Incorrect heating energy use for `AirLoopHVAC:UnitarySystem` in AFN simulation with distribution losses

[lymereJ]

Issue overview

The defect file includes an air loop with distribution losses (duct leakage and conduction). However, when distribution losses are excluded, the reported energy use increases, which seems incorrect—especially since both the leakage (supply and return) and the ducts are located within the model’s only conditioned zone. In that case, I would expect little change in results.

To illustrate this, I’ve included a second model along with the defect file. In that model, using a different unitary system (AirLoopHVAC:UnitaryHeatCool), the results with and without distribution losses are nearly identical, as expected.

A review of the outputs also suggests that in the defect file (OPT4), the reported duct conduction gains do not appear to account for system cycling, whereas the other model (OPT3) does.

Operating System (Multiple choices)

Any, MacOS

Operating System Version

26.3.1

Version of EnergyPlus

26.1

Unmethours link or helpdesk ticket number

N/A

Defect file

OPT4.idf is the defect file, OPT3.idf is included for comparison.
Archive.zip