Greetings Community, Note, this is just a sizing issue and not an hourly simulation problem.
I am a Trace 3D+ user and have uncovered some problems with the sizing of VRF indoor units when connected to a Multi System DOAS (OA delivered to back of VRF unit and mixing with RA) and just wanted to see if anybody else has noticed this. Trane says that the issue is with the energy plus engine and not their reporting.
The issues show themselves in the Trace 3D+ system component summary report in the airflow conditions at design table. For the cooling coil, the entering coil temperatures and humidity are a product of the mixed air (OA and RA), where the OA (delivered from the DOAS system) is the DOAS supply air dry bulb temperature used for sizing (53F in my case) and not the actual conditions I control to, which is a dehumidify and reheat control. This is causing under sizing. I am dehumidifying to 0.0087lb/lb humidity ratio and reheating to 65F. The energy simulation is working correctly, but the sizing is not.
For the heating coil sizing of the VRF indoor unit, the problem is also with the airflow conditions at design table. Here the coil is sized using the RA (room temp) and not showing any mixing with OA at all. This is also causing under sizing.
Has anybody else noticed this? I don't think this is too impactful for energy analysis, but it does impact the capacity of the equipment being used to meet all loads and it's corresponding energy efficiency.
I also think the same problem is occurring with zone-level WSHPs connected to Multi Sys DOAS. Best, Greg Estep
