On Jul 5, 2:40 am, John E. wrote:
Turns out the voltage in the shop was upward of 245 and the taps in the CNC's
power supply were set for 220.

As others have said, there's not much the wiring guy could have done
wrong to get 245 volts rather than 220. He hooked up what was there
and couldn't be expected to have detailed knowledge of what the owner
was going to run, what setting he had it on or how sensitive it was.

Does the owner have some reason to believe that this was not the
voltage in the new shop before the additions?