# 2500amps 120v from 3phase 480v 800amp service



## ElectricJoeNJ (Feb 24, 2011)

Your "boss" should know how to figure this out, I would hope. First you only say 120v. Are you talking 120/240v single phase or 120/208v 3 phase. This has an impact on the transformer sizing. Regardless both options are pretty much not doable. The 120/208v 3 phase service would require a 1000kva transformer to get 2500 amps. This trans would require 1200 amps on the 480 side. The 120/240v single phase service would require a 600kva trans and would require 722 amps on the 480 side, which doesn't leave much left.


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## Black Dog (Oct 16, 2011)

uniquecoattech said:


> I do not do much work with 3phase 480v, besides wiring equipment to it; I am wondering if this is possible for the service we have it.
> 
> My boss is looking at installing a 2500amp 120v service for a prototype project for a new design. I can't go into detail because he does not want it to leak out.
> 
> ...


You need a 480/208 volt transformer, but you will not get 2500 amps out of an 800 amp 480 volt system.

Welcome to the forum.:thumbsup:


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## dronai (Apr 11, 2011)

Hire someone who knows how to calculate and do this type of work. Trying to save money by going online to pick peoples brains, and doing an in house install, without all of the knowledge of the details, difficulties, and applications is asking for trouble.


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## uniquecoattech (Oct 7, 2014)

No, the boss (owner of the company) has his PHD in rocket science. He does not know much about the electrical wiring or wiring to code. I installed one 150amp 3phase 480v breaker to run the induction heater and we wanted to use 10 gauge wire . I had to PROVE to him he needed at least 1ga for the 10 foot test run. But back to the problem.

I figured we might not have enough amperage, but for testing 800amps should work since we would not have anything else running while testing. 

He is looking at 2500amps single phase 120v. he isn't even interested in the 208v or 240v so either work. But do to the ratings we would have to go with 120/240v since we are just working with a prototype that may never hit the market. 

In the long run which would be better 120V/208V or 120V/240V? Our main panel is rated for 1200amps but currently has 800amp main breaker. We would more than likely have to upgrade the wiring in the panel to handle 1200amps. Either way we will need the 1200amp upgrade. If it is better to get the 120V/240V we can at least wire for a test run and if all goes well upgrade the panel. IF it is better to go with the 120V/208V when we will get the panel upgraded and then test. I hope I have not totally lost everyone with my wording. Just want to know which way would be the best, most common, typical way of doing this. 

Thanks for all the help


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## uniquecoattech (Oct 7, 2014)

We are not planning on doing this ourselves. We are not sure when we are going to even start testing the new prototype. It might be a year from now. We are just interested in seeing what needs to be done. And to be honest, If I called a commercial electrician out here and had him tell us what we needed knowing we would might not even do this project. To me; that is wasting his time. This forum is to help and answer questions that is why I asked here. I do not do commercial electrical or work with 3phase. I would not even try to do this project. But having knowledge on what needs to be done. That is something I need to know before we continue.

Thank you again.


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## Meadow (Jan 14, 2011)

Ibtl


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## Meadow (Jan 14, 2011)

uniquecoattech said:


> No, the boss (owner of the company) has his PHD in rocket science. He does not know much about the electrical wiring or wiring to code. I installed one 150amp 3phase 480v breaker to run the induction heater and we wanted to use 10 gauge wire . I had to PROVE to him he needed at least 1ga for the 10 foot test run. But back to the problem.
> 
> I figured we might not have enough amperage, but for testing 800amps should work since we would not have anything else running while testing.
> 
> ...


He has a PHD in rocket science yet cant do basic thermo dynamics? If I calced the circular mils, heat dissipation area and a 90 degree celcuis insulation Id get at least a #4 copper wire. not to code but at least it will hold thermal boundaries.

Anyway, does this load have inrush or a duty cycle?


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## Speedy Petey (Jan 10, 2007)

You and your boss are both way out of your league. Please contact someone who can come on site and give you advice/help/work.


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