Fix VRF crankcase heater calculations for multiple compressors

[rraustad]

Pull request overview

• Fixes VRF Crankcase heater operation is inconsistent with temperature limits #11020

Description of the purpose of this PR

VRF Crankcase heater operation not as expected. Reported by help desk as issue 11020 and recently this unmet hours post.

https://unmethours.com/question/103176/vrf-crankcase-heater-operation/

Used example file VariableRefrigerantFlow_5Zone as defect file with Chicago weather.

Pull Request Author

• Title of PR should be user-synopsis style (clearly understandable in a standalone changelog context)
• Label the PR with at least one of: Defect, Refactoring, NewFeature, Performance, and/or DoNoPublish
• Pull requests that impact EnergyPlus code must also include unit tests to cover enhancement or defect repair
• Author should provide a "walkthrough" of relevant code changes using a GitHub code review comment process
• If any diffs are expected, author must demonstrate they are justified using plots and descriptions
• If changes fix a defect, the fix should be demonstrated in plots and descriptions
• If any defect files are updated to a more recent version, upload new versions here or on DevSupport
• If IDD requires transition, transition source, rules, ExpandObjects, and IDFs must be updated, and add IDDChange label
• If structural output changes, add to output rules file and add OutputChange label
• If adding/removing any LaTeX docs or figures, update that document's CMakeLists file dependencies
• If adding/removing any output files (e.g., eplustbl.*)
  • Update ..\scripts\Epl-run.bat
  • Update ..\scripts\RunEPlus.bat
  • Update ..\src\EPLaunch\ MainModule.bas, epl-ui.frm, and epl.vbp (VersionComments)
  • Update ...github\workflows\energyplus.py

Reviewer

• Perform a Code Review on GitHub
• If branch is behind develop, merge develop and build locally to check for side effects of the merge
• If defect, verify by running develop branch and reproducing defect, then running PR and reproducing fix
• If feature, test running new feature, try creative ways to break it
• CI status: all green or justified
• Check that performance is not impacted (CI Linux results include performance check)
• Run Unit Test(s) locally
• Check any new function arguments for performance impacts
• Verify IDF naming conventions and styles, memos and notes and defaults
• If new idf included, locally check the err file and other outputs

[rraustad]

These calculations start by adding in a baseline crankcase heater power. Then added in other values based on number of compressors. I could not follow what was intended so just came up with a different approach. Feel free to simplify code if a better method is conceived.

[rraustad]

VariableRefrigerantFlow_5Zone.idf:

AirConditioner:VariableRefrigerantFlow,
  15,                      !- Crankcase Heater Power per Compressor {W}
  3,                       !- Number of Compressors {dimensionless}
  0.33,                    !- Ratio of Compressor Size to Total Compressor Capacity {W/W}

Showing before changes in develop branch and then what looks like the correct answer from this branch.

This branch:

[rraustad]

While creating the unit test I realized that for water-cooled VRF the condenser water inlet node was controlling the crankcase heater. So I added a variable specific to the VRF condenser type to control the crankcase heater.

[rraustad]

This input for Ratio of compressor size to total does have an effect on crankcase heater power. For this reason I had to use a more detailed calculation as my attempt at simplification did not take this input into account.

[github-actions]

⚠️ Regressions detected on ubuntu-24.04 for commit 2c5d542

Regression Summary

• ESO Small Diffs: 703
• Table Small Diffs: 391
• MTR Small Diffs: 523
• Table String Diffs: 186
• EIO: 396
• JSON Small Diffs: 2
• ZSZ Small Diffs: 72
• Table Big Diffs: 36
• ERR: 14
• MTR Big Diffs: 2
• EDD: 4
• ESO Big Diffs: 10
• SSZ Small Diffs: 13
• JSON Big Diffs: 2

• View Results
• Download Regressions

[mitchute]

Thanks @rraustad. Merging.