I am trying to figure out how watts/ amps are needed to run a 3 1/2 ton ac unit, and breaker size on the fuze box?

Thanks
Scott

What does it say on the unit. Should tell you the load amps, running amps etc. I have a 4 ton, seer 13. Uses double 30 AMP on an AWG 10

The rating plate on the system will give you min and max breaker size. You will need to adjust for wire size on the length of the wire. 30 amp breaker on 10 AWG sounds a little on the small side for a 4 ton, but that's why they have rating plates.