Ok today I was installing a 10 ton AC on a rooftop. The name plate of the old unit said 208-230-3-60 meaning I had a 3 phase system. The disconnect box was only single phase (2 hot legs), other leg went straight into the ac to the contactor. I up-graded the box to a 3 phase box. Then I found out that I had Delta 3 phase meaning one leg was grounded/common. My question is did I have to upgrade the box to 3 phase or could I have used a single phase since my other leg is only a common?
