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Low Voltage lighting vs A.C.

Discussion in 'Electronic Basics' started by David B., Jun 13, 2007.

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  1. David B.

    David B. Guest

    I want to do some landscape lighting and wondering if using a 12volt
    system(20 watt bulb) is more efficient than normal 120 volt (20 watt Bulb).
  2. Phil Allison

    Phil Allison Guest

    "David B."

    ** In a word - no.

    But you may well find that only 12 volt is legally allowed on safety

    ....... Phil
  3. David B.

    David B. Guest

    Thanks Phil, Is there any advantage in using low voltage recessed ceiling
    lighting? Seeing that the fixtures are costlier than line voltage cans, why
    are they becoming so popular?
  4. Phil Allison

    Phil Allison Guest

    "David B."

    ** Its all about the looks.

    Spot lighting, pretty effects, full range dimming etc, et alia.

    ...... Phil
  5. Eeyore

    Eeyore Guest

    Low voltage halogen bulbs are more efficient than 120/230 volt tungsten

    Was that what you wanted to know ?

    Don't forget about the serious effect of volt drop due to cable resistance with
    low voltage lighting though.

  6. Rich Grise

    Rich Grise Guest

    If you use fat enough wire, the efficiency should be practically the same -
    the thing is, 12V doesn't kill pets or children.

  7. David B.

    David B. Guest

    I wanted to know if I would save on the electrtic bill by using 12volt. Will
    be doing lanscape and soffit lighting. I have 18 ga safty wire that I can
    use to minimize the voltage drop.
  8. Bob Myers

    Bob Myers Guest

    You won't save a significant amount, no. In fact, it is at
    least possible you'd wind up spending a miniscule amount more.

    Bob M.
  9. Charles

    Charles Guest

    I agree with Rich ... 12 volts is a lot safer than 120 volts. Also, it
    eliminates the need for conduit and expensive direct burial cable and that
    kind of stuff.

    Efficiency, general speaking, is poorer with low-voltage systems. Not a big
    issue unless you are going to have a rather extensive outdoor lighting
  10. Ken Fowler

    Ken Fowler Guest

    Your 20 Watt lamp will draw ~1.6 amps from 12 Volts. 18 gauge wire might be enough for one or two
    lamps but will not minimize the voltage drop. The system is not very efficient if power is lost in
    the wires. 14 gauge would be better.

    Ken Fowler
  11. Eeyore

    Eeyore Guest

    LOL ! Forget 12V then !

    Only the other day I was looking at ~ 4mm^2 cable feeding 50W halogen fittings.

  12. Eeyore

    Eeyore Guest

    Also those fittings have little depth so can be flush fitted. You couldn't
    easily do that otherwise.

    So, what are ppl going to have in their kitchens (the most popular place in the
    UK for low voltage halogens) when incandescents are banned then ?

    Back to those exposed tube florries ?

  13. David B.

    David B. Guest

    Hi Ken my mistake the wire is actually 12 ga. its not regular romax . Its
    the type used for emergency lighting and fire systems.
  14. Phil Allison

    Phil Allison Guest

    "David B."

    ** Then use compact fluoros - that is something they might be good at.

    You can get them now in ratings of 7 watts, or maybe less in " mini
    spiral" types with " warm white " colour.

    ....... Phil
  15. Jasen

    Jasen Guest

    low voltage halogen downlights last longer than mains voltage halogens
    and give better colour etc...

  16. John Larkin

    John Larkin Guest

    For the same reason 120 volt bulbs last longer than 240's: a short fat
    filament takes longer to evaporate.

  17. Phil Allison

    Phil Allison Guest

    "Jasen the ASD fucked kiwi MORON "

    ** Not the comparison that was asked about.

    ** BOLLOCKS.

    ........ Phil
  18. Ross Herbert

    Ross Herbert Guest

    It is much safer to use 12V for domestic outdoor lighting. Depending
    on the number of lights you wish to drive you may use either
    individual transformers for each lamp or a larger common transformer
    for a group of lamps. Because of the importance of maintaining low
    volt drop in the 12V cabling you will need to mount the supply
    transformer as close as possible to the individual lamp, or in the
    case of a common transformer, as close as possible to the centre of
    each group of lamps.

    In order to get the transformer as close to the lamps as possible it
    is usual to mount them on an outside wall or a verandah/porch support
    post, or in some cases, in an underground pit. This makes it mandatory
    for the transformers to be weatherproof where rain or water is likely
    to be encountered, or fully encapsulated for underground use.
    Individual lamps can be powered from a plug pack transformer designed
    for soft starting low voltage lamps eg Tridonic Atco ACT35-2 (see
    p.209 document below). Grouped lamps can be powered using the
    weatherproof LVL 6 or 10 series transformers (p.211) or the fully
    encapsulated LVL48A series (p.212) for underground applications. There
    should be similar versions for 120Vac applications from US

    If using a common transformer, then depending upon the wattage of each
    lamp, and the cable gauge & length, you may be able to connect more
    than one lamp on a 12V cable run. On longer runs it may be better to
    power 1 lamp per cable run. This will need to be determined by what
    circumstances and materials apply to your particular situation.

    This document while
    applying to Australia where 240Vac mains is the norm, contains
    information which is pertinent to low voltage electromagnetic lighting
    transfomers used anywhere, particularly with regard to the requirement
    for good regulation with variable load to increase lamp life.
  19. Eeyore

    Eeyore Guest

    Just a thought.

    Why not 24V ?

  20. Jasen

    Jasen Guest

    not the message I was respondinfg to.
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