away. This was in OpenStudio 1.5.3, but I really don't anticipate any change between 1.5.0 and 1.5.3. Can you provide any more details about your process that might provide some clues?

Kyle Benne gravatar image Kyle Benne  ( 2014-12-29 09:52:53 -0500 )edit

Thank you for looking into this. After further investigation I found two errors - one was that a heating and cooling setpoint were set too close together and this was causing the simulation to err out. The other issue was a rogue piece of equipment in a shaft zone that had no load and shouldn't have been there. Cleaning up those mistakes allowed the simulation to run smoothly.

DW gravatar image DW  ( 2015-02-05 16:37:40 -0500 )edit
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answered 2014-12-17 13:47:57 -0500

Often when OS fails early during a sim it's because the app has lost the connection to the weather file even though the path may still be present. Try browsing to the EPW and DDY files again.

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I browse to the EPW and DDY file and save before I run every simulation.

DW gravatar image DW  ( 2014-12-17 14:09:44 -0500 )edit

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Asked: 2014-12-17 12:11:36 -0500

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Last updated: Dec 17 '14