I have a commercial unit. When service was first connected, the meter reader said it was a 200A service but I have a single phase 200A 120/208 panel, 2-3/0 feeders + 3/0 neutral and a 3 phase 150A 120/240 panel (w/high leg) 1/0 feeders. Feed into building is believed to be 500 KCMIL but I'm not great at just looking at a wire and knowing the size. It looks too big to be 4/0 but there are no markings on it. I'm hoping the meter reader was wrong and it's actually 400A service. How do I determine?

 

I'm not an licensed electrician, and I can't see what you have there.

Determining what amperage service you have is more than just the wire gauge used.

I suggest that you consult a licensed electrician in your area. If you are going to add machinery to the area you are occupying, you will need a licensed electrician to wire it up for you anyway. You may as well get a detailed quote while you are at it. It will likely save you money in the long run.