Combining phase conductors in parallel sets

[jap]

If a groundhog could somehow get inside the PVC pipe, he could chew a hundred feet of insulation off of an ungrounded conductor and youd never know the difference.
That is unless he also chewed as small amount insulation off an insulated Equipment Grounding conductor, if it happened to be run with them, and then somehow created a path between them that would allow enough current to travel back through the EGC to the source, where it would have to be bonded to the neutral, to make it trip.


JAP>

 

[jap]

I'm hoping the Neutral bar is it is bonded to the Equipment Ground Bar somewhere in the gear.
I just dont see it.
Otherwise this switchgear is sitting there Floating.

 

[jap]

Then again,, this could be the loadside of a large breaker in a piece of gear,and the conduits we're looking at could actually be going out to feed something else.

Hard to tell with this picture.

JAP>

 

[don_resqcapt19]

Are we missing something here?

Doesen't a grounding conductor need to be in the conduits with the current carrying conductors?
You know, just in case there is a nick, a cut or ground hog should happen to occur in the wiring.:blink: "The ground wire makes the breaker trip"

I have always installed a complete set of wires in each feeder conduit.
Normally, The AHJ requires it.

I expect that the conductors in the picture are service conductor and the equipment is the service disconnect. Equipment grounding conductors are not used with service conductors that are fed from a grounded system.

 

[kwired]

Don hit the main point I was going to make - this is likely service equipment. I don't see any obvious bonding jumper on the "grounded conductor" bus, but at same time do not see any obvious insulator to isolate it from the frame either.

So where did they land all 6 of the EGC at the Utility Transfomer? since there's no Neutral pulled to this Gear?

Are we missing something here?

Doesen't a grounding conductor need to be in the conduits with the current carrying conductors?
You know, just in case there is a nick, a cut or ground hog should happen to occur in the wiring.:blink: "The ground wire makes the breaker trip"

I have always installed a complete set of wires in each feeder conduit.
Normally, The AHJ requires it.

I expect that the conductors in the picture are service conductor and the equipment is the service disconnect. Equipment grounding conductors are not used with service conductors that are fed from a grounded system.

 

[jap]

I agree that EGC"s are never pulled from a service transformer into a Service Disconnect.

I was just trying to make the point that it looked to me that they pulled what looked like, EGC's to the gear since the size of the conductors were so small.
I would have thought on a service of this size they would have pulled a full size, or reduced one size, Grounded Conductor to the gear.
Then landed them on the Neutral Bar.

I didnt notice they were taped Gray until someone mentioned it.

Is seperating the phase conductors from the grounded conductors even allowed?

Although it looks like it would be much more convienient to land the conductos, I've never pulled Phase conductors in seperate conduits.
We've always installed the phase conductors A,B & C and the grounded conductor all installed in the same raceway.

 

[kwired]

I agree that EGC"s are never pulled from a service transformer into a Service Disconnect.

I was just trying to make the point that it looked to me that they pulled what looked like, EGC's to the gear since the size of the conductors were so small.
I would have thought on a service of this size they would have pulled a full size, or reduced one size, Grounded Conductor to the gear.
Then landed them on the Neutral Bar.

I didnt notice they were taped Gray until someone mentioned it.

Is seperating the phase conductors from the grounded conductors even allowed?

Although it looks like it would be much more convienient to land the conductos, I've never pulled Phase conductors in seperate conduits.
We've always installed the phase conductors A,B & C and the grounded conductor all installed in the same raceway.

The grounded conductor only needs to be sized to the load it will carry, but in no case can it be smaller then the required grounding electrode conductor for service conductors or the required equipment grounding conductor for non service conductors. At a service you must run the grounded conductor even if it has no load connected to it. So if this is service conductors and there is little or no neutral load, they must at least be sized to 250.66.

 

[jap]

The grounded conductor only needs to be sized to the load it will carry, but in no case can it be smaller then the required grounding electrode conductor for service conductors or the required equipment grounding conductor for non service conductors. At a service you must run the grounded conductor even if it has no load connected to it. So if this is service conductors and there is little or no neutral load, they must at least be sized to 250.66.

Agreed.

But on a new 4000 Amp service, it would seem one would pull a Full sized Grounded conductor or at least a reduced Neutral, since there is a very good possibility that future neutral loads could easily exceed the minimum that was pulled to this gear. Unless this is a MCC or something like that.
I cant tell what it is by the Picture.

JAP>

 

[kwired]

Agreed.

But on a new 4000 Amp service, it would seem one would pull a Full sized Grounded conductor or at least a reduced Neutral, since there is a very good possibility that future neutral loads could easily exceed the minimum that was pulled to this gear. Unless this is a MCC or something like that.
I cant tell what it is by the Picture.

JAP>

Totally load dependent IMO. What if 90+% of the load is three phase motors and only a very small percentage is 277 volt lighting? Why install a full sized neutral when it is not necessary? What if there is no 277 volt load at all, and all lighting is supplied from other separately derived sources or is actually 480 volt equipment?

If this were retail, large data center, or other similar install with a lot of 277 volt loads then grounded conductor size is something to consider. If it is primarily industrial machines with almost no 277 loads .... grounded conductor is something rarely utilized at least at the 277 volt level. Even if a large plant has 277 lighting, that is typically a small load compared to the motor loads.

 

[qcroanoke]

Agreed.

But on a new 4000 Amp service, it would seem one would pull a Full sized Grounded conductor or at least a reduced Neutral, since there is a very good possibility that future neutral loads could easily exceed the minimum that was pulled to this gear. Unless this is a MCC or something like that.
I cant tell what it is by the Picture.

JAP>

The drawing in post #1 is what the OP is asking about. It shows a neutral being pulled.
The picture is an install that Iwire did.
Just thought I would mention that.
We seem to have gotten away from the original question.

 

[jap]

Totally load dependent IMO. What if 90+% of the load is three phase motors and only a very small percentage is 277 volt lighting? Why install a full sized neutral when it is not necessary? What if there is no 277 volt load at all, and all lighting is supplied from other separately derived sources or is actually 480 volt equipment?

If this were retail, large data center, or other similar install with a lot of 277 volt loads then grounded conductor size is something to consider. If it is primarily industrial machines with almost no 277 loads .... grounded conductor is something rarely utilized at least at the 277 volt level. Even if a large plant has 277 lighting, that is typically a small load compared to the motor loads.

Exactly the point I made earlier with just more words.
If we knew what the Gear was feeding it would probably make much more sense.

JAP>

 

[kwired]

Exactly the point I made earlier with just more words.
If we knew what the Gear was feeding it would probably make much more sense.

JAP>

I was just defending the argument that many think the grounded conductor needs to be same size as ungrounded conductors.

I think this concept becomes more of a reality for a 208/120 system then it is for most 480/277 systems, as 277 volt loads are generally limited to lighting, where 120 volt loads can be about anything.

 

[iwire]

Wow, so much speculation.

Regarding this picture I posted.

As I said above this is a picture a friend sent me a few years ago. He was doing an IR survey and wanted my code opinion on the isolated phases.

It is not my work so I can't answer many of the issues raised in this thread.

I can tell you this is a service, one clue to that is the 1.25" PVC coming out of the slab and heading up. I am 99% certain that is the raceway for the power company's remote meter. The CTs would be above the picture built into the gear.

When I zoom into the picture I can see that the bus bar is on insulators, no doubt somewhere in the gear is a large bonding strap.

As far as the reduced size neutral, I am all for it. There are very few 480Y/277 volt services that the neutral would need to be as large as the ungrounded conductors.

Think about it, the vast majority of loads on a 480 service are line to line loads. HVAC equipment, other mechanical equipment, transformer supplies etc. The amount of line to neutral loads at 277 will almost always be limited to the lighting and therefore always be a smaller percentage of the load on the service.

 

[tsample]

Don't do it

Don't do it

Be careful, although allowed by code, this type of installation has risk, lots of risk. Risk of ANY metal object near these feeders (rebar, support strut left in, gear chasis ect) causing heating and damaging conductors. Not fun to explain.