Hello from Colorado!!!!
Ok Guys, I need some help.

I went on a service call Friday to PETsMART Vet Clinic. All of there computer monitors keep blowing up, and have lost two CPU,'s.

The two CPU,'s, and monitors are all they have lost. None of the Vet equipment has been effected at all.

I went to each individual outlet and checked for loose wires, went to the main panel and did the same. Went to the outside of the building to find the transformer and to my surprise it is a straight feed from the city to the meter to the panel. So I checked the wires in the meter.

After that I checked all of my voltage, Phase1 - 121.2v, Phase2 - 122.4v, Phase 3 - 123.1, And 209v - 210v between.

I left my meter hooked up for over an hour to see if there were any fluctuations, but there were not.

ALL of the circuits that are having problems are IG, and have surge arrestors on them.

Someone please give me an Idea of where to go from here. I have come to a mental block.

HHHEEELLLPPP!!!! From Colorado!
JON

check to see if all the effected circuits are all on teh same phase.. what sounds to me is like there is a phase thats leakin to the iso grund bus bar.. im not sure.. this is a good one.. maybe it has something to do with harmonics and the surge sup's

-m

I thought the same thing about something going back on the ground, or even stray current.
I put a large load on the service including all of the normal equipment, and the only thing that changed was the load on the neutral.
I also had the thought that all the effected circuits were on the same phase, so I checked and they are all equal, three on each phase.
I would not know how, but could the Isolated ground cause some weird problem?

check to see if the circuit is on a shared neutral, sounds like it could be an intermittent neutral connection, causing the monitors to be in series on 208 volts. (intermittently)

Jon,
You can chase this indefinitely IMO. What you have already done has eliminated the obvious problems that we all would look for.

Unless you have logging type instrumentation so you can actually see what happens you are spinning your wheels.

Sell them a UPS to cover all effected equipment and call it good.

GJ

This is not meant as an insult, but what do you do when the UPS you just sold them not only doesn't cure the problem, but goes up in smoke too? This falls in the realm of a mechanic who changes parts until he finally gets to the right one. A UPS system is not a cure all for every power quality problem.

A detailed survey and analysis of the power system & grounding system is usually called for. I cannot over-stress the importance of investigating this area as most power quality surveys show that there are multiple deficiencies in the groounding system.

I find it strange that the surge arrestors have not smoked out as would be the case if a loose neutral was involved in either the service conductors or multi wire branch circuit.

You might wnt to take a look at all equipment in this building. Even some of the most innocent looking stuff can throw some serious transients on the line. Any X-ray equipment, copy machines or refrigeration equipment (including air conditioners) should be closely examined.

Whatever the outcome is, please let us know.

For more info on power quality, visit http://www.powerquality.com

Tom

Be sure to take your voltage readings at the equipment being served, when the circuit is at its peak load. Long distances,bad connections, and/or small wire can cause problems that a voltage test at the panel or meter won't show.

Where is the isolated gorund terminated?
Don(resqcapt19)

We have an old saying from my days in the Coast Guard. 95% of all equipment failure is due to operator error. Make sure the staff is not doing something stupid before you waste your time.

Computer monitors are very sensitive to the voltage supplied. A loose or missing neutral will have disastrous effects on the flyback transformer and should be eliminated before you continue your search.

I also agree with the bonding and grounding statement posted earlier. Bonding and grounding are the most common violations electrically speaking. It a subject that is sometimes misunderstood even by experienced electricians. Thee are often discrepancies between utility company specs, city specs and the NEC.

Tom,
Thanks for the link....some good info. there.

GJ

Some surge arrestors are better than others, some have LED indicators to show that you still have protection, check to see if they are still in good working order. I have seen them burned out and simply act as a multi outlet strip with no protection at all.
With an intermittent neutral connection on a multi-wire circuit strange things happen.

Hope I am not too late to respond. But, in the early days of computers, many manufacturers required separate "isolated" ground rods or fields. They wanted to eliminate noise on the lines so the sensitive computer equipment would not screw up the calculations. This meant that a fault, whether arcing or bolted, on the computer system would have to travel through the isolated ground, through the earth, then through the service ground system to get back to the main breaker for action. A low level arcing fault would unlikely not trigger the breaker to trip. I would check the isolated ground to make sure you are not getting some strange or stray voltage on it. This may mean renting some sensitive equipment from GE Supply or some other company. But it may find your culprit. Depending on the computer systems, you may now be able to tie the two ground systems together, and eliminate the problem. You will need to check with the manufacturer of the computers. Most newer computers of today don't require "isolated" grounds. Good luck.

Another thought. Have the city check their neutral. It may be intermittent causing voltage spikes.

Computers have come far, so has software. I wonder if there is a program that can monitor power quality? It would seem marketable....

Hello From Colorado!!!!
As of right now I have tried almost everything that has been posted here. Right now I have a recorder hooked up to the service and anouther to the troubled circuit.
I am at a total loss as to the cause. The circuits are good, the ground is good, the service is good, the city even came out and checked the transformer, and it is good.
The city is recording the transformer right now as well.
I really appriciate all the help you guys have given me and I have tried them all, but still at a loss!

JON;
maybe you need some insight from the guys that do the mega-bite thing...
try; www.doityorself.com

go to the computer section, they are all usually very helpful

[This message has been edited by sparky (edited 05-24-2001).]

As of right now I have tried almost everything that has been posted here.
Is the isolated ground properly bonded to the main/service panel ground?

There are meters ouy there that measure true RMS. These are made by fluke, and others. They can give you True Harmonic readings where other meters will not. They can read voltage and amperage. The harmonics can play havoc on the system. You have to have a pro be able to read the sine waves and trouble shoot the feeders, circuits, etc.
Good luck--Steve T.

DSpark- Yes I checked all of the IG's and they are all properly installed and bonded

Steve- I have a Fluke true rms sign wave, and voltage recorder on the circuit, and another on the service. Both of them are running print-out

Get another monitor from a different vendor, try it on the line. It could be they just have bad equip. (Simple is as simple does) Silvrbk says 95% of it is pilot error, I say 99%.

[This message has been edited by electure (edited 05-25-2001).]

If this facility has the pre-wired service building in the store check to see if when any part of the energy management system brings on a contactor for lighting, heat, etc. that a circuit is not connected to a grounded conductor in the terminal ducts where the circuits were terminated.

Hello From Colorado!!!!!
You guys are never going to believe what I finally found!
We got a call from the vet saying that they lost another one of their monitors. When I got there I went to the event recorder and there was a very sharp spike at the exact moment of the monitor going out.
I went to the daily log and saw that at the same time the delivery man for the feed store showed up about 20 min. before.
I went to where all the feed bins were and started moving things around and found an access in the floor to a storage room that no one knew was there. Opening the hatch I immediately saw a 4&11 J-box with no cover and NO WIRE NUTS!!!!
A small amount of feed was on the ledge next to the box and mouse sign everywhere. I got in a little closer to the box and could see a small arc mark on the box.
Looks like all my problems have been mice crossing the box to get to the fallen feed and making the IG and hot wire touch the side of the box for a split sec, but not enough to trip the breaker.
All my problems over an electrician(supposed) that didn't finish putting a box together!!!!!!!!! Don't that beat all.

JON

Wow,that is one for the books, glad to hear you located the problem.....good detective work.

All my problems over an electrician(supposed) that didn't finish putting a box together!!!!!!!!! Don't that beat all.

or the vet not controlling his mice....



congrats nj ! you have perservered!

What an interesting thread - with the last-case scenario being the result!!

New tech term for computer hardware faults - instead of "Bugs" [came from the moth that landed on the vacuum tube circuits of the ENIAC, causing a short], we now have "Rodents" !!!

Wow, what a mind-melt that one must have been!
This one's going into my "Check For Rodents, Too" file!! Just showing that problems can be nearly infinite as far as what to look for, and when they are infinite, it's probably something hidden and the least technical in nature!!

Once again, great thread!

Scott SET

Hat twisting nervously in hands, head held low, feet shuffling in the dust.....

I was way off base with my post and just flat wrong.
Does this mean I lose my posting license that I worked so hard for????

Great thread Jon, thanks for sharing it with us. These experience's are more valuable than many, many hours in the classroom. And we get to share them for free via this forum. Thanks to all who post.....I'm learning alot.

GJ

GJ,

I see no problem with your opinions, that's what we need to do is throw a bunch of ideas into the thread.

Your license is not endanger of being revoked by posting an opinion here!! Licenses become revoked when the Webster feels that too much BS is passed on as reality.
[P.S. - Bill, love that term "Webster"!! May I use it more often?? I'll pay royalties ].

I know that you were joking somewhat in your message, just want to make this point more apparent than the one under my hat, just in case someone might feel this is the way things work around here! [AKA 1 incorrect message and your officially kicked off the board! - man I would have been ace'd the first day!! with redundant 86'ing to follow!!].

There are some boards where a level of Ultra-Electro God is required for posting - less the flames overfloweth!!

Not here! We'll take minimum Electro-Wizard entry level and allow upto 3 mistakes in posts before you will be hunted down and tortured!

Scott SET - The Wannabe Eel-lektrikal injunear...

At first I was thinking Harmonics on the shared neutral, but the more i think about it it sounds like an open newtral. Anyways not a bad spot to chek first.