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12/3 so p 123-72-msha

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  • #16
    Originally posted by Broccoli1 View Post
    The Techy stuff:

    Household alternating current sets up a weak magnetic field and collapses it 60 times every second. Setting up and collapsing that magnetic field results in heat. A single cord by itself won’t create enough heat to be a problem. However, if you coil the cord so you have multiple strands running together, constructive interference increases the amount of heat generated. Coil a cord enough times, and run enough current through it and you can create enough heat to ignite household furnishings.

    Would winding the cord in a figure eight pattern mitigate this effect?
    Professional Auto Mechanic since 1974
    My own shop since 1981
    Cya Frank


    • #17
      Coiling a power cable and causing a magnetic field thus causing more heating is a myth and here is why. On all of these cables there are 2 conductors that carry the power, one with current flowing to the load and one with current flowing back from the load. This does reverse 60 times per second but the two currents are the same and cancel each other out as far as creating a magnetic field. They do have I^2*R losses (resistive heating) and this can be significant on a coiled extension cord that is overloaded. Magnetic heating is only significant with stronger alternating fields and iron cores due to hysteresis, eddy currents, and a few other effects.


      • #18
        Originally posted by Hardrock40 View Post
        Here in the manual for the 211, page 22

        When calculating max. cord length, remember to include conductor length from line disconnect device to input power receptacle.
        Input Voltage
        Input Power
        Phase Hertz Conductor Size Max. Cord Length
        120 V 1 60 14 AWG 27 ft (8 m)
        230 V 1 60 14 AWG 53 ft (16 m)
        Since the conductivity of 12g wire is 1.59 times 14g, by following Miller's recommendation you can run 84 ft of 12g. A current of 25A through 168 ft of 12g will result in a voltage drop of 6.7 V or less than 3% of 230 V. In this case the wire will dissipate 6.7 x 25 = 167W.

        A 100 ft of 12g at 25A results in about an 8V drop. Here the wire will dissipate 200W.