Isolated ground

Status
Not open for further replies.
Jim W in Tampa

Jim W in Tampa

Senior Member
Location
Tampa Florida
How can one deal with a isolated ground in typical modulor cubicals where an isolated ground is not available .Power pole has wiring for one but we do not have it available.There are 2 other normal outlets available per cubicle space.
 
Just hook the grounding conductor for the isolated circuit up to the equipment grounding conductor for the supply circuit that you ran to the cubical. The code does not require that this grounding conductor remain isolated back to the point of the main or system bonding jumper.
Don
 
I agree with Don.
If you were to not provide a supply to those receptacles, I foresee a call from the customer telling you that some of the receptacles are not working. Then I can see you trying to explain to them why you may not have terminated them...
 
might want to take a peek at 250.146 (D) and see if it applies to you.

In addition, I would check my specs or notes if this is new construction to see if engineer spec'd it.
 
dereckbc said:
If it were spec'd, he probable wouldn't need to ask any questions.
Click to expand...

Sorry, I don't follow your logic.

jim in tampa said:
How can one deal with a isolated ground in typical modulor cubicals where an isolated ground is not available .Power pole has wiring for one but we do not have it available.There are 2 other normal outlets available per cubicle space.
Click to expand...

The way I read this, ( and I could be wrong!:D ) he is asking how to get an isolated ground back to the receptacles for the cubicles. It is available at the power source, but not at the cubicle location. So he has some reason for wanting to get the isolated ground to the cubicle. Spec'd or otherwise, that is why he would need to be asking the questions - to have an isolated ground at the cubicle.


don_resqcapt19 said:
Quote:
might want to take a peek at 250.146 (D) and see if it applies to you.
I don't see any requirement there that would change anything.
Click to expand...

" The receptacle grounding terminal shall be grounded by an insulated equipment grounding conductor run with the circuit conductors. This grounding conductor shall be permitted to pass through one or more panelboards without connection to the panelboard grounding terminal as permitted in 408.40, Exception, so as to terminate within the same building or structure directly at the equipment grounding conductor terminal of the applicable derived system or service."


don_resqcapt19 said:
Just hook the grounding conductor for the isolated circuit up to the equipment grounding conductor for the supply circuit that you ran to the cubical. The code does not require that this grounding conductor remain isolated back to the point of the main or system bonding jumper.
Click to expand...

"so as to terminate within the same building or structure directly at the equipment grounding conductor terminal of the applicable derived system or service."


What am I missing????

( Sorry for the editing. I was having trouble with the quotes.)
 
Last edited:
Don

inspector23 said:
"so as to terminate within the same building or structure directly at the equipment grounding conductor terminal of the applicable derived system or service."
Click to expand...

I don't agree with 23's interpretation either but we have a few towns around me that apply it that way.

They feel if I have an IG outlet installed it must run back to XO, MBJ etc.

23, considering the NEC does not require IGs it only allows them, I am at a loss to understand why it is an inspectors business where it ends as long as it is terminated to an EGC at some point.
 
i never did understand the purpose of an ig, its redundant. if done properly it terminates at the xfrmer, the same place as all the other grounds, so imo its not really isolated. maybe im wrong and if i am please school me, but a ground is a ground is a ground.
 
iwire said:
Don

23, considering the NEC does not require IGs it only allows them, I am at a loss to understand why it is an inspectors business where it ends as long as it is terminated to an EGC at some point.
Click to expand...



The NEC does not require them, true. The first sentence of the code section states "Were required etc... That is exactly why I originally said to the OP to take a peek at the code section and see if it did apply to his situation. It could not be determined from the OP.

However, if it is deemed necessary and installed, the last sentence of the code section does have requirements where the IG ends up being terminated.
 
inspector23 said:
However, if it is deemed necessary and installed, the last sentence of the code section does have requirements where the IG ends up being terminated.
Click to expand...

That is an interesting interpretation.

I assume all the contractors you inspect run a single conductor from the receptacle grounding terminal directly to the XO or MBJ?

That must be a mess of 12 AWGs at those bonding points.:D
 
iwire said:
That is an interesting interpretation.

I assume all the contractors you inspect run a single conductor from the receptacle grounding terminal directly to the XO or MBJ?

That must be a mess of 12 AWGs at those bonding points.:D
Click to expand...

Nah, we just have 'em terminate a 500 KCmil at the XO and drop off a strand to each receptacle!:grin:

Seriously, they keep the IG's separate from the equipment grounds. Same conduit. They wire nut the IG's together and pigtail at the receptacles, same way they do the EG's (obviously the IG is not connected to the box!:roll: ) They have one separate home run back to the XO or MBJ.
 
Last edited:
inspector23 said:
Same conduit. They wire nut the IG's together and pigtail at the receptacles, same way they do the EG's (obviously the IG is not connected to the box!:roll: ) They have one separate home run back to the XO or MBJ.
Click to expand...

By your interpretation that is a violation as the conductor must run directly from the receptacle to the XO.
 
iwire said:
By your interpretation that is a violation as the conductor must run directly from the receptacle to the XO.
Click to expand...

The word "directly", in our jurisdiction, is interpreted to mean connected only to Ig's "directly", not to any EG's. Sorry, should have clarified that in previous post. :cool:
 
on all the jobs ive been on that spec igs you will have an ig bar in your panel,isolated from the can. more like an extra neutral bar, then from there back to the xfrmer. but again its completly redundant,but if thats what they pay for thats what they get.
 
inspector23 said:
The word "directly", in our jurisdiction, is interpreted to mean connected only to Ig's "directly", not to any EG's. Sorry, should have clarified that in previous post. :cool:
Click to expand...

I don't see any of that in the NEC.

It sounds to me more like your area is reading things into the NEC that are not there.

Consider what the NECs stated purpose is.

Practical Safe Guarding 90.1(A)

Can you point to an electrical hazard created by connecting the IG conductor to the EGC at the first panel instead of traveling onto the XO?

Then take a look at 90.1(B) Adequacy and 90.1(C)Intention.

My point is that IMO your area is treading into performance requirements.

JMO :)
 
mattsilkwood said:
on all the jobs ive been on that spec igs you will have an ig bar in your panel,isolated from the can. more like an extra neutral bar, then from there back to the xfrmer. but again its completly redundant,but if thats what they pay for thats what they get.
Click to expand...

Matt I agree, if they payed for it I do it. :)
 
iwire said:
I don't see any of that in the NEC.


Consider what the NECs stated purpose is.

Practical Safe Guarding 90.1(A)

Can you point to an electrical hazard created by connecting the IG conductor to the EGC at the first panel instead of traveling onto the XO?

Then take a look at 90.1(B) Adequacy and 90.1(C)Intention.

My point is that IMO your area is treading into performance requirements.

JMO :)
Click to expand...

I see your point. I cannot point to an specific electrical hazard, other than the interference issue. ( and you could easily debate if an interference issue is even an electrical hazard. )

But the section begins "Where required for reduction of electrical noise(electromagnetic interference) on the grounding circuit.....". In other words, this section only applies if you have determined a need for a specific issue.

In that sense, our position is we are "practical safe guarding", protecting the (argueably) electrical hazard, and providing provisions that are considered necessary for safety ( Adequacy) when - AND ONLY WHEN - you are required to use section 250.146(D)

We do not decide when it is required. The engineer or installer is in effect "designing" it when they decide to use IG's. Since the section is only used when required, again we are not designing a specification (intention), rather seeking compliance with the section once it is designed by someone else.:)
 
Last edited:
Ok my soulution was simple.I told the (non electrician installer) that his number 3 receptacles ,will not work and i refuse to connect them to the c phase.We seem to get into this often i end up with gray,pink and green with yellow.I have supplied all 3 phases and if he inserts a number 3 without that orange triangle it will work or he can install another number 1 or 2 (we must keep it at this level as they no speaka the english)Do i think i got thru NO.As to specs i am a month into this job with no real prints.Everything has been a nightmare and yes it actually has effected my sleep.I tried my best to get him to understand why i refuse to feed them.Gladly will if someone says they will pay the extra for what is totally stupid.6 cubicles sharing 1 IG just what good is that over shaing a simple ground ?Dont try to save my face ,if i missed something tell me.Welcome to cuba
 
Last edited:
Status
Not open for further replies.
Top