Why shouldn't compact fluorescent lightbulbs be used with dimmers?

My wife and I have been slowly replacing the lightbulbs in our house with the new energy efficient compact fluorescent kind that look like a cross between a fluorescent bulb and a conventional incandescent one.

The main lights in our lounge, however, are fitted with a dimmer switch and most of the CLF bulbs I’ve seen have “DO NOT USE WITH DIMMERS!” warnings on them.

I inadvertently put one in a while back and it worked just fine, but I’m wondering if there’s a safety reason for not using the CFL bulbs with a dimmer, or if it’s just because the bulbs won’t last as long? We almost never actually use the dimmer function, FWIW.

Anyone able to shed some light (excuse the pun :D) on this?

If used at full power, they’ll be fine in a dimmer, however, the bulb needs the full current flow in order to properly excite the vapor and cause the gas to fluoresce. If you’re on a dimmer, providing, say, half the electricity the bulb needs, you’ll have sporadic, flickery operation…which could cause premature damage to the bulb (I’m assuming the last part).

Not necessarily. I put three CFs on a dimmer and they lasted about one week. And the dimmer was on full brightness.

So I got my oscilloscope out and discovered the reason. When the dimmer was set to full brightness, it was not acting as a switch that is “on” (as you would expect). The circuit inside the dimmer module was still chopping up the current. This surprised me.

There are dimmable CFL bulbs available. I don’t know how they differ, though.

Doesn’t surprise me. Dimmers are cheeeeeeeeeap, which means that manufacturers are going to use the simplest circuit that works well enough. So, there you go.

I installed recessed lights in my living room/kitchen that use a standard base. Flourescents were too bright, so I installed halogens that work with dimmers. They use more power (35 W vs 15W) but that’s still less than incandescents.

Halogen lamps are incandescent. The difference is not so much one of efficiency but one of lifespan. Halogens contain a halogen gas (duh), the purpose of which is to prevent evaporating tungsten from the filaments depositing on the inside of the glass bulb and instead allowing it to redeposit back on the filament, extending its life. To do this, the filaments must be run at a higher temperature; due to the nature of incandescence, this does result in a somewhat higher luminous efficiency, that is, the amount of visible light produced per watt increases. This is an improvement of just a few percent over ordinary incandescent bulbs. CFLs are still vastly more efficient in terms of lumens per watt.

Because it makes all the food look sickly grey…ohhh, you said diMMers.

If money is no object or the socket in question is hard to get to, there are also LED bulbs.

I use a couple in hard-to-get-to or “always on” places.