Question-and-Answer Resource for the Building Energy Modeling Community
Get s tarted with the Help page
If you want to change the zone exhaust fan flow rate over the simulation, then you want to assign a schedule to the Flow Fraction Schedule Name input field. This should be a new schedule that isn't referenced by anything else in the model. You can then use the EMS Actuator for "Schedule Value" to set the fraction of maximum flow rate of the zone exhaust fan. This post has an example of using the schedule value actuator as an HVAC system on/off setting. Note that this schedule value actuator can only be applied to four schedule object types: Schedule:Year, Schedule:Compact, Schedule:File, and Schedule:Constant.