Question-and-Answer Resource for the Building Energy Modeling Community
 | 1 | initial version |
You need to specify ventilation requirements for the space. In your case, it seems like the best option will be to specify your ventilation requirements to match your exhaust flow. If you only want your exhaust fan to run when the DOAS is supplying ventilation air to the space, you could use the Coupled option, but if they are scheduled the same, it shouldn't be necessary. If the exhaust fan is unbalanced, the exhaust fan flow rate will be subtracted from the return flow for the DOAS. For the case in which DOAS flow matches exhaust flow, return flow will be zero. If you want to add energy recovery to account for heat recovery from the exhaust flow you will likely not want to set the exhaust fan as Unbalanced. If you set the Balanced fraction to 1, no flow will be subtracted from the return air stream and you can recover heat from the full "exhaust" stream. You can technically also connect the outlet node of the exhaust fan to the return path of a heat exchanger, but you most likely won't want to take that approach if you are trying to recover heat centrally from multiple exhaust streams.
