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1500-watt extended heater cord is hot.

Discussion in 'Electronic Basics' started by Tibur Waltson, Jan 26, 2004.

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  1. I use twice the cord of the same type for twice the distance for
    a Sears portable 1500-watt heater. The problem is that the
    cord is hot to the touch when we use it for a hour or more. But
    the cord is not hot if I use a normal distance cord design for the
    heater. How do I extend the heater cord twice the distance
    without getting the cord hot?

    TIA,
     
  2. Bill Vajk

    Bill Vajk Guest

    The cause of many a fire and death.

    Use much larger cord. Continuous duty (over 3 hours) derate the
    cable to 80% of normal. Personally, I *never* use anything smaller
    than 10AWG cable for electric heat. Considering the life-safety
    implications the added cost falls away to meaninglessness (in
    my world, anyway.) If you're running hundreds of feet, 10AWG might
    not be adequate either.
     
  3. Don Bruder

    Don Bruder Guest

    So you've now moved from trying to put two coils on your car or
    jump-start it with a welder, to trying to burn your house down by
    improper use of extension cords with electric heaters...

    Dude, you're a disaster looking for a place to happen. There's only
    possible thing to say about you: You're fucking NUTS! I take that
    back... maybe there are two things: You're a troll, and a particularly
    inept one.

    Investigation/exploration/experimentation is one thing, but the crap
    you're pulling outta your ass is neither. It's sheer stupid in action,
    and quite likely to get somebody killed. I'll look for you on the Darwin
    Awards. Hopefully, your award will come soon, before you kill an
    innocent bystander with yet another of your half-baked, hare-brinaed
    ideas.
     
  4. An extension cord for a heater is 'half-baked, hare brinaed'? Thats harsh.

    Its something that alot of folks would try to do. The fact that he is asking
    is a good sign, and allows the folks who really understand this stuff (not
    me, unfortunately) to weigh in.

    I'm a bit confused by this too. If you double the length of your wire, you
    double the resistance (since R = rho * length/cross sectional area). Since
    rho is fixed for copper at 10.4, and the area for a given mil (probably #16)
    is fixed, R is proportional to length.

    Because of this, and the fact that power dissipated by a wire is I^2R, the
    power dissipated is proportional to the length.

    I would guess that the ability of a wire to dissipate heat is also dependent
    on the length, since its almost certainly proportional to the surface area
    of the wire. However, this is where I'm probably wrong. Its probably the
    case that much of the heat is dissipated by connections to the ends, and
    consequently, while heat generation is constant along the length of the
    cord, the heat dissipation is non-linear wrt length...

    However, without proper knoweledge of the mechanisms behind heat dissipation
    in power cords, I would simply rely on a pre-built cord that was designed to
    handle 1500W. The following article has some interesting facts.

    http://www.cpsc.gov/cpscpub/pubs/16.html

    Here is a fairly cheap cord that will work properly, I think:

    <http://tools.mainseek.com/333R16P789K9-Coleman-Cable-02509-100'-12/3-SJTW-O
    range-Extension-Cord.html>

    Regards,
    Bob Monsen
     
  5. Don Bruder

    Don Bruder Guest

    Harsh? Perhaps. If so, it's no more harsh than the likely results of the
    screwball ideas that this accident-looking-for-a-place-to-happen has
    been floating in the past few weeks, under the guise of "investigating"
    and "experimenting". So yes, "half-baked and hare-brained" (and do
    please pardon my transposed "n" and "a" in the first posting) seems
    quite appropriate to me.
     
  6. Oh, I thought it was dialect... sounded Scottish...

    I'm guessing that a large number of the floor heaters sold in the US are
    used with improper extension cords, probably old lamp extensions. Its
    totally unsafe, and causes fires. Therefore, posting some information
    regarding this makes perfect sense.

    Also, the basics newsgroup is for these kinds of questions. You don't want
    to scare off newbies.

    Flaming responses such as yours should be reserved for important political
    or gun control discussions on sci.electronics.design. ;)

    Regards,
    Bob Monsen
     
  7. Zipperhead

    Zipperhead Guest

    Hey...If you drive a Ford you will try anything to get it
    started in cold weather.
     
  8. Dan Akers

    Dan Akers Guest

    Tibur Waltson wrote;
    "I use twice the cord of the same type for twice the distance for a
    Sears portable 1500-watt heater. The problem is that the cord is hot to
    the touch when we use it for a hour or more. But the cord is not hot if
    I use a normal distance cord design for the heater. How do I extend the
    heater cord twice the distance without getting the cord hot?"
    ____________________________________
    Re;
    Not much info Tibur... What size is the cord? You know; the "gauge
    number"? It is doubtful that the extension you are using is of the same
    size/material (same size conductor) if the cord temperatures are
    appreciably different. It sounds like you're using a #16 or #14 cord.
    The #16 would have a dissipation of about 1.3W/ft of twin conductor
    cord, making it quite warm (especially if coiled or covered by a rug or
    such); the #14 would have about 0.8W/ft. To be safe, I wouldn't use
    anything smaller than a #12 extension; the suggestion of #10 is even
    better.
    Having said that, I was under the impression that most, if not all,
    portable heater manufacturers advise against the use of "extension"
    cords for their heaters in the owners manual.

    -Dan Akers
     
  9. Bill Vajk

    Bill Vajk Guest

     
  10. Zipperhead

    Zipperhead Guest

    Well I live in Edmonton Alberta. The low tonite is forcast at
    -35C . I have a block heater and charger on the battery.

    My extention corn runs from the back of the house out across
    the sidewalk. I felt the cord.

    Nothing feels warm at all. Can I say " Cold as a witches tit".
     
  11. Zipperhead

    Zipperhead Guest


    I meant to say cord.. It's hard to type with frostbitten fingers.
     
  12. Bill Vajk

    Bill Vajk Guest

     
  13. Zipperhead

    Zipperhead Guest

    Sure..Five stores in Edmonton.
     
  14. Hmmm... please wait...I will go take a look again...

    My goodness, I'd been using a #18 extension cord
    designed for a 1200-watt heater. The problem is
    solved, thanks to all. I had the wrong impression that
    #18 AWG/2 is better than #16 . I didn't want to ask
    for a while because it sounds sooo "hare-brained." :)
    The original cord that doesn't heat reads 16 AWG/2
    90-degrees C. I have no idea what AWG/2 stands for.
    From now on I will use #10 cords.
    sci.electronics.basics serves more than
    straighten things out - it SAVES LIVES. Thanks!

    Tibur
     
  15. AWG is American Wire Gauge. The /2 means two wires.
     
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