NatLabRockies / NatLabRockies/EnergyPlus
VRF with single indoor+outdoor unit using more fan energy than comparable PTHP
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- Dominant language
- C++
- Stars
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- Avg merge
- 6d 21h
- Merged PRs (30d)
- 22
Description
Issue overview
We are modeling a multisplit system as a single AirConditioner:VariableRefrigerantFlow with a single ZoneHVAC:TerminalUnit:VariableRefrigerantFlow per zone and comparing it to a ZoneHVAC:PackagedTerminalHeatPump in a 5-story multifamily building.
We are surprised that the PTHP is outperforming the VRF, especially on fan power. The VRF has the same fan static, and efficiencies as the PTHP and the cooling capacities are close as well. The VRF coil's rated efficiencies are slightly lower.
Here are some relevant graphics: fan runtime and supply air temperature. The top line is the VRF. It looks like the VRF is choosing to run the fan longer at higher supply air temperatures, maybe minimizing the cooling energy where it might be better to minimize fan energy.
Details
- EnergyPlus Version 9.4
- Windows 10
- 64-bit
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Reproduce the comparison described for EnergyPlus 9.4 using a single AirConditioner:VariableRefrigerantFlow and one ZoneHVAC:TerminalUnit:VariableRefrigerantFlow per zone versus a ZoneHVAC:PackagedTerminalHeatPump. Begin with the fan-runtime and supply-air-temperature behavior shown in the issue; done means determining whether the VRF fan-energy difference is expected or identifying the implementation discrepancy and a focused regression case.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- cpp
- Domain
- tooling
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Needs clarification
- Newbie friendliness
- 30/100