Just had a new 4ton 15 seer Carrier performance series Central air system installed on Wednesday. I just noticed that when the system goes on all the lights in the house quickly dim. I don't remember the old system doing that but that was a 3 1/2 ton unit. Each of the lines are dedicated for the AC although one of them had to get upgraded to 220 for the air handler. My thinking is, why would all the lights dim if the AC is on completly separate electrical lines? The other thing is that I purchase a variable speed air handler and starts off slow and builds, I would think that would pull an even lesser load off the electrical.