Question-and-Answer Resource for the Building Energy Modeling Community
 | 1 | initial version |
You can check the err file first.
** Warning ** Calculated design cooling load for zone=106-N-TUNNEL-AHU101 is zero.
** ~~~ ** Check Sizing:Zone and ZoneControl:Thermostat inputs.
** Warning ** Calculated design heating load for zone=106-N-TUNNEL-AHU101 is zero.
** ~~~ ** Check Sizing:Zone and ZoneControl:Thermostat inputs.
** Warning ** Calculated design heating load for zone=100-N-COMMON-AHU101 is zero.
** ~~~ ** Check Sizing:Zone and ZoneControl:Thermostat inputs.
106-N-TUNNEL-AHU101 and 106-N-TUNNEL-AHU101 are zones supplied by AHU101. These 2 zones are not autosized correctly. I think that's the main cause.
Autosizing for cooling/heating load is not working well, but 106-N-TUNNEL-AHU101 and 106-N-TUNNEL-AHU101 have some airflow because the airflow rate of the AirTerminals are autosized according to the minimum outdoor air flow requirement. AHU101 is not a dedicated outdoor air system, so the outdoor air and the return air are completely mixed, and the mixed air is supplied to each zone. For these 2 zones, The supply airflow rate = The mixed air flow rate including the minimum outdoor air.
You can also check the Output:Variable Zone Air Terminal VAV Damper Position. The damper position (= Air Flow Fraction) of these 2 zones is always 1 while the damper position of other zones connected to AHU101 is 0.35.
There are some weird settings in your model, but I'm not familiar with HVAC system in Canada, so I won't go into detail. Just one example is inconsistency between Sizing:Zone and Sizing:System.
Zone Heating Design Supply Air Temperature Input Method is set to TemperatureDifference and Zone Heating Design SUpply Air Temperature Difference is 21deltaC in Sizing:Zone. However, AHU101's airloop does not have a reheat coil for each zone. AHU101 has a central heating coil, but the setpoint is fixed to 5ºC, which seems inconsistent with your Sizing:Zone settings.
