A three float system I worked on 'back when':
Float 1: Activate pump 'on' at a set level
Float 2: Activates second pump at a higher set level
Float 3: Activates high level alarm.
System was two, 3 phase sewage lift pumps at a strip mall.
Controller had two starters, and an alternating 11 pin relay. (From Grainger)
That's about all the details I remember.
