Question-and-Answer Resource for the Building Energy Modeling Community
 | 1 | initial version |
Some zones still have an unrealistic occupant density. The building code minimum is 5sqft/person (0.46sqm/person) for standing, assembly without seats. Some spaces have less than this. (see building code https://codes.iccsafe.org/content/IBC2024V1.0/chapter-10-means-of-egress#IBC2024V1.0_Ch10_Sec1004).
The main problem appears to be the DOAS. It accounts for 99.9% of the zone load.
One problem is that you have specified a very low humidity ratio for the DOAS sizing. 0.004 is saturated at freezing; I doubt the DOAS system will be operating the dehumidification coil at freezing temperatures. It will cause convergence problems. More realistic would be to set the humidity ratio closer to the expected space design humidity (60%RH @ 24°C = 0.011). Or use the default Humidity Ratio Difference method and value (0.005). I think the difference method is more realistic as it would prevent oversizing/convergence issues and it is better for a steady state operation. It is unrealistic to expect the system to be sized for maximum dehumidification during high humidity startup.
Another problem is that the specified Zone Humidistat Dehumidification Set Point Schedule (Inlet Air Humidity=0.6 constant) was specified as a dimensionless positive schedule. Per the InputOut reference, this schedule should be a percentage schedule that specifies Relative Humidity. Create a percent schedule set at 60 and assign this instead.
Another problem is that the design outdoor airflow per person has been specified as 31,783 cfm/person (15m3/s/person). This is way too high. For assembly type spaces the ventilation per person can range from 7.5-10 cfm/person (0.0035-0.0047m3/s/person) (see building code https://codes.iccsafe.org/content/IMC2024V2.0/chapter-4-ventilation#IMC2024V2.0_Ch04_Sec403.3.1.1).
Another problem is that there are many zones with zone exhaust fans; each with a high airflow of 42,377cfm (20m3/s). These zones are not associated with the DOAS, so it would not affect the DOAS sizing. However, if they are attached to an airloop system, it will cause the airloop outside airflow to be very large. You should review the size of these to ensure they are realistic.
https://imgur.com/a/FVRMYG9
