If you are looking to install a unit in a secondary home, you still should run the AC while you are gone during the hot humid season. You can run it at 76F but if you shut if off entirely, the air upstairs (the air being used to replenish the basement air) will be very humid and the unit will have difficulty to lower the humidity in the basement.
Running the AC at 76F will provide a benefits to the entire house and could actually cost less than shutting if off entirely and running a dehumidifier. The AC will lower the humidity upstairs and will therefore help when your ventilation unit brings drier air into the basement as it exhausts the damp humid air.
Performance results are maximized when the building is occupied. If home is vacant for a prolonged period of time, then the unit should be set to operate at low speed. A fresh air intake supply is recommended via a small opening in a window upstairs or a supply vent such as the ASV-90.
If you don’t plan on running AC, or to not install a supply vent for, while you are gone: Then you should shut the ventilation unit off and understand that unless you run a dehumidifier, the humidity will increase on hot humid days.