# Isolated ground circuits?



## erics37 (May 7, 2009)

ohmslaw said:


> Isolated ground circuits now have to be ran in the some conduit with only isolated grounds. Is this in the code or is it just what the client wants? Also if you have three 20 amp ig circuits how many grounds per circuit? Is it 1 #10 for the ig outlet and a #12 for the box? If you have multiple ig outlets on same circuit can the box and or device ground be shared? Thanks for any input.


The way I've always done IG circuits is to just pull two EGCs... one of them green, the other green with a yellow stripe. The green one performs all the raceway/box bonding, the green with yellow stripe goes straight to the IG receptacle terminal. I've put several receptacles on one circuit, nothing wrong with that.

Alternatively, if you're using metallic raceway suitable as an EGC then you can use that for your non-IG EGC. If you're in a health care facility, though, there might be some additional considerations.

And really, if the system is properly wired to begin with then IG stuff is just a waste of money.


----------



## BBQ (Nov 16, 2010)

None of it is NEC, it is all choice.

Ideally all the IG conductors would run back to the system bonding point, either the XO at the transformer or the bonding point at the service entrance.

But ....... if you had thirty 20 amp IG circuits you are not really going to run thirty 12 AWGs back to the bonding point. Typically you will collect the IGs together at a panel with an IG grounding bar and run just run one IG back to the bond point.


----------



## ohmslaw (Apr 2, 2011)

Doesn't the egc for the receptacle have to be #10 or is it only if they asked for it that way on the prints?


----------



## BBQ (Nov 16, 2010)

erics37 said:


> And really, if the system is properly wired to begin with then IG stuff is just a waste of money.


In some cases IGs can help with equipment that have communication circuits between them that carry the ground between them. Like a coax cable does, or audio inputs, or RS-232 data circuits etc.

But for equipment connected via fiber or Ethernet IGs do not do a thing.


----------



## BBQ (Nov 16, 2010)

ohmslaw said:


> Doesn't the egc for the receptacle have to be #10 or is it only if they asked for it that way on the prints?


Code wise only if the circuit conductors are 10 AWG but the specifications can ask for anything.


----------



## erics37 (May 7, 2009)

ohmslaw said:


> Doesn't the egc for the receptacle have to be #10 or is it only if they asked for it that way on the prints?


The function of the IG EGC is the same as if you had a regular circuit. It'd be minimum sized per table 250.122 based on the overcurrent device.



BBQ said:


> In some cases IGs can help between equipment that have communication circuits between them that carry the ground between them. Like a coax cable does, or audio inputs, or RS-232 data circuits etc.
> 
> But for equipment connected via fiber or Ethernet IGs do not do a thing.


Gotcha, makes sense :thumbup:


----------



## ohmslaw (Apr 2, 2011)

Thanks guys for your help. The print I have says all grounds wired directly to the receptacle must be #10. I didn't know if that was a code thing or just a spec. I will parallel the grounds on the same circuit, box and rec. About the conduits though is that another spec or code? Meaning ig with ig only in same conduit and not to mix with non ig.


----------



## TOOL_5150 (Aug 27, 2007)

BBQ said:


> In some cases IGs can help with equipment that have communication circuits between them that carry the ground between them. Like a coax cable does, or audio inputs, or RS-232 data circuits etc.
> 
> But for equipment connected via fiber or Ethernet IGs do not do a thing.


Ethernet can have a ground/shield. :thumbsup:

~Matt


----------



## BBQ (Nov 16, 2010)

TOOL_5150 said:


> Ethernet can have a ground/shield. :thumbsup:
> 
> ~Matt


I will certainly take your word for it.

How often do you see it out in the wild?


----------



## BBQ (Nov 16, 2010)

ohmslaw said:


> Thanks guys for your help. The print I have says all grounds wired directly to the receptacle must be #10. I didn't know if that was a code thing or just a spec.


Spec




> I will parallel the grounds on the same circuit, box and rec.


I am not sure what you mean.





> About the conduits though is that another spec or code? Meaning ig with ig only in same conduit and not to mix with non ig.


Just spec.


----------



## TOOL_5150 (Aug 27, 2007)

BBQ said:


> I will certainly take your word for it.
> 
> How often do you see it out in the wild?


Not often at all.. really the only time STP is necessary is in high emf areas and operating at gigabit speed.


~Matt


----------



## BBQ (Nov 16, 2010)

TOOL_5150 said:


> Not often at all.. really the only time STP is necessary is in high emf areas and operating at gigabit speed.
> 
> 
> ~Matt





Is the shield tied in at both ends or only one?


----------



## ohmslaw (Apr 2, 2011)

BBQ said:


> Spec
> 
> I am not sure what you mean.
> 
> Just spec.


Meant rec grounds tied with each other and box grounds the same on the same circuit.


----------



## Speedskater (Oct 2, 2009)

BBQ said:


> Is the shield tied in at both ends or only one?


Interference wise, connecting the shield at both ends is better.
But often the grounds are at different potentials, so lots of current would flow through the shield if both ends are connected.
If the send (transmitt) end is powered that's the end to ground.
Of course any co-ax must be connected at both ends.


----------



## Speedskater (Oct 2, 2009)

In general, the Hot, Neutral and Isolated Ground wires should have a one to one to one relationship to each other and be in close proximity to each other all the way from the panel-board to the out. They must all be in the same conduit.

This means that if you split the Hot and Neutral in a junction box, that's the point you split the IG.


----------



## knowshorts (Jan 9, 2009)

I love profit outlets. The racks are usually anchored to the ground. Even though it is not a true ground, you can get a reading. The grounding conductor in a lot of rack mounted equipment is bonded to the case of the equipment and as soon as it is mounted to the cabinet/rack the IG is lost.


----------

