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480v to 208 volt - efffect on amps?

1/20/15       
Will Dameron Member

Hope I'm posting this in the right place... not really sure,,,

I am in the middle of opening a woodshop - a community based shop where people will be able to purchase a membership, and come in and get to use the shop. As such, it is possible that many of the tools will be used at once, so I could potentially draw a lot of amps.

I'm in the middle of looking at buildings, but unfortunately I'm no expert at electricity. One of my prospective buildings has a 480v panel, (250 amps I believe), with a stepdown transformer to give me 120/208 volts. However, I'm not sure of how many amps are available on the 120/208 panel. I believe its 200, but I'm not sure.

My question is this - if I step down 480 volts to 208 volts, does my amperage double? Meaning I can get a total of 500 amps at 208 volt if I needed to?

If I did that, would I most likely need a second panel and/or transformer? I have calls out to electricians to come take a look, but scheduling these guys is like hearding cats. I figured I'd post here and see if someone can at least get me some preliminary answers. Thanks,

Will

1/20/15       #2: 480v to 208 volt - efffect on amps? ...
Bruce H

No. Tools that run on 440 volt will use 1/2 the amps on 440 volt that they will require on 220v. Unless you are purchasing industrial equipment most likely they are not going to run on 440 volts and might not even run on three phase. I'd say you need an electrician and your tool requirements to get this right.

1/20/15       #3: 480v to 208 volt - efffect on amps? ...
Will Dameron Member

I think I may have posted unclearly, or else the post was misread. Everything will run at its intended voltage - I have 2 480 volt machines, a bunch of 220 volt machines, and of course 110. I talked to an electrician today and he confirmed what I was thinking - when you cut in half volts, you double amperage. This is why a machines draw less amps when working on 220 then on 110. Power coming from the panel is the same - it comes in at 480, will go through a transformer to drop it to 208, into another breaker panel, and from there out into the shop. The second panel, the one that has been stepped down from 480 to 208, will more or less have double the amperage available then the 480 one would have. In any case, he's meeting me there Thursday to double check everything and advise accordingly. Thanks,

Will

1/21/15       #4: 480v to 208 volt - efffect on amps? ...
Bruce H

Still NO. The panel amps are what they are. your machines consume half the amps on 440 volts as compared to 220 volts. You will use twice the amps on 220 volts as compared to 440 volts. You do not have more amps available to use on 220 volts. If you panel has 200 amps that is what you have. Your machinery draw will be different depending on the voltage.

1/21/15       #5: 480v to 208 volt - efffect on amps? ...
Will Dameron Member

Ah I see. Well thanks for the clarification. I'm looking forward to meeting with the electrician tomorrow, and getting my head wrapped around all this. Sounds like the space may not have enough amps for me. Thanks,

Will

1/25/15       #6: 480v to 208 volt - efffect on amps? ...
Factory Owner Member

Bruce H,

If you have 200 amps coming in at 440 and you run it through a step down transformer, you will have 400 amps available @ 220.

1/25/15       #7: 480v to 208 volt - efffect on amps? ...
Will Dameron Member

Correct Bruce. I have confirmed this with an electrician, who has walked the building down with me.

My previous posts may have been unclear, or you may have misread, but if you have 200 amps coming in at 480, once you run it through a stepdown transformer to get 208 volts, you have cut in half your volts, but doubled your amperage, at the panel after the transformer. At that new panel, the one after the stepdown transformer, you have 400 amps available, at half the original voltage, meaning this building does have enough power for my needs.


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