Dimming Low Volt Undercabinet

Discussion in 'Electrical Forum discussion & Blog' started by crabapplemcn, Jun 3, 2009.

  1. crabapplemcn

    crabapplemcn New Member

    Messages:
    16
    I am not savvy with electrical and had a question about my set up. In new construction I currently have a switch controlling 2 outlets, one over each of 2 cabinet banks. There I will either plug in or hardwire the transformers (2). I then have low voltage wire running from those outlets location, in wall and stubbed out under the upper cabinets. I have 2 questions:
    - Will I be able to dim these undercabinets lights with this set up, and if so do I need a special type of dimmer and/or transformer?
    - Can I get any transformer to work this setup? The place I'm buying the lights at has their own transformers, but I don't necessarily need their particular ones do I?
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,802
    Location:
    New England
    Transformers come in two general types: electronic and magnetic. An electronic one will be smaller and lighter, but can produce some electical noise. A magnetic one is essentially just a big 'normal' transformer. Each of them can be used to dim lamps attached, but the type of dimmer MUST be matched to the type of transformer, or you could end up with either a fire or a very short-lived dimmer. The biggest thing is to ensure you get a transformer rated for the wattage of the lamps you want to use. Too big is going to produce excess heat, and waste energy. Then, the second thing is ensure the output voltage aligns with the bulbs you choose (lower voltages require heavier wires because of higher amperage).
  3. crabapplemcn

    crabapplemcn New Member

    Messages:
    16
    Thanks Jad
    The strips I am getting are various wattage (1-6) and are all 24DC Voltage. So you're saying I will need a 24V transformer? Will the low voltage wiring run by my electrician from the transformer to under cabs be sufficient to work these lights at 24dc volts? thanks
  4. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,802
    Location:
    New England
    If you've selected 24vac bulbs, then yes, you need a transformer designed for that. W/V=amps. You need to add up the watts to figure out the max load, then you can determine the gauge wire required. You'll need larger gauge wire that the equivalent 110vac lamp.
  5. Thatguy

    Thatguy Homeowner

    Messages:
    1,460
    Location:
    MD
    Are these LEDs?
  6. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,802
    Location:
    New England
    If the bulbs are solid state, then you may not be able to dim then with one of the conventional methods. Those may come with their own control system. A conventional bulb (incandescent), either normal tungsten, or a halogen bulb, don't care if they are powered by a/c or d/c, but you'll only get a/c out of a transformer. If for some reason the fixtures need dc, then you would need a power supply (which may contain a transformer). Those would need something internal to them to adjust the voltage, not a traditional dimmer.
  7. crabapplemcn

    crabapplemcn New Member

    Messages:
    16
    Thatguy
    Yes they will be led's
  8. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,802
    Location:
    New England
    As a basic entity, LED's operate off of DC voltage, and a transformer won't do much of anything. Make sure that the fixture says it can be dimmed, then follow their instructions about what type is suitable. If the fixture wants 24vdc in, if it is dimmable, it would have to be internal, and then you have to figure out a way to generate 24vdc.

    If it takes 24vac, then it is likely it can be dimmed...you really need someone that can decipher the spec sheet, or you'll end up with something that is both unsafe and won't work.
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