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Lighting FAQ:

LAST UPDATED: Jan. 23, 2010


(CLICK ON QUESTION TO GO TO ANSWER)

1. What type of fixtures should I buy?
2. Why do my bulbs burn out so quickly?
3. When the bulb burns out it sometimes shorts out the fuse and even explodes. Why?
4. Do I really save money by using those EL or SL (compact florescent) type light bulbs?
5. Do I really save money by using a dimmer?
6. Are halogen bulbs better than traditional bulbs?
7. Does frequent switching a fluorescent light on and off shorten its life span?
8. I would like to install 3x 12v halogen lamps in the bathroom. Would it be better to feed all three bulbs from one large transformer, or install a smaller, individual transformer for each lamp?
9. Can I use any size halogen bulb in my fixture?
10. How does one calculate the cost of operating a light bulb?
11. Should I replace a fluorescent bulb when it gets old, or wait until it burns out?
12. What are LED lights?



1. What type of fixtures should I buy?

Generally speaking, the type of lighting you choose will depend on the task at hand, and your preference in taste. This question cannot be easily answered, but if you click over to “4 Types of Lighting” and “Types of Light Bulbs and Their Uses”, you can get a much better idea. You can find even more on the topic in the "Tips and Info" section. There are also a few articles that may help.

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2. Why do my bulbs burn out so quickly?

Bulbs burn out prematurely for a number of reasons. The more common include:

A. The bulb not making good contact in its socket.

B. There could be a loose or otherwise bad connection somewhere in the line.

C. Changes in voltage from the Electric Company (including spikes, and surges).

D. Having the bulb in a fixture that does not let it disperse the heat it gives off (too closed up).

E. Putting in a higher wattage bulb than what is recommended for that particular fixture.

E. You may be using low quality bulbs.

As funny as it may seem, another possibility may be that there is no actual problem and the bulb actually finished its life expectancy. Most incandescent bulbs have a life span of between 700-1000 hours. So, for example, a standard bulb being used everyday for 5 hours, will last about 4.5-6 months. Even less, if you use it more frequently. A bulb that is on most of the day (as you may find in a store or office) will last half that time.

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3. When the bulb burns out it sometimes shorts out the fuse and even explodes. Why?

To explain, I must get a little technical. When the filament in the bulb breaks, an arc sometimes forms. This arc often expands until it is across the entire filament. Usually when this happens things get a bit unstable, since the more conductive arc would draw even more current. The arc easily becomes conductive enough that it draws a few hundred amps of current. At this point, the arc often melts the parts of the filament that the ends of the arc are on, and the arc glows with a very bright light blue flash, and at the same time, causing the fuse to burn or breaker to trip. Many good quality bulbs have a small built-in fuse inside the base that would normally burn before your breaker has a chance to trip.

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4. Do I really save money by using those EL or SL type light bulbs?

Well I suppose it depends. EL or SL bulbs, better known as compact florescent light (CFL), are designed to use 60-75% less energy, and to last 10 times longer, than standard bulbs. But there are two small problems. One problem is that there are many manufactures producing cheap, inferior CFL bulbs that are not “up to par” with what the quality brands have to offer. They have many shortcomings including shorter life span, less light (lumens) per watt, and some even start to dim considerably after a month or two of use. The better quality brands work much better, but they aren’t cheap. You can probably buy at least 25 or 30 incandescent light bulbs for the same price. But never-the less, due to their long life span and their efficiency, the CFL bulbs do save you some money on the long run.

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5. Do I really save money by using a dimmer?

Yes, but not as much as you think. Even though the light gets dimmed, the electricity saved is not proportional. For example, if you dimmed a 75 watt incandescent lamp by 25 percent, you will still be using around 66 watt. This is because the lamp still uses a lot of energy to generate infrared heat. The bulb becomes less efficient. Personally, I am not a big fan of dimmers, and recommend them only where absolutely needed.

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6. Are halogen bulbs better than traditional bulbs?

It depends on what is meant by better. Halogen bulbs are more efficient (although not by much) than the traditional incandescent bulbs, but they burn hotter and are more costly. Sometimes, it’s not a question of better or worse, but rather of what’s better for a particular job. Maybe you can get a better idea if you take a look at “Types of Light Bulbs and Their Uses”.

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7. Does frequently switching a fluorescent light, on and off, shorten its life span?

Yes, unfortunately that’s true. Therefore it is recommended that they be used where the lamp would be lit for a certain amount of time, and not switched off and on every few minutes. On the other hand, it does not mean that you should keep your fluorescent lights on all the time even if they aren’t actually being used. This will also be a waste of energy.

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8. I would like to install 3 small 12V (low voltage) halogen lamps in the bathroom ceiling. Would it be better to feed all three bulbs from one large transformer, or install a smaller, individual transformer ‎for each lamp?

I know that it sounds like a good idea to have one large transformer feeding to all three halogen lamps (mainly because of cost), but actually it would be much better to have individual transformers, one for each lamp. I would also recommend getting a good brand electronic transformer instead of the regular, heavier, coil type (step-down).

Having a number of bulbs running off one transformer can cause a number of problems. To begin with, should one or two bulbs burn out, the voltage would suddenly shoot up, possibly damaging the other bulbs that are still working. Due to the larger size of these transformers a special place would have to be designed to put the transformer where it can be accessed for inspection should there be a need. This can be a nuisance. Another small nuisance is the fact that if the transformer burns out or malfunctions, then ALL the halogen lights will go out.

Smaller electronic transformers, usually fit through the same hole as the fixture. They put out very little heat and make less noise than the coil type transformers. Being that you will have each lamp with its own transformer, should one lamp burn out, only that one lamp would cease to work. It would not cause a voltage surge, thus not causing the other bulbs to be damaged.

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9. Can I use any size halogen bulb in my fixture?

Usually using the same size and type bulb that came with the lamp is the best thing to do. If you are talking about the 220V (tube type) bulbs, then it would depend on the way the fixture is built. For instance, if you have a fixture where the bulb is completely covered, putting a larger wattage type bulb in can cause not only the bulb to burn prematurely, but can cause the whole fixture to burn up.

If you are using the low voltage type bulbs (12V), then much would depend on the transformer that was being used. Overloading the transformer will cause it to burn up. Some fixtures cannot handle the heat of a larger bulb.

Sometimes special bulbs are used to reflect most of the heat coming out of the bulb in a certain direction. These are used in special instances, and not replacing with the same type bulb can cause a fire and/or other damage. Before making any changes it is best to ask an electrician.

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10. How does one calculate the cost of operating a light bulb?

To calculate the cost of operating a bulb for one day - multiply the bulb wattage times the hours per day the bulb is used, divide by 1000, and multiply by the Electric Company's cost per kwh.

For example: 100 watts x 5 hours divided by 1000 x NIS 0.42 = NIS 0.21.

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11. Should I replace a fluorescent bulb when it gets old, or wait until it burns out?

There's nothing wrong with waiting until it burns out. However, fluorescent bulbs produce less light (lumens) over time. An old bulb may not only produce 25% less light than a new one, but the color changes slightly overtime. Therefore when replacing just one bulb in a multi-lamp fixture, the new bulb will be brighter and a slightly different color than the others.

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12. What are LED lights?

Light emitting diodes, commonly called LEDs are basically tiny light bulbs that don't have a filament that will burn out and don't get especially hot. They are illuminated solely by the movement of electrons in a semiconductor material, and they last just as long as a standard transistor.

The past few years have brought about the development of LED light bulbs which can replace many of the bulbs that are commonly used today in our homes. These relatively new type bulbs have an extremely long life and are low in power consumption. Although technology is always improving, as of now LED light bulbs have lower output (lumen) than incandescent bulbs, but are more focused. For the time being, they are used mainly for directional lighting, but this can change at any time.

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