# 240 volt three phase WYE?



## K2500 (Mar 21, 2009)

I'm not sure how it could, the math doesn't work.


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## Pete m. (Nov 19, 2011)

Didn't think it existed but who am I to question an electrical engineer.:blink:

Pete


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## gnuuser (Jan 13, 2013)

K2500 said:


> I'm not sure how it could, the math doesn't work.


I agree but heres a guide (pdf on transformers)

http://www.engineerjohn.com/ncsu5/ABB_Distribution_Transformer_Guide.pdf

it may help give more options


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## RePhase277 (Feb 5, 2008)

The engineer pulled the wrong spec from his Big File of Copy-and-Paste Plan Specs.

They ought to outlaw engineered electrical plans. Electrical installations across the continent would then be designed and evaluated by ACTUAL electricians and inspectors. And, I'm sure, improve in quality.


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## triden (Jun 13, 2012)

An engineer made a mistake. That's impossible.



Pete m. said:


> Didn't think it existed but who am I to question an electrical engineer.:blink:
> 
> Pete


You should if you find a mistake. Most engineers would be happy you found it.


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## Rollie73 (Sep 19, 2010)

Sure it exists....on paper, in the engineers twisted little world. 

Engineers never make mistakes.....they make revisions.


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## BBQ (Nov 16, 2010)

Maybe the EE is fine with 138 volt L to N & G.


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## micromind (Aug 11, 2007)

BBQ said:


> Maybe the EE is fine with 138 volt L to N & G.


Lol. I know what you mean, and such a system could indeed be connected, but the OP stated 120/240; which, as you know, does not exist. 

Some generators list 138/240 on the nameplate as well as the more standard voltages.


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## micromind (Aug 11, 2007)

InPhase277 said:


> They ought to outlaw engineered electrical plans. Electrical installations across the continent would then be designed and evaluated by ACTUAL electricians and inspectors. And, I'm sure, improve in quality.


I agree 100%!! Electrical engineering is, in my opinion, the most worthless trade that has ever existed. 

And the most expensive, in more ways than one......


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## Jlarson (Jun 28, 2009)

InPhase277 said:


> They ought to outlaw engineered electrical plans. Electrical installations across the continent would then be designed and evaluated by ACTUAL electricians and inspectors. And, I'm sure, improve in quality.


:laughing:

Yeah that's what I want to do, pay electricians to sit on their ass and crunch numbers and size stuff all day.


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## Meadow (Jan 14, 2011)

They do exist, just not practical for most aplications. Theoretically you could make one with 2 120 volt transformers and one 120/240 transformer. 

You need a "4th" phase which will need to be 180 degrees out of phase from one of the other 3.


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## Meadow (Jan 14, 2011)

Pete m. said:


> I am doing the plan review on an electrical design where the engineer is asking for a 120/240 volt 3 phase WYE transformer to be installed.
> 
> Does such an animal even exist?
> 
> Pete


 

Yes but rare:


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## micromind (Aug 11, 2007)

meadow said:


> Yes but rare:


The 3ø part is not 120/240, it's 120/208. The 120/240 part is single phase. 

120/240 3ø cannot exist.


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## JRaef (Mar 23, 2009)

meadow said:


> Yes but rare:


Wow, that's a new one on me! No idea that even existed, thanks for the new info, my day is now complete...

5 will get you 10 that the "engineer" who specified this was NOT thinking of that though, he/she was much more likely a noob that ASS-u-me'd that 240/120 3 phase 4 wire was a Wye system, not a center tapped Delta.

By the way, another clue to that engineer being unqualified:
OFICIALLY, if you are discussing 3 phase systems, the higher voltage is always supposed to be listed first, even if you fail to use the "Y" in the middle. So it would be 240/120 Delta 4 wire, or 208Y120, or 208/120, any of those is considered acceptable. If you list the lower voltage first, that is SUPPOSED to mean you are talking about a single phase service. So saying 120/240 would technically mean 1 phase, not 3 phase. This is specifically done to PREVENT this kind of confusion. If the person who made up those plans didn't know this, they are not really an EE. My instructors would have slapped my hand with a yard stick if I still did that after 4 years of college...

Now, having never known that this oddball configuration even existed, I wonder how that rule would apply?

208Y120/240 3 phase 5 wire?

PS: If you had a 240V 3 phase transformer with a Wye secondary, the Phase to Neutral voltage would be 139V. So you would have to call it 240Y139 or 240/139 to be correct, if such a thing existed.


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## Pete m. (Nov 19, 2011)

triden said:


> An engineer made a mistake. That's impossible.
> 
> 
> 
> You should if you find a mistake. Most engineers would be happy you found it.


I did ask the question. Doing plan review is not all that different than inspections... I have to have an NEC reason to not approve the design. What I came up with was 240.85. I used this section only because the design indicated single pole breakers on "B" phase.

Pete


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## frenchelectrican (Mar 15, 2007)

meadow said:


> Yes but rare:


I have see it few time but it is NOT common item as well it kinda tricky to balance the load on those dammed pot cans but they can handle a bit wacky loads like that.

I found few when I was in Wisconsin so next time I get back in Wisconsin I will take the photo of that otherwise my sister can do it for me.

However one major item you have to remember is you can not run delta and wye secondary ( triphase loads ) at the same time or you will smoke them quick.


Merci,
Marc


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## frenchelectrican (Mar 15, 2007)

JRaef said:


> Wow, that's a new one on me! No idea that even existed, thanks for the new info, my day is now complete...
> 
> 5 will get you 10 that the "engineer" who specified this was NOT thinking of that though, he/she was much more likely a noob that ASS-u-me'd that 240/120 3 phase 4 wire was a Wye system, not a center tapped Delta.
> 
> ...


It is not new to me it been around about 20 years but it getting more common for last few years and the 208Y120/240 volt combo you mention yeah it do show up but for seperated drops from a common transfomer location.

Merci,
Marc


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## triden (Jun 13, 2012)

micromind said:


> I agree 100%!! Electrical engineering is, in my opinion, the most worthless trade that has ever existed.


:001_huh: You must be joking - either that or disgruntled. EE's are the reason we have an electrical grid.


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## triden (Jun 13, 2012)

Jlarson said:


> :laughing:
> 
> Yeah that's what I want to do, pay electricians to sit on their ass and crunch numbers and size stuff all day.


And design breakers that close on the proper AC cycle to minimize current transients while they compute line to line trasmission fault currents to size them accordingly :blink:


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## Southeast Power (Jan 18, 2009)

Pete m. said:


> I am doing the plan review on an electrical design where the engineer is asking for a 120/240 volt 3 phase WYE transformer to be installed.
> 
> Does such an animal even exist?
> 
> Pete


It was a typo. Give them a call.


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## hardworkingstiff (Jan 22, 2007)

jrannis said:


> It was a typo. Give them a call.


That's a great way to approach it.

A lot of people are assuming the engineer in question is an EE. In NC (and I assume it probably is the same in other states) a PE can stamp electrical drawings even if his main field of study was something else.

I've dealt with an engineer that did not understand how a MWBC can help ease VD when both circuits are operating.

Instead of a phone call, if you have an email address, maybe send an email stating why a 240Y120 service can't exist and give him time to think about how to react. Unless of course you just want to try to embarrass the engineer, which is just kind of mean.


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## Pete m. (Nov 19, 2011)

hardworkingstiff said:


> That's a great way to approach it.
> 
> A lot of people are assuming the engineer in question is an EE. In NC (and I assume it probably is the same in other states) a PE can stamp electrical drawings even if his main field of study was something else.
> 
> ...


No... I don't want to embarrass the engineer at all. I sincerely believe it is a typo and I am sending him the plan review results for the whole project which contained other issues as well.

I think it is simply a case of "cut and paste" that went wrong on the designers part. After they receive the plan review results and they want to maintain that this system exists we will have further conversation.

Pete


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## RePhase277 (Feb 5, 2008)

Ah hell... 208... 240... 277... whatever it takes:thumbup:


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## Meadow (Jan 14, 2011)

InPhase277 said:


> Ah hell... 208... 240... 277... whatever it takes:thumbup:


And thats why we have intelli-volt ballasts:laughing::jester:


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