CKT WIRE COUNT

[kbsparky]

If you understand isolated ground each IG receptacle shouldn't share anything. Dedicated hot and neutral to each IG receptacle and the IG conductor goes back to the service entrance, not a sub panel.

Fortunately IG circuits are rarely needed today and are a waste of money.

-Hal

We recently did a project where they specified IG outlets to be mounted on an audio amplifier rack. Problem is, they also required those circuits to be installed in metal conduit.

AS soon as the audio amps were plugged in, the IG was physically connected to the building ground VIA the metal casing of the amps. Complete waste of money and resources.

But it made them feel good to have all those (non-)IG circuits in there!

 

[Alwayslearningelec]

Well, you said 10 "circuits". On a 3? wye system (e.g. 208/120V 3? 4W), the max is 3 hots to each neutral. You could also have 2 hots share a neutral. Obviously you can also have a two-wire circuit with one hot and one neutral. Therefore for 9 circuits the minimum number of neutrals is 3. Adding the 10th hot requires the 4th neutral.

Well explained thanks... Is it different for a single phase system?

 

[Alwayslearningelec]

If you understand isolated ground each IG receptacle shouldn't share anything. Dedicated hot and neutral to each IG receptacle and the IG conductor goes back to the service entrance, not a sub panel.

Fortunately IG circuits are rarely needed today and are a waste of money.

-Hal

So if you have an IG receptacle what wires are required? Hot and IG.... Separate neutral? Thanks

 

[infinity]

Well explained thanks... Is it different for a single phase system?

Yes, you need a minimum of 5 neutrals for 10 circuits.

So if you have an IG receptacle what wires are required? Hot and IG.... Separate neutral? Thanks

You need to clarify what you mean by required, the NEC would not require an IG or a separate neutral.

 

[Smart $]

So if you have an IG receptacle what wires are required? Hot and IG.... Separate neutral? Thanks

You need to clarify what you mean by required, the NEC would not require an IG or a separate neutral.

Short of clarification, I can say that in order to supply a 120V IG receptacle as intended, you must connect a hot, a neutral, and an IG conductor to the receptacle itself. If using a metallic wiring method, there must also be an EGC run with the others, whether it be conduit, sheath, wire, or combination thereof, to bonded the non-current-carrying metallic parts. There is no NEC requirement for a dedicated neutral. There is no NEC requirement that only one receptacle per circuit or IG conductor The NEC doesn't require anything regarding IG receptacles... it only permits an IG conductor to not be bonded to non-current-carrying metallic parts and EGC's amid its run.

 

[Alwayslearningelec]

Short of clarification, I can say that in order to supply a 120V IG receptacle as intended, you must connect a hot, a neutral, and an IG conductor to the receptacle itself. If using a metallic wiring method, there must also be an EGC run with the others, whether it be conduit, sheath, wire, or combination thereof, to bonded the non-current-carrying metallic parts. There is no NEC requirement for a dedicated neutral. There is no NEC requirement that only one receptacle per circuit or IG conductor The NEC doesn't require anything regarding IG receptacles... it only permits an IG conductor to not be bonded to non-current-carrying metallic parts and EGC's amid its run.

Thanks. So (2) IG different circuit would not share a neutral?

 

[Alwayslearningelec]

Yes, you need a minimum of 5 neutrals for 10 circuits.



You need to clarify what you mean by required, the NEC would not require an IG or a separate neutral.

How would you wire an IG receptacle? I'm sure spec/drawing notes would dictate more than likely, correct?

 

[kwired]

How would you wire an IG receptacle? I'm sure spec/drawing notes would dictate more than likely, correct?

Like Smart$ mentioned - the only thing the NEC has to say about IG is that it does not require the IG conductor to be bonded to other enclosures on its way back to source, yet a separate EGC is required to connect to all other non current carrying metal parts, raceways, etc. as one normally would do.

Whether or not separate hots or neutrals are run is not an NEC issue it is a design issue.

 

[Smart $]

Thanks. So (2) IG different circuit would not share a neutral?

Spec's or plans are usually the controlling factor. There is no NEC requirement to share or not.

 

[cdslotz]

All due respect, isn't this electrical wiring 101?

 

[Strathead]

Am I missing something? I have never run more than 1 IG wire in a conduit. The purpose of an IG wire is to provide a 0 volt reference to the voltage system source. Since it only bonds to the source this is how it is accomplished. You would not need several IG wires in a branch conduit any more than you would need parrallel IG wires from the source (transformer or service bond point) to each sub panel.

For Horsegoer, you aked a question without full information. First, is the system 3 phase or single phase, and second does the customer require separate neutrals for each hot? From there, IMO you need one ground, one isolated ground and the proper ratio of hots and neutrals spelled out elsewhere.

 

[Smart $]

Am I missing something? I have never run more than 1 IG wire in a conduit. The purpose of an IG wire is to provide a 0 volt reference to the voltage system source. Since it only bonds to the source this is how it is accomplished. You would not need several IG wires in a branch conduit any more than you would need parrallel IG wires from the source (transformer or service bond point) to each sub panel.

...

Nothing regarding number of IG conductors is NEC required. Its all in what's spec'd. Many EE's spec' one IG conductor per circuit.

 

[hbiss]

Many EE's spec' one IG conductor per circuit.

And many EEs don't know what they are doing, if they did they wouldn't have spec'd IG receptacles in the first place.

With all the different ways IG receptacles get wired, has anyone ever had a complaint about one not working?

-Hal

 

[Smart $]

And many EEs don't know what they are doing, if they did they wouldn't have spec'd IG receptacles in the first place.

At one time, way in the past, the served their purpose, when utilized properly... a big IF...!!!

With all the different ways IG receptacles get wired, has anyone ever had a complaint about one not working?

Only when their equipment don't power up

 

[hbiss]

At one time, way in the past, the served their purpose...

I think the reason they are spec'd today is the EEs are still using the same boilerplate they had from back in the 80's.

-Hal

 

[Strathead]

Nothing regarding number of IG conductors is NEC required. Its all in what's spec'd. Many EE's spec' one IG conductor per circuit.

It must be the area that you are in, or the 2 areas I have been in, because, while I guess some Electrical Engineers may mistakenly spec dedicated isolated grounds, I have never had one spec them yet.

 

[Smart $]

It must be the area that you are in, or the 2 areas I have been in, because, while I guess some Electrical Engineers may mistakenly spec dedicated isolated grounds, I have never had one spec them yet.

Last time I dealt with any IG spec's was for a near-Akron high school upgrade for computers. That was back in '98, IIRC. The EE spec'd H-N-IG for each circuit.

Prior to that, I used to travel a fair part of eastern US doing chain store conversions and renovations. I've seen every kind of IG installation you can think of... including IG's tied to a non-GES ground rod. :happyyes:

 

[fmtjfw]

If you can believe that isolated ground outlets are connected using isolated grounds then there is a lot of isolated grounds being used in retail, cash registers, etc.

 

[fmtjfw]

If you are concerned that unwanted signals may be induced into the Hot, Neutral, Grounding triplet, then you might use individual neutrals and individual isolated ground wires for each circuit as a twisted triplet (like a twisted pair). But this approach would only make sense if you were immensely paranoid.

I 've always been in favor of shared neutrals and shared grounds.

 

[Strathead]

Last time I dealt with any IG spec's was for a near-Akron high school upgrade for computers. That was back in '98, IIRC. The EE spec'd H-N-IG for each circuit.

Prior to that, I used to travel a fair part of eastern US doing chain store conversions and renovations. I've seen every kind of IG installation you can think of... including IG's tied to a non-GES ground rod. :happyyes:

Yeah, I have an ongoing argument with an Audio subcontractor. He insists that an isolated ground for his audio equipment is an isolated wire run to an isolated bus in the panel, and then a 3/0 to a ground rod isolated from other grounds. He insists that prevents hum in his audio system. I have argued with him until I am blue in the face, and he still believes that. I believe, I will never provide him with what he is asking for.

The most common mistake I see is that an Engineer only cares that he has a dedicated redundant ground back to the source sub panel.