Using Fluorescents – A Compilation

This concludes the very long series evaluating our turn from incandescent to fluorescent lighting.  This is a summary of the 6 posts.

Acronyms:1.  Efficiency

Fluorescents-1 Efficiency  From the manufacturers ratings, we found that CFL lamps used about 4 ½  times less power than the incandescent lamp of the same lumen value (light emission). Huge variation in these data, and it should be noted that these data were taken when the lights were new.

Supporting file, PDF:    How Fluorescent Lights Work.PDF

2.  Lifetime

Fluorescents-2 Lifetime  The rated lifetime of a bulb is the time it takes for 1/2 of the products made to fail.  CFLs lifetimes are at least 10 000 hours, and, although extended life ILBs match or beat the CFL ratings, we did not discuss them.  CFLs have several methods that will reduce lifetime.


Frequent power cycles damage CFLs

A  Rapid cycling.  This causes early failure, though details are bulb dependent and pretty much proprietary.

The basic rule is Switch Infrequently.

B. Elevated temperature. Use your FLs at rated temperature or prepare for early demise.  This means using a tube rated at 30º C (86º F) in the attic will shorten its service life.  If you use a standard CFL but screw it into a ceiling socket, the bulb overheat its own ballast and will cause its own failure.

C.  CFLs can be more expensive.  Use a CFL and its matching ILB  as intended, and the ILB could have a lower overall power drain than the CFL.  As-intended fluorescent use is continuous ON, do not switch.  As-intended incandescent use is ON when needed, OFF otherwise.   In offices and factories, fluorescent lighting always wins because these lights are always on.

D.  Use only the best brands.  This means buy the most expensive fluorescent bulbs.  Cheap lights use shortcuts in manufacturing that add to corporate profit, but are nothing but frustrations for the customer.

I wrote about my kitchen light (a 13″ 5/8″ diameter tube) that lasted 10 years, but the new replacements fail quickly.  Just happened again. It was a Phillips tube made in Poland, which lasted 3000, maybe 5000 hours.  I replaced it by another GE tube made in China.  This was the second dead-on-arrival unit (made in China).  Narrow diameter tubes are hard to make; they require careful manufacturing quality control.  Most of my observed failures come from China which has  real difficulty  consumer quality.  There is no EPA there, no OSHA, and it shows.

3  Lumen Depreciation (LD)

Fluorescents-3 Brightness  Fluorescents use phosphor screens and their intensity fades away with time.  This is the LD effect.  Incandescents show LD  but shortened lifetime makes the issue unimportant.  Tungsten Halide bulbs have lifetimes approaching FL lights, and show very small light decay.

A.  Aging.  Fluorescent intensity drops quickly from the initial rated lumen value during the first 1000 hour.  Intensity continues to drop thereafter, although not as quickly in some tubes (brand dependent).  Factories use scheduled maintenance change-out even though the lamps are glowing –  to keep productivity high.  People can acclimate to ever-decreasing light, though this can be a problem for older people who usually need brighter lights to let their eyes focus properly.  Waiting for the bulb to fail is reasonable for ILBs but not FLs.

B. Ambient temperature.  When any FL is used in an environment much different from the manufacturer’s optimal value, the intensity will drop below the peak lumen values by as much as 40%, independent of the lamp’s age.

4  UV

CFL-Sunglasses_imgFluorescents-4A UV  All fluorescent lamps emit ultra violet light at some low intensity.  It is advised to stay a foot (30 cm) or so away from the lamp.  Low quality manufacturing can lead to pin holes in the phosphor screen (the white powder on the inside of the tube).  This can be a problem, depending on hole size and user location. Incandescent lights do not emit UV.

5  Color

Fluorescents-5 Color  There are 2 indexes meant to indicate the quality of the color.

A.  CT Color temperature.    CT is the report of the best fit of the smooth continuous light from a heated object to the narrow spiky emission from a phosphor screen.  Two different phosphor lamps can fit to the same color temperature but one might miss most of the reds while the other misses most of the blues – much different human responses.  CT is helpful but is badly flawed.

Supporting file, PDF:  Color Temperature

B.  CRI Color rendition index.   CRI uses a 0-100 scale to compare the comfort of a fluorescent light with respect to an incendescent light with the same intensity;  100 means exactly like tungsten filaments.  This does not work very well (same reasons as the CT rating).  But, below a ranking of 80 the lighting is definitely unpleasant.  CRI is an international standard, which explains its use.

6  Environment

Fluorescents-6 Environmental Impact.  The major issue is that CFL will, indeed, contribute mercury to the waste stream.  We looked at the current large contributors, beginning with coal fired plants (more than 60 tons/yr,  58% of the total Hg), down to mercury thermometers (less than 1 ton/yr, 1% or less).  Assuming recycling compliance similar to all commodities in the past, CFLs will account for perhaps 2 to 3 tons per year.  Although well below the power plants, and therefore being hardly noticeable in the waste cleanup, it is twice or three times more than the mercury thermometers that generated a fire storm of political action.

I have to repeat:  (1) When we are looking at 60 tons/year of mercury coming from power plant smokestacks, why are we bothering about 3/4 ton/yr from our thermometers?  (2) On the other hand, if we have successfully banned sales of mercury thermometers through concentrated political warfare,  why are we hyping a much bigger pollution source?

Final Comments

click for a list our posts on illumination technology

Fluorescents are not superior to incandescents, but they do have their niche uses.  The outright ban on 100 W bulbs in 2012 and total incandescent ban in 2014 (with a few exceptions) is unjustified, but are a home run to manufacturers.  None of the arguments are stand-alone irrefutable.  In fact, if all our forms of lighting shift to makers who are unconcerned about quality, we are headed for trouble.

Fluorescent lighting, CFLs in particular, is a bumper-sticker green issue.  There is a great deal of showboating going on; people posturing about how awful the opponents are, so utterly without reason.   Here is just one.  Space down the link to the comment on Red Herrings, by Charles Frost.  Mr. Frost, I do drive a 2004 Honda Hybrid.  I support the proposal to raise mileage to 55 mpg in 10 years.   When I was a young man leaded gas was shown to damage children who played around major streets.  My wife and I bought unleaded gas (called “white gas” at the time) for 30% more per gallon, even though auto technicians said that it would ruin the valves;  We drove a car with 32 mpg, the best at that time –  and got a lot of negative comments.  I am concerned about the welfare of our children and theirs.  Such comments are (redacted) unjustified.

I had planned to respond to the pro-CFL comments in detail.   But really,  what’s the point?

Charles J. Armentrout, Ann Arbor
2011 Aug 17
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About LastTechAge

I am a physicist with years of work in fusion labs, industry labs, and teaching (physics and math). I have watched the tech scene, watched societal trends and am alarmed. My interest is to help us all improve or maintain that which we worked so hard to achieve.
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One Response to Using Fluorescents – A Compilation

  1.  lighthouse says:

    Agree with the post.
    There is the broader issue that all lighting has advantages, that energy saving is not the only advantage a product can have for a user, and that mandating energy saving on a given product changes its characteristics (as well as increasing price).

    Moreover, that switchover savings are marginal for many reasons, being a fraction of 1% of overall US (and EU) energy use, as referenced with US Dept of Energy stats and surveys etc, and that regardless of energy savings, there is no shortage of energy sources for electricity to justify enforced savings, and if there was a shortage, the price rise would reduce use anyway and increase the sale of energy saving products – without government legislation.

    A 13 point summary of the arguments used to justify light bulb regulations, and referenced reasons why those arguments don’t hold up

    Peter Thomes

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