No equipment ground pulled to sub-panel

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kwired said:
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.
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The MV neutral is not joined at one end. If you have multiple sources, chances are the secondary neutral also bonded various gear.


jaggedben said:
This ^
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Draw it out and prove me wrong :thumbsup:
 
romex jockey said:
depends what one considers 'conductor' kwired

~RJ~
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Well for this situation, anything that conducts.

mbrooke said:
The MV neutral is not joined at one end. If you have multiple sources, chances are the secondary neutral also bonded various gear.
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OK got me with that one, wouldn't even need to be MV, any situation where multiple services are allowed it could happen.
 
kwired said:
Well for this situation, anything that conducts.

OK got me with that one, wouldn't even need to be MV, any situation where multiple services are allowed it could happen.
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Now your thinking. :thumbsup: A good example would be a large indoor shopping mall with a dozen padmounts around the building exterior.


I also know of data center drawings where someone decided to use 240/416 3 wire, only to have a neutral derived via zig zag at each power center for the servers. The only debate was whether it violated code. In so far it would technically be legal.
 
jaggedben said:
Two of these next to each other, left to right.
View attachment 22504

There.

Now prove your point.
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There isn't current between the two loads and we were led a little astray with that situation vs what he was really trying to get after. Two utility feeds to a facility can easily have current flowing through anything bonded within the facility, some of that current may not even be associated with the facility at all. We have this with a single service but conductive paths to other other facilities anyway. Residential district with metallic water piping to every residence is sort of the same situation.
 
kwired said:
There isn't current between the two loads and we were led a little astray with that situation vs what he was really trying to get after. Two utility feeds to a facility can easily have current flowing through anything bonded within the facility, some of that current may not even be associated with the facility at all. We have this with a single service but conductive paths to other other facilities anyway. Residential district with metallic water piping to every residence is sort of the same situation.
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Yup.
And as I tried to point out earlier, the NEC can't or doesn't try to control things that are dependent on something that's outside the same premises. In the case of multiple services to a facility, the NEC can't know whether the utility uses one or more transformers to serve them. So that's all not really relevant to why the CMP changed 250.32(B). Nor do I see anything relevant regarding SDSs as defined by the NEC.
 
jaggedben said:
Yup.
And as I tried to point out earlier, the NEC can't or doesn't try to control things that are dependent on something that's outside the same premises. In the case of multiple services to a facility, the NEC can't know whether the utility uses one or more transformers to serve them. So that's all not really relevant to why the CMP changed 250.32(B). Nor do I see anything relevant regarding SDSs as defined by the NEC.
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Try my zig-zag example... :thumbsup:
 
romex jockey said:
beacsue the old 250.32(B) was amended due to parallel paths

~RJ~
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It was amended because of particular parallel paths, namely metal parts unintended as electrical conductors (such as water piping systems) possibly carrying ordinary neutral circuit current, possibly above ground.

If the code were to say:
1> you don't need an EGC between structures, but you do need to bond the neutral
and
2> you must ground the neutral at the separate structure if you don't run an EGC
and
3> you need to bond metal piping to the neutral at each structure (it does say this, 250.104)

...then the code is virtually guaranteeing that there will be instances where a main building supplies both water and electricity to an outbuilding, and there will be neutral current flowing on metal water pipes. (Just one example). These water pipes won't necessarily be underground, they might be exposed and could conceivably even develop touch potential to ground, especially if the buildings are made of wood. That's all made far less likely if an EGC is run between buildings and

That's quite substantively different from allowing current to flow through or to the earth, or on metal piping that is in the earth, or on building steel that is earthed. It's also all on one premises, unlike examples involving multiple services.

It seems like you and mbrooke are arguing that the change to 250.32(B) can't be made sense of because 'what about this, and that, and the other thing'. But it can be made sense of, because those other things are ... different ... in either electrically substantive or legally substantive ways. (The change might have been overkill, but that doesn't mean one can't understand the logic.)
 
jaggedben said:
If you'd like to spell it out, feel free, but I'm not going to continue with the guessing game. :bye: As best I can tell looking at zig-zag diagrams there is no parallel path for ordinary neutral current.
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Ok you have 3 wires from a wye grounded source. Now you pull a noodle off the zig zag for your 240 volt servers. Do you or do you not grounded the neutral?
 
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