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.

Thanks.

4 weeks is a long time. Especially on a used piece of equipment that
has been subjected to the strains and jostling of a cross town move.

Can you prove that the incoming voltage was 245 when the "electrician"
was on site?

Were the field connections made by the "electrician" made to a terminal
strip or to the original tails? IOW, Did he see/know that there were
tap options?

If it took 4 weeks to fail in the new shop, do you know that the old
shop didn't also have an overvoltage situation? Maybe the failure was
75% along before the move.

One of the side effects of the slowdown in manufacturing demand is that
there does appear to be an upward creep of utility supplies, in our
shop, this spring our water pressure began to creep upward to the point
where the TP valves on both water heaters began to dribble. Our supply
voltage is a few volts higher too.

If the "electrician" feels like he did miss something, he probably owes
the owner a pro-rated share of the cost, but if he feels he did the job
within the scope of the work he was hired to do, the owner ought to foot
the bill. Whether the 'electrician' gets future work or references
might factor into this....