Lighting, Bulbs, and Dimmers

In our real estate business, our tenants sometimes need guidance about lighting, bulbs, and dimmers.

For example, with dimmers, it is very important you choose the right kind of light bulb. Otherwise, you can get bulbs which do not work well with dimmers, such as flickering, or limits to low range. Conventional fluorescent bulbs should not be used on a dimmer, and it can be a fire hazard to try to use non-dimmable fluorescent bulbs with some kinds of dimmers. (More discussion below.)

There are different kinds of bulbs:

• Incandescent (the original old style) - cheap but not very efficient
• Fluorescent (conventional) -- do NOT use these with dimmers!!!!
• Compact Fluorescent Lightbulb (CFL) -- SOME can be used with SOME kinds of dimmers
• Halogen
• LED

Besides the color style you prefer, brightness, and particular application of lighting, which go beyond the scope of this article, there are other considerations such as safety and electricity cost.

The main two parameters of bulbs are (1) "lumens" of visible light put out, and (2) electrical power consumed (watts).

The original incandescent bulbs are the cheapest to buy but consume a lot more electricity. They work by just having a very hot filament which glows. Only a little bit of the power is visible light, i.e., low lumen rating per watt of electricity. Most of the power is invisible heat. This wastes electricity in two ways. The most obvious way is that most of the electricity consumed is invisible. Secondly, additional electricity is required in an air conditioned environment because the air conditioners must work more to remove this excess heat, e.g., a 100 watt light bulb requires an additional 100 watts of air conditioning (actually, more, since air conditioners are not perfectly efficient), so you pay twice for the electricity. Thirdly, incandescent bulbs don't last as long as other types, because the high temperature filament eventually fails with usage time and on-off cycles.

Halogen lights are basically incandescent light filaments but with more halogen gas (such as iodine or bromine) inside, which allows the filament to operate at higher temperatures and longer times, allowing more compact bright lights. Halogens also put out a somewhat different kind of light. Some homes have them for compact or artistic applications, but they get very hot and have their obvious drawback. Halogen lights are basically the same as normal incandescent bulbs but brighter, more compact, longer lived, and much hotter. There are some safety concerns due to their temperatures.

All other lights are based on entirely different technologies than incandescent bulbs.

LED lights are the most energy efficient, emitting specifically within certain narrow visible light bands, therefore with very high lumens per watt, and extremely long lifetimes. Their limitations have been expense per unit, and not being bright enough at a distance (such as for a ceiling lighting fixture for a whole room), though these issues have improved dramatically in recent years, which is why LED usage has taken off in recent years, despite LEDs having been around for decades. LED technology has gotten very interesting, especially the ability to change and tune the colors of lighting emitted by some lamps. Dimmable LEDs are on the market for some kinds of dimmer switches.

Fluorescent lights are very popular because they provide a lot of visible light for a small amount of power (high lumens per watt), are relatively economical, and are much longer lived that incandescent lights. Fluorescent lights have been the main plug-in replacement for incandescent lights.

An issue arises when using fluorescent lights with dimmers. There are "Dimmable CFL" lights, but you must look for this on the package. You should also look at the fine print which might say that you should not use the bulb with a dimmer.

With simple on-off switches, it doesn't matter. Things can get complicated only when you have a dimmer.

In the old days, dimmers worked by just reducing the voltage to the light, by varying the resistance in the dimmer knob as you turned it, which worked find with incandescent bulbs. However, dimmers tended to get hot, and not work well with new kinds of lighting which required a minimum threshold voltage and didn't respond well to variations in just voltage. Dimmers switched to being made of semiconductors, which are much more electrically efficient and give more options to providing voltage waveforms to lighting devices. Electronic dimmers basically change the 50 Hz power company's basic sine waveform into a much more complex waveform which varies the amount of power going to the light fixture. However, the 3 types of light fixture can respond in significantly different ways to this waveform.

In short, you should match the bulb to the dimmer's specifications.

A hazard with fluorescent lights is that some kinds of dimmer provide essentially a very quick on-off switch, such as 100 times per second, with "turned off" and "turned on" wait states of different durations, so that the longer the off state, the lower the brightness. (100 times per second is faster than the human eye and human brain can detect.) By keeping the same voltage but varying the wait time between cycles, a simple dimmer may work with different kinds of bulbs. Unfortunately, fluorescent lights can absorb a lot more electrical current under these circumstances, and can overheat (i.e., fluorescent bulbs they have variable resistance depending upon their state). Fires have been caused by fluorescent electronics catching on fire from overheating, though this is rare. Nonetheless, they can get very, very hot, and fail quickly or heat up your house more. (The "on-off" explanation is oversimplified but makes the general point.)

There is a lot more I could write about lighting and the human / mammalian eyes (including our pets), but it goes beyond the scope of this article. For example, you may notice that your eyes can detect some lights flickering as brightness varies, due to the differences in how your rods and cones operate. Different people may respond in different ways to different kinds of lighting. If you have an issue, it's best to just first experiment with different kinds of bulbs ... with whatever dimmer you happen to have.

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