More IG nonsense

[mbrooke]

IOW, where the IG remains isolated all the way back to the main or system bonding jumper, where the equipment grounding system originates, the more stable the IG reference is... but who runs the branch circuit IG all the way back to the main.

Only a select few who want a code complaint true IG.

It's usually just to the local panel then a feeder IG back to the main... so any 'noise' contributed by the branch equipment is 'looped' at the local level anyway.

IG amounts to an esoteric system and just how esoteric the designer wants to be.

And it might be enough- or it might not be enough to satisfy power quality requirements. The blunt truth is that most IGs are not real IGs, but rather feel goods or dangerous home brewed concoctions. Retail is a perfect example- techs feel the equipment is protected, but come reality its often just an orange special wired like a regular receptacle.


Manufacturers know that most IGs are a joke, and even where a true IG exists as soon as you interconnect stuff or it touches a typical rack it ends up being grounded through the buildings regular grounding system one way or another. As a result manufacturers are designing equipment that does not give a hoot what type of ground loops or ground voltages are present.

 

[GoldDigger]

Even if the house wiring implements NEC required earthing and bonding, the whole system can pick up voltages of all sorts courtesy of the POCO Multiply Grounded Neutral (MGN).
And those voltages can be different from the voltage on an isolated earth electrode.

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[mbrooke]

Even if the house wiring implements NEC required earthing and bonding, the whole system can pick up voltages of all sorts courtesy of the POCO Multiply Grounded Neutral (MGN).
And those voltages can be different from the voltage on an isolated earth electrode.

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Very true- but technically when you bond pipes and building steal (in commercial), you mask the potential relative to the EGCs because now everything is at 2 volts relative to remote earth, but zero volts to other bonded objects.

 

[kwired]

IMO, IG circuits are so misconceived. I even remember back in the 70's, seeing electricians actually changing EMT over to PVC at the Panel thinking they were "isolating" the ground!!
I've seen electricians pull in 2 - green wires, 1 for EGC and 1 for IG!!
After all, most of us already pull in an isolated ground in conduit calling it an EGC. When used properly, this EGC can easily be used as a IG conductor.
Thoughts?

The whole concept of "isolated grounding" is to avoid potential "loops" in the grounding conductor(s)/ other grounded components. This is best accomplished by complete isolation from other conductive paths other then at an origin point - typically at the service equipment. That is why you may see two EGC pulled, one is for bonding usual equipment, one is for the IG of the equipment you wanted the IG for.

That isolation is compromised though even if you did truly isolate an EGC all the way to the IG receptacle if you plug in something that has a metal frame bonded to the IG in the supply cord and that frame is sitting on some other bonded object, or maybe a communications cable shield is bonded to the frame as well as some other "grounded" object, now you have additional paths you were trying to avoid in the first place.