# NM IG cable



## WronGun (Oct 18, 2013)

Has anyone seen an NM type cable with an IG? 

If not would a 12/4 NM with a re-identified IG suffice ? 


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## JoeSparky (Mar 25, 2010)

12/2 Homerun to a main panel in a plastic box is an isolated ground


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## kb1jb1 (Nov 11, 2017)

Are you using it for Isolated Ground receptacles or do you just need an insulated grounding conductor? 
If it is for Isolated Ground receptacles, then I believe you need to use Steel jacket AC cable or the HCFAC type. The reason being some requirements dictate that no magnetic interference affect the conductors or the ground wire. The EGC is totally Isolated between the equipment and the Main service equipment. NM cable and Aluminum jacket does not shield from interference.


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## splatz (May 23, 2015)

WronGun said:


> Has anyone seen an NM type cable with an IG?
> 
> If not would a 12/4 NM with a re-identified IG suffice ?


I didn't think you could re-identify a #12 as an EGC, you can only re-identify #4 or bigger.


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## WronGun (Oct 18, 2013)

Its for a recording studio which I’ve done a couple before. We used an equitech power balancer distribution panel the last couple times. Manufacturer stated 12/2 nm is fine if dedicated and runs back to balancer which is normal since everything is dedicated anyways.

However, as of now this design doesn’t have a balancer instead a dedicated sub for IG studio feeds. I thought it would be nice to have an insulated Ground while using NM. 

The job is a lot easier and quicker with NM and plastic boxes. Nothing is drywall , walls are 12”-18” thick, foam everywhere. NM would be great. 


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## HackWork (Oct 2, 2009)

splatz said:


> I didn't think you could re-identify a #12 as an EGC, you can only re-identify #4 or bigger.


I thought that was only separate conductors, not cables?


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## CoolWill (Jan 5, 2019)

We always used a 12-3 and stripped the red bare to use as the regular ground and the green as the IG. But isolated grounding isn't nearly as important or helpful as eliminating ground loops at the equipment.


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## splatz (May 23, 2015)

HackWork said:


> I thought that was only separate conductors, not cables?


There is an exception for reidentifying white conductors in cables as ungrounded conductors, like for switch loops, but I don't know of anything like that for EGC. I just looked, 250.119.


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## Cow (Jan 16, 2008)

I would just use the usual isolated ground MC....but that's me.


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## WronGun (Oct 18, 2013)

Does an IG need to be insulated ? I don’t think since I’ve done this before per manufacturer. If not a 12/2 would be fine. 

What would be the point of an additional G when everything is NM and plastic. 

MC is fine, I don’t mind it but in this application it’s a big add on, nothing is really traditional and I’ve been asked if any costs could be cut. I think I would myself rather whip it out with NM. It’s easier to deal with in thick heavily insulated walls. 


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## Kevin (Feb 14, 2017)

I would use 3 conductor cable and re-identify the red to green and be done with it....

Sent from my new phone. Autocorrect may have changed stuff.


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## splatz (May 23, 2015)

WronGun said:


> Does an IG need to be insulated ? I don’t think since I’ve done this before per manufacturer. If not a 12/2 would be fine.
> 
> What would be the point of an additional G when everything is NM and plastic.


I think the idea is to not introduce the noise present on the EGC system of the building onto the ground prong of the IG receptacle and then onto the sensitive equipment that gets plugged into that IG receptacle. 

The isolated ground has to be insulated because there still has to be the usual EGC. If it's not insulated, how's it going to be isolated? 

Now I agree that the usual EGC isn't doing much if there's nothing else bonded to it - plastic boxes and plates, no regular non-IG receptacles, lights, switches, etc. on the circuit. But it's still required. 

I don't remember how the rules were re-written that allow you to run a ground wire for two wire circuits with no EGC, maybe you could just add a single conductor for the IG. 

In my experience nobody asks for an isolated ground casually. Somebody's spending a lot of money. Some engineer or other pain in the ass may very well look at it and sharpshoot your work if it isn't 100% by the book. So why **** around trying to squeeze it in between the lines. Go buy some AC with bond wire for the armor and a separate insulated green wire for the IG, made for the purpose, charge accordingly, and be happy


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## CTshockhazard (Aug 28, 2009)

If you do it with dedicated NM runs and plastic boxes, IG receptacles would be a complete waste of $.


If they demand the IG's :wallbash::




> *250.119 Identification of Equipment Grounding Conductors.
> (B) Multiconductor Cable.*
> Where the conditions of maintenance
> and supervision ensure that only qualified persons service
> ...


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## CTshockhazard (Aug 28, 2009)

what


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## CoolWill (Jan 5, 2019)

CTshockhazard said:


> If you do it with dedicated NM runs and plastic boxes, IG receptacles would be a complete waste of $.
> 
> 
> If they demand the IG's :wallbash::


So, just use 12-3 and use the red.


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## five.five-six (Apr 9, 2013)

WronGun said:


> What would be the point of an additional G when everything is NM and plastic.




It’s a noise drain.


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## B-Nabs (Jun 4, 2014)

five.five-six said:


> It’s a noise drain.


Not to be confused with a nose drain









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## five.five-six (Apr 9, 2013)

OMG, I had a friend convince me to use one of those things.... 

SMFH


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## WronGun (Oct 18, 2013)

I’ve used 12/2 in an IG studio. It was an acceptable method by the balancer manufacturer. 

It bonds with the main panels ground, it also has another ground going to rods. 

I don’t know everything about it. They claim
It reduces interference, among other things like not running power parallel to AV lines, etc. 


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## CTshockhazard (Aug 28, 2009)

five.five-six said:


> It’s a noise drain.



I'm by no means an expert, but drains are only connected on one end, hence the name.

The IG in these cases is to mitigate ground loops as most audio equipment also has a connection between the audio "ground" and the chasis.


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## CTshockhazard (Aug 28, 2009)

WronGun said:


> They claim...


:wink: There's several tricks, like keeping all of the audio equipment on one phase, but it's a band-aid for poor power quality, like N/G bonds past the service.


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## WronGun (Oct 18, 2013)

I’m trying to see if this is legal or not? Re-identifying a ground in 12/3. 

I may just figure for green MC and metal boxes. This is a gutted stand-alone commercial building 2 level. It’s not only a studio but the company office. It may just be best to go all MC But, It will be tougher in studio areas. 


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## CoolWill (Jan 5, 2019)

WronGun said:


> I’m trying to see if this is legal or not? Re-identifying a ground in 12/3.
> 
> I may just figure for green MC and metal boxes. This is a gutted stand-alone commercial building 2 level. It’s not only a studio but the company office. It may just be best to go all MC But, It will be tougher in studio areas.
> 
> ...


Yes, it is legal to re-identify a conductor in a cable for the purposes of isolated grounding. The code article was posted last page. 250.119


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