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Thread: CFL bulbs and dimmer switches

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    Automated Home Jr Member dsample's Avatar
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    Question CFL bulbs and dimmer switches

    I've heard that compact florescent bulbs flicker if the wrong type of dimmer switch is used. Is this true, and if so, is there a way to know if a particular dimmer (eg. ZDP210/ZDW230) would be compatible?

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    Automated Home Legend chris_j_hunter's Avatar
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    not sure of your answer, other than to say the lamps have to be of the four pin variety & HF ballasts are more than a good idea ... another option might be Varilights ... some discussion here :

    http://www.automatedhome.co.uk/vbull...ead.php?t=1952

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    Moderator toscal's Avatar
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    I know Megaman do dimmable CFLs.
    Many dimmers require a minimum load to work properly. And this may cause the flickering if this minimum load is not met.
    I have heard but can't verify this, that some of the dimmable CFLs aren't very smooth when changing brightness, they tend to go in steps, so it may be hard to get the desired brightness.
    Here is a link for Megaman http://www.megamanuk.com/
    Their document on number of lamps on a dimmer switches http://www.megamanuk.com/products/di...tity-guide.pdf
    and a place that sells them
    http://www.gwsupplies.co.uk/lamps/c/...+cfl+bulbs.htm
    Last edited by toscal; 6th December 2008 at 11:10 PM.
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    Automated Home Jr Member dsample's Avatar
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    Quote Originally Posted by chris_j_hunter View Post
    not sure of your answer, other than to say the lamps have to be of the four pin variety & HF ballasts are more than a good idea ... another option might be Varilights ... some discussion here :

    http://www.automatedhome.co.uk/vbull...ead.php?t=1952
    I'd just found the Varilight site. They look like what I'd want but there are 2 types, dimmable and switch dimmable.

    The two types of dimmers that I'd heard of were voltage regulation and frequency regulation (turning the light on/off very fast). I'm assuming from the names that dimmable is voltage and switch dimmable is frequency, would this be correct?

    The other thing I noticed was that they're 20W, that seems quite high for a CFL, my normal ones are 4-6W.

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    Automated Home Legend Karam's Avatar
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    For the Varilight I believe dimmable means you can dim them with a dimmer, whereas switch dimmable means you can dim them using a conventional switch - presumably something like press switch they start fading up press again they stop, that sort of thing (but I don't know for sure). Certainly we have tested the dimmable variants and what we find is that you can dim them reasonably smoothly once you are above the turn on threshold. In other words there is a minimum level below which they just go to OFF directly and vice versa. I think this is inherent behaviour since it was the same across a few dimmers and also would make sense from a technology point of view. I seem to remember packaging implying minimum was 2% but I don't think it was anywhere near that in terms of subjectively perceived minimum dimness - more like 20%.

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    Automated Home Legend chris_j_hunter's Avatar
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    They seem to be cleverer than that ! To quote the Varilight web-site :

    The range ... includes Switch Dimmable EnergySaver+ lamps ... these can be dimmed from a standard light switch. Thanks to the innovative DigiFlux ballast technology, flicking the switch on & off puts the lamp into a dimming cycle. Once the desired brightness is reached another flick of the switch sets the light level. This level is stored & the lamp will illuminate at this level (even if it is at the minimum) until the level is reset.

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    All of the major DIY chains now stock dimmable CFLs

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    Automated Home Guru jpdw's Avatar
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    Default Govena dimmable

    I recently spotted that Screwfix were selling a dimmer-dimmable so got one to try. Although I don't think the catalogue mentions the brand, it's Govena.
    (Made in Poland -- makes a change from China :-) ).

    I've only used it briefly so far but I was a bit disappointed:

    Whilst it seems to have quite a good dimming range and is "smooth" as you dim it, the bulb seemed to buzz more than I'd want. I was going to put it in the living room, but decided it would probably be too annoying... so best in higher traffic areas where you dont mind a bit of noise.

    Still, it's a progression. A year ago, the "switch dimmable" was state-of-the-art yet only seemed to allow several fixed positions ie 40/60/80/100%.
    Jon

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