Bruce L. Bergman wrote:
On Sat, 4 Jul 2009 23:40:18 -0700, John E.
wrote:

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.

What is the legal and moral responsibility of each party?

What will not be helpful are replies about the character or intelligence of
either of the players or their actions.

The nominal utility power as supplied is supposed to be 240V. 5
volts over is a touch hot, but not out of the bounds of normal
tolerances - turn everything on in the neighborhood some hot August
afternoon with the AC units cranked, and tell me what the voltage
reads then...




That is not always the case. I'm a little rusty when it comes to 3 phase
distribution, but I've dealt with some things like this in a machine
shop friends of mine own. The voltage depends on the service to the
building. Some shops have 208V and some have 240V, and we've had to
reconfigure machines from time to time that were purchased from other
locations, or run some off buck/boost transformers if they were not
configurable. Perhaps someone more knowledgeable can fill in the details.

It's good practice of course to measure the voltage and double check the
configuration of the particular machine prior to applying power.

$4K seems pretty high though, did anyone look into repairing the damaged
board?