# 120/208y trans/ 120/240V 3 wire panel



## jdkars (May 20, 2011)

Can a three phase 120/208y transformer run a 120/240V 3 wire panel at 208V utilizing 2 hot legs from transformer and X0 as the neutral and just not using the 3rd leg from transformer?


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## BBQ (Nov 16, 2010)

jdkars said:


> Can a three phase 120/208y transformer run a 120/240V 3 wire panel at 208V utilizing 2 hot legs from transformer and X0 as the neutral and just not using the 3rd leg from transformer?


You would be giving up one third of the transformers KW.

But yeah I think I could find a way to do this code compliantly even if it is a not a great way to go.

I suggest getting a 3 phase main breaker panel.


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## reddog552 (Oct 11, 2007)

*Single phase from 3 ph*

I have done this a couple of times,ineficent YES it will work.Usually what Ive done has only been temporary get a machine up and running and wait on the proper trany get there.


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## jdkars (May 20, 2011)

*update*

Aye I agree with you fully on getting a 120/208y 4 wire panel to go with the 208/120y 3P transformer. The company I am hosted by doesnt want to buy any equipment and only wants to use what they have. Sadly this does mean 1/3 power of the transformer is lost and severely limits the capability of the panel but as for now they only intend to use this for very low 208v and 120v service.


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## Chris Kennedy (Nov 19, 2007)

I would be inclined to check the tranny's specs to see how it would handle the unbalanced load.


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## kaboler (Dec 1, 2010)

Hahahaha whacky, but good to know.


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## AFOREMA1 (Nov 23, 2009)

But then how do you get your 240 v for double pole breakers wither the 120/208 3 phase panel hook up?


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## 10492 (Jan 4, 2010)

He didn't get the answers he wanted Here .

So he asked in this area.

My answer stays the same.

I like the "good news" part.


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## 10492 (Jan 4, 2010)

jdkars said:


> The company I am hosted by doesnt want to buy any equipment and only wants to use what they have.


You can't make this stuff up.

And when someone gets hurt, caused by your lack of knowledge, expertise and general common sense, are you or your hosting company really gonna care?


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## noarcflash (Sep 14, 2011)

why would anyone care about how inefficent the trans is running ?
I would only care about how fast the meter is spinning, assuming it's the padmount trans outside the building.


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## joethemechanic (Sep 21, 2011)

AFOREMA1 said:


> But then how do you get your 240 v for double pole breakers wither the 120/208 3 phase panel hook up?


You don't, you get 208 V

Some loads are fine on 208, others well,,,,,,,,,,,,,


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## AFOREMA1 (Nov 23, 2009)

joethemechanic said:


> You don't, you get 208 V
> 
> Some loads are fine on 208, others well,,,,,,,,,,,,,


Thanks, I knew that just messing with the op.


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## joethemechanic (Sep 21, 2011)

You might be able to do some fine adjustment with different taps and end up with something like 139/240V . 

A big plus to that is your coffee pot makes coffee much faster :laughing:


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## joethemechanic (Sep 21, 2011)

Dnkldorf said:


> What is your electrical related field/trade:
> facilities maintenance supervisor
> 
> 
> Dude, call an electrician or call the fire department.



After reading the other thread I tend to agree

208V Delta with a center tap in one winding?

would that be for powering all the 104 V loads???????????


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## RIVETER (Sep 26, 2009)

joethemechanic said:


> After reading the other thread I tend to agree
> 
> 208V Delta with a center tap in one winding?
> 
> would that be for powering all the 104 V loads???????????


You seem to know your stuff.


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## Shockdoc (Mar 4, 2010)

jdkars said:


> Aye I agree with you fully on getting a 120/208y 4 wire panel to go with the 208/120y 3P transformer. The company I am hosted by doesnt want to buy any equipment and only wants to use what they have. Sadly this does mean 1/3 power of the transformer is lost and severely limits the capability of the panel but as for now they only intend to use this for very low 208v and 120v service.


Cheap now gets expensive later.


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## RGH (Sep 12, 2011)

I would be concerned about a triplen harmonic. Nonlinear load supplied by the 4wire/3ph wye.. Did you consider this? can be very very dangerous. Use a bigger nuetral?


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## joethemechanic (Sep 21, 2011)

RGH said:


> I would be concerned about a triplen harmonic. Nonlinear load supplied by the 4wire/3ph wye.. Did you consider this? can be very very dangerous. Use a bigger nuetral?


Do you think the triplen harmonic issue could be solved by disconnecting the unused phase winding from the center of the wye and creating a V?

There would still be a power factor issue because of all the excess iron but I doubt they are getting penalized for PF by the PoCo


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## RGH (Sep 12, 2011)

That could work, or install a nuetral for each phase. They gotta make it tough or everyone would do it lol !!! No matter what I think voltage issuses are a coming!!


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## Speedskater (Oct 2, 2009)

I think that "triplen harmonic's" will only be a problem in systems that have lots of Switch Mode Power Supplies (SMPS) like in PC's or lots of Variable Speed Motor Drives on all three phases. The third harmonic distortion generated by these devices is all in phase and places a heavy load on the Neutral conductor.


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