Isolated Ground

[superdave02]

Good afternoon. Can a three gang box contain (3) 120v 20a isolated ground receptacles, three separate circuits, and one isolated ground conductor back to the isolated ground bar?

 

[Barney B]

Assuming all conductors to be #12 AWG, a standard 3-gang metal device box with not less than 2¼" depth would be required if the IG EGC is the only wire-type EGC present.

 

[superdave02]

Assuming all conductors to be #12 AWG, a standard 3-gang metal device box with not less than 2¼" depth would be required if the IG EGC is the only wire-type EGC present.

That did not answer the question. Can three 120v circuit use one isolated ground wire if in the same box?

 

[don_resqcapt19]

That did not answer the question. Can three 120v circuit use one isolated ground wire if in the same box?

The code does not care, but most specs will require each circuit to have its own equipment grounding conductor.

 

[superdave02]

The code does not care, but most specs will require each circuit to have its own equipment grounding conductor.

No specs, NEC, isolated grounding conductor NOT EGC

 

[curt swartz]

No specs, NEC, isolated grounding conductor NOT EGC

If no spec's why install an IG at all. NEC never requires it. Its 100% usless for today's equipment anyway.

 

[LarryFine]

Yes, Dave, it is permitted. Sometimes, an isolated bus is installed in a sub-panel, and a single IG conductor run from there back to the MBJ location.

 

[petersonra]

That did not answer the question. Can three 120v circuit use one isolated ground wire if in the same box?

I don't think they are even required to be in the same box to use the same wire as an IG.

 

[infinity]

No specs, NEC, isolated grounding conductor NOT EGC

Then I would pull a single IG conductor. The NEC doesn't care how you do it so it's a design issue.

 

[don_resqcapt19]

No specs, NEC, isolated grounding conductor NOT EGC

The isolated grounding conductor is the EGC for the equipment that is plugged into the receptacle.

As others have said, the NEC never requires an isolated grounding conductor. The only requirement in the NEC is that the isolated grounding conductor be an effective fault clearing path. In you case, any combination of one to three isolated grounding conductors will be code compliant. If there are no specs, why are you even installing an isolated grounding receptacle?

 

[tom baker]

Typically for IG ckts I would post a picture of a teddy bear.
But there are a few applications where they seem to be effective, audio sound for one

 

[Strathead]

The code does not care, but most specs will require each circuit to have its own equipment grounding conductor.

I don't really agree with this. I have seen where specs do require this, more often in audio applications, but I have seen many times where there was no such requirement. Also, it is unnecessary in most cases where an isolated ground is actually a valid concern (edited this where I said called for), IMO.

 

[don_resqcapt19]

I don't really agree with this. I have seen where specs do require this, more often in audio applications, but I have seen many times where there was no such requirement. Also, it is unnecessary in most cases where an isolated ground is actually a valid concern (edited this where I said called for), IMO.

There is no code reason, and very likely no technical reason to ever use an isolated ground system.

When I said most specs, I was saying that wherever I had a project specification that required an isolated ground, it required a separate isolated grounding conductor for each circuit. Have not seen such a specification in a very long time.

It is very simply a design issue and the only code concern is that the equipment connected have an effective ground fault clearing path. That path can either be a standard equipment grounding conductor, or an isolated equipment grounding conductor.

The term "isolated equipment grounding conductor" probably should be replaced with "insulated equipment grounding conductor" as it is not "isolated" from the electrical system. It is insulated so that the only connection to the electrical system is at the equipment and at the location of the main or system bonding jumper whichever applies.

 

[Speedskater]

Many audio application "isolated ground" systems are poorly done and are a negative on audio performance.
Ideally the EGC path length from component to component should be as short as practicable.

 

[petersonra]

Many audio application "isolated ground" systems are poorly done and are a negative on audio performance.
Ideally the EGC path length from component to component should be as short as practicable.

Ideally, the signal maybe should not be referenced to ground.

 

[4-20mA]

Many moons ago I wired up a dollar general and the POS's needed dedicated isolated grounds for harmonic issues. So computers or like the other guy said audio (electronics) run these grounds a lot. In hospitals we used to have orange recepts for Isolated grounds too I think it was.

Isolated just means to its own seperate ground iirc.

 

[4-20mA]

Many audio application "isolated ground" systems are poorly done and are a negative on audio performance.
Ideally the EGC path length from component to component should be as short as practicable.

Insert ground loop isolators... lol... old school ha

 

[tom baker]

In hospitals we used to have orange recepts for Isolated grounds too I think it was.