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Thread: Continuous load question

  1. #1

    Continuous load question

    I have another question regarding Injection Molding Machines.

    Since it is an all electric machine. At times watching watching the amperage on the meter it will go to zero. Once the heaters are hot they only cycle on and off briefly (PID control) And when the machine is waiting for the parts to cool there aren't any motors running.

    The machines are hooked up and do run 24/7 but there isn't a high continous current load. It comes in blurps with each movement of an axis.

    So is it still considered a continuous load ???

    Thanks
    Mike Miller

  2. #2
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    Quote Originally Posted by mmiller
    So is it still considered a continuous load ???
    Per the definition of continuous load in Article 100 no, it is not.

    The maximum load would have to continue for more then 3 hours and I doubt that is possible with the machine you describe.

  3. #3
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    I would not call that "Continuous." You need to account for 125% of the largest motor, when calculating the load. But you don't have to account for 125% of the entire load current, since this machine does not run for 3 or more hours without stopping.
    Charles E. Beck, P.E., Seattle
    Comments based on 2008 NEC unless otherwise noted.

  4. #4
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    Bob, that's the second time in two days that you posted an answer nearly identical to mine, and managed to squeeze it in while I was typing mine. Why don't you save yourself some trouble next time, and simply say that you agree with what Charlie is about to say in the next post? :grin:
    Charles E. Beck, P.E., Seattle
    Comments based on 2008 NEC unless otherwise noted.

  5. #5
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    Quote Originally Posted by charlie b
    You need to account for 125% of the largest motor, when calculating the load.
    Charlie I don't even think we have to do that assuming this is a machine that was assembled as a unit and comes with an all encompassing label,

    Of course I would expect that someone included some extra when labeling the unit.

  6. #6
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    Quote Originally Posted by charlie b
    simply say that you agree with what Charlie is about to say in the next post? :grin:
    :grin:

    I always agree with you when your right*.













    *Right: Full agreement with Bob :grin:

  7. #7

    OC protection then is...

    So my OC protection and conductor size can be based on 125% of the largest motor load and not the total listed load on the name plate ?

    It gives 3 different loads and a total

    Motor
    Heater
    Control

    The heaters have to be up to temperature before the machine can run so there is never really both (motor & heater) of those full loads at once anyhow.

    you guys have been a great help to me

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