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#76478 - 02/09/01 05:15 PM ISO-Grnd or ISO-circuit
sparky Offline
Member

Registered: 10/18/00
Posts: 5545
I'm always getting calls from people who want to plug thier new computer in, and can't decide into what.
I've called the maker's tech support many times, with mixed results.

Most want grounding, some will ask for a GFI to replace a 2-wire receptacle, a few want a dedicated circuit,very few want an Iso-ground. On the bizzar side,one chain i service insists on iso-grounds to the closest sub-panel ( I really think that guy just likes to walk around saying "ISO-Grounds") , and i did have an individual insist on a seperate ground rod some years ago.

Enter the UPS & or Power conditioner man, and you can apparently throw out that last paragraph.

It's my sense that there is a little less hoo-haa on the subject, now that computers are more refined, and cost less than they used to.

My Q is how do the rest of you guys in the field deal with this???

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2014 / 2011 NEC & Related Books and Study Guides
#76479 - 02/09/01 10:22 PM Re: ISO-Grnd or ISO-circuit
Scott35 Offline

Broom Pusher and
Member

Registered: 10/19/00
Posts: 2724
Loc: Anaheim, CA. USA
Sparky,

You've touched on a subject that I have some passion for, many ideas, quite a bit of designing around, studied and given design consultations to other ECs on.

I must warn you first off that my replies will definitely be long, in order to fully explain stuff.

With this in mind, would you and everyone else in this forum mind if I participate in this thread

Let me know, and if yes, I'll begin replies.


Scott "S.E.T."
_________________________
Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!

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#76480 - 02/10/01 04:30 AM Re: ISO-Grnd or ISO-circuit
sparky Offline
Member

Registered: 10/18/00
Posts: 5545
Scott, go for it !
please keep my 3-sylable limit in mind...

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#76481 - 02/10/01 04:56 AM Re: ISO-Grnd or ISO-circuit
sparky Offline
Member

Registered: 10/18/00
Posts: 5545
Just a thought to add, grounding seems to be one of the hardest concepts in this trade.

I see NEC articles hashed out , many ending at the "theory" angle.

It appears as if we as a trade lack certain fundamentals pertinent to grounding.


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#76482 - 02/10/01 05:34 AM Re: ISO-Grnd or ISO-circuit
Bill Addiss Offline
Member

Registered: 10/07/00
Posts: 4196
Loc: NY, USA
Sparky,

I think that We, "as a trade", I mean the guys in the trenches may have a better grasp on the fundamentals of gounding than the "Theorists" that specify IG and mean a grounding rod alone and no bonding of the neutral in a 3phase Y transformer. They must teach that in MIS school, I have no Idea where they get that from.

Scott, maybe you, as an 'EE type' can give us some insight into this rationale?

Bill

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#76483 - 02/10/01 06:11 AM Re: ISO-Grnd or ISO-circuit
Tom Offline
Member

Registered: 01/01/01
Posts: 1069
Loc: Shinnston, WV USA
I'm interested in what Scott has to say.

It is my experiance that 99.9999% of electronic equipment does not need isolated grounding.

75% of the isolated ground receptacles & circuits that I've seen are a code violation. The worst being the one's that involve a ground rod that is not bonded to the electrical systems ground.

The best book I've ever read on grounding is "Soares Book on Grounding."
Tom
_________________________
Few things are harder to put up with than the annoyance of a good example.

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#76484 - 02/10/01 09:37 AM Re: ISO-Grnd or ISO-circuit
resqcapt19 Offline
Member

Registered: 11/10/00
Posts: 2209
Loc: IL
I think that the reason there are so many problems with "grounding" is the choice of the word itself. 99% of what we call "grounding" is really bonding. By using the word "grounding" many people in the trade automatically start to think about a connection to earth. The word grounding should be reserved for the grounding electode system and grounding electrode conductor, everything beyond that is bonding.
Don(resqcapt19)
_________________________
Don(resqcapt19)

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#76485 - 02/10/01 10:17 AM Re: ISO-Grnd or ISO-circuit
sparky Offline
Member

Registered: 10/18/00
Posts: 5545
Good points, i got Soares a while back, it is a very understandable book and relavant to specific articles within 250
I'm a highlighter guy, so it now looks like my kids got to it...

Maybe some of the confusion is generated by the "theorists" , or maybe the terminology is simply flawed..????

[This message has been edited by sparky (edited 02-10-2001).]

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#76486 - 02/10/01 04:11 PM Re: ISO-Grnd or ISO-circuit
sparky66wv Offline
Member

Registered: 11/17/00
Posts: 2339
Loc: West Virginia
Got a troubleshooting call myself from a local pharmacist. One of their computers is crashing and the 'puter guru insists that it must be a power quality problem.

I don't have an oscilloscope, so bear with me here.

The voltages fluctuate normally between 119 and 121 volts, but occasionally will drop suddenly to 114 and build back up. I realize that the voltages are within "normal" ranges, but does the sudden drop point to anything? Nothing that we know of seems to correlate with the voltage drop by a machine turning on automatically, etc.

Checking the current was more bizarre... it fluctuated rapidly between 3 and 15 amps with every imaginable number randomly appearing between. The computers, routers, hubs and printers were on but idle at this time.

All other circuits in the 120/208V 3 phase panel showed normal fluctuations in voltage and current. The voltage was steady on the questionable circuit on the line side of the breaker, but fluctuated as described above at the receptacles.

Would ISO grounds, isolating the neutrals from 4-wire "networks" to each leg having it's own neutral, and/or UPS (or line conditioners) help in this circumstance?
_________________________
-Virgil
Residential/Commercial Inspector
5 Star Inspections
Member IAEI

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#76487 - 02/11/01 08:35 AM Re: ISO-Grnd or ISO-circuit
sparky66wv Offline
Member

Registered: 11/17/00
Posts: 2339
Loc: West Virginia
I'm moving my questions over to "Power Quality Primer"... I should have stopped there first!
_________________________
-Virgil
Residential/Commercial Inspector
5 Star Inspections
Member IAEI

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