I'm using eQuest and I'm modelling a multifamily building that has a dedicated outdoor air system. It's 100% OA, DX coil for cooling and gas furnace for heating.
The DOAS is supplying fresh air at 55°F in cooling mode and 70°F in heating mode to:
- Supply registers in the corridors (just a ventilation grille)
- Indoor units of a VRF/VRV system in the apartments.
I initially created a dummy space and zone to defined it as the control zone of the DOAS system, which is right now a Packaged-Single Zone (clearly a poor choice here) (explained in this energy-models.com video)
For my VRV systems, which are Packaged Single Zones (per Daikin's recommendation on modelling VRV units), I've set the OA-FROM-SYSTEM to be my DOAS.
For all my zones receiving fresh air, both corridors and apartments served by VRV, I've defined the outdoor air flow in the ZONE:OUTSIDE-AIR-FLOW attribute.
I was wondering how I should model my corridors. Right now I've put the 8 corridors and two storage zones under the DOAS system (so 8 corridors + 2 storage + Dummy Zone = 11 Zones), but I'm getting two warnings that I'm not sure I can safely ignore or not.
I've defined the DOAS, per mech plans, to have SYSTEM:SUPPLY-FLOW: 4000 cfm SYSTEM:MIN-FLOW-RATIO: 1 SYSTEM:MIN-OUTSIDE-AIR: 1
* CAUTION *********************** DOA RTU System defined as an OA-FROM-SYSTEM has 11 CONDITIONED ZONEs - only one was expected.
* WARNING *********************** DOA RTU System defined as an OA-FROM-SYSTEM has OA flow requirement of 2180. CFM but its calculated/specified OA flow is only 889. CFM. Its MIN-OUTSIDE-AIR has been reset to meet the requirement, however it is strongly recommended you re-run with this MIN-OUTSIDE-AIR specified.
Here are the questions I really have:
- Regarding the caution, am I supposed to put my corridors somewhere else such as only having one dummy zone under my DOAS?
If yes, where should I put them?
If not, what system should I use? (clearly the Packaged Single-zone is a problem here...)
Regarding the warning: the 2180 CFM is the sum of the Zone:outside-air-flow I've defined for the systems served by VRV units. I have floor multipliers so it should be 3270 CFM. For example, I've got one zone that receives 190 CFM and has a multiplier of 3. Am I supposed to input 190 CFM or 3*190=570 CFM for this zone? (I think 190 is fine because it does the computation correctly for the corridors... see below)
eQuest calculated 889 CFM. That's 850 CFM from corridors (it does take into account multipliers correctly here), plus 39 CFM for my dummy zone. I'm not sure how it computed these 39 CFM. How should I adjust that?
My entire "HVAC System / Zones" section is located here for more information.
