[mitchute]

Pull request overview

• Fixes scenario where parallel PIU's with backdraft damper leakage and an AirLoopHVAC:ZoneMixer on the return path don't conserve mass from across the air loop.

Description of the purpose of this PR

CalcAirMixer decides whether a return path AirLoopHVAC:ZoneMixer should add a parallel PIU's backdraft damper leakage. The check compared ZoneEquipConfig(z).ReturnNodeAirLoopNum(r), which is an air loop number, with InletNodeNum, which is the mixer's inlet index. In a single-loop model, air loop 1 matches inlet 1 of every return mixer. So the leakage was added even when the leaky zone does not return to that mixer, for example when it returns through a AirLoopHVAC:ReturnPlenum that has already added the leakage.

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[mitchute]

Testfile: PIULeakReturnMixer.idf.txt

Develop

This branch

[mitchute]

No diffs expected, or seen locally. We don't currently have a file in our examples that cover this.

File	Parallel PIUs	Leakage curve set	Air loops	Return path
5ZoneWarmestParallelPIULeak.idf	1	yes	1	ReturnPlenum only
5ZoneAirCooledConvCoef.idf	2	no	1	ReturnPlenum only
5ZoneAirCooledConvCoef_VSFan.idf	2	no	1	ReturnPlenum only
PIUAuto.idf	1	no	1	ZoneMixer
Standard621SimplifiedProcedure_PIUterminal.idf	1	no	1	ZoneMixer