How often and long should my fresh air intake run?
In our area, these systems are required to make sure that your house has sufficient fresh air to combat sick building syndrome.  The amount of fresh air required is based on a lot of sophisticated equations of square feet, number of occupants, etc. But after all that, not one word is mentioned about how long it should run in a given 24-hour period. It is totally left up to the home owner. If you have an active house  hold with the doors opening several times a day with normal coming and going.  You don't need any additional fresh air.  If you are a shut-in with very little coming and going, I would say 15-minutes twice per day.