Severe error calculated density of air is negative

edit

I have upgraded the provided defect file (v8.7) to energyplus v9.4.0 and got an actual hard crash. So I went ahead and created an issue at NREL/EnergyPlus#8412. I will report back if a resolution is found.

Workaround: The problem is explained in more details on https://github.com/NREL/EnergyPlus/is..., but basically you want to NOT autosize the tank (volume and height at least) for now.

For eg, given that your WaterHeater:Sizing objects indicate "Nominal Tank Volume for Autosizing Plant Connections" of 30 m3 for HW ST and 0.1 m3 for HW Aux, do something like this in the WaterHeater:Stratified:

  WaterHeater:Stratified,
    HW ST,                   !- Name
    General,                 !- End-Use Subcategory
    30.0    ,                !- Tank Volume {m3} <= Enter hard value
    2.0,                     !- Tank Height {m} <= Enter hard value
    [...]

  WaterHeater:Stratified,
    HW Aux,                  !- Name
    General,                 !- End-Use Subcategory
    0.1,                     !- Tank Volume {m3} <= Enter hard value
    1,                       !- Tank Height {m} <= Enter hard value
    [...]

With that change, the file wile run to completion.