Baseline HVAC Model System-8 VAV PFP Boxes with Outdoor Air Unit

Thank you for the quick response. In addition, we also provide several unconditioned rooms equipped only with outdoor air units in our proposed model, no VRF units included in these rooms. If in baseline case, conditioned rooms receive their fresh air from the main HVAC system, then what about these unconditioned rooms which only require fresh air intake? In this case, should we model identical outdoor air units for these rooms aside main VAV system?

Thank you for the quick response. In addition, we also provide several unconditioned rooms equipped only with outdoor air units in our proposed model, no VRF units included in these rooms. If in baseline case, conditioned rooms receive their fresh air from the main HVAC system, then what about these unconditioned rooms which only require fresh air intake? In this case, should we model identical outdoor air units for these rooms aside main VAV system?

Thank you for the solid answers. Is there any LEED regulation in limiting the tolerance of unmet hours? We use EnergyPlus as our energy model and there we can mod the tolerance up to 10 degC. Is it realistic (and allowed) to just increase this throttling range to compensate a great number of unmet hours? We have this unmet hours issue since we add independent OAU (Outdoor Air Unit) in each of VRF conditioned zone. Any suggestion? Regards,

1) Would you show us how to calculate and apply extra load from OAU in e+? I have tried to increase max dry bulb and wet bulb temp proportionally on SizingPeriod:DesignDay but it ended up in substantial rise of energy consumption, especially when I applied this on baseline model. I doubt it would solve the issue since unmet hours always appeared (even it did get shorter). 2a) I have checked the website, yet there are no specific case involving OAU and VRF in the same zone. I posted question there, wish they could help. 2b) I might missed something, but I really want to know about OAU and DOAS, are they the same? I read on somewhere that DOAS is a whole OA system which consist of many OA Terminal Units serving multiple zones. E+ model this as AirLoopHVAC equipped with fans, cooling coils, mixer etc more like an AHU. Therefore, OAU I used here is just a single unit without any link or duct and not connected to any other unit. I model this in E+ as ZoneHVAC:OutdoorAirUnit, equipped only with supply and exhaust fans. Could you light me up on both terms? 3) We are still gathering detailed mechanical specifications from our HVAC team. Currently, in proposed HVAC model I can only define gross rated cooling COP at each VRF condenser and the amount of outdoor air requirements in each zone. Is this still too far from enough? 4) In E+, it is possible to introduce OA without installing independent OAU by using mixer embedded inside VRF's TU. When I implemented this, with the exact same amount of OA provisions, there was no unmet hours problem occurred. How this could be happened? Logically, it would behave similar with the OAU equipped. Regards,