EnergyPlus Crashes with Optimum Start for VRF

asked 2026-03-03 02:55:29 -0500

Keigo
5876 ●1 ●57 ●38 https://www.linkedin.c...

A bug report.

I tried modelling optimum start control to zone VRF.

I used an ExampleFile: VariableRefrigerantFlow_5Zone.idf (V25-2-0).

Originally, AvailabilityManager:NightCycle is modelled in one of ZoneHVAC:TerminalUnit:VariableRefrigerantFlow objects: TU1 in the idf file. I replaced it with AvailabilityManager:OptimumStart. Then, EnergyPlus crashed with few clue in the err file.

The idf file is here.

Some findings:

Crashed with other versions e.g., V25-1-0, V23-1-0, V9-4-0 and V8-9-0.
Crashed regardless of Control Type of AvailabilityManager:OptimumStart
Simulated successfully for ZoneHVAC:FourPipeFanCoil with another idf file. The crash seems to be specific to ZoneHVAC:TerminalUnit:VariableRefrigerantFlow.

This post is about optimum start for VRF. I wonder if @apdavis or @Julien Marrec has successfully modelled optimum start for zone VRF.

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Comments

Thank you for your prompt review.

The ExampleFile I had tested optimum srart for FCU is 5ZoneFanCoilDOASCool.idf. It has an air loop. When I remove the air loop, yes, I get the same crash.
I tested optimum start with another ExampleFile: VariableRefrigerantFlow_5Zone_wAirloop.idf. There is no crash as you suggested. However, optimum start does not work properly, which might be specific to ZoneHVAC:TerminalUnit:VariableRefrigerantFlow because optimum start modelled in 5ZoneFanCoilDOASCool.idf seems to be working propoerly.