I am trying to hardsize the outdoor air requirements for my models in Openstudio 1.12.0, and I'm having problems in getting the systems to use the value of the outdoor air I have given as an input
I'm running two models:
- Model 1 (baseline) has VAV systems serving on OS:AirLoopHVAC loops serving the corridor zones , ZoneHVAC:PackagedTerminalHeatPump serving apartment zones and ZoneHVACPackagedTerminalAirConditioners serving office and exercise zones.
- Model 2(Proposed) has ZoneHVACPackagedTerminalAirConditioners serving apartments, Make up air units serving corridor zones, and furnaces serving the eercise and office zones.
I want to specify the outdoor airflow rate for all these systems. With regard to this, for the Make up air units, as per the answer provided for [https://unmethours.com/question/10181/mau-airflow-night-setback/] , the outdoor air provided in "OS:DesignSpecificationOutdoorAir" for the spacetypes of the zones overrides the the value entered in the MinimumOutdoorAirFlowRate in OS:ControllerOutdoorAir and DesignOutdoorAirFlowRate in OS:Sizing:System.
However, OS:DesignSpecificationOutdoorAir does not override values of outdoor air I enter in "outdoor-air-flow-rate-when-no-cooling-or-heating-is-needed" under OS:PackagedTerminalAirConditioner or in ZoneHVAC:PackagedTerminalHeatPump. The values entered in DesignOutdoorAirFlowRate in OS:AirLoopHVAC and MinimumOutdoorAirFlowRate in OS:AirLoopHVAC:OutdoorAirSystem also override the DesignSpecificationOutdoorAir value.
Is this always the case? Does anyone know of a clear heirarchy of which entry overrides the other, specifically for each of these systems? (PTAC,PTHP, VAV and Makup air units). Why is this level of precedence different only for a make up air unit when compared to other systems? I am not able to find any documentation which says one clearly overrides the other, and the modelling suggests that this may be system specific. Can someone clarify?
Also, when I check the energyplus output files for a system, say, ZoneHVAC:PackagedTerminalHeatPump, there are two values of outside air: the User-Specified Outdoor Air Flow Rate and the Design Size Outdoor Air Flow Rate. How is this design size outdoor airflow rate value calculated? Does it use the inputs from DesignSpecificationOutdoorAir?
