I have become a Journeyman electrician in 1987. In 1999 I purchased one of Mike Holts books. I read it and it has helped me. In 2014 I reread it and took the Masters exam in the state of Michigan and passed. I have since been a fan of Mike Holt books and teachings. One problem that I still have is when calculating loads and applying all that I have learned and I come up with something different than the manufacturer has installed to their equipment that I am hooking up and responsible for.

example: I have a 12.5KVA Load at 230vac single phase. It goes to a Mag plate to hold dies in a CNC mill. Voltage available is 480vac. This Magnet is a continuous load. After my calculations the load comes in at 32.5amps @ 480vac. So I would size the conductors with a #8awg THHN on the primary of a 12.5KVA. This is what I believe to be correct for the primary. The Secondary current came out to be 67.92amps at 240vac. This would require a #4awg THHN. However, when I looked at the unit the manufacturer has placed a single phase #10awg 3 conductor Cable on the output to the mag unit. I will call Manufacturer soon however, I was hoping to get comments on others who have run into this problem.