Fluorescent "Light Bulbs"

I like to save money. One of the things I do to save cash is to replace incandescent bulbs with their fluorescent equivalent whenever possible. After all, the cost for 17 watt-hours is only 17% of the cost for operating a 100-watt incandescent bulb for an hour, isn’t it? And they don’t burn out. Not for a long, long time.

One thing that bugs me, though, is that there are no exact equivalent (external dimensions) fluorescent replacements for most home applications. If I want to put a fluorescent bulb in my kitchen, I’d have to change the whole fixture or leave the globe off. Fluorescent bulbs are either too wide at the base or too damn long to fit in most common ceiling fixtures.

Some fluorescent bulbs come pretty close to the dimensions of a standard incandescent lightbulb. Is there some minimum size for some fluorescent component that keeps them just a bit too big for some home uses? Why can’t someone make a fluorescent bulb that can directly replace an incandescent bulb?


An incandescant lamp is just a tiny element that gets white hot when connected to a supply, in fact in electrical terms it is just a resistor and needs no peripheral components to work.

Flourescants on the other hand produce their light by forming a plasma arc across a gas medium and to get an arc to jump a gap between electrodes requires a high voltage, but once the arc has been struck the resistance of the pathway falls dramatically and so the voltage across it has to be controlled at a lower level.

As you can imagine this amunt of control introduces a need for other components which have to be crammed in somewhere, hence the straight replacements for conventional buulbs have a larger body.

The tube itself is folded around but there still needs to be a certain arc length to produce the necessary are and the tube needs a certain wall area for the coating to be large enough to convert enough of the arc to give useful light.

They are getting smaller all the time as new materials come on line.

also for short duration lighting, incansescent is still the way to go. the flur. bulbs require a high starting current. IIRC starting the older tubes took as much energy as running the light (once lit) for 15 minutes - not sure about compact fluor.
if the above is true for compa. flour.:
so in a closet where the light might be on less then a minute, you have been running the 17 watts for the equivlant of 16 minutes for those tubes.

17W x 16min = 272 watt-minutes
100w x 1min = 100 watt-minutes = less power

As casdave noted, fluorescents are getting smaller all the time. They are also coming in more and more “styles” to approximate the range of incandescent bulbs.

Anybody know if it is true that you are not supposed to use a fluorescent in a “closed” fixture, like a ceiling fan with a globe on it??

While we’re at it, does anybody make a three-way compact flourescent bulb, for three-way lamp sockets? I thought I heard about one 5+ years ago, but I’ve never come across one.

I’ve got a 3-way flourescent, from Home Depot. They also sell globe-type bulbs for applications where the bulb is visible.

Green Bean–I’ve never heard of any restriction on placing a compact fluorescent inside a closed fixture. If anything, it would be safer than an incandescent, because CF lights give off less heat than incandescents.

I believe CFs are now available for use with dimmer switches.

I vaguely remember watching a home-improvement show a while back where they were installing some kind of spot lighting to illuminate paintings. The lights required a very high voltage feed, so they had a separate controller/power box and ran the wires to tiny little bulbs. I’m a little vague on the details though.

I wonder if you could do the same kind of thing for flourescents?


Illuminating art is a serious business, the wavelength of the light has to be carefully controlled for correct colour blalnace and the heat projected from it also has to be kept to a minimum to prevent damage to the object, such as fading, especially paintings.

Rather than being high voltage lighting they generally use very low voltages at high current, around 12V with a 60W lamp hence a current of around 5Amp.The lamps themselves are kept at a good distance from the object to lessen the mount of heat projected onto it.

To get the low voltage, which has to be very stable or it could affect the properties of the light and energy emitted from the lamp, requires toroidal transformers and if the object to be illuminated is particularly important there may even be a precision switched mode power supply which controls the supply to a nicety.

I think I understand what Smackfu’s getting at, and it’s a good question.

It sounds like he’s referring to spot halogen bulbs, which often operate DC and have a separate, bulky power supply that a number of them hook into.

The equivalent in fluorescent bulbs is what is commonly called the ballast–the big housing that the old tubes on the ceiling of your office plug into, or the integrated blob at the base of your compact fluorescent bulb that the twisting glass tube emerges from.

I think the question is: is it possible to move the ballast even farther away from the bulb? Could you run long wires from a fluorescent bulb back to a concealed ballast, thus eliminating the need to have that bulky thing attached to your lamp/ceiling/etc.?

Toadspittle, et. al.:
That concealed ballast idea sounds pretty good. It shouldn’t be difficult to design a fluorescent lamp with a built-in ballast, so you could just plug in a tube element and off you go. How compact are the smallest fluorescent bulb replacements anyway? I’ve seen globe-types that are fairly compact, but have fat base (I have two for porch lights – one at the front of the house, and one at the back). I use a ring-style bulb-replacer (commercial name’s “Circlite”, I think) in the garage (where I often forget to turn the light off). I also have a rectangular-ring 3-way in a lamp in my living room, but it’s too big for me to put the globe on the lamp. :stuck_out_tongue:


First off, the ballast is NOT the big housing that the tube plugs into. Take the shield off and you will see inside a large metal box, usually black that have wires running to the outlets where the tube plugs into. This is the ballast. It is usually approximately inches long. The ballast is similar to a transformer (similar, not the same) and provides the initial burst of power to create the arc needed to light the tubes. These ballasts get VERY hot (to the point I’ve needed to wear leather gloves to replace them), which is why Green Bean may have heard you aren’t to use a fluorescent tube in an enclosed space. I don’t have my copy of the National Electrician’s Code handy, but I’m sure there are rules about that, since most of the NEC deals with preventing fires and electricution.


Yes it is. As an electrician, one of our biggest jobs was retrofitting all the Walgreens in the St Louis area. We would take out the old magnetic ballasts and replce them with electronic ballasts. The electronic ballasts are lighter, don’t run as hot, last longer, and conserve energy. One electronic ballast made for a 4-tube fixture would be used to light 4 one-tube fixtures. We would simply run wires through the empty housing to the housing that held the ballast, often 9 or 10 feet away.

The problem with running wires in your home from a distant location to the tube is that ballast wires are unprotected. They have insulation, but unlike ROMEX, they are loose and not wrapped together inside a Code-approved protecting. You cannot have wires in your home running unprotected, so you would need to run the wires through conduit. And the ballast itself, as stated before, gets very hot and needs to be in an approved enclosure (such as the fluorescent tube fixture housing).

And don’t even get me started on the need to ground these things!

Until it’s more cost effective to run ballasts seperately from the lighting fixture (without having to use more conduit and another fixture to house the ballast), I doubt you’ll see this done anytime soon. And as for doing it yourself in your home, I don’t any inspector would pass this if you decided to sell your house as the idea doesn’t sound as if it goes along with the current National Electrical Code book.

Let me clarify:
“This is the ballast. It is usually approximately inches long.”

Should say “It is usually approximately 9 inches long.”

Having shot a job years ago in this place, I can testify to the fact that Duro-Test Light Bulbs makes a line of full-spectrum fluorescent tubes. They made grow lights, and other lights in full-spectrum daylight. That is to say, not ** just** 5600 degrees Kelvin, but a full spectrum within that temperature. I just bet they make smaller bulbs, that have a true-looking daylight.

I got one of the coolest souvenirs on a job ever, at that place. I used to have a small plastic Tin Woodsman figure from the Wiz of Oz, on my camera gear. While we were shooting, our client asked if he could take it from me. At the end of the day, I was given a very large incandescent light bulb…with the Tin Woodsman vacuum-sealed inside of it, wrapped to the center glass pin with filament wire. One of a kind. ( Won’t light, I suspect…) :smiley:


Compact fluorescents types are changing almost daily, so it can be hard to make generalizations. Several types do specify that they should not be used within an enclosed fixture. Several are not rated to operate in temperatures below freezing. Some of them are getting very close to the standard incandescent A-lamp size.

Unfortunately, the most innovative ones don’t frequently don’t show up in the Home Depot for a while. Some examples which will fit standard lamps can be found at

The spring shaped, dimmable ballast ones match the size and light output of standard incandescent lamps pretty well. I haven’t tried that particular type myself yet, though.

Toadspittle asked:

I did an energy conservation audit for a hotel several years ago, and I know that at the time there were a couple of firms marketing special lamp and ballast combinations specifically for the hotel industry. (Not just the ballast plus plug-in PL lamp that is most common now.) The ballasts were located within the base of the table lamp, and the lamp portion in the usual place. However, since the lamp would not work without the ballast, this would make it less attractive for the guests to steal. That was a real concern for these clients — they didn’t want to spend $10 a pop on lamps, just to have them all walk away with the guests.

k2dave noted:

The inrush current for compact fluorescents (or even standard fluorescents) is nowhere near that large. That was one of the “lighting myths” that was debunked at an EPA Energy Star Buildings seminar I attended a couple of years ago. I agree, however, that incandescent would be the way to go for a closet light. Chances are, it will only operate on the order of 100 hours or so per year (assuming you turn it off when you’re not using it.) I wouldn’t waste the expense of an expensive CF lamp with a 10,000 hour life on a space that will only use pennies worth of energy. It’s a real cash outlay to outfit your house with CF lamps. Get the most bang for your buck by putting them in the lighting fixtures you use the most — living room, kitchen, etc. Also put them in the fixtures that are the hardest to get to to change out lamps — They’ll pay for themselves in the aggravation they save you. (10,000 hour rated life vs 750 for most incandescents) They WILL pay back in energy savings, too(even though it still hurts to shell out that much money for a lamp.)

(Note to moderator: Was it ok to cite the RealGoods site above as a reference? It is a commercial site, but I am in no way affiliated with them. They just had good pictures and description of the lamps. My apologies if this was not acceptable…)