No equipment ground pulled to sub-panel

[kwired]

You aren't, but picture a property with multiple MV-LV rooms through out.


What code section forbids this?

Without looking, the same section(s) that don't let you bootleg a conductor from the neutral terminal of a receptacle to the EGC terminal of the receptacle. We keep current carrying grounded conductors isolated from equipment grounding conductors beyond main/system bonding jumpers.

 

[david]

Interesting discussion exterior SDS are required to have the neutral earthed at an exterior location
and allowed a SBJ at the SDS and also allowed SBJ at the building main disconnect.

In that situation earth is not considered a path for objectionable current the same as a utility transformer supplying a service

In the OP situation at the time of installation (assumption) earth was allowed as a path between the service at the residence and the main panel at the garage and a single conductor acting as a neutral / equipment ground between both locations

I do not believe the electrical inspector looking at this existing 3 wire feed to the garage is going to require a fourth conductor to be installed, (assumption)

 

[mbrooke]

Without looking, the same section(s) that don't let you bootleg a conductor from the neutral terminal of a receptacle to the EGC terminal of the receptacle. We keep current carrying grounded conductors isolated from equipment grounding conductors beyond main/system bonding jumpers.

What about a system where you use zig zag to derive a neutral? What about MV wiring?

 

[jaggedben]

What about a system where you use zig zag to derive a neutral? What about MV wiring?

What do either of those things have to do with objectionable current?

 

[mbrooke]

What do either of those things have to do with objectionable current?

They create it.

 

[jaggedben]

They create it.

I don't see how.

 

[romex jockey]

In that situation earth is not considered a path for objectionable current the same as a utility transformer supplying a service

Rather amazing how mother earth has no objection to complete Y-Y poco systems w/solid noodles, made to multitudes of common paths such as municipal h20 /gas systems / data lines .....~RJ~

 

[mbrooke]

I don't see how.

By creating parellel paths.

 

[kwired]

What about a system where you use zig zag to derive a neutral? What about MV wiring?

By creating parellel paths.

You still need to run separate neutral and EGC conductors beyond any main bonding jumper. The EGC has lots of parallel paths, but we intentionally make it non current carrying except for temporarily during fault conditions.

MV wiring still must follow same rules. POCO's MV wiring uses MGN and has parallel paths, but it isn't designed per NEC requirements.

I don't do MV, but I'd guess a lot of it outside POCO distribution doesn't supply line to neutral loads and would be a reason to not see separate neutral and ground conductor with feeders/branch circuits, all there needs to be is the ungrounded conductors and an EGC.

 

[jaggedben]

By creating parellel paths.

1) Not for secondary neutral current.
2) A parallel path is not necessarily objectionable.

 

[mbrooke]

You still need to run separate neutral and EGC conductors beyond any main bonding jumper. The EGC has lots of parallel paths, but we intentionally make it non current carrying except for temporarily during fault conditions.

MV wiring still must follow same rules. POCO's MV wiring uses MGN and has parallel paths, but it isn't designed per NEC requirements.

I don't do MV, but I'd guess a lot of it outside POCO distribution doesn't supply line to neutral loads and would be a reason to not see separate neutral and ground conductor with feeders/branch circuits, all there needs to be is the ungrounded conductors and an EGC.

What code section forbids a Y-Y though?

 

[mbrooke]

2) A parallel path is not necessarily objectionable.

Which means code allows parallel paths, technically.

 

[jaggedben]

Which means code allows parallel paths, technically.

So what was your point?:lol:

The code does not allow parallel paths from one structure to another, except per the exception discussed above.

 

[jaggedben]

What code section forbids a Y-Y though?

I don't think the code allows Y-Y to have the neutral bonded on the primary side at the transformer. I think that was the point.

How does a Y-Y create parallel paths, exactly?

 

[mbrooke]

I don't think the code allows Y-Y to have the neutral bonded on the primary side at the transformer. I think that was the point.

How does a Y-Y create parallel paths, exactly?

Draw it out. Two wye-wye transformer at opposite ends of a facility.

 

[jaggedben]

Draw it out. Two wye-wye transformer at opposite ends of a facility.

Yeah, not seeing it. Perhaps you left out some assumptions about grounding and/or bonding.

 

[mbrooke]

Yeah, not seeing it. Perhaps you left out some assumptions about grounding and/or bonding.

Nope- I don't assume. Draw it out- you'll see it.

 

[kwired]

What code section forbids a Y-Y though?

Nothing, but your primary neutral is bonded at the source and not the load end, just like any other loads that utilize a neutral conductor. Can't have a parallel path when conductors are only joined together at just one end.

 

[jaggedben]

Nothing, but your primary neutral is bonded at the source and not the load end, just like any other loads that utilize a neutral conductor. Can't have a parallel path when conductors are only joined together at just one end.

This ^

 

[romex jockey]

Nothing, but your primary neutral is bonded at the source and not the load end, just like any other loads that utilize a neutral conductor. Can't have a parallel path when conductors are only joined together at just one end.

depends what one considers 'conductor' kwired

~RJ~