fluorescent light bulb's don't work with Timer's?

Discussion in 'Electrical Forum discussion & Blog' started by bjferri, May 11, 2008.

  1. bjferri

    bjferri DoD Army

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    Why is it when I put a fluorescent bulb in a light that is on a timer it starts to blink, even though the timer os off? I have lots of timers around my house instead of the regular switches...does this mean I cannot use this type of bulb?
  2. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

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    I don't see any reason why this should happen, if everything is properly wired. A switch is a switch. Are these timers mechanical or solid-state?
  3. bjferri

    bjferri DoD Army

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    The timers are solid state. I don't understand this. Not that I'm an electrician, I don't think I wired them incorrectly.
  4. jimbo

    jimbo Plumber

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    Lighting control devices....timers, photocells, and motion sensors.....can be problematic with fluorescent. Especially electronic devices like your timer.

    Here is the reason......

    Simple electronic in-line devices like maybe your timer are designed to replace a simple on/off switch in a box where only the HOT wire is present, not a ground or neutral. Therefore, they way they work is to "steal" a tiny amount of current. That is when the timer or photocell wants the lights to be OFF it is still passing just a few milliamps of current to operate its circuits, and be ready to switch when the time arrives. For incandescent bulbs, this current just passes through the bulb, and is so small that it does not even cause a little glow. But, flourescent bulbs DO NOT LIKE this set-up. It will cause the flickering etc. that you are seeing.

    The only solution is to get a timer which is specifically rated for fluorescent. They are much more expensive, and often require a neutral and/ or a ground to be present in the switch box, and you may or may not have that.

    Also, you have to look specifically at what kind of lamps/ballasts you have. Some of the timer/photo/motion devices will be rated for MAGNETIC ballast only, some for ELECTRONIC only, and some for BOTH. For a look at some devices and specs, try www.wattstopper.com
  5. hj

    hj Moderator & Master Plumber Staff Member

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    timer

    Many nonmechanical timers are labled specifically that they are not suitable for devices with ballasts.
  6. bjferri

    bjferri DoD Army

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    I got it! Thanks. I do have the 3-wires needed; however, these timers are new and were expensive (maybe $15 or so) so I'll hold off. Thanks again!!
  7. jimbo

    jimbo Plumber

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    Unfortunately, @ $15, these fall in to the category of "cheapies". Think $35 to $55 for what you need.
  8. Alectrician

    Alectrician DIY Senior Member

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    They somehow need the closed circuit provided by the incandescant filiment to operate.

    2 wire photo cells are the same way.
  9. Ian Gills

    Ian Gills Senior Robin Hood Guy

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    I hate to be a kill-joy but I have the same problem with light switches with LED lights in them (to find them in the dark) and I have found that some brands of CFLs do work and do not flicker.

    It's trial and error, but I have had lots of success with the Lights of America brand.

    Another trick, is that if you have a device that uses more than one bulb, a chandalier for example, you can use CFLs + one ordinary incandescent. The presence of the single incandescent will stop any flickering.
    Last edited: Jun 2, 2008
  10. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    CFL could use an electronic ballast or a magnetic one...my guess is a magnetic one might be more likely to work.
  11. SteveW

    SteveW DIY Senior Member

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    Intermatic makes a switch capable of use with fluorescent bulbs - EI600. If it's like the model it supersedes, which I have in my house, it has a little motor which mechanically moves a SPST load switch. Mine has a AAA battery which needs to be replaced about once a year, since it operates the switching motor.
  12. Bill Arden

    Bill Arden Computer Programmer

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    My X-10 light switches have "latching" relays and work fine.

    My earlier research showed that most inline dimmers and photo cells would slowly charge the 200 volt DC capacitor until the "start up" circuit starts. The bulb would then flash as the switching power supply drained the main capacitor.

    The old style (plug in bulb) CF lights are also ok, but are less efficient.

    motor driven timers are also fine with CF lights.
  13. Ian Gills

    Ian Gills Senior Robin Hood Guy

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    Interesting. What do you mean by "old style plug-in bulb"?

    Are those like the circular CFLs that have four prongs that plug into a plug on the light?

    Like this: [​IMG]

    or

    perhaps these: [​IMG]
    Last edited: Jun 3, 2008
  14. Bill Arden

    Bill Arden Computer Programmer

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    Actually both of those since they tend to use magnetic ballasts and a starter.

    Although I've now seen both with electronic ballasts.
  15. jimbo

    jimbo Plumber

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    Circline bulbs are usually magnetic ballasts. The plug in bulbs...if they have 2 pins that is usually a magnetic ballast, and if they have 4 pins, that is electronic ballast.
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