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  • Miller 330A BP problem

    I picked up a Miller 330A BP a little over a year ago and I am having a problem with it tripping the breaker. It happens at various times, sometimes right after I turn on the machine but mostly after I have been welding for 10 or 15 min. The key is that it trips the breaker right when I step on the pedal to start welding. I can have the the torch in mid air Not making contact or making a arc and it still dose it. Usually it does it several times and eventually stops or I just quit welding.

    Now I know I am on a circuit too small for the machine but to me it shouldn't matter because #1 I am welding at around 90-100 amps and #2 this doesn't seam to have anything to do with overloading the circuit (it happens when there is no arc) But for the record I am on a 220 volt single phase 50 amp circuit, I should have it on a 100 amp circuit.

    Any help or ideas on how to fix this? I am in the process of running a bigger circuit but I have to rewire the whole garage to get a 100 amp circuit on my service. But I suspect the problem may be something else.
    Attached Files
    Last edited by Pepe; 03-09-2009, 09:10 PM.

  • #2
    do you have a clamp on ammeter to see what the welder is drawing when it kicks the breaker?
    Bobcat 225NT
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    • #3
      Miller 330A/BP

      My guess is there is nothing wrong with your machine. The 330 was the standard of the industry for many years and is still very popular and reliable. As all transformer type machines do, this one has a large main transformer and it takes a large amount of energy to build up that substantial magnetic field it needs to operate. The net result is that when you slam that big guy on the line-and you do every time you hit the foot pedal regardless of whether or not you strike an arc, a very large inrush current flows into the transformer. Each one of these 'hits' is heating up your 50 amp breaker. I suspect you can go up to your cold machine, turn it on, hit that foot control half a dozen times without an arc and your breaker will trip. Mine always did. Ran my 300 amp on 60 amp breaker for many years and almost every time the breaker tripped it was result of operating foot control several times in rapid succession. Realistically, though, 50 amps is very dicey. weldersales

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      • #4
        Originally posted by bretsk2500 View Post
        do you have a clamp on ammeter to see what the welder is drawing when it kicks the breaker?
        Yes I do, and I was considering making up a pigtail 220v plug so that I could measure the input power amperage.

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        • #5
          Would definitely be the inrush.

          Cheers

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          • #6
            My 330A/BP tripped a 100 amp breaker at 240 volts pretty annoyingly frequently when tigging above 150A. I couldn't even strike an arc when I tested it on a 50A breaker.

            I can't say that there's nothing wrong with your welder, but I CAN say that a perfectly fine 330A/BP will blow through 50 breakers as fast as you can reset them.

            My suggestion is to wire in a 150A-200A subpanel directly to your bus bars and feed it from there. A 100 amp breaker is the very minimum you can get by with for doing little things. It doesn't draw 100A all the time, it just draws a lot more than a hundred for a moment when you step on the pedal.

            80% of failures are from 20% of causes
            Never compromise your principles today in the name of furthering them in the future.
            "All I ever wanted was an honest week's pay for an honest day's work." -Sgt. Bilko
            "We are generally better persuaded by reasons we discover ourselves than by those given to us by others." -Pascal
            "Since we cannot know all that there is to be known about anything, we ought to know a little about everything." -Pascal

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            • #7
              I have to agree.
              Breaker WAY too small. And now that it's been tripped so much, it's now weak and will trip easier.
              That machine has a huge transformer and just pulling in the contactor to weld will give a big inrush to the transformer.

              Good luck

              Andy

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              • #8
                My biggest problem is that I have a 150 amp service. I could put in a larger service but PG&E (the local electric company) has a rule that I must upgrade my underground conduit even though my existing conduit is sized properly for a 250 amp service. This would mean I would have to cut and dig up about 40 ft of my concrete driveway as well as the street. $$$$$$$

                I looked into getting a variance but that was going to piss off a lot of people and probably cause problems for myself. So it looks like I can run a 100 amp sub panel off my main just for the welder. It probably would be cheaper to get a newer inverter type machine.

                What you guys are saying about the inrush makes total since and I am sure that is my problem. Thanks for the input.

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                • #9
                  Do you guys have "motor start" breakers, this type of breaker would def help

                  Cheers

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                  • #10
                    If I had a 150 amp service, here's what I'd do:

                    I'd wire a 60 or 100 amp cutout (the type you see within 6 feet of an outdoor AC or heat pump unit) directly to the busbars of the breaker box.

                    Then I'd wire the welder into the cutout box.

                    That setup would give me the two critical things I need: overcurent protection (provided by the 150A main breaker) and a means of disconnect (cutout box).

                    And if I lived in PG&E territory, I would do this on the down-low since it is all inside.

                    But that's just what I'd do.

                    80% of failures are from 20% of causes
                    Never compromise your principles today in the name of furthering them in the future.
                    "All I ever wanted was an honest week's pay for an honest day's work." -Sgt. Bilko
                    "We are generally better persuaded by reasons we discover ourselves than by those given to us by others." -Pascal
                    "Since we cannot know all that there is to be known about anything, we ought to know a little about everything." -Pascal

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                    • #11
                      I'm getting ready to wire my 330A/BP.

                      From the main load center, I'm looking to put in a 150 amp breaker in, wire that to a line disconnect box, then connect this to the welder.

                      Does this sound right?

                      Where can I get the line disconnect switch boxes? I remember seeing a nice one at a local welding shop that had a blade type switch you pulled out. I could have sworn it said Miller Welds on it. Most of the AC ones I see are only rated 60amps.

                      My main service box is an old Zinsco box (3 phase, 4 wire, 225 amps, 240 V) and has 6 spots for huge 3/4" wide breakers. There's about 12 spots for 1/2" wide breakers as well. The smaller ones have a sticker that says no more than 100amps.

                      The larger 2 or 3 pole 150amp breakers are $200-400!!!

                      Originally posted by Bodybagger View Post
                      If I had a 150 amp service, here's what I'd do:

                      I'd wire a 60 or 100 amp cutout (the type you see within 6 feet of an outdoor AC or heat pump unit) directly to the busbars of the breaker box.

                      Then I'd wire the welder into the cutout box.

                      That setup would give me the two critical things I need: overcurent protection (provided by the 150A main breaker) and a means of disconnect (cutout box).

                      And if I lived in PG&E territory, I would do this on the down-low since it is all inside.

                      But that's just what I'd do.
                      Last edited by jcw; 03-18-2009, 10:50 PM.
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                      Miller 330 A/BP

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