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"Plant flows do not resolve" with multiple variable primary pumps

asked 2023-02-01 01:25:23 -0500

Keigo's avatar

updated 2023-02-01 09:53:32 -0500

I got the following severe error during the sizing run.

   ** Severe  ** Plant flows do not resolve -- splitter inlet flow does not match mixer outlet flow 
   **   ~~~   **  Environment=WINTERESIGNDAY HTG 99.6% CONDNS DB HVAC Sizing Pass 1, at Simulation time=01/21 05:00 - 06:00
   **   ~~~   ** PlantLoop name= CHWLOOP CHILLED WATER LOOP
   **   ~~~   ** Plant Connector:Mixer name= CHWLOOP CHW SUPPLY MIXER
   **   ~~~   ** Mixer outlet mass flow rate= 50.063643 {kg/s}
   **   ~~~   ** Plant Connector:Splitter name= CHWLOOP CHW SUPPLY SPLITTER
   **   ~~~   ** Splitter inlet mass flow rate= 1.417500E-002 {kg/s}
   **   ~~~   ** Difference in two mass flow rates= 50.049468 {kg/s}
   **  Fatal  ** CheckPlantMixerSplitterConsistency: Simulation terminated because of problems in plant flow resolver

Actually, I have already identified the cause of the severe error.

  • Multiple variable chilled water primary pumps is the cause. One variable chilled water primary pump or multiple constant chilled water primary pumps does not cause the error.

    image description

  • The error occued only in the large model. The maximum chilled water loop flow rate of the model is 3.42m3/s. I tried to reproduce the error with small models, but I couldn't.

  • The presence or absence of bypass pipes are irrelevant to the error. I have tested.
  • I found this post when I searched the word "CheckPlantMixerSplitterConsistency", but my case is irrelevant to EMS. The error also occured in the following hot water loop of another large model without EMS. The maximum hot water loop flow rate of the model is 1.16m3/s.

image description

   ** Severe  ** Plant flows do not resolve -- splitter inlet flow does not match mixer outlet flow 
   **   ~~~   **  Environment=SUMMERDESIGNDAY CLG 1% CONDNS WB=>MDB HVAC Sizing Pass 1, at Simulation time=07/21 00:24 - 00:36
   **   ~~~   ** PlantLoop name= HWLOOP HOT WATER LOOP
   **   ~~~   ** Plant Connector:Mixer name= HWLOOP HW SUPPLY MIXER
   **   ~~~   ** Mixer outlet mass flow rate= 13.100580 {kg/s}
   **   ~~~   ** Plant Connector:Splitter name= HWLOOP HW SUPPLY SPLITTER
   **   ~~~   ** Splitter inlet mass flow rate= 5.837538E-004 {kg/s}
   **   ~~~   ** Difference in two mass flow rates= 13.099997 {kg/s}
   **  Fatal  ** CheckPlantMixerSplitterConsistency: Simulation terminated because of problems in plant flow resolver

I wonder if anyone else has experienced the same error. Is it a known bug? Is there a better solution than integrating variable primary pumps into one? The weird thing is that the error in the chilled water loop occurred on a winter design day, and the error in the hot water loop occurred on a summer design day. There may be a setting to avoid it, but I don't know. The error occured in V9-6-0 and V22-2-0. I'm sorry, but I can't share my idf files.

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I found that the error can occur even during custom run.

   ** Severe  ** Plant flows do not resolve -- splitter inlet flow does not match mixer outlet flow 
   **   ~~~   **  Environment=CUSTOMRUN, at Simulation time=01/01 19:00 - 20:00
   **   ~~~   ** PlantLoop name= CHWLOOP CHILLED WATER LOOP
   **   ~~~   ** Plant Connector:Mixer name= CHWLOOP CHW SUPPLY MIXER
   **   ~~~   ** Mixer outlet mass flow rate= 55.505827 {kg/s}
   **   ~~~   ** Plant Connector:Splitter name= CHWLOOP CHW SUPPLY SPLITTER
   **   ~~~   ** Splitter inlet mass flow rate= 32.206071 {kg/s}
Keigo's avatar Keigo  ( 2023-02-02 19:21:55 -0500 )edit

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answered 2023-12-13 23:33:08 -0500

Keigo's avatar

updated 2024-01-31 20:38:41 -0500

Not an answer. The severe error has not yet been resolved.

As I could not reproduce the the error with ExampleFiles, I uploaded my 3 idf files showing the error here, but the access is restricted for now. Although the project names are hidden and the locations are changed for confidentiality, I can only pass the files to EnergyPlus developers to fix the bug. Please let me know your email address to grant access.

I posted a new issue: https://github.com/NREL/EnergyPlus/is...


UPDATE

I reproduced the error with a virtual building that I can share with everyone. The model has two chillers each with a primary variable pump. Please donwload the idf file here. Please use the epw file in the same folder.

I hope the bug is fixed as soon as possible.

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@Keigo thanks for being so detailed with this question Im learning a bit from you posting this question

antonszilasi's avatar antonszilasi  ( 2023-12-14 00:32:48 -0500 )edit

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Asked: 2023-02-01 01:25:23 -0500

Seen: 170 times

Last updated: Jan 31