there is the main thing I kept thinking about while reading the past few posts. As long as the source is from service panel the EGC comes from same point as the neutral. If there is GFP there also would be operational issues with a N-G connection downstream.
If primary comes from the service equipment, other than color of insulation the EGC and/or GEC connect to same place anyway. There is no current on this conductor during normal operation as long as you don't create any parallel path to a 277 volt circuit neutral. The neutral current from the separately derived 120 volt circuits is trying to return to secondary XO, not the primary neutral.
I get all that. But if I see a white or gray conductor as in this install and it is connected to the X0 rather than directly to the EGC bus I would call this a violation. And what if there is already a wire type EGC in the raceway? Now you have 2-a white or gray and a green one. And all this is predicated on the circuit originating in service equipment and we don't know that from the OP. Bottom line it is hack and shows a lack of understanding.
Agreed.
Again presuming originating at service equipment, only thing wrong (code violation) with it is insulation color, physically it is not going to introduce any hazards otherwise. And again the secondary neutral current isn't finding a way back to the primary source, it is seeking the secondary XO terminal. No violation in having parallel paths in the EGC network, it happens all the time. Just is redundant to have two conductors following same path.
Like a multi-core transformer bank with line to neutral operating individual units. To a single core three phase transformer you pretty much never need a primary neutral, just an EGC on the primary and a GEC for the secondary, one conductor can do both if done correctly.
The grounding conductors are common, so there is an additional path for secondary neutral current via the primary neutral being connected to the secondary neutral. The path would include the incorrectly landed primary neutral, the system bonding jumper for the secondary, the main bonding jumper for the service, and the equipment bonding conductors and any other metallic path, such as building steel and water pipe systems that are connected to the electrical bonding system.
Move the incorrectly landed primary neutral over to the case of the transformer and now it is no longer incorrectly landed, but electrically it is still the same.
The grounding conductors are common, OP's installation there is no primary current on said conductor The primary circuit only utilizes the ungrounded conductors. Electrically (and presuming this comes from the service equipment) it is no different than running an EGC other than color of the insulation.
