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dimmable CFLs false advertising

brucet9 | Posted in General Discussion on March 24, 2009 08:24am

I saw dimmable CFLs from FEIT at Lowes yesterday. The label says “Compatible with most dimmers” Turns out it’s just false advertising.

I noticed that all the dimmers on display at Lowes and at HD say “for incandescent and halogen lights” on the labels. Lutron and Leviton offer a very limited selection of fluorescent dimmers on their websites, but not at HD or Lowes.

FEIT “tech support” guy said that using their dimmable CFL in a non-compatible dimmer will work, but shorten its life. I asked which dimmers were included in “most”. He said he didn’t know, I’d have to call the dimmer companies. The dimmer companies recommend only their fluorescent dimmers – less than 10% of their product lines.

I guess FEIT thinks that 10% of dimmers = “most”. Those who don’t ask will get shortened product life and have to buy more CFLs.

BruceT
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  1. User avater
    BillHartmann | Mar 24, 2009 08:53pm | #1

    I am not sure, but I think that Feit is just covering their rear for dimmable CFL's that really are only marginally dimmable.

    As far as I know those special flourscent dimmers are not for CFL's, but working with special ballast and those they only work fixtures that are desgined for dimming.

    At least some systems use a 0-10 volt control signal to control the ballast.

    .
    William the Geezer, the sequel to Billy the Kid - Shoe
    1. brucet9 | Mar 25, 2009 06:04am | #2

      "I am not sure, but I think that Feit is just covering their rear for dimmable CFL's that really are only marginally dimmable."
      And so are Lutron and Leviton when they say "incandescent only". They don't want legal liability when someone fries a houseful of "marginally dimmable" CFLs."As far as I know those special flourscent dimmers are not for CFL's..."Feit customer service did confirm that their dimmable CFLs may be used with:
      "Incandescent dimmers that require forward phase."
      "Magnetic low voltage dimmers."
      "Electronic low voltage dimmers that require reverse phase"Since my original post I stopped by a lighting specialty house that sells all sorts of lighting fixtures and every sort of lamp; incandescent, fluorescent, CFL, halogen, neon, led, 120V, low voltage, you name it.There the owner told me of high failure rates - upwards of 30% - with dimmable Title 24 compliant compact fluorescents when they first started getting them. He had experience with dimming ballasts for long tube fluorescents that had to be "burned in" for 48 to 96 hours before dimming them, so he called the compact fluorescent manufacturer and asked if that could be the problem. After escalating through 4 people in customer support he finally got to an engineer who said "Of course they need to be burned in, but marketing has final control over the instructions on our packaging." Once his contractors started burning them in the failure rate dropped to near zero.With respect to Edison-base dimmable CFLs, he told me that they do work fine with dimmers for incandescents (forward phase type) but it is important to always start them at full power, then dim them. Starting them at pre-set dimmed levels (as most people do with dimmers) can reduce a CFL's working life to just 25% to 30% of rated; 2,000 hours instead of 8,000. Oddly enough, the CFL makers don't mention that fact on their labels. He said that Title 24 compliant compact fluorescents have more robust ballasts that can take more abuse than the throw-away ballasts in Edison-base dimmable CFLs.BruceT

      1. User avater
        BillHartmann | Mar 25, 2009 04:55pm | #4

        Thanks for the feedback.How I have knowledge of all of the details about the different lights and dimmers, specially the bit about the "burn in".But I did not hear anything that raises questions in my mind.Except;""Incandescent dimmers that require forward phase."
        "Magnetic low voltage dimmers."
        "Electronic low voltage dimmers that require reverse phase""But what I think that this is what they are talking about. Standard incandescent dimmers use electronic switches called Triacs. Those are off until they are triggered and then stay on until the current drops. That is at the zero crossing. And then it is off again until triggered again.So for 1/2 setting the voltage is off until the peak of the cycle where it is fired and stays on until the end of the cycle.Actually I should say 1/2 cycle as they work the same on the positive cycle and the negative cycle of the AC.The problem with magnetic loads is that they are inductive and thus when they are switched on the current is delayed. So that the load might not draw enough current to keep the switch on. I am not sure, but I suspect that the dimmers spec'd for magnetic loads have a trigger that continuously fires an SCR. Also some extra filters to handle spikes when the load turns off.The so called "electronic transformers" are actually electronic switching power supplies. They immediately convert the AC into very rough DC. Then there is an electronic switch that chops the signal at a very high rate (typically 50,000 - 100,000 per second). Then feed to a transformer. At high frequency the transformer can be very small and light weight. Besides being smaller they can also have special internal controls to adjust voltages or currents of the load.I am not sure what the dimmers are, but I think that they use a switch that can be turned off in the middle of the cycle. So they start at zero with the AC cycle and increase up to a point where they are turned off. Just the opposite of way the basic dimmer. That is why they use the phase "forward phase" & "reverse phase". I am not sure what problem is with ordinary dimmers and switching power supplies. But they are capacitive input and will draw a (relatively) large surge of current when power is applied and with the dimmer switching on at the peaks the surges can be large.But I know that the switching power supplies that Juno uses for their track lighting and 50 W MR-16 bulbs work fine with regular dimmers..
        William the Geezer, the sequel to Billy the Kid - Shoe

  2. Danno | Mar 25, 2009 02:27pm | #3

    Don't worry--in my experience, they dim themselves in a couple days! First day I install them I think, "Wow, lots of white light for the wattage! Almost like daylight." Couple days later I'm turning them on and wondering why it's so dark with the lights on--like when they're new, it's a bright sunny day when you turn them on, and then a month later it's like it's gonna rain any minute! 

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