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Use of Extension Cord

Discussion in 'Electronic Basics' started by [email protected], Nov 18, 2005.

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  1. Guest

    Is there a specific reason why the instructions of some electrical
    appliances say not to use an extension cord? Some appliances that I can
    think of are a vaporizer, warm mist humidifier, some TVs, VCRs, and
  2. Ralph Mowery

    Ralph Mowery Guest

    The main reason is many extension cords are made out of # 16 wire (or small
    wire). That will not carry the high current of some devices. I don't see
    the VCR or telephone needing a bigger wire but a microwave, some laser
    printers, airconditioners, and other high current devices will draw lots of
    current. The wiring in the walls for the 120 volt circuits are usually made
    of # 12 or # 14 wire for 20 or 15 amps of current.

    There would not be any problems running a short drop cord to anything if you
    used # 12 wire and the proper plugs for the drop cord. Well, maybe a
    tripping hazard if you put where you could step on it , or some fire hazard
    if the insulation on it got frayed .
  3. Terry

    Terry Guest

    Since the poster specifically mentions devices which do not take 'heavy
    amounts' of electric current my suggested answer would be 'For safety';
    since there could be danger of tripping on the wire and/or pulling over an
    electrical device in say a child's or adult's bedroom, thus spilling water
    (possibly hot?) in the presence of electricity. A possibly lethal
    Check life insurance policies; standing in wet slippers or bare feet on a
    water soaked floor/carpet trying to clean up a broken electric device is not
    Also many people have no understanding of electricity and quite blithely
    will plug a 'heavy' electrical using device such as a 1200 watt microwave
    into an extension cord designed for, at best, a few small Christmas tree
    lights and then wonder why the extension cord melts/catches fire and burns
    the house down. Check house insurance. Although the insurance company might
    deem that kind of cause 'negligence' by the policy holder!
    Another mistake can be plugging too many devices into the one extension
    cord, not of adequate rating/size to carry the total amount of electric
    All seems rather too obvious to ask? But I've seen some horrors!
  4. Gentlemen

    This is a important subject and I must compliment you on this discussion.

    One other reason for following the manufactures instructions on this issue
    is that of electrical shock caused by two appliances being at two different
    or opposite potentials.

    A few weeks ago we heard of the Preacher who was electrocuted while standing
    in the baptismal fount in his church.

    He had just reached for a microphone, which in most likelihood was connected
    to a sound system where the integrity of the grounding system, (if there was
    one) had most likely been violated. This is, as my experience as a
    electronics technician, working on electro-communications devices, common
    place. Inappropriate use of extension cords defeat the manufactures
    intents to make the product shock proof.

    This is the reason that I take the liberty of making comment on the issue.


  5. Do you know for sure that it wasn't the other way around? A bad
    heating element in an ungrounded water heater and a properly grounded
    sound system would have killed him as well.

    I had a commercial sound business for 20 years, and I only found a
    couple systems that weren't properly grounded. In fact, the racks or
    backboards had a bare solid copper 8 AWG ground wire tied into the
    building's grounding system in most locations. A lot of the cabling was
    in EMT that was bonded to the building's ground system, as well. In
    some cases I also ran a 14 gauge green THHN wire through the conduit to
    bond the far end of the conduit back to the rack or backboard.

    The only bad installs I found were done with Radio Shack or similar
    equipment by a fly by night outfit.
  6. Peter Hucker

    Peter Hucker Guest

    Am I to assume here that US electrical cords are terrible compared to UK ones? All UK extension cords are rated at 13 amps (for 3kW devices) and have a 13 amp fuse in the plug so you cannot overload them. I assume in the US this would be 26 amps (ouch! THICK wire!).
    I don't think I've ever read any instructions, fineprint, terms and conditions, or policies in my life. I have more important and/or more interesting things to do with my time!
    Er..... FUSE anyone? Don't tell me they have unfused extension cords in the US? And I thought you chose 110 volts for SAFETY......
    I've been electrocuted 6 times at proper mains voltage (240, not your pansy 110), and I'm still alive.


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  7. Ralph Mowery

    Ralph Mowery Guest

    ones? All UK extension cords are rated at 13 amps (for 3kW devices) and
    have a 13 amp fuse in the plug so you cannot overload them. I assume in the
    US this would be 26 amps (ouch! THICK wire!).
    conditions, or policies in my life. I have more important and/or more
    interesting things to do with my time!
    the US? And I thought you chose 110 volts for SAFETY......The standard US outlet is 120 volts and good for either 15 or 20 amps. It
    is fused or the breaker is rated for one or the other currents. There are
    almost no drop cords in the US that have fuses or breakers in them. I
    don't think there is any kind of standard current ratings for them either.
    Lots of them are listed as from 6 to 18 feet long and some are even 2
    conductors without the ground. They are usually only # 16 wire.
  8. Peter Hucker

    Peter Hucker Guest

    That's almost as unsafe as letting Joe Public use a handgun!

    We outlawed the old method of fusing each outlet decades ago. 2 conductor wire is only used on the equipment itself if it's double insulated.

    P.S. you didn't include "Peter Hucker wrote" at the start of the post, hence I will not see your replies by automatic filtering (I just happened to be in here).
  9. John Fields

    John Fields Guest

    In the US we have a variety of extension cords available, the
    variety encompassing choices in both both wire size (AWG, BTW) and

    As such, we can choose what we need without being forced to buy an
    extension cord with more copper in it than we need and a fuse which,
    at 13 amperes, will be largely useless except in the case of a gross
    short at the load end of the cord.

    Here, in the US, we've opted for a circuit breaker in the service
    panel which can be reset in case of an overload instead of a
    sacrificial fuse in the extension cord which _must_ be replaced if
    the extension cord is to be brought back to life.

    Makes more sense to me...
    Like posting about your ignorance?
    Whatever the reason, I can guarantee that if you pinch across your
    240 mains with both hands at the load end of your fused extension
    cord and you take a hit across your chest and I do the same at the
    end of my 120V unfused extension cord I'll have a better chance of
    surviving the hit than you will.
  10. Peter Hucker

    Peter Hucker Guest

    Myself, and everyone I know, do not buy an extension cord then use it for one purpose for the rest of its life. They get moved around. You cannot predict what you will want to plug into it in the future. And they are so cheap you may aswell get the 13 amp ones.
    It's not useless at all. It prevents the extension cord from overheating, that's what the fuse is for. The fuse in the equipment's plug stops its cable catching fire. To put a fuse of the full capacity of the wall outlet off in the fusebox is stupid, because you will most likely plug a device into that outlet with a low power consumption and a thin cord, which is now not protected.
    Yes more modern houses here have circuit breakers instead of fuses in the fusebox, and people who are obsessed with safety, I just have fuses.

    My point is the circuit breaker or fusebox fuse doesn't know what an overload is. It breaks at the rating of the outlet, not the appliance and it's cord.
    Ignorance of what? How dangerous American electrical systems are? They are more or less exactly how we used to do things. Now it's illegal here.
    Because you have circuit breakers. We do too. I don't as it's an old house and I haven't changed them. This has absolutely nothing to do with whether the extension cord is fused or not. If I removed the extension cord fuse, I would be no more likely to survive.

    Electrocution occurs when you have a weak heart. In fact statistics show that most injuries and deaths occuring from electrocution occur due to secondary accidents. Electric drill electrocutes you and you fall off your ladder, etc.
  11. Michael

    Your are correct that these sort of problems most often happen when the
    installer is a fly by night using less than professional equipment.

    Also note that in my remarks I had avoided speaking in absolutes since I did
    not know for absolute fact that their where no other factors involved.

  12. Guest

    I wasn't talking about using an extension cord with any heavy duty
    appliances such as a microwave or dryer. I meant the
    appliances/electronics that I mentioned (vaporizer, single room
    humidifier, tv, vcr, telephone).
    I could see where using an extension cord with a vaporizer or
    humidifier might pose a safety/tripping hazard with some people
    (especially children) and I understand that. But I wanted to know if
    there are any other reasons the manuals say not to use them.

    I don't see what the problem would be with using a regular extension
    cord with a vcr, tv, or cordless telephone since they're often located
    in areas of a room where the cord is not exposed. One of my problems is
    that my tv, vcr, and cable box can only be put in one area of the room
    and there is only one outlet there. This means that I can only plug in
    the tv and cable box. Where am I supposed to plug in the vcr at? That's
    why I need an extension cord. But of course, the manual says not to use
    it (and the same thing for the cordless telephone).

    If it's a safety reason like people tripping over it then that's
    something I don't need to worry about. But if there's some other reason
    then I'd like to know. I think the manufacturers should say why in the
  13. ehsjr

    ehsjr Guest

    One is not "still alive" after being electrocuted.

    Or are you talking about reincarnation?

  14. Ralph Mowery

    Ralph Mowery Guest

    As far as the electrical hazzard due to the power or current goes , if the
    total current drain is small such as a VCR, dvd, or telephone then there is
    no problem. For the TV and all the things like VCR and DVD that go with it,
    I like to use one of the power strips. Some have a minor surge protector
    built in. Probably not very effective. I do have a high dollar one on the
    TV setup and also on the computer equipment. Not that I put too much faith
    in them, but I got them at a very good price. I think they may have helped
    save the stuff in the house when a transformer went out on a power pole
    during a storm. The strips shorted but the equipment was fine. The
    electronic control on the oven went out.

    One other thing you can do is to look around at the stores and you can find
    a product where you take off the plastic cover on the wall and plug in a
    much larger adaptor that will have 4 or 6 outlets in it. The screw will
    hold it to the receptical.
  15. Peter Hucker

    Peter Hucker Guest


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  16. John Fields

    John Fields Guest

    That's just foolish. If I need a ten foot extension cord for a
    floor lamp burning a 100 watt light bulb I certainly wouldn't need,
    or want, a 13 amp monster with a fuse in it when #18 zip cord and a
    15 amp breaker in the service panel would be perfectly fine for my
    By the same token, if I plugged my 100 watt lamp into the wall with
    your 13 amp fused monster extension cord, the thin wire in the lamp
    won't be protected and could easily set fire to something if, for
    some reason, 13 amperes was was allowed to flow through it for an
    extended period of time. If you want _real_ protection, fuse the
    And your 13A extension cord does essentially the same thing when
    supplying a low-amperage appliance with a 13A supply.
    What does your smug: "I don't think I've ever read any instructions,
    fineprint, terms and conditions, or policies in my life. I have
    more important and/or more interesting things to do with my time!"
    sound like?
    All that means is that you've taken a step "forward" into more
    dangerous territory. We still have 240 V coming into every
    household for use by high-power appliances (A/C, clothes dryers,
    water heaters, electric ranges, and the like, but we also have the
    transformer secondary's center tap coming in as well. That allows
    us to use a much safer 120V for all our other needs. It's also
    cheaper to make smaller appliances that run on 120V since, for
    example, 120V transformer primaries need only be wound with half the
    number of turns as a 240V transformer for the same output voltage.
    You don't have much of an attention span, do you?

    You broached the subject of our choosing 120V for reasons of safety,
    and I was pointing out that whether we did or not, 120V is
    _inherently_ safer than 240V. The extension cord, circuit breaker
    and all the rest of it have nothing to do with it, since the fact
    remains that a 240V hit is harder than a 120V hit. Four times
    harder for the same body resistance and same contact time if you
    consider the power being dissipated in the body. Also, 240V will
    cause much more violent muscle contraction, leading to the greater
    likelihood of secondary injury.
    No, electroction occurs when you are shocked to death as was pointed
    out by another poster.

    It's also entirely possible to have a fine heart but to die from
    fibrillation caused by even a moderately weak shock.
    Then the cause of death wasn't electrocution.

    Electric drill electrocutes you and you fall off your ladder, etc.

    In that case the cause of death (if you weren't dead before you hit
    the ground was a broken neck, a concussion, whatever. But _not_

    To belabor a point, since being shocked by 240V is a much more
    physically dramatic event than being shocked by 120V, it's much more
    likely that you'll be thrown off the ladder by a 240V drill than by
    a 120V one, which bring us back to the _fact_ that 120V is safer
    than 240V.
  17. Peter Hucker

    Peter Hucker Guest

    And your lamp would stay there forever would it? And you'd never want to plug something else in next to the lamp? Do you never move anything around in your house?

    Besides, what you stated above is not safe - you have a FIFTEEN amp breaker for a ONE amp bulb?!?!? An how many amps can a #18 cord take?
    Of course the lamp is fused. All UK mains plugs have fuses, by LAW.

    Adding a 13A extension cord does not remove any protection which is already there by plugging the appliance in without an extension. The 13A fuse in the extension cord stops you plugging two 13A appliances into the end of it and melting the extension cord.
    It sounds like I realise they are a waste of time. Instructions are for people who don't have a clue how something works. The other things I listed are of no interest to anyone but a parasitical scumbag (you may know them as lawyers). In fact normal people can't understand them anyway - I once saw an agreement which contained ONE single sentence spanning the whole A4 (letter size to you) sheet of paper! Lawyers need to take basic English lessons.
    I wasn't talking about voltage. I was talking about your location of fuses, see above.

    But since we're on voltage, it's a lot more convenient to have every outlet the same, I can plug anything into any socket.

    Just a minute, does that mean you can use a 240V appliance you bought over here when you go back to the US? I thought you were 110V only.
    The reason I mentioned the fuse is thatyou did - "end of your fused extension cord".

    Anyway 240V may be more dangerous, but we can have much thinner cables. And it ain't as dangerous as you make out anyway.
    Just doesn't happen. Are you suggesting I have an unusually strong heart?

    Read the link I posted to the other pedant.
    The CAUSE of death was a faulty appliance.

    If I pushed you off a ladder and you broke your neck, you seem to be saying it wouldn't be called murder.
    Who uses corded drills anyway?
  18. John Fields

    John Fields Guest

    Neither of those is to the point, which is that an extension cord
    with a 13 amp fuse in it is very nearly the same as an outlet with a
    15 amp breaker in the service panel.
    And a THIRTEEN amp fuse for a ONE amp bulb _is_ safe?
    #18 has a resistance of 6.385 milliohms per foot, so with 15 amps
    flowing through it it'll drop:

    E = IR = 15A * 0.006385 ohms = 0.0957V ~ 0.1V

    per foot, and the power it'll dissipate will be

    P = IE = 15A * 0.1V = 1.5 watt per foot,

    hardly anything to get worried about, especially with thin
    None of ours do, so I guess you're the pansies after all.
    It sounds to me like you're a conceited idiot. Instructions are
    what you read in order to operate something properly, no matter how
    much of a clue you think you might have.

    You were talking about safety, and regardless of where the fuses are
    located, 120V is inherently safer that 240 in case of a shock.
    All our 120V sockets are the same, so so can we. Our 120V sockets
    are different from out 120V sockets for obvious reasons, but they're
    all the same also, so that's not a problem either.
    Probably 90-95% of the US is 120/240, so yes, of course we can. The
    only problem is the difference in frequency, you being on 50Hz and
    us being on 60, but that often turns out not to be a problem at all.

    Unfortunately for you, if you buy 120V appliances here and take them
    back with you you'll be out of luck unless you buy a 2:1 transformer
    to run them on.
    What are you, a child? At this point we're discussing safety and
    whether a line is fused or not makes no difference in terms of being
    shocked to death. Do you think that the 13 amp fuse in the
    extension cord is going to blow before you're dead if you take a hit
    across your chest?
    You can have cables with smaller diameter conductors for the same
    load dissipation, but you need thicker insulation.

    And, it's not "may be more dangerous", it's "_is_ more dangerous",
    so stop trying to trivialize the difference.
    No, an unusually thick head.
    Why? I see that you like to play fast and loose and, when you make
    a mistake, refuse to own up to it and, instead, cast aspersions on
    who caught you. You're a dishonest little prick.
    No, the cause of death was a broken neck.

    The reason for the accident was a faulty appliance. Big difference.
  19. Peter Hucker

    Peter Hucker Guest

    You're missing the point completely. The 13 amp fuse in the extension cord is NOT to protect things you plug into it. These should already be protected by the fuses in their own plugs. The 13 amp fuse in the extension cord is to protect the extension cord from being overloaded, by a total of more than 13 amps worth of devices being plugged into the end of it.

    Just as your fused outlet does NOT protect the appliance you plug into it, as the appliance (and it's cord) are most likely of a lower current rating than the outlet. The fuse is to protect the OUTLET from being overlaoded.
    So you have just told me that a #18 cord will happily take 15 amps. Yet earlier you compared it to a "13A monster" as though the 13A one was overkill?

    When I said pansies I was referring to electric shocks. I don't wish my house to burn down and cause me financial losses when I am not at home to operate the extinguisher.

    No, the instructions are read if you don't know how to use the device.

    But you have a mixture of different voltage and current outlets - must be highly inconvenient, aswell as providing the possibility of people plugging the wrong thing in the wrong place.

    Try writing that again!

    Anyway you said you had different current outlets earlier. Just what outlets do exist in US homes?
    Yes I noticed. Someone came to me with a £300 (!) coffeemaker (he's a perfectionist with coffee) that was imported from th US and was 120 volts. The store wanted £80 for a transformer which was bigger than the coffeemaker! I got him one for £30 from ebay (ex-building site isolating transformer).
    No, but you were wittering on about my FUSED extension cord as though the fuse would make it more dangerous.

    If we had a thinner insulation it would not be as resistant to getting damaged. A UK 240V mains cord most likely has enough insulation for a few kV (the flimsy ribbon cable for IDE hard drives for example is rated at 300 volts!), but if it was only just thick enough, it would get damaged through handling.
    It is more dangerous, but it's still trivial.

    That wouldn't stop my heart getting knackered.

    You don't get it at all do you? You're a pedant. Go look it up and learn something.

    This is like talking to a brick wall. You don't get it at all do you? You're a pedant. Go look it up and learn something.

    Too complicated for you was it? Cause is what makes the thing happen. The cause in the murder case is me. The cause in the drill case is the faulty drill.

    No, a simple question, as they are inconvenient. Any appliance which requires you to climb or move around a lot is a hell of a lot easier to use if it's cordless.
    I can use my cordless drill in the rain.
  20. That's a very common extension cord, and the most likely reason
    consumers are advised against using them. It is, again, very common
    for consumers to bypass safety grounds in their use of 'lektrizdy.
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