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Duty Cycle and Fan on Demand

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  • Duty Cycle and Fan on Demand

    Of course we all weld with two stop watches to monitor our weld time and cool down time so we don't exceed the duty cycle of our welder Those who want to brag about their 100% duty cycle industrial power sources - please go haunt some other thread. I do not have a 100% duty cycle machine and this question is not about 100% duty cycle machines.

    Miller included a feature on many of their machines which they call "fan on demand" which runs the cooling fan only as required to maintain the temperature of the machine. If I operate my Diversion 165 at an amperage corresponding to its 30% duty cycle rating for 3 minutes I am, in theory, supposed to wait 7 minutes for it to cool. However, the "fan on demand" will shut off the fan after perhaps 3 - 4 minutes.

    So my question, (any Miller reps on the forum?) is...

    Is it safe to consider that the necessary cool down period has elapsed when the "fan on demand" shuts off the cooling fan - thus allowing me to start welding again?



  • #2
    Personally, its up to you to know your limits, so what, the fan comes on, keep on welding. If and when the machine shuts down. There's your limit.


    • #3
      Thanks cruizer (I think). Seems I remember Clint Eastwood saying something relate to
      its up to you to know your limits
      and not in a very flattering sense. I trust you are referring to the limits of the machine

      That said, the fan comes on shortly after I initiate welding. If I am really pushing it hard I will need to stop after a couple or 3 minutes to get more filler, re-position myself or what I am welding or some other reason. Just out of habit I allow the machine a little cooldown time.

      I am not sure that it is a good idea to allow the machine to heat up until it hits its safety shutoff temperature. At least the books say that is not a good idea. In fact the only time I recall doing that was on my Hobart Handler 180. I was running some flux core wire over at my neighbor's place. The machine quit welding. The fan was running but no wire feed. I suspected that I had overheated it. I walked back to the house to get the manual to find out how to reset the thermal protection. By time I got back it had cooled down and was working again. I just took a break every so often and finished the job with out further issue.




      • #4
        Sorry, yes the machine limits. And the fan will come on with the machine just sitting there on and unused, often to check if a fan is working, I just leave the machine on and do something else till it kicks on. (inverters)

        Very seldom can you actually test the limits of the machine to make it shut down till it cools off.

        Say your 180 for instance, yes you over shot the tolerance, however, the machine is really a 030 wire machine and pushing it on 035, you were likely running 035. At 030 the machine would likely have never shut down
        Last edited by cruizer; 10-20-2012, 10:28 AM. Reason: apparently I mistplaced an I for a U in shut


        • #5
          My opinion has always been that you can weld up to the duty cycle time and if the fan shuts off early the machine must be col enough to weld again.


          • #6
            Thanks again cruizer,

            I was indeed running .035 flux core.

            And thanks walker,

            I am thinking the same thing. Perhaps someone from Miller will chime in with the Company line.



            • #7
              I never use the fan as my timer. Depending on the temperature in my garage, the fan on my Diversion 180 might come on after only 1 minute of welding at 65 amps. Of course it could be 100 degrees in my garage during the summer. But the fan is on more often than not.
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