230V 1-phase for welder

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Old 08-10-09, 11:11 AM
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230V 1-phase for welder

Hi everybody!

I have a Miller welder which needs 230V 1-phase. I have a panel that has 208/110V in it (a transformer sits above the panel).

I read in a similar post that somebody took 2-110V lines to get 230V...My question is if I can take a 2-pole 40amp breaker (the welder needs 80A) and just take 2-110V lines to an outlet w/ ground and get it to work? I am confused though since that would be 2-phase then rather than 1-phase due to the 2 hot wires... Can somebody please help me?

Thank you!!!
 
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Old 08-10-09, 11:48 AM
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A transformer on a normal power line is center tapped. You have 2xx volts between the beginning and end of the secondary winding. Voltage between center tap and either end is one half of 2xx. Example: Normal residential power supply you have 240v between each end. and 120v from center tap to either end.

When someone says they are taking two 120v lines to make 240 v they are wrong. They are actually taking the two hot leads on the transformer and yes if you measured to the center tap that would be 120v but that is not relevant.

From every thing you wrote my guess is this is not a single phase residential setup but a three phase commercial setup with a multi-tap not center tap transformer. The welder will probably work on 208 but that is all you are getting out of that transformer. Bottom line this is not DIY. Call an electrician.

Have you actually measured the voltages? Modern building would be more likely to use 120v.
 
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Old 08-10-09, 11:57 AM
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Yes, it's commercial. I got 3 phase 480V coming into the transformer... So would I have to get a different transformer to get 230?
 
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Old 08-10-09, 12:05 PM
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Do you have a 240 tap on the transformer? Does the manufacturer say the welder won't work on 208? Most welders will. Again though if you are not an electrician you should not be working on 480 3 phase. Don't mean to be rude but your post indicates a lack of basic knowledge.
 
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Old 08-10-09, 12:08 PM
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Just to add....even residential electricians shouldn't really be messing with commercial stuff...2 really different animals as I (barely) understand. At least that's what my neighbor back in VA told me.
 
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Old 08-10-09, 12:23 PM
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Now all the stuff about who should mess with it, my lack of knowledge aside... If any of you would have this problem, how would you get 230V 1-phase, with residential or commercial voltages available? I would just like to hear/read a way to do it...
 
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Old 08-10-09, 12:30 PM
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.My question is if I can take a 2-pole 40amp breaker (the welder needs 80A)
Again you show a lack of even basic residential knowledge. A 2 pole 40amp breaker is just that 40a. Really for your own safety and everyone in the building don't do this yourself. Check if the welser works on 208v. It almost certainly does but wheather the transformer that powers the panel can supply 80a plus all other loads is another question. Call a comecial electrician.
 
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Old 08-10-09, 12:31 PM
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Well as I said..no Pro...but residential is easy...its the same as your A/C, dryer and ranges use. OK, most times it's a little closer to 240..but that's w/in acceptable ranges for most all equipment.

The 80 amps would require some heavy duty wiring though. Bout the biggest loads in most homes is 50A.
 
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Old 08-10-09, 12:41 PM
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Many, if not most, Miller arc welders are commercial machines and would have input taps for 208, 240, (maybe 277) and 480 volts input power. The higher the input voltage the lower the amperage and the smaller the required wiring . If the only input voltage on your machine is 240 volts then you need to either use a "buck-boost" transformer to raise the 208 volts to 240 volts or you need a transformer to lower the 480 volts primary service to 240 volts. Of these two transformer options the buck-boost will be the less expensive although still not cheap.
 
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Old 08-10-09, 12:44 PM
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Most likely if it's commerical you have 208/120 3 phase coming in your panel. Anyway you should be able to hook up a 40 amp single phase welder to that at your 208 voltage. Properly if you check your voltage will be 210 or so. I would have a electrican hook this up for you to make sure everything is properly wired correct.
Jim

 
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Old 08-10-09, 01:10 PM
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@ ray2047: I get it

@ everybody else: Thank you for your tips and trying to give me a solution
 
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Old 08-10-09, 01:26 PM
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Ok ob1...glad you didn't get all offended (some new folks do). The main rule of this site is better safe than lose a member...lol.

Kinda like the doctors oath..."first, do no harm".
 
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