A building is composed by three towers that have the basement, the ground floor, and the first floor in common.
The system for the baseline model shall be System 8. According to G3.1.1 “each floor shall be modeled with a separate HVAC system”. Anyway, since the second floor (and the third one, the firth one…) of a tower has nothing in common with the second floor of another tower, I would consider modeling separate HVAC systems for the 2nd floors of every tower a reasonable solution.
Do you agree?