# 480 volt corner grounded delta system



## midwesterner (Mar 27, 2012)

today I installed a single phase transformer on a 480 volt corner grounded delta system. I needed 120v would anyone had known how to wire the transformer?? Luckly for me there was the same setup down the road I could look at and copy the terminations
any experts out there care to educate me


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## Cletis (Aug 20, 2010)

*bad*

It is found that, although this type of service is less expensive than solidly grounded wye service, 480 V corner-grounded delta service may not provide a safe working environment if used for oil-field service. The problems found include: dangerous step and touch potentials can exist; nonautomatic isolation and location of phase-to-ground shorts; ground currents objectionable to residents living in the area; ground potentials have been known to cause solid-state starters to start in the off position; lightning arrestor application may be unsatisfactory; AC interference to communication equipment; higher dielectric stress on two phases; and higher magnitudes of transient overvoltages


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## midwesterner (Mar 27, 2012)

this is an existing service for an irrrigation pump no other loads. the costomer wants to be able to plug in an electric fencer. the poco is not going to switch out the transformer bank for a fencer that uses very little electricity


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## Meadow (Jan 14, 2011)

You would first need to pick up a transformer sized to meet the fence load and any future loads that could pop up (recommended but no required) (ie, service outlets)


Dont copy any set up you see as that one may have been improperly installed or is for a different application. 

Run 2 legs of 480 plus an EGC to the unit. One leg on H1 the other H2. Egc bonds to the case. This takes care of the primary.

If the secondary is 120 only then from your 120 panel run a single hot to X1. Run a white and a green to X2. Bond the green from X2 to the frame again and then run that along with the white to the panel. 

For 120/240 run to hots the secondarys. Then take the center tap and do the samething as done to the X2 above. 

Note that this explanation does not cover fusing requirments. 

Google "seperatly derived system" if you need pictures


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## D-Bo (Apr 15, 2012)

Cletis said:


> It is found that, although this type of service is less expensive than solidly grounded wye service, 480 V corner-grounded delta service may not provide a safe working environment if used for oil-field service. The problems found include: dangerous step and touch potentials can exist; nonautomatic isolation and location of phase-to-ground shorts; ground currents objectionable to residents living in the area; ground potentials have been known to cause solid-state starters to start in the off position; lightning arrestor application may be unsatisfactory; AC interference to communication equipment; higher dielectric stress on two phases; and higher magnitudes of transient overvoltages


Nice copy and paste job bud


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## midwesterner (Mar 27, 2012)

thanks for the reply but I believe you are incorrect. 

I have wired several transformers just not on this system. 
If i didn't copy the other tansformer I would still be there in the rain


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## Meadow (Jan 14, 2011)

midwesterner said:


> thanks for the reply but I believe you are incorrect.
> 
> I have wired several transformers just not on this system.
> If i didn't copy the other tansformer I would still be there in the rain


In what way? 


The secondarys do not change, you would wire the primary as you would on a solidly grounded wye system. From the 480 panel: 1 EGC to the unit, 1 phase and another phase either the one thats grounded or the second on thats not. The grounded primary incoming phase is never to be fused at the disconnect if its cabable of such.


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## midwesterner (Mar 27, 2012)

I first wired the transformer close to what your describing. 
primary side: I brought 2 phases out 1 tied to H1 and the other to H4, I tied H2, and H3 together. on the secondary side I tied x1 and x3 to one wire feeding the 120v circuit and tied x2 and x4 to the other wire feeding the 120v circuit. this configuration gave me 120v between the two wires leaving the transformer but I had 320v on one leg to ground and 280 volts on the other leg to ground


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## midwesterner (Mar 27, 2012)

after the first try i began trying every combination on the transformers wiring diagram. I could not get rid of the voltage to ground


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## varmit (Apr 19, 2009)

You need to ground one side of the transformer secondary, usually the X2 - X4 connection. Otherwise, you have no true reference to ground, so your meter will have random, meaningless readings.


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## mbednarik (Oct 10, 2011)

meadow said:


> You would first need to pick up a transformer sized to meet the fence load and any future loads that could pop up (recommended but no required) (ie, service outlets)
> 
> 
> Dont copy any set up you see as that one may have been improperly installed or is for a different application.
> ...


You can't use the EGC as a GEC. The secondary side depending on location needs it own GEC and electrodes or a separate path to the existing electrodes. I had a failed inspection because of this.


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## Meadow (Jan 14, 2011)

mbednarik said:


> You can't use the EGC as a GEC. The secondary side depending on location needs it own GEC and electrodes or a separate path to the existing electrodes. I had a failed inspection because of this.


True but I was mainly refering to the fact that both the equipment grounds from the 480 panel and the on to the 120 panel along with the GEC and the X2 bushing need to be bonded to the case together.


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## Meadow (Jan 14, 2011)

midwesterner said:


> I first wired the transformer close to what your describing.
> primary side: I brought 2 phases out 1 tied to H1 and the other to H4, I tied H2, and H3 together. on the secondary side I tied x1 and x3 to one wire feeding the 120v circuit and tied x2 and x4 to the other wire feeding the 120v circuit. this configuration gave me 120v between the two wires leaving the transformer but I had 320v on one leg to ground and 280 volts on the other leg to ground


Varmit is correct; did you ground the secondary as needed? Good chance your meter is picking up capcitive induction between the primary and the secondary so to speak. 

Can you post a pic of the transformer or its wiring diagram? That will clarify things.


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## midwesterner (Mar 27, 2012)

I have the pic on my iphone but I dont know how to get it on here. the transformer is an eaton S20N11P01P 
single phase 1 kva transformer


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## brian john (Mar 11, 2007)

midwesterner said:


> today I installed a single phase transformer on a 480 volt corner grounded delta system. I needed 120v would anyone had known how to wire the transformer?? Luckly for me there was the same setup down the road I could look at and copy the terminations
> any experts out there care to educate me


 
You would hook it up like any single phase transofrmer coming off a 3-phase service.


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## brian john (Mar 11, 2007)

midwesterner said:


> after the first try i began trying every combination on the transformers wiring diagram. I could not get rid of the voltage to ground


 
You need to ground either X1 or X4.


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## brian john (Mar 11, 2007)

meadow said:


> You would first need to pick up a transformer sized to meet the fence load and any future loads that could pop up (recommended but no required) (ie, service outlets)
> 
> 
> Dont copy any set up you see as that one may have been improperly installed or is for a different application.
> ...


 
Assuming you have X1 and X2 as your only secondary connections you can ground either side.

In the OPs case X1 and X4, same thing ground either terminal, just wire the distribution properly.


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## brian john (Mar 11, 2007)

midwesterner said:


> I have the pic on my iphone but I dont know how to get it on here. the transformer is an eaton S20N11P01P
> single phase 1 kva transformer


 
This is a basic 8 wire transformer h1-h4 and x1-x4.
1. The manufacture supplies a drawing and this transformer has the drawing on the face of the unit.
2. A simple continuity check would resolve any wiring issues.
3. Any ungrounded system as you set up will have varying voltages to ground.


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## midwesterner (Mar 27, 2012)

This is how the transformer is wired:
x2, x4 with the hot to the 120v panel
H4, 1 leg of the 480 
x3, x1, H1 and the nuetral to the 120v panel
H2, H3


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## 360max (Jun 10, 2011)

http://www.eaton.com/Eaton/Products...&sorder=&pagenum=4&litlibtarget=2000000000435

*wiring diagram 3A* is for your specific transformer (S20N11P01P 
single phase 1 kva transformer)


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## frenchelectrican (Mar 15, 2007)

midwesterner said:


> I first wired the transformer close to what your describing.
> primary side: I brought 2 phases out 1 tied to H1 and the other to H4, I tied H2, and H3 together. on the secondary side I tied x1 and x3 to one wire feeding the 120v circuit and tied x2 and x4 to the other wire feeding the 120v circuit. this configuration gave me 120v between the two wires leaving the transformer but I had 320v on one leg to ground and 280 volts on the other leg to ground


Which way you bring the 480 volts ? ungrounded part or grounded part 

I will post the photo for refernce real quick so we can see where this go wrong.










Merci,
Marc


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## Meadow (Jan 14, 2011)

midwesterner said:


> This is how the transformer is wired:
> x2, x4 with the hot to the 120v panel
> H4, 1 leg of the 480
> x3, x1, H1 and the nuetral to the 120v panel
> H2, H3


The H1 to the 120 volt panel doesnt sound right to me.:001_huh: Heres what it should be: 
H1 to one 480 leg. H2 and H3 are wire nutted together. H4 to the other 480 leg. Green to frame. Primary is done.

Now for the secondary:
X1 and X3 wire nut them to 120 hot wire. X2 and X4 wire nut to white and second green. Take second green to frame before going to your 120 panel. At the 120 panel there should be hot, white and green only. 

Hope this helps:


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## brian john (Mar 11, 2007)

midwesterner said:


> This is how the transformer is wired:
> x2, x4 with the hot to the 120v panel
> H4, 1 leg of the 480
> x3, x1,* H1* and the nuetral to the 120v panel
> H2, H3


 
While H1 may be the grounded conductor on the primary you do not connect this to the secondary. Assuming you grounded your secondary PER THE NEC, you have now violated the NEC by grounding the primary downstream from the main service a BIG NO NO. You need to change this ASAP

H1 to any phase

H2, H3 tied together

H4 to any other phase

X1, X3 tied together

X2, X4 tied together


Ground either X1, X3 or X2, X4 and the other set (the ungrounded set) are your energized conductor when referenced to ground.


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## Big John (May 23, 2010)

D-Bo said:


> Cletis said:
> 
> 
> > It is found that, although this type of service is less expensive than solidly grounded wye service, 480 V corner-grounded delta service may not provide a safe working environment if used for oil-field service. The problems found include: dangerous step and touch potentials can exist; nonautomatic isolation and location of phase-to-ground shorts; ground currents objectionable to residents living in the area; ground potentials have been known to cause solid-state starters to start in the off position; lightning arrestor application may be unsatisfactory; AC interference to communication equipment; higher dielectric stress on two phases; and higher magnitudes of transient overvoltages
> ...


 Busted. :laughing:
 
-John


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## BBQ (Nov 16, 2010)

Big John said:


> Busted. :laughing:
> 
> -John




:thumbup::thumbup::thumbup:


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## Awg-Dawg (Jan 23, 2007)

Big John said:


> Busted. :laughing:
> 
> -John


 
Wow, someone ripped off Cletis' post.:jester:


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## D-Bo (Apr 15, 2012)

Awg-Dawg said:


> Wow, someone ripped off Cletis' post.:jester:


Was there ever any doubt


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## careriwes (Oct 19, 2012)

*240V corner grounded system*

I have a 240V corner grounded Delta system. The poco nor any of several local electricians identified this system correctly. I think I should use the same type of transformer to get 120v (CH 3A). I know I can use just one leg of my incoming line and get two 120v out of the transformer. To balance my load correctly though I think I should be using both of my hot incoming phases (and the ground phase). Can you guys help me Please?


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## midwesterner (Mar 27, 2012)

frenchelectrican said:


> Which way you bring the 480 volts ? ungrounded part or grounded part
> 
> I will post the photo for refernce real quick so we can see where this go wrong.
> 
> ...


The only primary conductor I brought to the transformer is the A phase (ungrounded)


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## midwesterner (Mar 27, 2012)

brian john said:


> While H1 may be the grounded conductor on the primary you do not connect this to the secondary. Assuming you grounded your secondary PER THE NEC, you have now violated the NEC by grounding the primary downstream from the main service a BIG NO NO. You need to change this ASAP
> 
> H1 to any phase
> 
> ...


I guess I'm not following you. H1 is not the grounded conductor. I didn't use the grounded phase on the primary side. 
Do you still see a safety issue??


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