# Transformer question



## ESPelectricNC (Oct 30, 2015)

Ok guys! Help out the residential service man. I have a commercial job that has a 3phase 120-208 and I need to set a panel that requires 2-60amp breakers 480v. Any advice would be appreciated. Thanks!


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## wildleg (Apr 12, 2009)

ESPelectricNC said:


> Ok guys! Help out the residential service man. I have a commercial job that has a 3phase 120-208 and I need to set a panel that requires 2-60amp breakers 480v. Any advice would be appreciated. Thanks!


what's the question ?

did you look to see if there is any 480 prior to the 208 ?
are you asking how to buy a 480/208 transformer ?
do you know the power requirements for the panel you are trying to size ?
something else ?


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## ESPelectricNC (Oct 30, 2015)

What type and size transformer would I need to feed a panel consisting of 2- 60amp breakers. Got 208 3phase and I need 480.


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## don_resqcapt19 (Jul 18, 2010)

You really need to know the actual load, but if you just go by the breaker size you will need at least a 100 kVA transformer, larger if the 480 volt loads are motor loads.
What size is the 208 volt service and how much is the existing load?


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## RePhase277 (Feb 5, 2008)

And do you need 480, or 480/277?


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## ESPelectricNC (Oct 30, 2015)

Thanks! It's refrigeration equipment that I was asked to supply the electric for. I did ask for the load and was told by the refrigeration contractor that he needed the 2- 60 amp breakers at 480. I assume set a small panel at 277-480. I also would like to add an outlet off the panel as well.


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## JRaef (Mar 23, 2009)

ESPelectricNC said:


> Thanks! It's refrigeration equipment that I was asked to supply the electric for. I did ask for the load and was told by the refrigeration contractor that he needed the 2- 60 amp breakers at 480. I assume set a small panel at 277-480. I also would like to add an outlet off the panel as well.


OK, you keep saying "panel" as if that's the only issue, it isn't. If the site only has 208V, you cannot get 480V from it by just adding 480V breakers! You will need a transformer to step up your 208V to 480V. That then requires knowing details about the load so that you avoid buying a transformer that is too small or wasting money on a transformer that is too big. As was said, if the equipment is motors, the transformer must be sized to handle the starting current of those motors, otherwise the lights dim and the computers wink out. Then also as mentioned, you need to assess the size of your 208V service. If you need 120A at 480V, then that becomes almost 300A at 208V! If you only have a 200A service drop on 208V, 't ain't gonna work...


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## ESPelectricNC (Oct 30, 2015)

I know I need a transformer and that's my question. What kva size? Only info I have as far as load is 2-60amp 480 circuits needed. The 120-208 200amp panel that's existing does not have much load on it.


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## freeagnt54 (Aug 6, 2008)

@;


ESPelectricNC said:


> I know I need a transformer and that's my question. What kva size? Only info I have as far as load is 2-60amp 480 circuits needed. The 120-208 200amp panel that's existing does not have much load on it.



Let's say that equipment is pulling 100 amps 3 phase 480 that's means 231 amps from your 208 primary. That 200 amp panel isn't going to cut it.

Without knowing more information. You would probably be safe with 112.5 kva transformer. If you find out the FLA of that equipment and its low enough a 75 kva may be possible but would be seriously pushing it.


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## ESPelectricNC (Oct 30, 2015)

Good point. I'll have to request more info. I do have 3phase on the primary. Not sure if that lowers the load needed?


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## don_resqcapt19 (Jul 18, 2010)

ESPelectricNC said:


> Thanks! It's refrigeration equipment that I was asked to supply the electric for. I did ask for the load and was told by the refrigeration contractor that he needed the 2- 60 amp breakers at 480. I assume set a small panel at 277-480. *I also would like to add an outlet off the panel as well.*


A 480/277 volt receptacle outlet is somewhat rare in commercial installations.


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## don_resqcapt19 (Jul 18, 2010)

ESPelectricNC said:


> Good point. I'll have to request more info. I do have 3phase on the primary. Not sure if that lowers the load needed?


We assumed that you had 3 phase as 208 is a common 3 phase system voltage. It does not change the load, in fact, if you only had single phase, this would be much more difficult.

You will have to do a complete load calculation for the existing service and for the new loads to see if you even have enough power to do this. 

If this is a commercial installation, you may be able to get the maximum demand over the past year from the utility and use that in place of a complete load calculation for the existing service.


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## dawgs (Dec 1, 2007)

It may be cheaper to add a 480V service.


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## ESPelectricNC (Oct 30, 2015)

It's a shell of a building with several high bay's, a couple of small offices and a bathroom. Very little existing load. 
I was going to wire up 4 more small offices and power up a sign. No problem until they dropped this cooler on me. I work alone doing mostly service calls. Hate to admit but I'll probably have to let this one go unless I bring in a friend with solid commercial experience which I tried to do. I think this one is a goner. Thanks all for your input.


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## RePhase277 (Feb 5, 2008)

ESPelectricNC said:


> It's a shell of a building with several high bay's, a couple of small offices and a bathroom. Very little existing load.
> I was going to wire up 4 more small offices and power up a sign. No problem until they dropped this cooler on me. I work alone doing mostly service calls. Hate to admit but I'll probably have to let this one go unless I bring in a friend with solid commercial experience which I tried to do. I think this one is a goner. Thanks all for your input.


For $43000 I'll go to NC and help you out.. you provide all the materials.:thumbup:


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## ESPelectricNC (Oct 30, 2015)

Haha yeah! If by materials, you mean beer's, c'mon! After a few I'll talk you down on the price :beers::stuck_out_tongue_winking_eye:.


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## oliquir (Jan 13, 2011)

do they need 60 amp 480v single or 3 phase??


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## frenchelectrican (Mar 15, 2007)

oliquir said:


> do they need 60 amp 480v single or 3 phase??


I am pretty sure it is 3 phase..

Now i willl give the OP a chance that he can hevay up to 400 or 600 amp service that way it will be large enough..

And also there is a headup about refrigid contractors is ask for cut sheet or manufacters specs


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## Southeast Power (Jan 18, 2009)

ESPelectricNC said:


> Good point. I'll have to request more info. I do have 3phase on the primary. Not sure if that lowers the load needed?


OK,
Lets back up a bit.
You mentioned primary.
Makes me think that you have a transformer.
This leads me to believe that maybe, you have a 3 phase 480 volt disconnect ahead of your transformer.
Can you intercept the primary side of the transformer and install a 480 volt panel?
You can then feed the transformer out of that panel.
All of this is contingent upon the size of the primary feeder.


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## just the cowboy (Sep 4, 2013)

*Check with manufacture*

First check with the manufacture and see if the unit comes in 208v or see if they can include the xformer as part of there package.


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## AK_sparky (Aug 13, 2013)

If the equipment needs 480V with 2 breakers, it is a single phase item, power is:
480 x 60A = 28.8kVA

37kVA transformer would be sufficient, unless you have high inrush.

It would seem strange though that equipment would be 60A 480V single phase. As suggested, get a cutsheet or better specs from the supplier of the equipment.


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