Question-and-Answer Resource for the Building Energy Modeling Community
 | 1 | initial version |
I'm assuming you fan to use a Fan:ZoneExhaust object. Like most E+ objects, you can usually gain a lot of valuable information by looking at the Input/Ouput reference guide of EnergyPlus. This should become a reflex.
Here is the documentation for Fan:ZoneExhaust
As stated in the introduction paragraph (emphasis is mine)
The way in which the exhaust fan impacts central air system can be controlled by declaring what portion of the flow has been balanced by simple airflow from infiltration, ventilation, or mixing. However it is important to note that presence of an exhaust fan does not by itself drive any simple airflow such as infiltration, ventilation, or zone mixing. There is no comprehensive automatic mass balancing between air system flows, exhaust flows, and the separate simple airflows. For balancing, the simple airflows need to have their own input objects that need to be coordinated with the exhaust fan.
The field Balanced Exhaust Fraction Schedule Name will be of interest to you too. By default, "it is assumed that all the exhaust air is assumed to be unbalanced by any simple airflows". What it means is that it will be reflected at the central air system (if you have one) by:
- Limiting the return air going to the central handler
- If the exhaust airflow is bigger than the regular return, the OA mixer will draw in even more airflow to compensate
In your case, I guess it depends where the air for the kitchen hood is coming from. If there is a a direct intake (even if just a passive duct or something), I'm not sure you should even bother to use a zone exhaust fan, but rather just a central handler. If you do want to, you'd have to make sure you create an infiltration component that matches your zonal exhaust, fan set the Balanced Exhaust Fraction Schedule Name to always 1.
