John Larkin wrote:

On Sun, 05 Jul 2009 02:58:00 -0400, Spehro Pefhany
wrote:


On Sat, 4 Jul 2009 23:40:18 -0700, the renowned 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.

IMO, 11% high voltage over nominal should not "fry" the controller
board in the first place.




Yes. The controller was overly fragile, or it may have just had a
random failure unrelated to supply voltage. That happens.

If the owner blames the electrician, don't use him again. Sue the
power company for providing 245.


John

You can only do that if the electric company is actually providing that
245V.
It's possible they are providing 480/460 V 3 Phase, and a in house
transformer is being used. If that is the case, then there should be
taps on the primary side to adjust this how ever, this measurement
must be taken with at least 50% load of the shop on it to get a true
reading.

245V is not uncommon and shouldn't cause any issues, actually,
induction motors run better on peppier voltages.


I may sound like I'm getting fired up over this with multiple reply's
I have made, it's nothing against you John how ever, this comes from
events that I have seen take place at work where expensive electronics
just went faulty on normal use and caused a lot of down time and
material loss. The powers to be that don't know anything about the field
start pointing fingers and when they research to see who was the last one
to have their hands in the machine no matter how long ago it was. They
think its a good justification to start blame storming. Some time people
loss their jobs when they did absolutely nothing wrong only to save the
ass of some one else!.