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120-240-480

Discussion in 'Home Power and Microgeneration' started by m Ransley, Jul 6, 2004.

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  1. m Ransley

    m Ransley Guest

    Does a 240v house use less energy than a 120v. If so why is
    everything 120. If so why isnt 480 used for central AC. I understand
    long distance transmission, but in a house does it give a % difference.
     
  2. Ray

    Ray Guest

    The short answer is that it's just convention -- they started out with
    110-120V @ 60 Hz, and changing it would be too expensive. In Europe,
    OTOH, the convention is 220V @ 50 Hz.

    I'm sure that safety was a factor in the original decision. If you get
    zapped with 120V, you probably won't die. Some do, but it's generally
    because the person has been weakened in some way, is wet, or some other
    factor.

    Factories use higher voltage because factories use a whole lot of power,
    and you can transmit more power through a given wire if you use a higher
    voltage. Also, the electric motors can use smaller gauge wire
    internally if the voltage is higher.

    In a factory, professionals are responsible for the safety of the
    system. Generally, anyone who is messing with the system is presumed to
    know what he is doing. At home, kids have been known to stick keys and
    pennies into wall sockets.

    I have worked with live 120V circuits. I know that if I touch it, it'll
    hurt, but isn't likely to kill me. I get paranoid around the 440V
    3-phase stuff, though.

    An illustrating story:

    My father is the plant manager at a large brass manufacturing factory.
    One day, an electrician had to work on the live 440V 3-phase service.
    Before he came, my father put some plywood on the floor to give him
    something other than concrete to stand on. Also, he stood by with a
    long 2X4 (board). When the electrician asked what he was doing, Dad
    replied that he would use the board to pry him off if he managed to get
    locked on to the circuit. Luckily, nothing happened. :)


    Ray
     
  3. dont think so, the main reason for 480 distro is that you get less
    loss in the cable, as power loss is a fuction of resistance and
    current, if you double the voltag, you half the current.
    so you just transform down to 120v (230v in europe)for the local cable
    to the user

    480v is a quite dangerous in a household.




    martin

    Serious error.
    All shortcuts have disappeared.
    Screen. Mind. Both are blank.
     

  4. In a country where we have 240 volts as household power and 415 volts (3 x
    240 volts) in some houses and in factories (Australia) may I say a few
    things about our power supply, just as a point of interest.

    All appliances in Australia are 240 volts, but some cookers (Ranges) can be
    wired for 2 phase (2 x 240 volts) operation, and some air conditioning units
    (larger ones) are 3 phase (415 volt) units.

    First of all 415 volts is not a single cable carrying 415 volts, it is 3
    cables each carrying 240 volts, between neutral or earth, or you get 415
    volts between any two of those 3 phase cables.

    While it is possible to connect ones body between 2 of those 3 phases, it
    is a pretty hard thing to do, and anyone getting electrocuted is usually
    connected between one wire (phase) and earth (240 volts).

    Household power in Australia is 240 volts, IE one of the phases, and they
    run 415 volt wires down the street, (3 phase + neutral) and for households
    that use 240 volts they get one phase and neutral coming in to the house.
    The load is balanced by the first house in the street getting "A" phase, the
    second getting "B" phase and the third in the street getting "C" phase, and
    so on and so on, so the load is balance over the three phases.

    There are no transformers in the power supply in the house in Australia, as
    there are in the USA, but we run direct from the street mains.

    If you have a large air conditioning unit in a home, they will run in 3
    phase power, and then the load is split over the 3 phases in the home. IE
    some power circuits (outlets) are on "A" phase, some on "B" and some on "C",
    while the air conditioning system runs on the whole 3 phases. The hot plate
    (Range) is then connected to usually 2 of the phases, while the oven is on
    the third.

    In modern homes they have a 80 amp single phase 240 volt cable feeding the
    home. This is protected by a HRC fuse (High Ruptured Capacity) "cartridge
    fuse" and then you have a RDC (Residual Current device) also called a ELCB
    (Earth Leakage Circuit Breaker) that some people call a safety switch that
    protects people from electrocution if you touch a live connection and
    something that is earthed. The RDC is to endeavour to protect anyone from
    being electrocuted by connecting between a phase wire and earth, it does not
    protect one from connection between a phase wire (240 volts) and neutral
    (Black wire).

    The household power is the distributed via either fuses or circuit breakers
    on the switchboard throughout the home.

    All power points (Power outlets) in Australia are earthed, as are all hard
    wired appliances (Cookers, Ranges, Ovens, Air Conditioning Systems etc).

    The earth wire (green on old wiring or yellow and green in the new) is
    connected to the neutral (black wire) in the switchboard and this is called
    MEN (Multiple Earth Neutral) the earth then carries on to be connected to
    both a water pipe and an earth stake in the ground. In a single phase house
    the phase (active) wire is usually red in colour.

    In the country areas that are sparsely populated in a few areas they use a
    system called SWER (Single Wire Earth Return) this is a 480 volt system that
    a single wire carries the power to the home, farm or whatever, and at the
    end of that wire is a transformer that breaks down the power to 240 volts,
    the power then runs into the home on cables like a convention system. The
    transformer picks up its power from the 480 volt line and returns it to the
    power station via the earth, hence the name.

    I have seen some pretty big motors running on 3,300 volts, now that is nasty
    stuff :)
     


  5. In a country where we have 240 volts as household power and 415 volts (3 x
    240 volts) in some houses and in factories (Australia) may I say a few
    things about our power supply, just as a point of interest.

    All appliances in Australia are 240 volts, but some cookers (Ranges) can be
    wired for 2 phase (2 x 240 volts) operation, and some air conditioning units
    (larger ones) are 3 phase (415 volt) units.

    First of all 415 volts is not a single cable carrying 415 volts, it is 3
    cables each carrying 240 volts, between neutral or earth, or you get 415
    volts between any two of those 3 phase cables.

    While it is possible to connect ones body between 2 of those 3 phases, it
    is a pretty hard thing to do, and anyone getting electrocuted is usually
    connected between one wire (phase) and earth (240 volts).

    Household power in Australia is 240 volts, IE one of the phases, and they
    run 415 volt wires down the street, (3 phase + neutral) and for households
    that use 240 volts they get one phase and neutral coming in to the house.
    The load is balanced by the first house in the street getting "A" phase, the
    second getting "B" phase and the third in the street getting "C" phase, and
    so on and so on, so the load is balance over the three phases.

    There are no transformers in the power supply in the house in Australia, as
    there are in the USA, but we run direct from the street mains.

    If you have a large air conditioning unit in a home, they will run in 3
    phase power, and then the load is split over the 3 phases in the home. IE
    some power circuits (outlets) are on "A" phase, some on "B" and some on "C",
    while the air conditioning system runs on the whole 3 phases. The hot plate
    (Range) is then connected to usually 2 of the phases, while the oven is on
    the third.

    In modern homes they have a 80 amp single phase 240 volt cable feeding the
    home. This is protected by a HRC fuse (High Ruptured Capacity) "cartridge
    fuse" and then you have a RDC (Residual Current device) also called a ELCB
    (Earth Leakage Circuit Breaker) that some people call a safety switch that
    protects people from electrocution if you touch a live connection and
    something that is earthed. The RDC is to endeavour to protect anyone from
    being electrocuted by connecting between a phase wire and earth, it does not
    protect one from connection between a phase wire (240 volts) and neutral
    (Black wire).

    The household power is the distributed via either fuses or circuit breakers
    on the switchboard throughout the home.

    All power points (Power outlets) in Australia are earthed, as are all hard
    wired appliances (Cookers, Ranges, Ovens, Air Conditioning Systems etc).

    The earth wire (green on old wiring or yellow and green in the new) is
    connected to the neutral (black wire) in the switchboard and this is called
    MEN (Multiple Earth Neutral) the earth then carries on to be connected to
    both a water pipe and an earth stake in the ground. In a single phase house
    the phase (active) wire is usually red in colour.

    In the country areas that are sparsely populated in a few areas they use a
    system called SWER (Single Wire Earth Return) this is a 480 volt system that
    a single wire carries the power to the home, farm or whatever, and at the
    end of that wire is a transformer that breaks down the power to 240 volts,
    the power then runs into the home on cables like a convention system. The
    transformer picks up its power from the 480 volt line and returns it to the
    power station via the earth, hence the name.

    I have seen some pretty big motors running on 3,300 volts, now that is nasty
    stuff :)
     
  6. m Ransley

    m Ransley Guest

    There are no in house transformers in USA ,
     
  7. Ray

    Ray Guest

    He is probably talking about the large cans on the pole.

    In America, if you look up at the telephone poles, you'll see two or
    three thin wires at the very top level. These wires distribute the
    power around the neighborhood at something like 40,000 volts (I don't
    recall the exact voltage, and I believe it varies).

    Anyhow, that large transformer may service just one house, or it may
    service half a dozen or so. It depends on the size of the transformer
    and the distance between the houses.

    I take it from his explanation that they don't carry the multi-kilovolt
    power wires into the neighborhood, but actually feed 220V (wye
    connected) / 418V (delta connected) three phase power to the
    neighborhood.

    By the way, an American or Canadian house is supplied with what could
    technically be called 110/220 two phase, or 220V center-tapped. The
    secondary winding of the big transformer on the pole provides 220V, and
    a center tap (which is grounded) allows this to be split into separate
    110V circuits.


    Ray Drouillard
     
  8. Please check the power supply on your TV set or on your door bell
    ringer.

    Regards,

    John Phillips

    "No man really becomes a fool until he
    stops asking questions."

    Charles Proteus Steimentz
     
  9. m Ransley

    m Ransley Guest

    John Phillips
    That isnt what Ran Rod Sword of Baal; from Australia meant, is it. He is
    refering to mains supply . He stated there are no tranformers in
    Australia as there are here in the US.
    So they have no tranformers in Australia?
     
  10. Ray

    Ray Guest

    I explained that.

    He is saying that 330/415 three-phase is transmitted directly about the
    neighborhood. In North America, the neighborhood is supplied by
    multi-kilovolt lines, and each house or small group of houses is
    supplied by a transformer. The fact that the transformer is at the top
    of the power pole is a moot point. Perhaps he knows that, and perhaps
    he doesn't.

    By the way, if you doubt it (and live in N.A.), look at your service
    entrance. It goes to a large can near the top of the power pole. Maybe
    your neighbors are served by the same can, and maybe they aren't.


    Ray Drouillard
     
  11. I will disagree with you here. From personal experience I have found
    that 120 is more likely to "hold" you on the wire than higher
    voltages. I've been "clamped" to 120 before, arm to arm, and only my
    weight pulling me off saved me. On the other 220, when working in the
    industrial environment (before OSHA), tended to cause so much muscle
    contraction that it kicked me off. When you get to higher voltages
    than these you get damage no matter whether you are held or kicked
    off.



    Kirk

    "Moe, Larry, the cheese!", Curly
     
  12. PCK

    PCK Guest

    By the way, an American or Canadian house is supplied with what could
    definitly not technical as all technicians electricians and engineers i`ve
    met
    call it single phase as well as most apprentices carpenters and bricklayers
    call it 2 phase and try to explain it to me ;).
    it is the same phase only a different voltage.
    2 phase is actually half of a 4 phase system requiring 3 conducters
    including
    a neutral. potential of these phases are 90 degrees displaced when measured
    to neutral
     
  13. Ray

    Ray Guest


    I can't disagree with you, having had no real experience. I have been
    hit by 120 AC, by an 80 uF capacitor charged with a couple hundred
    volts, and by either the grid or driver supply (160 or 300 V DC) on my
    ham radio. None of them locked me on. Neither have I ever seen anyone
    get locked on.

    Similarly, my father was taking precautions based on what he had heard.
    As far as I know, nobody has ever gotten zapped with 440 in that shop.
    I'm sure it would wake you up, though -- assuming you survive. It's
    nothing to trifle with.


    Ray
     
  14. Ray

    Ray Guest


    It is definitely a correct technical description. My EMD
    (electromechanical devices) professor discussed it with the class.

    It can technically be called 120V two-phase (the phases are 180 degrees
    apart), but is generally called 220 V center-tapped because the
    secondary winding on the transformer supplies 220V, and that winding has
    a center tap.


    Ray Drouillard
     
  15. Steve Spence

    Steve Spence Guest

    It's all about amps and watts. A device that uses 200 watts at 240vac uses
    ..83 amps. The same device (200 watts) at 120 vac uses 1.66 amps, requiring
    heavier wire. The device is going to use the same amount of watts, to do the
    same amount of work ......
     
  16. Just to add to the explanation: The higher the voltage, the more risky it
    is when things go wrong (both in use and in original installation).

    So... in the US we started with 120V for residential use where customers
    actually come in (near) contact and pretty much remained with it - with a
    240V option for the higher power-draw circuits.

    Higher voltages are commonly used in commercial or industrial settings, so
    you'll have the various 277 and 480 volt combos running around to the
    heavy duty equipment.

    Voltages above that are very rarely used in actual equipment, but you'll
    find such things as 13,000 volt lines bringing the power to the factory
    complex (or some large office buildings) where it's then reduced to the
    more common ones.
     
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