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  1. #11
    Join Date
    Sep 2009
    Location
    South Carolina
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    570

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    Well shorter lengths for me now. Good information. Those cords was meant to hang on the wall of the shop or trailer and only play out what was needed.

    I'll have stay aware of anything that will be a heavy load on them and unwrap when that is the case.

    I never bought an extension cord on a retractable reel but they sell a lot of them. Surely the instructions don't state to pull the whole thing out.

    I bet the cord reel that melted in the pic was way overloaded for a long period and would have probably failed even stretched out, the fact it was on a reel probably greatly reduced the time it took to do so.

    Had a waterbed heater cord burn through the wood underneath the mattress and never tripped the breaker nor burn a hole in the rubber water bed.

  2. #12
    Join Date
    Dec 2007
    Location
    Los Angeles
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    2,862

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    Quote Originally Posted by elvis View Post
    I've never heard that on the ac side. So why?
    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.

    Retractable cords are usually used on tools that are not a constant load but if you were to connect a heater or high wattage worklight you do risk overloading the cord.

    For Hardrock- he also wants to pretty much run the 12/3 right at it's limit, if not over iffin' he runs his MM211 on it @ 150amps.
    Ed Conley
    http://www.screamingbroccoli.net/
    MM252
    MM211
    Passport Plus w/Spool Gun
    TA185
    Miller 125c Plasma 120v
    O/A set
    SO 2020 Bender
    You can call me Bacchus

  3. #13
    Join Date
    Dec 2007
    Location
    Los Angeles
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    10g and bigger or 12/3 with a heavy jacket and 100' lengths:

    When coiling up the cord at the end of the day, stand with your feet slightly apart and pull the cord toward you coiling up the cord between your legs.

    For heavier cords you start in the middle of the run and coil up half the cord/cable, flip it over and then pull in the other half of the run.

    Ed Conley
    http://www.screamingbroccoli.net/
    MM252
    MM211
    Passport Plus w/Spool Gun
    TA185
    Miller 125c Plasma 120v
    O/A set
    SO 2020 Bender
    You can call me Bacchus

  4. #14
    Join Date
    Dec 2007
    Location
    Los Angeles
    Posts
    2,862

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    One more tip:

    put some mason line on each end so you can tie up the cord neatly

    Ed Conley
    http://www.screamingbroccoli.net/
    MM252
    MM211
    Passport Plus w/Spool Gun
    TA185
    Miller 125c Plasma 120v
    O/A set
    SO 2020 Bender
    You can call me Bacchus

  5. #15
    Join Date
    Sep 2009
    Location
    South Carolina
    Posts
    570

    Default

    Good tips, I tried it this evening and it works pretty good.

    I also decided to make a cord 65' instead of 100. Haven't tried it out but I think it will work fine.

  6. #16
    Join Date
    Sep 2005
    Location
    East Tennessee
    Posts
    141

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    Quote 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

  7. #17
    Join Date
    Apr 2011
    Posts
    10

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    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.

  8. #18
    Join Date
    Sep 2012
    Location
    AZ
    Posts
    52

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    Quote 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.

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