I don't get to publish whatever I want in prestigious magazines, so I'll do my open comment session here to share my views, address misleading and even wrong information appearing in
"Out with the old, in with the new Obsoleting linear fluorescent lighting" authored by Jeff Hungarter, product portfolio manager at Cree as appearing in page 36 of July 2014 issue of Electrical Business
www.EBMag.com
Cree is an LED manufacturer located in Durham, North Carolia with a mission to "drive 100-percent adoption of LED lighting" and a vocal opponent of "fluorescent lighting".
A copy of it is available at:
https://www.creelink.com/exLink.asp?19706952OV78E19I37602548
Yeah, I've got a just a tiny bit of a problem when someone uses extreme positive skew to paint their technology overly bright and flattens a competing technology they dislike very dark and let them cancel each other out so
you think they have an exceptionally high Expression Rendition Index. Like light bulbs that make some colors sickeningly vivid and flatten some colors so they cancel out and get a good CRI
"LED lighting is
poised to obsolete fluorescent lighting by
delivering no-compromise solutions that
perform better than the fluorescents they
replace, exceed end user experience and offer
real economic value."
Non-sense comments, obsolete and erratic statements and omissions by Cree can expect to get questioned. Not every reader is
ignorant about lighting technology. I gather that this author comes from marketing or management background. Perhaps Cree is still and apprentice at electric discharge lamp technology from
some of the comments they make to the press.
"Rather than settling for the flickering and
inadequate light that T5 fluorescents designs
provide, Tops installed linear LED luminaires
that delivered 90 CRI (colour rendering
index) and 70% energy savings over the T5
fluorescent option."
They were obviously told wrong and the 70% energy savings is not realistically possible. You need 260 LPW for that. Name one commercially available LED fixture that makes 4,450 lm for 17.1W. You can not include dimming controls in this as it is just as easily available for T5. What flickering and inadequate light ?
Here is what we can get with T5 in modern times (at the time you wrote that piece) and I will name real life components:
Advance ICN-2S54-T@277 57W input 1.04BF ballast. You LED people call this a "driver".
Philips F54T5/841 HO EA ALTO 49W lamp. 82 CRI.
Lithonia 2VT5 1 54T5HO ADP LPS835. 95% efficiency fixture.
As supported by documentation here:
http://download.p4c.philips.com/l4bt/3/332470/t5_high_output_energy_advantage_332470_ffs_aen.pdf
90% LLM @ 20,000
86.7 LPW
78 LPW @ 20,000 hrs.
T5HO(high output) runs at about double the power density of non-HO T5s aobut about three times that of T8, and they suffer in lumen maintenance a bit. This idea is valid for solid state fluorescent lamps as well.
For example, the new Cree 825 lm consumer lamp called the 4 Flow is rated at 75 initial LPW which uses eight LED packages, but the previous generation used ten identical looking LED packages to make 800 lumens and had a rated initial efficacy of 84 LPW.
?There [are] a lot of sacrifices we've been living with in this fluorescent world,? Unfortunately, the above two examples are one of those compromises in this fluorescent world. You do wear out the fluorescent phoshors at a higher rate when they're pushed
harder.
"LED luminaires can offer
better light quality and
demonstrate consistent colour
and light quality across different
luminaires over the lifespan of
an installation"
Compared to the common metal halide lamps, I agree, but I don't agree in the context of this article. Apparently the IES questions it too.
IES said "it's still a question" in January 2014.
http://www.ies.org/lda/HotTopics/LED/20.cfm
The ":" between hours and minutes on my stove display has probably seen 50,000 real hours and I don't notice color shift from rest of the segments. These are low power direct emission LEDs which is the solid state equivalent of clear
neon sign tubes that do not use phosphors. Practically all LED lighting products are solid state fluorescent lights which rely on "fluorescent technology" to produce significant portions of final output. The only difference is how the phosphor
is tickled to emit light.
"Unlike linear fluorescents,
which die at the end of life
and will not emit light, LED
lighting does not die at the
end of its life."
Your car will just shut off when you run out of gas rather losing performance and efficiency with decreasing fuel level like fluorescent lamps. LEDs behave more like a flashlight with alkaline batteries and get dimmer and dimmer with you ponder when you should change the batteries.
"Lifetime is
determined by a rating called
L70, which means that, after
the lifetime hours, the lamp
will perform at about 70% of
the original light output, which
is the percentage at which the
average human eye has been
known to notice a difference."
This is a lousy excuse for having the worst lumen maintenance of EVERY lamp technology except metal halide and mercury vapor. pcLED solid state fluorescent lamps have to deal with degradation of phosphors, LEDs and plastic components. L70 is generally the warranty threshold for LED warranties. Read carefully. If it plummets to 75% after a few months and settles down and wear out very slowly form 75% to the threshold 70%, the warranty likely won't consider it defective. L90 is much more reasonable standard. The obvious solution is to start at a lower output level with a source that degrades less and do not
need an aggressive wattage boosting compensator to maintain an acceptable light level.
I believe there is only ONE SSL product with the test results publicly avaialble for performance beyond 10,000 hours and tested in a statistically significant sample size. This is the 10W 940 lm lamp Philips sold for a short period. It uses 18 ceramic package LEDs each capable of handling 3W or so, they're only fed less than 10W shared across all 18 (driver/ballast in base consuming a portion of 10W). It's built differently from most LED lamps so it doesn't mean much. Most LED lamps are the less durable smothered-in-phosphor type. It's a well documented fact that increasing the driving powr per package (which usually holds multiple LED chips within) increases degradation and decreases initial efficacy.
The earlier 800 lm Cree lamp used 20 12v LEDs. The later version used 12 24v LEDs. The newest 4 FLOW uses eight LED packages that look very similar to the second version and efficacy dropped from 84 LPW to 75 LPW.
If L70 doesn't get booted from commercial applications, solid state fluorescent lighting products with lumen performance far worse than 700 series lamps (banned in July 2014) may fill their place and create an acceptance for slouching performance of LED lamps.
Commercial linear lighting replacement ought to be held to L90 standards which would be competitive with RE80 lamps WITHOUT the use of SSFL degradation compensation like Lithonia's nLight N80. We can bring back F96T12/HO/CW 110W lamps and make them have excellent output maintenace too if we can get around it by using an electronically ballast to compensate like in
the same way as N80. You'd have to push to around 25W per foot using old cool white phosphor blend to get fluorescent lamps to degrade to the amount generally allowed for LED solid state fluorescent lamps.
The functioning mechanism of solid state fluorescent lamps are not hermetically sealed in a glass bulb like all other lamps and they have additional susceptibility to damage from volatile solvents or ammonia or self-destruction from out-gas from materials used in luminaires as demonstrated in Cree's internal test.
www.cree.com/xlamp_app_notes/chemical_compatibility
Damage to acrylic diffuser is given a special consideration for fixtures used in industrial environment.
"LED components emit no
ultraviolet (UV) light, offering
benefits ranging from improved
produce environments for retailers
to decreasing HVAC loads."
UV output never mattered with any lighting source in the amount of cooling load. How did such a non-sense get approved for public release?
People who do not know what they're talking about should stop submitting articles to magazines.
"LED luminaires are designed to last
longer, instantly tackling failure concerns and
extending the average lifetime of the fixture.
For instance, the average lifetime of an LED
fixture nears 50,000 hours compared to the
30,000-hour lifetime of typical fluorescent
lamps. When you factor that, on average,
linear fluorescent luminaires are expected to
fail halfway through their rated life, adopting
LED technology eliminates maintenance
expenses associated with continued relamping.
Gone are the days of customers with a large
stockpile of fluorescent light fixtures."
Half of fl. lamps are expected to fail at rated life. The failure curve is not linear. B10 is around 70%.
The vast majority of T8 systems that you would look at side-by-side with LEDs are parallel wired.
50% rule of thumb is reasonable group-relamp timing for the design that runs series wired F40T12 magnetic ballast systems, but this isn't the system LED people are crying about.
T5HO and 32W T8 are very standardized. Lamps have fairly good consistency between batches. Compatibility and specs for replacement ballasts are almost universal. You only need spare fixture parts to repair physical
damages. The only thing guaranteed about LED fixtures is that they fit in place of ceiling panels. Driver is the point of common failure and there's no universal replacement like fluorescent ballasts.
