Delta wye with primary neutral landed to XO.

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Bumpskr

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Union electrician
I'm on a job where a delta wye(480-110/208) has a neutral pulled with high voltage wires( so it's a 277/480 to 110/208) and landed on XO.
So XO has grey neutral, white neutral and ground wire. I have never seen primary neutral landed on XO. Primary is a delta, meaning no XO connection. This can't be right.....??? Because now there is a physical connection between primary and secondary neutrals. Not induced like the windings.
It hasn't been energized yet.
Please help
 
You do need to ground the secondary. If no building steel, no metal water pipe, you possibly running a GEC back to the service panel, which other than the gray color you possibly end up with about the same thing, size of conductor could be wrong (probably on the small side) for this just depends. There is no need for neutral on the primary, and as you said there is no place to even connect one if you for some reason wanted to on a delta primary.

Now if you have separate EGC GEC, or in some cases you can run one conductor sized to be the primary EGC and the Secondary GEC and if that were done plus the separate neutral - the neutral serves no purpose and isn't needed.
 
I agree with Texie the primary neutral should be removed as it shouldn't be there in the first place. Just for clarity the secondary voltage is 208Y/120 volts.
 
If the source is service equipment and (it) comes off a common neutral and EGC busbar at the source, that wire at the X0 could be a primary side EGC, and OK to terminate at the SDS common grounding bonding busbar, where the GEC and system bonding jumper would also be.

If the source connection is anything other, it would form a second N to G connection for the service SDS and should be removed. It would put primary side neutral current on the facility grounding system, making it noisy (objectionable also but opinions on that vary).

I've seen guys try to run a GEC with the supply conductors also, but never seen it successfully done. So many restrictions and requirements on the GEC, easier to run it seperately.

Look to see if it may be the primary side EGC, that could be OK. Your transformer does not need or want a primary side neutral.
 
__dan said:
If the source is service equipment and (it) comes off a common neutral and EGC busbar at the source, that wire at the X0 could be a primary side EGC, and OK to terminate at the SDS common grounding bonding busbar, where the GEC and system bonding jumper would also be.

If the source connection is anything other, it would form a second N to G connection for the service SDS and should be removed. It would put primary side neutral current on the facility grounding system, making it noisy (objectionable also but opinions on that vary).

I've seen guys try to run a GEC with the supply conductors also, but never seen it successfully done. So many restrictions and requirements on the GEC, easier to run it seperately.

Look to see if it may be the primary side EGC, that could be OK. Your transformer does not need or want a primary side neutral.
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If it is an EGC is should not be white/gray. But yes there does need to be one and a bond to the secondary circuit
 
What can happen? Is it dangerous? The boss told me the engineer said to leave it in. I don't get it. This CAN'T be legal. To have a primary neutral ,secondary neutral, and ground all landed on the XO. Now there is a physical connection between primary and secondary. The inspector didn't catch it
 
There already is a physical connection between the X0 and the neutral from the 480 volt panel because the neutral is grounded somewhere else. IMO it should be removed at the X0.
 
Bumpskr said:
What can happen? Is it dangerous? The boss told me the engineer said to leave it in. I don't get it. This CAN'T be legal. To have a primary neutral ,secondary neutral, and ground all landed on the XO. Now there is a physical connection between primary and secondary. The inspector didn't catch it
Click to expand...
The issue is not that you have a connection between primary and secondary. The issue is you are connecting the grounded conductor of the supply system the the equipment grounding system at the transformer in violation of 250.24(A)(5).
This could cause problems, especially if the service has GFPE. I'll say it again, the grounded conductor on the primary supply should be removed.
 
I agree with Dan post #5: if the supply
Originates at the service equipment, the conductor is essentially just an egc or egc. Color may be an issue for the former. If it doesn't meet the requirements to be an egc or gec, I don't really see any violation leaving it connected. That said, I would probably disconnect it just to avoid future confusion.
 
Bumpskr said:
What can happen? Is it dangerous? The boss told me the engineer said to leave it in. I don't get it. This CAN'T be legal. To have a primary neutral ,secondary neutral, and ground all landed on the XO. Now there is a physical connection between primary and secondary. The inspector didn't catch it
Click to expand...

You will likely get large circulating currents between both sides of the transformer. The one time I seen it done, the 75KVA transformer was making loud groning noises until it was disconnected. And that is in addition to the warnings given earlier.
 
Bumpskr said:
What can happen? Is it dangerous? The boss told me the engineer said to leave it in. I don't get it. This CAN'T be legal. To have a primary neutral ,secondary neutral, and ground all landed on the XO. Now there is a physical connection between primary and secondary. The inspector didn't catch it
Click to expand...
As Infinity said, you already had a physical connection, by bring the 480V neutral to the X0 and then also connecting an EGC to the X0 you are creating a downstream N-G bonding point.
 
jim dungar said:
As Infinity said, you already had a physical connection, by bring the 480V neutral to the X0 and then also connecting an EGC to the X0 you are creating a downstream N-G bonding point.
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Wouldn't this also mean that some of the neutral current for the 120 volt circuits would return on the 277 volt neutral? IMO this would be objectionable current.
 
electrofelon said:
Guys, I don't think he is using a Delta wye in reverse. The primary neutral landed in the XO is electrically no different than a egc or gec
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Who said that this was reverse wired? It's a Delta/Wye with the "delta" neutral landed on the Wye secondary.
 
infinity said:
Wouldn't this also mean that some of the neutral current for the 120 volt circuits would return on the 277 volt neutral? IMO this would be objectionable current.
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No, because there are no ungrounded conductors common to both sources.

This is just like utility primaries and secondaries sharing common neutrals.
 
electrofelon said:
Every compliant install is that way. Change the color to green and call it an egc if you want.
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You are correct it is a correct install for a green grounding conductor however it is not for a white neutral conductor.

Unless this conductor originates directly from the service point ground bus it maybe more complicated than simply changing its color.
 
electrofelon said:
Every compliant install is that way. Change the color to green and call it an egc if you want.
Click to expand...
If there is a neutral on the primary side connected to the bonded X0 of the secondary you have then connected the grounded conductor to the metal case in violation of 250.24(A)(5).
 
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