Transformer grounding

jap

Senior Member
Not everything has a neutral. If all loads are 3 phase or line to line you don’t need it. Motor circuits for instance don’t need it. Heating sometimes. Lighting is better if you use a tranny anyways.
The illustration shows a neutral brought to the panel.
The line that they are trying to depict from the center point of the Y connection to the terminal block as a bonding jumper would actually be the neutral in this scenario.

Not just a jumper

JAP>
 

jap

Senior Member
If you look at the windings they're also black so I'm not see where the color representation changes anything. When compared to the two transformer photos posted they clearly show that the black line merely represents the internal manufacturer's connection of the transformer windings to the X0 terminal.
The colors mean nothing to me.

Even if every line on the diagram was purple, I'd still call the connection between the center point of the Y to the terminal block a neutral in this case.

JAP>
 

infinity

Moderator
Staff member
Location
New Jersey
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Journeyman Electrician
The colors mean nothing to me.

Even if every line on the diagram was purple, I'd still call the connection between the center point of the Y to the terminal block a neutral in this case.

JAP>
Have you ever seen a transformer that is manufactured like in the graphic?
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
In my opinion, the terminal bar in the upper bar in the OP pic is not a grounding block, it is a neutral terminal block, and it is isolated from the transformer case. That's why there is a jumper from it to the case.

Thus, the wire from X-0 to this terminal bar, as well as the bar itself, is the neutral, regardless of whether the load requires it, or whether, or where it is bonded to a GEC or EGC. If factory installed, its color is not relevant.
 

jap

Senior Member
In my opinion, the terminal bar in the upper bar in the OP pic is not a grounding block, it is a neutral terminal block, and it is isolated from the transformer case. That's why there is a jumper from it to the case.

Thus, the wire from X-0 to this terminal bar, as well as the bar itself, is the neutral, regardless of whether the load requires it, or whether, or where it is bonded to a GEC or EGC. If factory installed, its color is not relevant.

Exactly.

That's why it's so important where the neutral to the load side panel is terminated.

If the neutral coming from the panel was landed on the center of the Y instead of the terminal block, the line in the graphic drawn from the center of the Y or XO to the terminal block would be a bonding jumper since that block is connected to frame and other GE's, and, would be sized as a bonding jumpers.

If the neutral coming from the panel is landed on the insulated terminal block as in the graphic, that same line is the connection from the Y point or XO terminal of the transformer to the terminal block and is serving as the neutral and that conductor would have to be sized to carry the entire neutral load.


JAP>
 

ActionDave

Chief Moderator
Staff member
Location
Durango, CO, 10 h 20 min without traffic from wing
Occupation
Licensed Electrician
The other drawing showed XO's point of origin extended to a terminal block.

JAP>
That’s it would be impossible to illustrate those connections clearly on that little dot at the center of the transformer secondary. Besides on a real life transformer the neutral point is brought out of the transformer windings like the picture infinity posted so the line is a fairly accurate representation.
 

jap

Senior Member
That’s it would be impossible to illustrate those connections clearly on that little dot at the center of the transformer secondary. Besides on a real life transformer the neutral point is brought out of the transformer windings like the picture infinity posted so the line is a fairly accurate representation.
Your post #16 pretty well sums it all up.

JAP>
 
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