Liability & responsibility of electrician?

"John E."

** What a STUPID troll !!!

The PSU in the CNC blew cos it was a pile of shit PLUS the design was 100% incompetant cos it gave no protection to the delicate and expensive load.

Bet it was old and way past use by date too.

Piss off TROLL !!

.... Phil

Probably a good call, since modern switchers, which the DC supplies for these things usually are, can handle up to about 265 volts. Even a bit more, typically.

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...

If they were seeing 250V - 255V or more, then I'd call the Utility and get the transformer taps knocked down a notch.

If the power supply on the CNC computer had changeable taps, and the last guy that touched it didn't have any reason to look to see what it was set for, IMHO it's nobody's fault. Especially if the shop they moved from and the one they moved to had the same nominal operating voltage, and they knew it - I'm not going to open 50 machines looking for the unexpected when I'm charging by the hour unless I have a good reason to... Just "Git Er Done" and go home.

If he had a reason to look inside and saw it was on the 220V tap he should have moved it to the 240V - or told the owner - it's good practice to follow but there's no responsibility to look involved.

And I wouldn't expect 255V on the 220V tap to kill it. Now if it was set for 208V input and you fed it off the 'High Leg' from an Open Delta service that's hovering around 280V to ground, THEN I'd expect fireworks. Open Delta High Leg voltages can bounce around and go even higher, then something flashes over...

That would be the /one/ time I'd call it against the Handyman, putting the high leg on the control circuit would be a big goof. You are supposed to put the regular 240V legs on the A and C phases coming in, and the 'High Leg' Orange lead to B phase and NOT the controls.

The average power supply is supposed to feed +5V, +12V & -12V etc. to the computer board, and have Crowbar protection so that's all that gets through. If the supply blows up and lets line voltage through to fry the controller board (even if you put an over-voltage on the input) that's a badly built power supply.

Otherwise, it's entirely possible that it just reached End Of Life and decided to go out in a spectacular manner, and the move had nothing to do with it. The timer that makes things blow up three days out of warranty finally went off.

Unless you want to spend a lot of money on Electronic Forensics to analyze the power supply failure, "The world may never know..."

-->--

PS - Have to trim off alt-r.c.m to make this go, 4 crosspost limit.

"Archimedes' Lever" "Phil Allison"

** Unlikely it was a SMPS based on the OP's admittedly poor and incomplete info.

Cos SMPS do not have multi-taps for AC input voltage - PLUS if an off-line switcher fails from overvoltage, it just blows the fuse and goes dead.

But losing regulation and over-voltaging the load ( as was alleged by the OP) is another scenario altogether - more often associated with old age or the failure of one of a few critical components in the regulation loop.

..... Phil

You're an idiot. If you are wiring POWER runs, you had better know what your loads are, and how they get connected.

My drier sees 250VAC. Low voltage stuff in this house gets 125VAC.

Everything is working just fine.

Jon

Is that burning cotton I smell?

Drier has a temperature limiter, so although the slightly higher voltage results in a slightly quicker "turn on" time for the elements, they still are shut off at the same temperature regardless of incoming voltage.

Jon

It's called a thermostat

Of course. I was jesting.

Before there were UPS's there were constant voltage transformers, the most popular made by Sola. UPS's put out really crap AC, and are designed to work with a switching power supply as a load.

Sola transformers were used with all sorts of things, there may be one that fits your needs. I used them with computers that had linear power supplies, but I think they will work with motors, it's worth checking out.

Geoff.

--
Geoffrey S. Mendelson, Jerusalem, Israel gsm@mendelson.com  N3OWJ/4X1GM

I guarantee it doesn't match yours.

You seem to think that since you understand the rules of making a connection that you understand electrical power.

I doubt seriously that you have such a grasp of the industry.

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?

I rented a house for a while that had unusually high line voltage. It varied from around 122V to 125V depending on the time of day. If it was much higher than that, I'd be concerned, but anything from 115V to 125V is pretty normal.

A friend of mine over in the UK is near the end of a long run from the transformer that powers his street. His voltage varies considerably, from as low as 220V to nearly 250V.

Oddly enough, that's exactly what I've measured (give or take a few tenths) in the MSOE power lab (which is equipped with 208V 3 phase), and very nearly the same at my own bench at home.

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms

CNC's

CNC electronics cost about 4-8 times as much to fix as normal electronics. Shrug..its called :"the going rate" unfortunately.

Gunner

"Lenin called them "useful idiots," those people living in liberal democracies who by giving moral and material support to a totalitarian ideology in effect were braiding the rope that would hang them. Why people who enjoyed freedom and prosperity worked passionately to destroy both is a fascinating question, one still with us today. Now the useful idiots can be found in the chorus of appeasement, reflexive anti-Americanism, and sentimental idealism trying to inhibit the necessary responses to another freedom-hating ideology, radical Islam"

Bruce C. Thornton, a professor of Classics at American University of Cal State Fresno

You can get a license without being in the union.

Excuses do not make you qualified. Especially if the tests you took were way back in '74.

Bwuahahahahaha! I'll bet your skill set matches your price schedule. Low and lame.

Hummm? Yeah, you'd probably be better at that.

Doubtful.

What is that a pussy surfer boy threat?

I will live far longer than a twit like you.

tenths)

nearly

Your apparent conflation of single phase systems and 3 phase systems only serves to confuse outsiders.