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  1. #1
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    Oct 2004
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    Default Stick welder query

    I have a simple transformer welder plugged into a 15A circuit.
    Every so often, when switching it on at the power point, it trips out the contact breaker in the fuse panel. It's a bit annoying to have to reset it each time it does that. If it switches successfully, no further problems and I can weld merrily away.
    Is there some type of special contact breaker that I could fit, that can cope at switch on?

    Jordan

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  3. #2
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    Default

    I think D type/curve circuit breakers are recommended for inductive loads.

    Having said that I reckon there is something else going on. Could just be a faulty circuit breaker.
    Cheers.

    Vernon.
    __________________________________________________
    Bite off more than you can chew and then chew like crazy.

  4. #3
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    This is how I would tackle this problem
    1) get the welder tested as there could be a problem with it. If there is too much metal dust and moisture inside the welder it could be partially shorting out on start up
    2) check there is nothing else connected to the 15A circuit.
    3) If you using an extension cord of any kind get that checked out and make sure it is a 15A cord

    If all of the above checks out it may be problem with the 15A circuit itself e.g. it may be fitted with a fast acting 16A breaker.
    A sparky can change this for you to a slower acting circuit and if necessary a 20A breaker.

    Given the sporadic nature of the welder I suspect 1) Welders should be occasionally cleaned internally to reduce this problem.

  5. #4
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    Default

    Thanks

    I'll give the welder a clean to start with.

    Jordan

  6. #5
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    May 2011
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    Murray Bridge SA
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    Default

    Hi Jordan, I've found that it is usually the circuit breaker that is at fault, as there can be quite a sudden load on the breaker (told by BIL sparky), I had him fit a 20amp breaker and that solved the problem.
    Kryn

  7. #6
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    Thanks, but I'm a little nervous about that fix.
    A higher amp breaker could stop it tripping, but it's a 15A circuit.
    The wiring is rated for 15 amps, so in theory could carry up to 5 amps more before it tripped out, possibly overheating the cable if there were a short at the welder or anything else I plug in.
    I might sound like a nervous nelly, but if an insurance investigator saw that, as no doubt he would after a fire, it'd be embarrassing.

    As mine is now, the breaker only trips sometimes on switch on, due to inrush current I guess, but if it switches on it stays on OK.
    So the RCD safety switch part of it is not indicating an earth leakage problem.
    A special 15A breaker that can handle a higher inrush current could be the answer, but these seem to be in the hundreds of dollars.
    I'll check the cheap fixes first.

    Jordan

  8. #7
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    If the 15A circuit has been correctly installed it should cope with a much higher temporary start up current than 15+5 A .
    It's not unusual for start up currents on a 3HP (15A) to be in the range of 50-60A.

    The type of breakers that are usually installed in domestic wiring are "C Breakers".
    Circuits that run Welders and Motors that have high start up currents are sometimes fitted with "D Breakers" that can handle big start up currents for longer.
    They should not cost much more (a few $) than "C" type breakers. The arm and a leg part may come from what a sparky charges to install and test the circuit.

    Page 82 on this document http://www.bnr.com.au/product_data/pdfs/4%20series.pdf
    Describes the various types of breakers and their application.
    It specifically refers to using a "D" type breaker for a Welder Circuit.

  9. #8
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    With a 20A contact breaker fitted though, the cables etc could be subject to near 20A for a long time, not just at startup.
    Thanks for mentioning the D type breakers. I might have been looking up the wrong sort of thing, if they are really only a bit more expensive than the common type.

    Jordan

  10. #9
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    Quote Originally Posted by nadroj View Post
    With a 20A contact breaker fitted though, the cables etc could be subject to near 20A for a long time, not just at startup.
    True, but that's not a problem of the wiring can handle it. Some household circuits with only 10A GPOs connected to them have C20A breakers fitted


    Thanks for mentioning the D type breakers. I might have been looking up the wrong sort of thing, if they are really only a bit more expensive than the common type.
    Jordan
    Good to hear.

  11. #10
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    I suspect you have a problem somewhere in the circuit, either welder or switch gear. I have never known a transformer welder to trip out a circuit breaker upon start up.
    As BobL said, even a C curve circuit breaker is rated for an inrush current many times the breaker rating.
    Many people misunderstand how a circuit breaker works. A 15A breaker will not trip instantly at say 16A (or even 20A for that matter), most likely it will take a period of some minutes for the bimetal strip to heat sufficiently to trip. Once tripped of course, it will trip at lesser intervals because it is already pre heated to a degree. For a 15A breaker to trip instantly would require a current of probably at least a 150A. A 9" angle grinder for example may well pull 50A as an inrush current, working on the 5X rated current rule. Even more if it is used on a long extension lead with small cross section wire. Voltage drop = Amperage increase for the same workload = hot leads and hot tools with shortened lives.
    One down and dirty way to check for arcing within your welder would be to remove the covers, UNPLUG IT FIRST, then in a darkened room, presumably your shed at night, plug it in and flick the power point on. Any arcing will be obvious in the dark, hopefully accompanied by the breaker tripping, allowing you to further investigate. Stay well clear of all the uncovered bitey bits while you do this.
    If you are lucky, you will see a trace where the arcing has been taking place, if in fact it has, when you remove the covers.
    Definitely something amiss though.

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