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24 volt switches

Discussion in 'Home Power and Microgeneration' started by Don Miller, Jul 20, 2006.

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  1. Don Miller

    Don Miller Guest

    I'm looking for a source for 24-volt DC rated wall switches. (that look
    like a conventional wall switch - not an automotive toggle switch) I need 7
    of them to control 24 volt ceiling fans. Just 'on' and 'off', not a speed
    control switch.

    Any leads would be appreciated.

    Don
     
  2. What current requirement???
     
  3. Some of the old "snap action" AC light switches worked fine on low
    voltage DC - at about 50% load rating(7 amp). They were used on DC
    distribution systems that were relatively common on the east coast? in
    the early 40s. Also used with "delco system" rural electrification
    plants (24 or 32 volt)
     
  4. Check out some marine sites, they carry 24 volt switches and appliances.
     
  5. Where do you get the facts to support the claims?

    *- Lamps incandescent and fluorescent last longer
    (I have never seen any claim that DC operated incandescent last longer)
    (fluorescent on DC requires inverter/ballasts. Good electronic ballasts
    do provide better lamp life if they are programmed start or rapid start)

    *-"brushless" DC motors can now be made cheaper than AC motors
    ("brushless" DC motors are AC motors with dedicated inverters. I have
    never seen any that are lower cost than AC motors)

    *-All major long distance power transmission is DC these days.

    BTW: Fuses and circuit breakers are lower cost for AC ratings.
    Bill Kaszeta
    Photovoltaic Resources Int'l
    Tempe Arizona USA
     

  6. Actually, there is SOME truth to this statement, as DC does not cause
    the filament to"buzz". This is not a major factor, but SOME designs of
    coiled tungsten incandescent filaments DO last longer on DC.

    High frequency electronic ballasts also provide better tube life than
    60Hz standard ballasts.
    Brushless DC motors are basically AC motors with electronic switching
    built in (to make their own AC)- so are still more expensive than
    straight 3 phase (or multiphase)AC motors.Multiphase is cheaper than
    single phase because of inherent self starting ability - no start
    assist caps or switches required.
    Not ALL. SOME.
    Mechanical switching of AC is MUCH simpler than DC.Arc quenching on DC
    switches can become a major factor, particularly on
    reactive(inductive) loads. Electronic switching of DC gets simpler,
    but still not as simple as switching AC, where Zero Voltage switching
    can be accomplished
     
  7. How do you figure that?
     
  8. Most definitely NOT.
     
  9. Vaughn Simon

    Vaughn Simon Guest

    The above is one of the most even-handed and (as far as I can see) accurate
    posts that I have seen in a long time.

    There is a lot of lore about incandescent lamp life. One of the most often
    repeated "facts" is that on-off cycles reduce bulb life. My experience (15
    years in traffic signals) is that bulb design and hours are the main
    determinates of bulb life, (with the additional proviso that the filaments of
    old lamps are very brittle and will not survive much physical abuse). A lamp
    blinking 24/7 in a 50-50 cycle would last just about twice as long as an
    identical lamp that was burning steady 24/7. I have seen exactly that situation
    thousands of times. Also, the lamps in the yellow section of a traffic fixture
    would last far longer than the reds and greens even though they all had exactly
    the same number of off-on cycles.

    Vaughn
     
  10. JoeSP

    JoeSP Guest


    It's important to remember that a 24V circuit will require about 5 times the
    amperage as a 120V circuit of the same wattage. A regular switch may not
    cut it.
     
  11. JoeSP

    JoeSP Guest

    Drink it in, because such things are all too rare on here.
     
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