Equipment is designed to operate +/- 10% of the nameplate rating. In the
case of taps like what happened here, the taps are supposed to be set by the
electrician to fall within the 10% range. With the taps set at 220v the CNC
machine was good to operate from 218v to 242v. As the power installer, it
was the electrician's responsibility to verify the voltage coming into the
building and adjust the taps on the machine accordingly. He was paid to
correctly hook up power to the machine and failed to do so.


"John E." wrote in message
obal.net...
I have been asked to offer an opinion in a sensitive situation.

A machinist moved his shop across town and required some rewiring (3-phase
outlets, conduit, etc.) in order to locate some machines where he wanted
them.

He hires a guy who's not a pro (and later discovers is not insured) but
has
done shop wiring before and had a good attitude and track record. The guy
does good work. No complaints about the quality of his work.

Owner throws the switch, all works fine.

The story continues 4 weeks later when the very expensive CNC fries its
controller PCB to the tune of $4000.

Turns out the voltage in the shop was upward of 245 and the taps in the
CNC's
power supply were set for 220.