Flickering lights on circuit with low voltage and line voltage bulbs

Discussion in 'Electrical Forum discussion & Blog' started by davidwie, Apr 18, 2011.

  1. davidwie

    davidwie New Member

    Messages:
    11
    Hoping someone can give me some ideas on a flickering light situation. Here is the background:
    *
    On a single circuit I have 6 low voltage lights and 6 line voltage high hats. They are all controlled by 4 switches, 1 of which is a dimmer. When first installed 5 years ago, it worked fine with incandescent bulbs in the high hats. A few weeks ago I switched the incandescent to CFLs. Two weeks later the low voltage lights are flickering (even when not using the dimmer). The CFLs are working fine. The flickering does not happen right when the lights are turned on. It takes anywhere from 2 to 20 minutes for the flickering to start.
    *
    I switched the CLFs back to the incandescent and it still happens. Any ideas what it could be?
    *
    Thanks a lot!!
    David
  2. DonL

    DonL Jack of all trades Master of one

    Messages:
    4,218
    Location:
    Houston, TX
    Hello davidwie,

    Most normal CFL bulbs should not be used with dimmers. Maybe you did install dim-able ones ?

    It sounds like you may have a bad SCR / FET in the dimmer. Maybe a loose wire.

    SCRs / FETs are cheap devices to buy, and can be replaced.

    Good Luck on your project.

    Have a Great day.

    DonL
  3. davidwie

    davidwie New Member

    Messages:
    11
    Thanks for your response DonL,

    Could it be the dimmer even if when I turn on the lights with a normal switch on the circuit the low voltage lights still flicker? Remember there are 3 normal switches on the circuit also.

    Thanks again! I may justy try replaceing the dimmer with a regular switch.

    David
  4. DonL

    DonL Jack of all trades Master of one

    Messages:
    4,218
    Location:
    Houston, TX
    David, It would be depending how the Dimmer is wired in the system.

    You should be able to just bypass the dimmer for testing to see if it still flickers.

    Some dimmers, when OFF still pass the voltage threw them, Depends on the design.

    DonL

    P.S. May just be a connection that got disturbed, When you changed the bulbs.
    Last edited: Apr 18, 2011
  5. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    Most CFL are not dimmable. Even if you got dimmable, bulbs, there is almost no chance that your old DIMMER is compatible with flourescent. I think if you replace the dimmer with a proper switch, you flickering problems will go away.

    We all have to rethink the dimming concept thanks to alfgore. A fluorescent compatible dimmer will cost you a C note. Dimmable bulbs are also pricier. LED's are a mixed bag. Many are not dimmable, some are, but may require specialty dimmers.
  6. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,059
    Location:
    New England
    Some dimmers cannot be used with some low-voltage fixtures. It depends on the way the system makes the low voltage (i.e., what kind of transformer it has - magnetic or electronic). If you use the wrong type of dimmer, it will fail. Sounds like this may be what's happening. Next biggest thing would be a loose connection somewhere. The easiest thing may be to hardwire the connection and eliminate the dimmer, or replace it with a normal switch. If the problem goes away, you know it is the dimmer. It can take some time for the dimmer to fail if it isn't compatible with the low-voltage circuit.
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