Thread: Dim-able CFL bulbs

Handyman WIRE - Handyman USA : DIMMABLE-CFL-Bulbs ?

I thought this was pretty interesting. I wasn't aware there was such an item. They sound extremely rare but it may make me change my write up a bit. Up to this point I've just said that CFLs can't be on dimmer switches.... which I guess is technically incorrect.

The part about them staging down in levels rather than gradually is probably the best indicator.

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I just put one in my bathroom above the tub. It's marginal at best. The upper end dimming isn't too bad, but then it just shuts off about 1/2 way down. I will probably replace it with an incandescent bulb. The technology is not quite there yet, imo.

I bought a few at the local big orange box store and I returned them cause they stink. Like Jim said they don't dim well and mine made a buzzing sound at all of the dimmed levels.

For dimmers, and nearly every room in my house has dimmers, I have found that the best solution is halogens, either PAR or Edison base. All of the others, including "dim-able" CFLs and tungsten incandescent, display poor performance either in light color or buzzing.

I have CFLs everywhere it doesn't matter (basement, shower, laundry, garage, etc.) and all of my dimmers are Lutron made after 2004 (Diva and Maestro). I know better than to look for CFLs at the big box stores (of which I now have both blue and orange varieties). Perhaps my local supply shop just didn't have the good dimmer-friendly CFLs (being 6 years ago, maybe they've gotten better) but I haven't had any luck with them. Asking for different color spectrums of dimmer-friendly CFLs might be going a little far.

My local shop does have dimmer-friendly LED lamps but at $100+ each I've opted to stay with halogen units.

I moved a lot of my PAR20's to MicroBrite dimmable CFL and they are great. Most of them have been in for going on almost 4 years with no problems. The light is not the usual cold CFL, very warm and inviting.

Not as bright as a halogen or an incandescent but in my application (10 lights in a tall ceiling room) it does the job.

R20 Dimmable Compact Fluorescent Floods - 2.5 Inch Diameter

John-

Originally Posted by Corn Walker

I have CFLs everywhere it doesn't matter (basement, shower, laundry, garage, etc.) and all of my dimmers are Lutron made after 2004 (Diva and Maestro). I know better than to look for CFLs at the big box stores (of which I now have both blue and orange varieties). Perhaps my local supply shop just didn't have the good dimmer-friendly CFLs (being 6 years ago, maybe they've gotten better) but I haven't had any luck with them. Asking for different color spectrums of dimmer-friendly CFLs might be going a little far.

My local shop does have dimmer-friendly LED lamps but at $100+ each I've opted to stay with halogen units.

Those CFLs don't work with the Maestro dimmers either. One of the things I like about the Maestro is the multi-location dimming which is why I shell out the big bucks for them.

Ironically, the "soft-start" feature of the electronic dimmers like the Maestro makes for shorter-lived CFLs but longer-lived incandescent bulbs. Go figure.

Ooh good tip, I use Maestro in a few other places in my house, all on Halogen or Incan.

Tx!

Originally Posted by Corn Walker

Those CFLs don't work with the Maestro dimmers either. One of the things I like about the Maestro is the multi-location dimming which is why I shell out the big bucks for them.

Ironically, the "soft-start" feature of the electronic dimmers like the Maestro makes for shorter-lived CFLs but longer-lived incandescent bulbs. Go figure.

Originally Posted by ben jacks

Maestro is a solid state dimmer. The Micro-Brite data specifically states not to use electronic dimmers on their CFL products.

I'm not sure "solid state" matters a whole lot. It's really about how the dimmer comes on. Most of Lutron's electronic dimmers are "soft start." They start form near-zero volts and decrease resistance until the selected light level/voltage is reached.

Lutron does make a fluorescent-compatible dimmer but I've never tried it. I suspect it's a "hard start" dimmer that produces full voltage and then reduces to the required light level. Unlike their incandescent dimmers, it requires a neutral return path. Regular electronic dimmers leak a small current through the lamp circuit to power the electronics, which can damage some ballasts. With a neutral conductor at the switch they can have a truly open circuit when the light is off. Perhaps paired with some of the newer dimmable CFLs this could work to be an effective solution.

As far as soft-start goes, one of the reasons I used the electronic dimmers is because they eliminate the momentary voltage spike of traditional open throw switches. This voltage spike is partly responsible for the reduction in lifespan for incandescent lamps.

Originally Posted by ben jacks

Why is Micro-Brite so specific about not using electronic dimmers? Could the dimmable CFL life be because of the chopped wave-form versus analog dimmer differences?

I'm not sure. Both the Maestro and other slider or rotary dimmers are "electronic dimmers" that use triac designs rather than the rheostats of old. Some include capacitance devices as well as PWM controllers as I suspect of the CFL-specific Maestro dimmers.

The Micro-Brite bulbs are cold cathode, which are typically more tolerant of dimmers but there may be something about their design I am missing. It's possible they use a diode controller design, which is not compatible with dimmers unless the diode polarities are matched.

I have a couple of these dim-able CFL's in my canned lights in the family room area. I don't remember the brand, but they are a name brand bought at either Lowes or HD almost 2 years ago. I stay away from off-brand CFLs. I'm not sure of the age of the dimmer--it was put in by the prior owner. Just the standard push and turn dial type.

Anyway, I find they dim fine as long as you let them warm up before dimming them.

Also, as to a comment above, in this application they are actually brighter than normal incandescent lighting because the light disburses wider in the room because the bright portion of the CFL inside the "flood" light enclosure is closer to the protective glass.

Originally Posted by ben jacks

Are you referring to a Zener shunt? I do not follow matched diode polarities you mention.

Some lights (both incandescent and CCFL) use a diode to reduce power to the lamp by clipping the wav). The problem is that for some dimmers that operate on a series circuit that includes the lamp (such as the Maestro), the clipped wave form interferes with their control circuitry if you use more than one.

Since diodes are polarized, if you were to use two diode lamps with inverse polarities the approximate sine wave of the circuit appears unclipped to the dimmer. If both diode lamps have the same polarity the current draw would be doubled in one voltage direction and zeroed in the other. This can cause flickering of the lamps, particularly during startup, and reduce lamp longevity.

The CFL-specific Maestro has a neutral terminal which allows the control circuitry to operate independently of lamps connected to it. It is listed for use with their dimmable ballasts, so I don't know how it might operate with other CFL lamps.

If only they provided one. I might have to take one of mine apart and hook it up to the test bench. I don't have the CFL model but now I'm curious to see what they've done.

Except for the fact that the Maestro uses the lamp to complete the circuit for its control unit (and I admit it is problematic for CFLs to have this very low current constantly on), I don't know why they would single them out as being "electronic" since all of the other dimmers are also triac-based. Whether using a solid state voltage divider circuit or a manual control, they both feed into the triac which is what sets the pulse timing.