# How to power 240 V loads from a padmounted transformer?



## Shockdoc

WHAT DO YOU NEED 240 volts for? Most everything will operate on 208 volts. There are buck n boost transformerss available for equipment that dead on needs 230 volts to function.


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## hjsterling

Ok,
So there're some *buildings* served each with a 120/240 V delta bank. It's an old service, and 40 years ago 120/240 V delta was typical. Some (a lot of) buildings have changed to 120/208 V, but some others not. And I can't _force_ them to change. If they want 120/240 V, that's what they get. But still, I need to bury those cables.


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## wildleg

So bury the cables. What's the problem ? Where is the service point ? Can't you install handholes/manholes and extend the feeders ? I don't understand what the issue is.


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## Shockdoc

Whats wrong with tapping two phases to a neutral ? What exactly is 240 volts that needs 240 volts. Many utility companies run a three phase feeder and tap single phase power 120/208 for individual services off of the same run. Every appliance in a residence thats marked 240 volts will run perfectly on 208 volts. I don't see what you're dilema is.


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## hjsterling

My dilemma is:

I work *for *the utility company.
Nominal voltage is 120/240 V ± 3%. Lower or higher than this, and we're penalized.
Clients have 120/240 V. I can't change it because "it's my best of interests". They want 120/240 V, they have it, period.
Padmounted transformers are not 120/240 V secondary, but 120/208 V.
I'm talking about buildings served with *pole* banks of 50/50/75 kVA transformers, 100/100/100 kVA, and such. DELTA, NOT WYE.
Underground service = no poles = no delta pole banks.
See my point? 
Edit: oh I forgot to mention. These are commercial buildings; in the front side there are showrooms, in the back side they receive trucks with merchandise. And they have a lot of air conditioning load.


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## Shockdoc

hjsterling said:


> My dilemma is:
> 
> I work *for *the utility company.
> Nominal voltage is 120/240 V ± 3%. Lower or higher than this, and we're penalized.
> Clients have 120/240 V. I can't change it because "it's my best of interests". They want 120/240 V, they have it, period.
> Padmounted transformers are not 120/240 V secondary, but 120/208 V.
> I'm talking about buildings served with *pole* banks of 50/50/75 kVA transformers, 100/100/100 kVA, and such. DELTA, NOT WYE.
> Underground service = no poles = no delta pole banks.
> See my point?
> Edit: oh I forgot to mention. These are commercial buildings; in the front side there are showrooms, in the back side they receive trucks with merchandise. And they have a lot of air conditioning load.


"its your best interest", Are they drug kingpins? Are they currently wired with a high leg? There's no codes down there, install two single phase padmounts and wire them open delta.


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## hjsterling

Shockdoc said:


> "its your best interest", Are they drug kingpins?


No, they're not. And we the utility company aren't either. But that's how the rules are. You want 120/240 V, 120/208 V, 277/480 V, 240 V only, 480 V only? You got it. And it has to be ± 3%. But you want 120/240 V, I can't give you 120/208 V. Besides, the worst voltage I can give you in 240 V is 232 V. So 208 V is not an alternative.



Shockdoc said:


> Are they currently wired with a high leg?


Nope. They have... you guess it. 120/240 V.



Shockdoc said:


> There's no codes down there,


Yes we have. They're NEC 1999 adaptations.



Shockdoc said:


> install two single phase padmounts and wire them open delta.


No can do. HUGE space problems. I'm talking about 2 meter sidewalks. Besides, what would you do with a 75/75/167 kVA delta bank?


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## wildleg

I don't see how you can have 120/240 delta without a high leg. Can someone show me a diagram of that transformer ?

Are you sure you don't just have several split phase 120/240 transformers in a bank ?


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## Shockdoc

hjsterling said:


> No, they're not. And we the utility company aren't either. But that's how the rules are. You want 120/240 V, 120/208 V, 277/480 V, 240 V only, 480 V only? You got it. And it has to be ± 3%. But you want 120/240 V, I can't give you 120/208 V. Besides, the worst voltage I can give you in 240 V is 232 V. So 208 V is not an alternative.
> 
> 
> Nope. They have... you guess it. 120/240 V.
> 
> 
> Yes we have. They're NEC 1999 adaptations.
> 
> 
> No can do. HUGE space problems. I'm talking about 2 meter sidewalks. Besides, what would you do with a 75/75/167 kVA delta bank?


It sounds as if your stuck between a **** and a hard place. Why not just leave things as be and just go underground with your drops


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## oldtimer

Shockdoc said:


> It sounds as if your stuck between a **** and a hard place. Why not just leave things as be and just go underground with your drops


 I like your metaphor.:jester:


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## hjsterling

Shockdoc said:


> It sounds as if your stuck between a **** and a hard place. Why not just leave things as be and just go underground with your drops


Because THE GOVERNMENT wants it underground. And no, I am NEVER stuck between a *ock... but between a rock.



wildleg said:


> I don't see how you can have 120/240 delta without a high leg. Can someone show me a diagram of that transformer ?


Well, the Shockdoc question was, "are they currently wired with a high leg?" My answer meant that they (the clients) are not wired with a high leg, simply because no one is using it. Of course the delta banks have a high leg.



wildleg said:


> Are you sure you don't just have several split phase 120/240 transformers in a bank ?


But I have. We just don't use the high leg. We have connected 2 or 3 of these transformers to form a delta. The higher kVA transformer is used for the 120 V loads. Therefore is commonly more loaded than the other one(s). That's it.


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## Shockdoc

hjsterling said:


> Because THE GOVERNMENT wants it underground. And no, I am NEVER stuck between a *ock... but between a rock.
> 
> No pun intended, just a NY phrase
> 
> Well, the Shockdoc question was, "are they currently wired with a high leg?" My answer meant that they (the clients) are not wired with a high leg, simply because no one is using it. Of course the delta banks have a high leg.
> These are single phase services?
> 
> But I have. We just don't use the high leg. We have connected 2 or 3 of these transformers to form a delta. The higher kVA transformer is used for the 120 V loads. Therefore is commonly more loaded than the other one(s). That's it.


I have never seen a three phase transformer closed delta 120/240. you might find yourself running either single phase lines as well as your three phase 120/208


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## hjsterling

It's a HUGE problem we have here. See, the government want us (the utility company) to bury all cables in the commercial area of the city. Wye transformer banks, no prob, single 1 phase transformers, no prob. But delta transformer banks...


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## Jlarson

wildleg said:


> I don't see how you can have 120/240 delta without a high leg. Can someone show me a diagram of that transformer ?


We could show you one but it hasn't been invented yet.


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## Southeast Power

I must be missing the whole question. I see three phase open delta pad mounted transformers every day. The electrical system in Panama should be identical to the in here in the States. 
What exactly is the problem?


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## John

hjsterling said:


> Hi. I'm new to this forum, so any advise will be welcomed.
> My problem is this. I need to relocate underground a three phase line. There´re several open-delta and closed-delta transformer banks, all 120/240 V secondary, connected to it. But there're no padmounted transformers as such. What can I do?
> I'm from Panamá and the nominal voltage is 120/240 V.
> Thanks for the help.


Is this what your are talking about? If so you need to run 4 wire underground. 

View attachment 4226


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## hjsterling

jrannis said:


> I must be missing the whole question. I see three phase open delta pad mounted transformers every day.


Three phase, 13200 V delta, 120/208 V Y, padmounted? Ok.
Three phase, 13200 V delta, 120/240 V delta, padmounted??? 
Show me one, please. Just ONE. And who sell them.


jrannis said:


> The electrical system in Panama should be identical to the in here in the States. What exactly is the problem?


Read my previous posts.


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## hjsterling

John said:


> Is this what your are talking about? If so you need to run 4 wire underground.
> 
> View attachment 4226


Yes, John. Now show me where do I (the utility company) put its transformer. (Note I wrote transformer (singular).) Oh, and a pole one it's not an option. All the system MUST go underground.


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## micromind

How about an underground vault large enough to hold 3 pole-mount pots? 

I haven't seen one if a few years, but they certainly do exist.

I've seen a few pad-mount pots that are 4160, 12.5KV, or 25KV primary and 120/240 3ø 4 wire delta secondary.


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## John

micromind said:


> How about an underground vault large enough to hold 3 pole-mount pots?
> 
> I haven't seen one if a few years, but they certainly do exist.
> 
> I've seen a few pad-mount pots that are 4160, 12.5KV, or 25KV primary and 120/240 3ø 4 wire delta secondary.


I have seen some like that in basements.....seriously scary ****



hjsterling said:


> Yes, John. Now show me where do I (the utility company) put its transformer. (Note I wrote transformer (singular).) Oh, and a pole one it's not an option. All the system MUST go underground.


http://www.mhprofessional.com/downloads/products/0071467890/0071467890_ch15.pdf

http://www.surplusrecord.com/sre/037957.htm

Now just put it in an underground vault and you are good to go…


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## Southeast Power

hjsterling said:


> Three phase, 13200 V delta, 120/208 V Y, padmounted? Ok.
> Three phase, 13200 V delta, 120/240 V delta, padmounted???
> Show me one, please. Just ONE. And who sell them.
> 
> Read my previous posts.


Its usually a big transformer with a smaller transformer next to it. We have it everywhere here.


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## Bob Badger

hjsterling said:


> Yes, John. Now show me where do I (the utility company) put its transformer. (Note I wrote transformer (singular).) Oh, and a pole one it's not an option. All the system MUST go underground.



You build an underground vault and place individual 'pole mount' transformer in it.

Not really uncommon.


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## hjsterling

Ok, firstly thanks for all your posts, secondly sorry for my late reply, i was busy Saturday.



John said:


> http://www.mhprofessional.com/downloads/products/0071467890/0071467890_ch15.pdf
> 
> http://www.surplusrecord.com/sre/037957.htm


I admit those two links make a hell of a good reading, thanks John. BUT... I couldn't find the 3-ph, padmounted, 120/240 V, transformers you were mentioning about.



jrannis said:


> Its usually a big transformer with a smaller transformer next to it. We have it everywhere here.


Yes. We do either. BUT pole-mounted. And I need to design an underground net, and keep the 120/240 V to clients.



micromind said:


> How about an underground vault large enough to hold 3 pole-mount pots? I haven't seen one if a few years, but they certainly do exist.
> 
> 
> 
> John said:
> 
> 
> 
> I have seen some like that in basements.....seriously scary ****
> Now just put it in an underground vault and you are good to go…
> 
> 
> 
> Bob Badger said:
> 
> 
> 
> You build an underground vault and place individual 'pole mount' transformer in it. Not really uncommon.
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Click to expand...
Click to expand...

Mmm. Good idea. Never thought of it. From what I read in John's links, those TXs must be submersible ones. Ok. Question: how about heat build-up? The transformers must be ventilated. First thing that comes to my mind is to build a subsurface transformer sidewalk vault (http://www.ensa.com.pa/pdfs/NormasSubte/13_Capítulo%2012%20(Normas%20de%20Construcción%20Subterránea_ver.2.2).pdf, page 22 of 47). It has two ventilation grilles. Probably it has to be a little bit bigger, though.



micromind said:


> I've seen a few pad-mount pots that are 4160, 12.5KV, or 25KV primary and 120/240 3ø 4 wire delta secondary.


That's what John wrote before. I'd like to see and read more about it. But I'm afraid those ones are especially built, by solicitation. Am I right? Anyone here?

Edit/adding: I forgot to mention. The water table is a really big problem here. You can certainly say those TXs will be under (salt) water all the time. You see, my humble city is based on an island with land fillings. (http://en.wikipedia.org/wiki/Colón,_Panama, http://en.wikipedia.org/wiki/Colón_Free_Trade_Zone). Therefore, _everything _inside this vault must be waterproof.


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## Southeast Power

jrannis said:


> Its usually a big transformer with a smaller transformer next to it. We have it everywhere here.


Ours are pad mounted too. One big one with a smaller one next to it. Just like the pole mounted ones.

Ill send a pic if you like.


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## hardworkingstiff

I've seen a power company install side by side single-phase pad mount transformers with underground conductors to provide a Delta service.

I'm confused though, you said


> Well, the Shockdoc question was, "are they currently wired with a high leg?" My answer meant that they (the clients) are not wired with a high leg, simply because no one is using it. Of course the delta banks have a high leg.


I'm really confused here. If no one is using the high leg, why do you need to provide a 3-phase Delta service? Why not just provide a single-phase 120/240-volt service?

Are you reading what you are posting? Do you understand how confusing your statements are?


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## hjsterling

hardworkingstiff said:


> I've seen a power company install side by side single-phase pad mount transformers with underground conductors to provide a Delta service.


And I'm sure I could do the same if I had all the space in the world. Which I don't have. Just imagine a Beverly Hills commercial sidewalk with three of those side by side. Unacceptable, right? Same here. And no, no alleys between buildings to place them.



hardworkingstiff said:


> I'm really confused here. If no one is using the high leg, why do you need to provide a 3-phase Delta service? Why not just provide a single-phase 120/240-volt service?


Because in older times, people required 120 V service for single phase loads, in addition to three-phase 240 V for special equipment (say, freight elevators). And they haven't changed their system since then. And the utility company can't change their system if not requested by the client.



hardworkingstiff said:


> Are you reading what you are posting? Do you understand how confusing your statements are?


Erm, no. I don't think I'm being confusing. What I think it can cause confusion is that my case is very unconventional for most of you. But then again, I'm not in USA or Canada.


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## Shockdoc

Whynot supply them w/ 120/208 and throw in bucknboost transformers to achieve 240 volts for loads that require them?


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## hjsterling

jrannis said:


> Ours are pad mounted too. One big one with a smaller one next to it. Just like the pole mounted ones.
> 
> Ill send a pic if you like.


Pretty please, i'm curious.

PS you quote yourself. Heh. Not used to see that.



Shockdoc said:


> Whynot supply them w/ 120/208 and throw in bucknboost transformers to achieve 240 volts for loads that require them?


Thought of that last weekend. The issue is space. Besides I would have to deal with two transformers (one 13200 - 120/208 V and other 208 - 240 V) for each service. But definitively an alternative.


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## hjsterling

(can't find the Delete buttom.:blush


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## hardworkingstiff

Are the customers using the high leg? You said no.


> Well, the Shockdoc question was, "are they currently wired with a high leg?" My answer meant that they (the clients) are not wired with a high leg, simply *because no one is using it*. Of course the delta banks have a high leg.


The question is, do you need 240-volt single-phase, or 240-volt 3-phase (which includes the high leg that you stated nobody is using.


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## hjsterling

hardworkingstiff,
Clients do not need the high leg. They don't have 208 V loads. I repeat, delta banks have a high leg. It's inevitable. That doesn't mean clients use it.
Then, what clients need is 240 volt 3-phase. AND 120 volt single phase. Hence, 120/240 V 3-phase delta.


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## hardworkingstiff

hjsterling said:


> hardworkingstiff,
> Clients do not need the high leg. They don't have 208 V loads. I repeat, delta banks have a high leg. It's inevitable. That doesn't mean clients use it.
> Then, what clients need is 240 volt 3-phase. AND 120 volt single phase. Hence, 120/240 V 3-phase delta.


You do understand don't you, that a 120/240 V 3-phase delta has a high leg, right?

And, if no one uses the high leg, they in effect are just using a single-phase service. Therefore, if no one is using the high leg, you don't need a 3-phase delta you only need a single-phase 120/240V service.


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## hjsterling

hardworkingstiff said:


> You do understand don't you, that a 120/240 V 3-phase delta has a high leg, right?
> 
> And, if no one uses the high leg, they in effect are just using a single-phase service. Therefore, if no one is using the high leg, you don't need a 3-phase delta you only need a single-phase 120/240V service.


http://en.wikipedia.org/wiki/High-leg_delta

Now I get it. You're talking about the phase called high-leg. That wire is called high-leg simply because its phase-to-neutral voltage is 1.732 (square root of 3) times higher than the phase-to-neutral voltage of the other phases. So you and I have been talking about the same stuff.

Therefore, yes, they're using "the high-leg" in the "high-leg delta system", for the 3-phase loads. But no one's using its "high-leg voltage".

Now, _smile..._ it's contagious.


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## Shockdoc

Around here the utility co will supply you with whats most convienient to them, special needs are payable by the customer. I would welcome a closed delta service over an open delta any day of the week. I have installed simple buck transformers in he past for individual loads that required full 240 volts at a cost of about $140 ea


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## hjsterling

See, Shockdoc, it's the government who wants to bury all cables, and no TXs on sidewalks. No client has requested anything. If so, they'd have to pay it, too.


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## hardworkingstiff

hjsterling said:


> See, Shockdoc, it's the government who wants to bury all cables, and no TXs on sidewalks. No client has requested anything. If so, they'd have to pay it, too.


Burying all of those cables has got to be project with some duration, so it seems like it would be easy enough to order transformers configured the way you want them in time for the need.


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## hjsterling

Right now my alternatives are:

Bob Badger's idea (underground vault transformers).
Shockdoc's idea (transform 13200 V to 120/208 V, then 208 V to 240 V).
Convince each and every client (one by one) to shift to 120/208 V. Which will be a real pain in the grass.
Order special TXs.
So. That'll be all for now. Thanks to you for all of your comments. If anyone knows of any other idea, let me know.


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## micromind

The idea of using 120/208 and buck-boost transformers won't work on a service, only individual single or 3 phase loads that don't involve the neutral.

If you boost the 208 up to 240, you'll also boost the line-to-neutral voltage from 120 to 138. 

If you change the services from a delta to a wye, you'll also need to change the meters; they're different. The meter base is the same for delta and wye, but the meter itself is different.

Rob


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