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Limit to Quantity of Chillers in EnergyPlus

asked 2018-05-07 06:19:38 -0500

jt1234's avatar

Using OpenStudio I occasionally come across large data centers with chiller plants containing >10 chillers and each time I face a limit on the number of chillers I can use. OpenStudio allows all chillers to be created and appropriately translates them to the IDF, but it appears EnergyPlus will only operate a max of 10 chillers. Is this a known Eplus issue or is there an underlying issue somewhere else? Is there a fix for this issue besides combining multiple chillers into single component? Thanks.

Note: this has occurred across multiple versions of OpenStudio and Energy Plus.

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I don't think there is a limit for the number of chillers in EnergyPlus. Could you send me a copy of the IDF file that is created when you have more than ten chillers. jglazer at gard dot com.

JasonGlazer's avatar JasonGlazer  ( 2018-05-08 06:50:35 -0500 )edit

Jason - I just sent you an IDF file. As I was compiling this test model I think I determined the underlying issue. During the OpenStudio --> EPlus translation process all the chiller objects get translated to the IDF, but the only the first 10 sequentially get added to the PlantEquipmentList control. So maybe this is an OpenStudio translation issue?

jt1234's avatar jt1234  ( 2018-05-08 08:41:45 -0500 )edit

You may be right. Have you tried editing the IDF file to add the objects to the PlantEquipmentList manually?

JasonGlazer's avatar JasonGlazer  ( 2018-05-08 08:46:35 -0500 )edit

I just tried, but received an error. It does look like EnergyPlus may have an equipment limit on the PlantEquipmentList: BigLadder

jt1234's avatar jt1234  ( 2018-05-08 09:13:47 -0500 )edit

In your original question you said that you had tried this with other versions of EnergyPlus. Would it be possible to send me the version from 8.8 or 8.7? I think the answer is different for those earlier versions but I want to double check with a file from an earlier version.

JasonGlazer's avatar JasonGlazer  ( 2018-05-10 06:48:31 -0500 )edit

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answered 2018-07-31 12:52:34 -0500

Internally, EnergyPlus supports any number of equipment in a PlantEquipmentList (and CondenserEquipmentList) but the input definition in the IDD file is hard-coded to 10 (not extensible). This will be fixed for the version 9.0 release, see issue #6871.

Note as of v8.9, any changes to the idd file require that EnergyPlus be rebuilt to propogate those changes to the internal JSON schema. If you happen to be using v8.8 or earlier, you can edit the idd file to make these objects extensible and it should run fine with more than 10 pieces of equipment.

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Asked: 2018-05-07 06:19:38 -0500

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Last updated: Jul 31 '18