Isolated Ground Circuit

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Little Bill

Little Bill

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I know little about the "voo-doo" of these type circuits, but enough to know that I don't believe they accomplish anything. With that said, I've been asked to bid on a job that calls for some isolated ground receptacles.

My question is can more than one isolated ground be on the same circuit?
If so, how do you run from one receptacle to the rest?
If some receptacles are in a separate room (same building) can you jump over to the other room to pick up those receptacles?

Is it common when using cable (MC or NM) to re-identify one of the ungrounded conductors for the isolated ground?
 
We would use IG MC cable, it will have a green and a green with yellow along with the circuit conductors.

I am not sure what you mean by 'jump over' the IG must run with the circuit conductors, back to the panel they originate from and ideally back to the bonding point at the service or SDS that supplies the circuit.
 
Little Bill said:
My question is can more than one isolated ground be on the same circuit?
If so, how do you run from one receptacle to the rest?
If some receptacles are in a separate room (same building) can you jump over to the other room to pick up those receptacles?
Click to expand...

An IG is not one wire. Basically it's the same as a regular EGC it's just not pig tailed to any metal junction boxes or any sub-panel EGC buss bars, kinda like getting in the car pool lane on the freeway while all the other cars are stuck in that stop and go traffic.

A lot of houses have isolated grounds in them by nature of the wiring methods. If you use NM and PVC boxes for a kitchen counter top circuit you have a IG circuit.
 
iwire said:
We would use IG MC cable, it will have a green and a green with yellow along with the circuit conductors.

I am not sure what you mean by 'jump over' the IG must run with the circuit conductors, back to the panel they originate from and ideally back to the bonding point at the service or SDS that supplies the circuit.
Click to expand...

I meant run the cable over to another room. I know the EGC runs with the other conductors.

ActionDave said:
An IG is not one wire. Basically it's the same as a regular EGC it's just not pig tailed to any metal junction boxes or any sub-panel EGC buss bars, kinda like getting in the car pool lane on the freeway while all the other cars are stuck in that stop and go traffic.

A lot of houses have isolated grounds in them by nature of the wiring methods. If you use NM and PVC boxes for a kitchen counter top circuit you have a IG circuit.
Click to expand...

I understand what an IG is I just didn't know if you can have multiple receptacles on one circuit and if that circuit could be in more than one room.
 
Little Bill said:
I meant run the cable over to another room. I know the EGC runs with the other conductors.
Click to expand...
Yes you can do that.

I understand what an IG is I just didn't know if you can have multiple receptacles on one circuit and if that circuit could be in more than one room.
Click to expand...
Yes you can do that.

Probably the easiest way is to use that special mc that iwire mentioned, it has two greens in it. I have used 12-3 mc, stripped the red insulation off at the connector for the regular egc and used the green for the isolated ground in a pinch.
 
ActionDave said:
A lot of houses have isolated grounds in them by nature of the wiring methods. If you use NM and PVC boxes for a kitchen counter top circuit you have a IG circuit.
Click to expand...

But with just a quick surface thought (no research) I don't think you could put an IG receptacle on the circuit and it would only be an IG if the house had only one panel and the neutral and ground bond point was in that panel. Regarding the IG receptacle, I guess you could use one, but only if you used non-metallic screws for a plastic or nylon cover plate, technically, because the yoke and the screw could become energized similar to the old light switches with no ground screw.
 
Little Bill said:
I understand what an IG is I just didn't know if you can have multiple receptacles on one circuit and if that circuit could be in more than one room.
Click to expand...

As you stated, I believe IG's are basically voodoo. As such, I suggest you don't overthink it. I think of the IG ground wiring as more similar to another separate neutral, common or grounded conductor (your choice of the term) system than another ground wire, with the one exception that it can "share" circuits of the same phase as well as circuits from separate phases. When you think of it this way, you can see that basically you need one and only one IG with proper current carrying capacity, in any physical "branch" of an electrical distribution run. Does that make sense?
 
HCF cable would work for circuit utilizing an isolated ground as well - in other then health care areas anyway.
 
ActionDave said:
An IG is not one wire. Basically it's the same as a regular EGC it's just not pig tailed to any metal junction boxes or any sub-panel EGC buss bars, kinda like getting in the car pool lane on the freeway while all the other cars are stuck in that stop and go traffic.

A lot of houses have isolated grounds in them by nature of the wiring methods. If you use NM and PVC boxes for a kitchen counter top circuit you have a IG circuit.
Click to expand...
I thought the isolated ground devices the green screw wasn't connected to the device yoke, wouldn't be the case in the kitchen, right?
 
GerryB said:
I thought the isolated ground devices the green screw wasn't connected to the device yoke, wouldn't be the case in the kitchen, right?
Click to expand...
He's talking about regular receptacles, NM wiring, plastic boxes, wood framing, i.e. everything non-conductive other than the wiring... which makes the ground isolated.
 
GerryB said:
I thought the isolated ground devices the green screw wasn't connected to the device yoke, wouldn't be the case in the kitchen, right?
Click to expand...

That's correct, but if you used an NM cable with a plastic box and standard device the EGC would be isolated because it's only connected to the device.
 
IG Rec are only part of the wiring. If you have multiple IG rec. the device grounds are put on an isolated ground bar then grounded to EGC. This is very popular on computer circuits around super computers.


Sent from my iPhone using Tapatalk
 
No magic

No magic

It's not voodoo, it's basic electrical/electronic theory, i.e., Kirchoff's law:

At any node in an electrical circuit, the sum of currents flowing into that node is equal to the sum of currents flowing out of that node.

Unless the single-point ground system utilizing the isolated grounding receptacles is effected as an entire system then, yes, it is not going to do much good in eliminating ground loops and/or circulating currents. It really doesn't do much for most residential installs unless equipment with a sensitivity is installed.

IEEE Green and Emerald have great explanations of this.
 
ActionDave said:
. I have used 12-3 mc, stripped the red insulation off at the connector for the regular egc and used the green for the isolated ground in a pinch.
Click to expand...

What!!!

Don't you know that the lands will fall, the seas will rise, and the heavens will be torn asunder for such an action?

That conductor is smaller than #4 and all laws of physics are thrown out the window. The NEC says so.:D
 
jumper said:
What!!!

Don't you know that the lands will fall, the seas will rise, and the heavens will be torn asunder for such an action?

That conductor is smaller than #4 and all laws of physics are thrown out the window. The NEC says so.:D
Click to expand...
Only if you put tape on the insulation. That will cause all your children to be born clothes-less and money-less. I was careful and got rid of the insulation. It's the only safe thing to do.
 
chris kennedy said:
Your kids were born with cloths on? :blink:
Click to expand...
I don't know, they could have been. To tell the truth my goal was to stay as far away from the action as I could. Stressful situations are bad enough; combine it with bodily fluids and unchecked emotion and all I wanted was out.... Nobody there would let me out of the room so I stayed at the head of the bed holding my wife's hand.
 
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