Isolated Ground Identification

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Wraprail

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Greeting to all,

Being a noob here let me start with a happy hello from Sin City
I left a brief bio in my profile which I know is worthless info
but trying to start off on the right foot so there you go.
Now to my first request of you all.
I am working on a fairly large project inside a major strip property
where My position is that of a plain old pipe mechanic/fish tape puller
who only speaks english in a spanish speaking world. After running some
M/C cable I got a glimpse of the plans and noticed the letters IG all around
this area (photo attached) and I am assuming this means Isolated Ground?
My question is does this require a separate designated iso ground panel?
We have no such panel. Can a regular old (new) installed panel have isolated
ground circuts inside and what is required? Besides the obvious extra wire and
devices. None has been installed and we are all covered up so o'm justwondering
if I should blow the lid on this or if anybody really cares
thanks in advance.
Peace out.
 
The NEC doesn't really care if you use an IG system or not as long as there is an EGC with the branch circuits. Since this is a design issue it's up to the designer to tell you if a non-IG system is acceptable. For the most part IG systems are no longer used because they're not worth much.
 
I actually have an answer, and it's right

I actually have an answer, and it's right

An isolated ground is a separate grounding conductor from your equipment ( boxes and conduit, equipment) it requires a completely separate cable from an insulated ground bar ( separated from panel like qa neutral bar.) to your main service "bullseye" connection where your neutral and ground are bonded. Sorry you wasted some mc and some time, but those boxes should have both. One green and one green with a yellow stripe. Your equipment ground goes to your boxes and the isolated gets connected to the recep. to prevent fault currents from damaging sensitive equipment. The recepticles are orange and have a triangle to i.d. them.. Theory stating that current travel the path of least resistance, I think the isolated ground should be a smaller conductor than your equipment ground. My buddies brought it up a long time ago that it's still bonded at the same place, but the smaller wire should not get current riding it with another less resistive path available.Hope you haven't pulled your feeders in yet.
 
Tom welcome to the forum.


Tom the lectrician said:
An isolated ground is a separate grounding conductor from your equipment ( boxes and conduit, equipment) it requires a completely separate cable from an insulated ground bar ( separated from panel like qa neutral bar.) to your main service "bullseye" connection where your neutral and ground are bonded.
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The service or the bond at a separately derived system. Running the IG back to the bonding point is ideal but not an NEC requirement, the IG can connect to the normal EGC at any point the designer chooses.



to prevent fault currents from damaging sensitive equipment.
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I do not believe that is it, my understanding is the IG helps keep prevent placing current on grounded signal wires between equipment such as the shield in R232 combinations or say the shield in a coax cable.

The receptacles are orange and have a triangle to i.d. them..
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Orange is common but not a requirement, you can get them in most colors.

Theory stating that current travel the path of least resistance, I think the isolated ground should be a smaller conductor than your equipment ground.
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Electricity takes all available paths and using a smaller conductor on the IG would not change that. It would also be an NEC violation. The IG has to follow the same sizing rules as any EGC.



but the smaller wire should not get current riding it with another less resistive path available.
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That is untrue.


The current will not just take the easy path, it will take both paths proportionally to the impedance of the paths.
 
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No I'm pretty sure it's in the specs of a plan to run it back to your service bond
.Otherwise it wouldn't be isolated at all. That would be pointless. I haven't done this in about 8 years since building gas stations buy I will suggest...always read the specs in advance to a job. Some places require o lya few circuits in a pipe, and so on. You can fail inspections if your inspector is hip to those IG receps and the way it is to be installed. But if it's worth doing once, it's worth doing....And I would check the sizing of those grounding conductors, I'd bet the isolated is smaller gauge, if designed right. Even oversizing the equipment ground would be better if you don't want to have them the same size. Theory says it will and should take the least resistive path to ground. I'd have to trip a breaker with a clamp on it to prove it though.
 
Plus if they didn't have it as a requirement on the job, it wouldn't be on the print. If it's spec'd then only revising and re stamping them would get you out of it. That's the job, bro. Gotta do it how they designed it for their equipment, devices, computers and whatever. It's usually for a p.o.s. system. Like at every retails tore with cash registers, lottery, gas equipment, etc.
 
Tom the lectrician said:
No I'm pretty sure it's in the specs of a plan to run it back to your service bond.
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Or to the source of the SDS supplying the circuits, whichever is closer. In a large Las Vegas project, that's much more likely.

When you get to it though, in most places IG circuits aren't worth the extra copper needed to install them. Sure, some POS systems specify them, but I'll offer that their specs haven't changed in 25 years and the people at the company don't even know why you might want IG. And if they do, they're probably wrong.
 
If the job truly requires IG, check you MC closely. IF the IG requirement was caught early enough in the job the MC supplied may be a type such as MCAP where you can use the internal ground as your IG and the jacket as the standard ground
 
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