independent ground

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What is an "independent ground"? Typically an "IG" is called an isolated ground. Which IMO are a waste of money.
 
Maybe they were usefull back with mainframe computers connected via coax.
With ethernet we have voltage isolation between PCs and I don't feel the IG serves any usefull purpose. Mike Holt states the IG is worthless.
 
Independent Ground? No such thing, did you mean Isolated Ground Receptacle? If so as Tom stated it is an antique 80's technology.
 
sorry guys i did mean isolated , but they are big in retail chains,lowes, walmart, home depot,ect. i recently did a lowes and they go so far as one pipe one circuit with an ig talk about a waste of money!
thats just something to think about the next time you wonder why that new pair of kleins is so expensive
 
mattsilkwood said:
but they are big in retail chains,lowes, walmart, home depot,ect.
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That makes a little more since and I suspect I know why. Could these be used at the POS stations? For whatever reasons the POS equipment still uses signal I/O means that use ground as part of the signal path like RS-232 rather than ethernet. That being the case then they would have to use IGR, especially since all the cable distances would be extreme.
 
mattsilkwood said:
sorry guys i did mean isolated , but they are big in retail chains,lowes, walmart, home depot,ect. i recently did a lowes and they go so far as one pipe one circuit with an ig talk about a waste of money!
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The company for whom I work builds and services all the stores you mentioned, as well as others. As long as the engineers keep spec'ing them, we will keep installing them. Yes, they are a complete waste of time and money.
 
dereckbc said:
That makes a little more since and I suspect I know why. Could these be used at the POS stations? For whatever reasons the POS equipment still uses signal I/O means that use ground as part of the signal path like RS-232 rather than ethernet. That being the case then they would have to use IGR, especially since all the cable distances would be extreme.
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OK, now I have foot in mouth disorder. Is there still a valid use for IG? I was under the impression that it was pretty much useless nowadays.
 
IG isn't actually used to prevent ground loops, because the IG is still tied to the system neutral/ground at the bonding point.

It's really more for minimizing the electrical noise brought into the sensitive equipment via the power cord, by isolating it from the effects of impedance in and/or voltage on the conduit system.
 
peter d said:
OK, now I have foot in mouth disorder. Is there still a valid use for IG? I was under the impression that it was pretty much useless nowadays.
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You didn't stick your foot in your mouth; IG for the most part is a waste of time. The point I was making is most of the Point OF Sales systems still use 80’s technology communications protocol like RS-232.

RS-232 uses an unbalanced signal transmission using ground as a signal path. Modern communications uses balanced signal transmission like Ethernet or optics where ground reference has no meaning.
 
zyhml said:
is there any code required this?
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Okay, not exactly in those words, but my point was that the IG EGC still eventually connects to the system neutral, via some EGC or other, due to the main bonding jumper.

Ideally, for maximum effectiveness (as this IG EGC is allowed to pass through one or more panels on its way to its termination), it is landed where the main bonding jumper is.
 
dereckbc said:
For whatever reasons the POS equipment still uses signal I/O means that use ground as part of the signal path like RS-232 rather than ethernet.
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That has finally seemed to go away with most new POS equipment.

(BTW - In this thread "POS" means Point Of Sale)

More of the equipment is using Cat 5, however we still have a large customer with a certain vendors coupon printer that uses a shielded cable.
 
iwire said:
That has finally seemed to go away with most new POS equipment.

(BTW - In this thread "POS" means Point Of Sale)

More of the equipment is using Cat 5, however we still have a large customer with a certain vendors coupon printer that uses a shielded cable.
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In the past year or so, we have wired (both for power and networking) several POS systems, and they have all been CAT-5 and still specified IG wiring and receptacles.

I comply, of course, because I'll do whatever the customer pays for (legally, of course). The POS people specify IG, and will blame any problems on me if I don't comply.

However, nobody specifies the wiring type, so I use 12-4 MC and strip the red as the non-IG box EGC, and use the green as the IG EGC for the receptacles.
 
LarryFine said:
I comply, of course, because I'll do whatever the customer pays for (legally, of course).
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Same here. :)

The POS people specify IG, and will blame any problems on me if I don't comply.
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I agree, don't want to leave room for finger pointing.

However, nobody specifies the wiring type, so I use 12-4 MC and strip the red as the non-IG box EGC, and use the green as the IG EGC for the receptacles.
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12/3?

Anyway I have done the same thing with the red in the past but feel it almost always violates 250.119(B).

I have switched to IG MC or Hospital grade AC for IG circuits,
 
iwire said:
12/3?
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LOL, yes, that's what I meant. I was recently explaining to one of my guys that rubber cord is the only cable type where the EGC counts in the conductor quantity (as far as I know), and it caused a brain hiccup.
Anyway I have done the same thing with the red in the past but feel it almost always violates 250.119(B).
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It's never been an issue, and I pass 99% of my inspections on the first go-around.
 
LarryFine said:
It's never been an issue, and I pass 99% of my inspections on the first go-around.
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So that means what? :)

It means the inspector did not notice or chooses not to enforce the rules.

It is still a violation and you are really going to be in a tough spot if you run a bunch of these circuits and you suddenly get nailed for it.

To each their own but I don't think we should be recommending that people remark the red to green or bare without pointing out 250.119(B). :)

Price the job based on using IG-MC or Hospital grade AC, both are code compliant ways around using the red even if it means stocking another cable type.
 
I believe that IG was created as a way to "patch" problems caused by improperly installed sub-panels. If the grounds and neutrals are connected together (improperly) in a sub-panel, there will be neutral current on equipment grounding conductors. This is interpreted as "noise". It is allowable to install an IG equipment grounding conductor all the way back to the N-G connection at the main service, thus by-passing much of this "noise". Installing an IG conductor only back to the sub-panel would accomplish little or nothing. In a properly installed electrical system, there would be no improper neutral-ground connections, so there would be no neutral current on the equipment grounding conductors, so IG receptacle would accomplish nothing. It is only on improperly installed systems that they provide any benefit.
 
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