# Grounding this delta transformer



## Tortoise83 (Dec 3, 2012)

Hello internet people. First time dealing with this style of transformer. Having trouble with the grounding aspect. Typically I will bring my grounding electrode into the transformer and terminate it to my system neutral, and of course all my other grounding conductors, bonding jumpers and such. I have never seen an x4 before, usually x0? My question is where do I terminate my grounding electrode in this system, do I use my electrode from my primary side? Do I just run a new electrode from building steel to transformer without bonding it to the neutral (x4). Thank you for your time.


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## Laroc3 (Jul 20, 2013)

Looks like the x4 to me if you need 120v loads.


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## Tortoise83 (Dec 3, 2012)

The x4 is my neutral, I have 120 across x1 and x2 to x4, 220 from x3 to x4. My question is how do I ground this system. The manufacture of the transformer said to not connect a grounding electrode to x 4, so where and how to I ground this system seeing as it is considered a separately derived electrical system?


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## Laroc3 (Jul 20, 2013)

Tortoise83 said:


> The x4 is my neutral, I have 120 across x1 and x2 to x4, 220 from x3 to x4. My question is how do I ground this system. The manufacture of the transformer said to not connect a grounding electrode to x 4, so where and how to I ground this system seeing as it is considered a separately derived electrical system?


In canada we bond are neutral to ground, meaning x4. Mans isn't x3 to x4. Going to be 208 v.


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## Tortoise83 (Dec 3, 2012)

That's what I've always done as well. I'm just trying to figure out why the manufacturer told me not to, maybe he's wrong but I want to be sure, everything I've read in the code book and researched online is telling me to tie in at x4. Very frustrating.


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## dronai (Apr 11, 2011)

http://forums.mikeholt.com/showthread.php?t=120608


http://www.electrical-contractor.ne...ew_3_Ph_3_Wire_Center_Tap_Gro.html#Post177455


http://www.electrical-contractor.ne...ew_3_Ph_3_Wire_Corner_Grounde.html#Post177456


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## Tortoise83 (Dec 3, 2012)

Those diagrams show that I do ground at x 4 as well. CT delta, do you agree?


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## dronai (Apr 11, 2011)

Tortoise83 said:


> Those diagrams show that I do ground at x 4 as well. CT delta, do you agree?



Except they all say 3 wire not 4 wire delta. Someone on here will know. I would think if there is a center tap (neutral or voltage divider), you would bond as you do with a wye xfmr, but not sure.


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## dronai (Apr 11, 2011)

Tortoise83 said:


> Those diagrams show that I do ground at x 4 as well. CT delta, do you agree?


 
Read this by Micromind


http://www.electriciantalk.com/f2/delta-delta-transformer-voltage-problems-1387/


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## Tortoise83 (Dec 3, 2012)

I am going to wire it up, I will see what happens when inspector gadget comes out, thanks for all your help, I really appreciate it.


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## hardworkingstiff (Jan 22, 2007)

Tortoise83 said:


> I am going to wire it up, I will see what happens when inspector gadget comes out, thanks for all your help, I really appreciate it.


You'll be fine grounding X4 (that's what you are supposed to do).

I understand your concern and apprehension.


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## wildleg (Apr 12, 2009)

x4 is your derived neutral, and therefore your ground. 
think about it this way - if you don't ground x4, how will you have a 120 volt reference to ground from x1 as well as x2 ?

if you were to use it as a delta-delta , then you would ground to a corner, and not x4.


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## Southeast Power (Jan 18, 2009)

Tortoise83 said:


> View attachment 37977
> 
> 
> View attachment 37978
> ...


What is the load!
Is it a machine or are you feeding a panel?


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## Big John (May 23, 2010)

If you ground X4 you will end up with 208 volts to neutral on B phase. 

You need to be certain that whatever is connected to this phase will not be burned up by overvoltage.


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## Tortoise83 (Dec 3, 2012)

jrannis said:


> What is the load! Is it a machine or are you feeding a panel?


I'm feeding a panel


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## Tortoise83 (Dec 3, 2012)

Big John said:


> If you ground X4 you will end up with 208 volts to neutral on B phase. You need to be certain that whatever is connected to this phase will not be burned up by overvoltage.


I understand , the voltage is 208 from x3 to x4 with no ground attached to x4, with only the primary side hooked up.


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## Tortoise83 (Dec 3, 2012)

Thank you for your replies, I have wired many transformers, most of them delta to y configurations, I don't understand why the manufacturer would tell me not to connect x4 to a grounding electrode, it goes against everything I understand about grounding a separately derived system.


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## hardworkingstiff (Jan 22, 2007)

Tortoise83 said:


> I'm feeding a panel


Do you know why they went with Delta/Delta instead of Delta/Wye?


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## Tortoise83 (Dec 3, 2012)

hardworkingstiff said:


> Do you know why they went with Delta/Delta instead of Delta/Wye?


I think it's a lot cheaper for a delta than a y transformer.


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## wildleg (Apr 12, 2009)

Tortoise83 said:


> Thank you for your replies, I have wired many transformers, most of them delta to y configurations, I don't understand why the manufacturer would tell me not to connect x4 to a grounding electrode, it goes against everything I understand about grounding a separately derived system.


because they were reading the instructions for delta-delta, not for
delta-delta high leg, which is what you are connecting.


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## Walkman (Aug 16, 2014)

Tortoise,

I hate to dredge up an old post but this is very interesting. You seem to have a pretty good handle on transformers but then a manufacturer advised you to not ground the X4. Did you ever figure out why? It looks like a fairly straight-forward installation to me; was he thinking you were going with an ungrounded system or something? 

Sincerely,
Very Curious


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## Frizratz (Jul 14, 2014)

It is pretty uncommon to go Dela/Delta.
Any engineer I've worked with discourages that. 

If you are feeding a panel and it has a lighting load, you will now have a high leg. 

If the reason to go Delta /delta is money, then some one is shortsighted.


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## Tortoise83 (Dec 3, 2012)

High leg nailed it, they were reading directions for a different transformer. This is the first time I've seen and x 4 terminal, typically it's an x0, that's the only reason I got confused.


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## Meadow (Jan 14, 2011)

Ok first off lets set this straight.

What is this feeding? 

Are you looking for an ungrounded, corner grounded or center grounded high leg system? 

Don't just ground the center tap or leave it floating. I am sure a delta was specked for a reason, it is important to find out why. 

Also, depending on grounding the ratings of the breakers AIC will change.


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## Meadow (Jan 14, 2011)

Frizratz said:


> It is pretty uncommon to go Dela/Delta.
> Any engineer I've worked with discourages that.
> 
> If you are feeding a panel and it has a lighting load, you will now have a high leg.
> ...


Unless your looking for no phase displacement (very unlikely at the 600 volt level) or ungrounded power an delta delta is of no advantage.

One reason however could be 240 volt power instead of 208. In cases like this a 240Y/138 drive isolation transformer would be a better choice. Unless of course this was in stock over a drive isolation unit.


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