Breaker Size
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Thread: Breaker Size

  1. #1
    Join Date
    Feb 2007
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    Breaker Size

    Hi Guys

    I have a new to me Miller Syncrowave 351 - it will need to hook up to a 200AMP panel that has plenty of room on it and will not often have other things going on if the Welder is running ...

    The unit does not have power correction capacitors

    According to the manual, that means it needs a full 200 AMP breaker - is that what other people's experience is?

    Am I correct that if I go down in breaker size (to say 150 or 125) that means I limit the amperage I can use? is that limitation a straight 2 to 1 ratio (deriving from 400 amps of welding at wide open throttle needing 200 amps of breaker)?

    Thanks

  2. #2
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    Re: Breaker Size

    I'm running mine on a 100 amp breaker.
    Lots of welding amps available with my little breaker

    Yes, a smaller breaker will trip at a lower welding output.
    Dave J.

    Beware of false knowledge; it is more dangerous than ignorance. ~George Bernard Shaw~

    Airco 300 - Syncro 350
    Invertec v250-s
    Thermal Arc 161 and 300
    MM210
    Dialarc
    Tried being normal once, didn't take....I think it was a Tuesday.

  3. #3
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    Re: Breaker Size

    Thanks Dave

    So, if watts=amps x volts and I went with a 150amp breaker

    220v x 150a = 33,000w

    Does this machine convert the voltage to 30? - that doesn't seem right b/c that gives 1100 amps to keep the formula even

    Said differently, how many amps of welding would the welder put out at 150 amps of breaker?

    Thanks!
    Last edited by edl; 03-20-2019 at 08:02 AM.

  4. #4
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    Lockhart,Tx (BBQ capitol of the world)
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    Re: Breaker Size

    "According to the manual, that means it needs a full 200 AMP breaker"

    Only if you are going to be welding at the maximum welder output all the time.
    If you don't ever go over 200 amps welder output then a 100 amp breaker will be fine.

  5. #5
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    Re: Breaker Size

    Thanks Rexcormack

    I would like to take advantage of the thing being a beast from time to time...the max i can put on is 150amp breaker...now i am just trying to figure out how many welding amps that is to know what setting not to exceed on the welder....

  6. #6
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    Re: Breaker Size

    Quote Originally Posted by edl View Post
    Thanks Rexcormack

    I would like to take advantage of the thing being a beast from time to time...the max i can put on is 150amp breaker...now i am just trying to figure out how many welding amps that is to know what setting not to exceed on the welder....
    You'll know when you trip the breaker. It's not easy to calculate. A breaker will hold more amps than it is rated at for brief periods. And most of the time your only welding in brief periods, not continuously.
    Tim

    Miller
    MM 252, 350P

  7. #7
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    Re: Breaker Size

    Quote Originally Posted by edl View Post
    Thanks Dave

    So, if watts=amps x volts and I went with a 150amp breaker

    220v x 150a = 33,000w

    Does this machine convert the voltage to 30? - that doesn't seem right b/c that gives 1100 amps to keep the formula even

    Said differently, how many amps of welding would the welder put out at 150 amps of breaker?

    Thanks!
    No need for calculations, here is the chart from my syncro 350 - check out the input amps at the correct voltages for non-PFC.

    230 vac at 130 amps input = 29,900 watts.

    34 vac at 350 amps output = 11,900 watts.

    Not very efficient power usage for big power, but it'll get'er done


    Name:  syncro 350 input.jpg
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    Last edited by MinnesotaDave; 03-20-2019 at 10:07 AM.
    Dave J.

    Beware of false knowledge; it is more dangerous than ignorance. ~George Bernard Shaw~

    Airco 300 - Syncro 350
    Invertec v250-s
    Thermal Arc 161 and 300
    MM210
    Dialarc
    Tried being normal once, didn't take....I think it was a Tuesday.

  8. #8
    Join Date
    Oct 2014
    Posts
    525

    Re: Breaker Size

    It is 240 volt power.

    At 240 volt a 125 would be plenty.

    You are not likely going to trip that 150. Your fine. Many are fed with 100 because often that is all you can get for a particular panel and even that makes do in just about every case.
    Last edited by danielplace; 03-20-2019 at 12:29 PM.

  9. #9
    Join Date
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    Re: Breaker Size

    If he runs 200 amp wire to the machine why would he need a breaker at all?
    Miller Challenger 172
    Miller Thunderbolt AC/DC 225/150
    Miller Maxstar 150 STL
    Victor 100C
    Victor Journeyman
    Oxweld OA
    Harris O/A
    Smith O/A little torch

    No, that's not my car.

  10. #10
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    Apr 2006
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    Re: Breaker Size

    The breaker must not exceed the wire capacity going to the welder outlet. Don't just increase the breaker size until the capacity of the building wire after the breaker is determined.

  11. #11
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    Re: Breaker Size

    Quote Originally Posted by triptester View Post
    The breaker must not exceed the wire capacity going to the welder outlet. Don't just increase the breaker size until the capacity of the building wire after the breaker is determined.
    Dedicated welder circuits fall under a special category and the wire is sized for the load including duty cycle.

    As a result, welding circuits can have "undersized" wire.

    There is a chart for it.
    Dave J.

    Beware of false knowledge; it is more dangerous than ignorance. ~George Bernard Shaw~

    Airco 300 - Syncro 350
    Invertec v250-s
    Thermal Arc 161 and 300
    MM210
    Dialarc
    Tried being normal once, didn't take....I think it was a Tuesday.

  12. #12
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    Re: Breaker Size

    Actually a series of charts. Table 630.11(A) in NEC gives multipliers varying with duty cycle. Name:  630.15.jpg
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    Many machines don't provide I1eff. Multiply by factor offered. Example:

    350 @ 40% Duty .63 x 130=81.9 Amps. or

    300 @ 60% Duty .78 x 114=88.92 Amps.

    Go then to Table 310.15(B)(16). Copper, or aluminum is likely to have 90 degree insulation. But terminals are likely rated 75 degree C.

    Conductors are copper: #3
    aluminum: #2

    Back to 630.12(A). 200% of rated primary current. I'll guess a 228 amp breaker is not available for this panel. Big B may be right, no circuit breaker is needed. I do wonder how I'd derive 200 amps of power from a buss without a breaker. Most manufacturers will offer a 4 place breaker with internal common trip, not cheap.
    An optimist is usually wrong, and when the unexpected happens is unprepared. A pessimist is usually right, when wrong, is delighted, and well prepared.

  13. #13
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    Re: Breaker Size

    Quote Originally Posted by Willie B View Post
    Actually a series of charts. Table 630.11(A) in NEC gives multipliers varying with duty cycle.

    Many machines don't provide I1eff. Multiply by factor offered. Example:

    350 @ 40% Duty .63 x 130=81.9 Amps. or

    300 @ 60% Duty .78 x 114=88.92 Amps.
    Perfect example of why my 75 amp breaker trips sometimes, but my 100 amp breaker never does

    (on my syncro 350)
    Dave J.

    Beware of false knowledge; it is more dangerous than ignorance. ~George Bernard Shaw~

    Airco 300 - Syncro 350
    Invertec v250-s
    Thermal Arc 161 and 300
    MM210
    Dialarc
    Tried being normal once, didn't take....I think it was a Tuesday.

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