Posts Tagged ‘fluorescents’

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California Lighting, Final Thoughts

Wednesday, July 22nd, 2009

All in all, the California Title 24 legislation is pretty progressive. With regard to lighting, it is really focused toward making you think about the lighting in your home. You really have two primary approaches toward lighting your living space: either committing fully to fluorescent lighting or using dimmers throughout your home for energy savings. The state is also clearly looking forward to LED lighting, but frankly the industry isn’t ready to support that yet. However, the rate of growth is so strong it will only be a few more years before that changes.

If you commit to fluorescent lighting remember to consider the color temperature and color rendering index of each lamp. Right now people aren’t accustomed to the way everything appears under fluorescents, but I think in a generation the quality of fluorescent lighting will become our new “normal.” With technological advances the fluorescent and LED sources will improve and either the manufacturers will make them more like natural light or (more likely) we’ll just grow to accept the spectral profiles of those sources.

However, if you aren’t ready to make that leap yet you can use dimming systems. I think everyone should use dimming in their homes even if they don’t care at all about energy efficiency, since I believe the quality of life benefits shouldn’t be ignored.

And instead of just using local dimmers, hopefully this will stimulate the use of wider-ranging lighting systems. System that enable you to program lighting for entire rooms rather than just adjusting each circuit. There are countless options out there so don’t feel limited by the adoption of more stringent energy efficiency standards as they progress from the west coast eastward.

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Posted in Dimming, Fluorescent (and CFL), General Knowledge, Homeowner Tips, Incandescent | No Comments »

Residential Fluorescent Lighting

Tuesday, July 14th, 2009

So, yesterday I posted a process I might go through to replace a fixture in my home with something more energy efficient. However, it isn’t really what I would do in my own home because I like everything to be dimmed. That includes fluorescents.

A good number of fluorescent and compact fluorescents can be dimmed using dimming ballasts. That does NOT include the self-ballasted CFLs with the screw-in base that you find at the hardware store. GE has come out with a self-ballasted replacement CFL that can be dimmed, and I’m sure others either have or will have soon their own versions. However, these can only be dimmed about 50% before they just turn off. They aren’t worth it.

Instead, I would have to buy separate dimming ballasts and install them myself. I would also have to change out my dimmers to a special versions for fluorescent lighting or perhaps install an interface. Some fluorescent dimming is done using two-wire ballasts, which would be easier to install using existing wiring, but the better dimming is accomplished using three-wire ballasts, which requires a third connection between the dimmer or interface and the ballast.

Fluorescent dimming ballasts typical have a minimum power setting of 1%, 5%, or 10%. For residential use I always recommend using 1% ballasts. This is because reducing the power doesn’t look like the same amount of light reduction. If you dim fluorescents down to a 10% it looks like it has only been dimmed down to about 30%. This just isn’t low enough for use in homes. Instead, using a 1% ballast means the lighting will look like it has been reduced to about 10%.

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Finding a More Efficient Lamp

Monday, July 13th, 2009

As I was finishing up my previous post about efficiency pitfalls, I realized that I had started an example which could be useful in and of itself. So I’m going to take it a step further.

Situation Summary: I have an existing fixture in my home that I want to make more efficient. It is a surface mount that looks like a glowing bowl stuck on the ceiling. It uses two 75 watt bulbs. The light in the room is more or less acceptable, although it is a little dim and I would like it to be slightly brighter if possible. Looking up the information about the existing bulbs, I see that the total lumen output of both bulbs is 2,340, so I know I want to at least match that and if possible increase it slightly.

I could have just substituted my 75 watt incandescent bulbs for 20 watt self-ballasted CFL bulbs, based on the label on the box that says to replace my 75 watt bulbs with the 20 watt CFLs. The energy savings is good, since now my fixture only uses about 40 watts instead of 150, meaning I’m saving about 73%. However, the mean lumens of those CFLs are only 965, so the new total would only be 1,930. Since I thought the room was already a bit too dark, going from 2,340 lumens to only 1,950 is going to make me unhappy over the long term, and I run the risk of someday switching back to the incandescents. (Note, the initial lumens of this bulb are listed as 1,150, which brings my total up to 2,300 and almost a perfect match to my existing. However, that is initial lumens and won’t last for the lifetime of the bulbs. They will continue to depreciate and my room will get darker and darker, so it is an unfair comparison to use the initial lumens.)

Fearing the decreased light output, I buy two 26 watt self-ballasted CFLs because I see that the mean lumens for those are 1,365, meaning my new arrangement will provide me 2,730 lumens! I’d be saving about 65% energy by using 52 watts, but I discover that the 26 watts lamps are bigger than my existing incandescents and they won’t fit in my fixture. The bowl hits the ends of the lamps preventing me from reattaching it.

Now I recall reading my own post from yesterday. I go to my local electrical supplier and buy a replacement fixture for the existing. Based on my post, I’m now using a long “blob” instead of a bowl on the ceiling. I get 2,772 lumens, so I am very happy with the new lighting level in the room, and I’m only using 32 watts. That’s a savings of about 75%, better than the savings from those CFLs! Granted, I’ve now bought a new fixture as well as lamp, and I had to be very careful about my lamp and ballast choice, but I’m much happier with the final result.

Of course, this just shows that in order to make the best choice you need to have some knowledge, but that’s what this blog is for. Feel free to send me questions or reply to my postings to get more information.

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Posted in Fluorescent (and CFL), General Knowledge, Homeowner Tips, Uncategorized | 4 Comments »

Efficiency Comparison Pitfalls: Systems

Friday, July 10th, 2009

Another pitfall with comparing lamp source efficiency is the entire system’s efficacy.

With incandescent and halogen sources, the wattage on the label is pretty much what you get.

  • Technical info, you don’t have to read or understand this: the “what you see is what you get” assumes that the voltage matches. That is, a normal 100 watt light bulb will consume 100 watts at normal household voltage of around 120V. If the voltage is increased, the wattage increases, and if the voltage is decreased the watts consumed also decreases. Some manufacturers use this effect to create longer life and energy savings bulbs; for example, GE sells a 100 watt 130 volt lamp (3,000 hour life) which is labeled for 120 volt use as using 89 watts (8,300 hour life). Of course, the light output also decreases, and it decreases faster than the energy savings: losing 25% of the light output while only saving 11% of the electricity consumption.

Discharge sources, like fluorescent, require some form of control gear to regulate the electricity being consumed. The wattage label on the bulb is not the wattage which will actually be used in the system because the lamps can’t regulate their energy consumption themselves. They require a ballast to do that for them.

Since the ballast is what actually controls the wattage consumption, you have to calculate the efficiency of the system using both the lamp (for the lumen output) and the ballast. Professionals use the term efficacy instead of efficiency to remind themselves that they are dealing with the multipart system rather than just a lamp. So if you compare the efficiency of an incandescent bulb to a fluorescent replacement, you have to make the comparison against the system’s efficacy, not the lamp efficiency.

For the self-ballasted compact fluorescents you pick up at Wal-Mart the comparison is still fairly easy, since the ballast is included as a part of the lamp and the wattage listed on the box is for the ballast. In that regard, you can compare a regular light bulb off the shelf with the CFL next to it. However, if you live somewhere like California, where they have outlawed the use of medium screw based sockets in new construction (emphasis on new), you can’t use a self-ballasted CFL anymore.

Instead, you have to look at the efficacy of the lamp/ballast combination. Different ballasts will have all kinds of different ratings and properties that make reviewing them mind-numbing for the average person who just wants a light bulb. The take away is that the lamp ballast efficacy will be different than the lamp source efficiency. Usually it is less, although sometimes a system can have better efficacy than its lamp’s efficiency.

  • Technical info, you don’t have to read or understand this: Ballasts affect the lumen output out the lamps they control separate from the age issue I discussed previously. The affect is known as the “ballast factor,” which is the ratio of what the ballast does to the lamp it is powering versus the fictitious “perfect laboratory ballast” which is used to give the lumens shown on the lamp box. The number is a percentage (real output divided by “perfect” output) and written to two decimals (0.77 or 1.53). You will see ballast factors greater than 100%, accompanied by a wattage higher than the wattage listed for the lamp alone. To determine actual lumen output, you have to multiple the listed lumens by the ballast factor. This new lumen value is what you use to determine the efficacy of the system, along with the ballast’s wattage for that lamp. One ballast may have different ballast factors for different lamps, which will be listed. For easy comparison of ballast factors among different ballasts, there is also a “ballast efficacy factor,” which is the ballast factor divided by the input watts. The higher this BEF the more efficient the lamp/ballast combination, so you can compare ballasts for the same lamp that may have different wattage usage.

An example to demonstrate that you have to look at both the lamp and ballast:

I’m using a 4′ long linear T8 lamp, like you see in a 2′x4′ office fixture that is recessed in a grid ceiling made up of 2′x2′ tiles. To be specific, it is a GE F32T8/SPX35/ECO, which provides 2800 (mean) lumens for 32 watts. My first ballast option is going to be a GE “Residential Grade ProLine” ballast (GE232-120-RES). The lumen output for one lamp is 2,772 (mean lamp lumen times the ballast factor). The system wattage is 32, so the efficacy of the system is 86.6 LPW. I then substitute the “Residential Grade” for a regular “ProLine” ballast (GE232-120-N). The lumen output for one lamp is now 2,632. The system wattage is 36, so the efficacy is now 73.1 LPW. I want to try one more ballast and I choose the “UltraMax Instant Start Multi-Voltage High-Efficiency” because the name sounds cool and highly efficient (GE132MAX-L/ULTRA) The lumen output is now 2,156. The system wattage is 25, so the efficacy is 86.2 LPW.

To choose my ballast, and because I don’t care about how much each one costs for this example, I discount the “ProLine” ballast since it gives me similar output to the “Residential Grade” ballast with less efficacy. Now, I have to choose between the “Residential Grade ProLine” and the “UltraMax.” They have similar efficacies, so I have to choose which I want based on the lumen output. What I haven’t told you yet is that I’m replacing a surface mounted fixture in my home that uses two 75 watt bulbs. The lumen output of the existing fixture that I am trying to match is 2,340, which falls between the 2,772 of the “Residential Grade” ballast and the 2,156 of the “UltraMax.” Rather than decide based on the efficacy or the wattage of each individual ballast I have to select the ballast based on the light output. I decide that I always though the room was a little bit too dark anyway and so I choose the “Residential Grade” ballast. Now, I’ve got a touch more light than before while saving about 75% of the energy, dropping from 150 watts down to just 32!

PS: I’ve written this using fluorescent lighting as the examples, but the same is true for all the gas discharge sources, like metal-halide, high-pressure sodium, etc. High-pressure sodium is an especially efficient light source, although it suffers from all those color temperature and color rendition problems discussed in previous posts.

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Posted in Fluorescent (and CFL), General Knowledge, Homeowner Tips, Incandescent | 2 Comments »

Efficiency Comparison Pitfalls: Age

Thursday, July 9th, 2009

Following up on yesterday’s post, efficiency pitfall number one: age.

An incandescent or halogen light bulb is a fairly closed system. It can be stuck in a socket and what you see is what you get. A 100 watt light bulb is going to be pretty consistent over time. There will be some decrease in the light output as the tungsten filament gets burned up and bits of it get stuck to the inside of the glass envelope, darkening the glass. However, for the most part the lamp will burn out and the filament break before the decrease in light output becomes much of a factor. Tungsten-halogen lamps do slightly better, since the halogen gas inside the bulb makes the tungsten that gets burned off reattach to the filament and basically “recycle” itself, but even though the lamp will last longer and suffer from less darkening it will still break before those changes tip the efficiency equation too much.

Unfortunately, the same cannot be said for the various discharge sources like fluorescent, compact fluorescent, or the various HID types. While a filament does exist in these lamps, the real work of making light is done by the gas discharge. (Check some of my previous posts about fluorescent lighting for a summary of how it works.) The light bulb does not just “burn out,” but instead slowly degrades over time putting out less and less light.

This means that the efficiency of a fluorescent or compact fluorescent decreases over time if you are just using the lumens per watt calculation. For example, the day you install a brand new CFL 26 watt twist self-ballasted lamp you’ll probably get about 1,700 lumens. However, since the output of fluorescent lamps decreases over time, manufacturers also publish the “mean lumens,” which is the lumen output at about 40% of the lifespan of the lamp, which in our example case is 1,365 lumens. So the efficiency has dropped from 65 LPW when brand new to 52 LPW. The lumen output will continue to drop until the lamp reaches the end of its life.

Granted, the lower efficiency of 52 LPW is still much better than the 17.5 LPW of the 100W lamp we’ve replaced (see yesterday’s example). However, remember that you also have 20% less light. So after a while, the new CFL lamp isn’t providing the amount of light you used to have with the old incandescent lamp. This is the point when some people give up and go back to the old lamp, or they add a reading lamp using another incandescent lamp.

Professionals try to counterbalance the lumen decrease by working depreciation factors into the system when they are planning out what lamps to use in a project. We will intentionally over-light a space from day one knowing that eventually the lamps will decrease in output to the level we want for the longer term. The first 100 hours of a CFL or fluorescent is when the decrease is the most rapid, which is called “seasoning.”

As another age related problem, fluorescents don’t necessarily “burn-out” like incandescents and simply stop working. Sometimes, often times, they will just continue to get darker and darker and darker and don’t simply stop turning on. This is why professionals recommend having a maintenance schedule for replacing your fluorescent lamps based on time, not waiting for the lamps to stop working. (What? No one told you this? Yes, if you are going to use CFLs you should keep track of how old the lamps are replace them on  a schedule. And yes, it’s much more of a hassle than just waiting for the bulbs to stop working.)

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How Do I Know What’s Efficient?

Wednesday, July 8th, 2009

I have fielded a variety of questions from people trying to figure out what kind of lighting is more or less efficient than others. Many people understand that lower wattage is better, from a consumption view, but they don’t necessarily feel like they are comparing apples to apples when they try to compare incandescent to compact fluorescent or LED.

The way to determine efficiency of any given source is to figure out how much light you get for the amount of power used. Using the lowest wattage source may not be the most efficient approach if it doesn’t give you enough light and you end up adding more. The lighting industry uses a measurement called Lumens per Watt, or LPW. We take the total lumen output of the source divided by the wattage so we can make direct comparisons.

For example: a regular 100 watt light bulb for a table lamp, with clear glass so you can see through it, will provide about 1,750 lumens (it will say this somewhere on the box). Since it uses 100 watts, you divide 1,750 by 100 and figure out its efficiency is 17.5 LPW. Now you can compare that to a compact fluorescent replacement lamp (with a screw in base for your lamp) and find that it provides about 1,700 lumens for only 26 watts. The CFL lamp has an efficiency of a bit over 65 LPW. Therefore, we can say that the CFL lamp is almost 4 times as efficient as the incandescent.

To provide some general guidance I’ll type up a quick list of some sources and their LPW ranges:

  • Standard incandescent bulbs range from around 4 to 20 LPW
  • Tungsten-halogen bulbs range from around 18 to 22 LPW
  • Low wattage compact fluorescents range from around 20 to 60 LPW.
  • High wattage compact fluorescents range from around 50 to 80 LPW.
  • Linear fluorescents range from around 65 to 95 LPW.
  • LEDs range from around 5 to 40 LPW, although there is so much development of LED sources right now this range is likely to change quickly.

As with everything I write about lighting, there are some caveats. I’ll discuss a few of those in upcoming posts.

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Posted in Fluorescent (and CFL), General Knowledge, Homeowner Tips, Incandescent, New Tech | 1 Comment »

Color Rendering Index

Monday, July 6th, 2009

Equally important as the correlated color temperature for fluorescent lamps, the color rendering index (CRI) is used to determine how things are going to look under fluorescent lighting. The CRI is a made-up scale ranging from 0 to 100, where 100 is the expected color rendition of incandescent/halogen sources

The colors of objects that you see are actually those colors being reflected back at you. If you start with white light shining on “red” object, the blue and green parts of the white light are absorbed by the object and the red is reflected back for you to see. If instead of a “white” light that has a good balance of red, blue, and green, you have a “white” light that is weak in the red part, the blue and green still get absorbed by the object, but there is less red to be reflected back at your eye. The same object is going to look less “red” under the second “white” light.

Since an incandescent source is like a black-body radiator, the color spectrum of of the light generated by the filament has a decent mix of all the visible colors. However, since the colors present in the “white” light of a fluorescent is made up by phosphors which each do just a part, there can be a poor mix of colors in the light. The better the phosphors do at creating that mix of colors the better the CRI rating.

The more important color is, the higher the CRI of your lamp should be. Manufacturers will make similar lamps (in terms of size, power, etc.) with different CRI ratings since the lower CRI lamps can be made more cheaply. People will either select the lower CRI lamps because color doesn’t matter as much as cost or because they don’t know that there is a difference. For example, for linear tube fluorescents, like you find in offices, the cheaper lamps will have CRI ratings in the low to mid 70s and the higher quality lamps will have CRI rating in the low to mid 80s.

For your home or office I recommend getting the lamp with the highest CRI you can find. For standard fluorescents I only specify lamps with a minium CRI of 85. For compact fluorescents I have to drop my minimum to a CRI of 82, since higher CRI rated lamps aren’t readily available.

Note that both the CRI and the CCT of a fluorescent lamp will be printed on the lamp itself, so if you need to find out what something is you can just look at it. For a linear tube style, the information will be printed on the glass at one of the ends. For a compact fluorescent lamp the information will be printed on the base. Most of the time the information is just printed as “82 CRI” and “3500K.” Sometimes only the manufacturer’s coding will be printed, but typically it will show the CRI by either a “7″ or “8″ somewhere in the lamp code (for low to mid 70′s or low to mid 80′s as appropriate) and the CCT as the first two digits of the CCT (such as 27 for 2700K or 35 for 3500K).

To see an example of what happens when you use a lamp with a low CRI rating most people can probably just find a nearby streetlight. Many streetlights are still high-pressure sodium because HPS lamps are very energy efficient. However, they also have a CRI around 22 and a CCT of around 1800K. That’s why the “orange glow” of a streetlight makes everything look orange or gray.

If you have streetlight around you that look more “white” than orange they are either very old mercury lamps (which are now banned from new installation but utility companies who stockpiled them can use up their inventory until they replace the fixture) or metal halide lamps. They probably have a CCT of around 4000K and a CRI ranging from about 50 (mercury vapor) to 65 to 75 (metal halide). There are also new ceramic metal halide lamps that can have a CRI as high as the low to mid 90′s.

Using streetlights doesn’t provide a perfect example since the darkness of night also affects how we perceive colors, but it’s a good shorthand.

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Color Temperature Basics: Summary

Friday, July 3rd, 2009

I hope the previous discussion of color temperature is useful. There is a lot of technical information that goes into understanding and effectively using color temperature. Here are some key points that you can rely on as being useful to you.

  • Color temperature usually only matters for non-filament sources: fluorescents, compact fluorescents, metal-halide, induction, etc. (and it’s really the correlated color temperature, so it will be labeled CCT)
  • There are many options for color temperatures of fluorescent lamps. Don’t just pick something up because it’s on the shelf. Think about the space and select a color temperature that is going to help. You may need to go somewhere and see some samples of different color temperatures before you decide.
  • Higher color temperatures give a greater perception of brightness. There are complex optical reasons for this that you don’t really need to understand, just know that a CCT of 4000K will appear brighter than a CCT of 3000K even if the measurable quantity of light is equal.
  • Color temperatures higher than 4200K tend to be perceived as too cold for comfort. They are useful for very visually-intensive tasks, so you find them in manufacturing facilities where there are lots of small parts being used, but not homes or professional offices.
  • Color temperatures lower than 3000K will seem to be too amber during the daytime. Things may appear to be visually “mushy.” However, at night 3000K can be very nice.
  • Typically, places used and lit during the daytime benefit from higher color temperatures and places used and lit during the nighttime will benefit from lower color temperatures.
  • Dimming fluorescents will not shift the color like it does with incandescents and halogens. This is actually a negative, since during the daytime you need higher lighting levels and a higher color temperature to be comfortable, but in the evening you’ll want to turn down the intensity and color temperature.
  • I have found the best middle of the road CCT for fluorescents is 3500K. No single color is going to be the best for every purpose, but 3500K is a pretty decent compromise.
  • If you have fixtures will multiple lamps you can mix a warm and a cool to try control the balance of “white” light better. However, don’t mix colors from a single-lamp fixture to the next since it will be start to look just plain weird.

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Color Temperature Basics: Fluorescents

Thursday, July 2nd, 2009

The real meat of the color temperature discussion is with regards to fluorescent and HID (high intensity discharge) sources. Color temperature is tricky for fluorescents because it is based on heating the black-body object to get a color. However, fluorescent sources do not have an object to heat since there is no (functional) filament. Instead, it is a gas discharge process, so color temperature doesn’t really apply. Instead, we use the CCT, or “correlated color temperature.” This is just an approximation of the color temperature the manufacturer is trying to achieve with their mix of phosphors inside the lamp.

The reason CCT is important is because there are so many different phosphor mixes that can be used. Unlike incandescent lamps, there is a wide range of mixes and each mix, relating to a CCT, establishes what we see as “white.” It is this establishment of “white” that makes any and all of this matter.

By using a different phosphor mix, we make white objects appear either warm or cool, based on the (correlated) color temperature of the light source. All other objects, from artwork to skin color, reflects the same “bias” toward the color we have established as white light. This is why early adoption of fluorescent office lighting was so painful. The phosphor mix and color temperature of the light was shifted so far toward the higher, cool end of the lighting range people didn’t like the way things looked. There were other problems, but the main thing most people took away from the experience was an association of fluorescent lighting being “cold.”

However, we could just as easily make our fluorescent lighting “warm” by using lamps with a CCT with a lower number. For example, you could use lamps with a CCT of 2700 to try to match the incandescent lamps you are used to having in the home. In my experience, most people don’t like a fluorescent lamp with a CCT of 2700K either, since it doesn’t look like a regular incandescent lamp with a color temperature of 2700K. That’s part of the “correlated” aspect, and there is also some color rendering issues which I’ll discuss in following posts.

The trick to good fluorescent and compact fluorescent lighting is finding the CCT you like for any particular use. In more residential settings, a 3000K lamp may be preferred, whereas in an office or kitchen 3500K may be better. You can’t just pick one and use it for everything, although that would be preferable to not picking at all and just installing whatever shows up. Selecting the right color temperature is a part of the lighting design process.

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Color Temperature Basics: Why Should You Care?

Tuesday, June 30th, 2009

I mentioned during the introduction to fluorescents that I would have follow-up posts about color temperature and CRI (color rendering index). I’m going to kick this off with color temperature and an explanation of why anyone would care about it.

relative-color-2One of the biggest problems with artificial lighting is that our eye and brain determine a lot of color information by comparison instead of some sort of mental color wheel. I’ve stuck an image file into this post to provide an example. The image to the right is made up of exactly 3 colors, but the purple color appears to be either a lighter or darker purple depending upon whether the adjacent color is the blue or the pinkish color. Also, the purple bar that runs all across the middle seems to change color from one side to the other.

The issue for artificial lighting is that as we look around us, our eye spots the brightest source of light and our brain “sets” that as white light. We are mentally doing the opposite of the what my sample image shows: instead of using relativity of colors to “see” either bright or darker versions of purple when the purple is actually the same, we are using relativity of colors to see different versions of “white” and then perceiving that as always the same “white.”

For the common user, a lightbulb (unless a specialty colored lamp) is going to be perceived as white. For the professional, we know that different sources are giving us different whites and we need a way to document the differences. We do that by specifying the “color temperature” of the source.

For the next post, I’ll explain what color temperature actually is and how we come up with the numbers.

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