The Twelve Questions you must answer in specifying LED's

How does heat affect the life and output of LED’s? How can one manufacturer's management of heat differ from others?

Where is the Relume product manufactured?

How do LEDs perform in Low-Visibility Weather Conditions?

Why are the lumens to watt ratio so much lower in LED fixtures compared to current HID bulbs?

What is color temperature?

Why is the color range so large 5,500K - 7,000K?

What is color rendition or visual acuity and why is it important when discussing lighting options?

My light meter is not registering any light output from LED lighting fixtures?

Why do the Relume Fixtures use less LEDs than anybody else, yet give the same light output?

What LED do you currently use and what is the Lumen per watt rating?

What is your recommendation for current technology replacement with LEDs?

What are the drawbacks to the new fluorescent lamps I've heard so much about?

Are LED Lights more or less likely to attract bugs?

I'm curious about the power factor related to LED lighting versus HID lighting?  We have a parking deck application using HID lighting now.  Their utility rate structure has a power factor component to it.  It's not just a penalty if you drop below 85%, it actually works like a credit if you are anywhere above 85%.  I thought that HID lighting ballasts had low power factors, and I'm curious if an LED installation would save energy and help with the power factor?

We had a slide from Ann Arbor that showed that each 1 LED Light fixtures saves 2 tons of CO2 what was the source of this stat?

CRI Index comparisons...they commented that the reference to a Metal Halide being 65 is not accurate. They say that modern Metal Halides are at 85-90? Please explain slide difference.

Condensation on the lens.....do we get condensation on the lens due to cold outside and hot inside? Do we have any testing?

Lumen deprecation and LLF...we advised that the industry norm is 0.95 (they advised that they use 0.65 for MH that includes a factor or the light and a factor for the "stuff" that builds up on top. Please confirm how we publish 0.95 and what it is made up of.

Q: The Twelve Questions you must answer when specifying LED's:

1) Is your LED supplier a reliable company?

Relume Technologies uses three LED suppliers, Cree, Inc. and OSRAM Opto Semiconductors, Inc. and Seoul
Semiconductor, Inc. All three are considered leading manufacturers of high brightness, lighting class LEDs, specializing
in high quality and long lasting components. All three companies supply reliable and consistent components.
Relume proprietary technologies when combined with a high performance LED offers the best performance combination
available today. Relume’s patented Silver Circuitry is truly revolutionary offering heat extraction on demand which
means Relume products run cooler, perform better and cost less.

2) Has your supplier provided an IESNA LM-80 test report?

The Illuminating Engineering Society of North America (IES) is the recognized technical authority on illumination. For
over 100 years; its objective has been to communicate information on all aspects of good lighting practice to its members,
to the lighting community, and to consumers, through a variety of programs, publications, and services. IES finalized and
published IESNA LM-80-08 on September 22, 2008.

The purpose of LM-80-08 is to allow a reliable comparison of test results from independent laboratories by establishing
uniform test methods. It addresses the measurement of lumen maintenance testing for LED light sources including LED
packages, arrays and modules only. It does not provide guidance or recommendations regarding prediction estimations or
extrapolations for lumen maintenance beyond the limits as defined by the manufacturer.

LM-80-08 has been adopted to provide enhanced reliability and transparency in LED lifetime calculations. Most LED
manufacturers do not yet have data prepared in a way which conforms to LM-80 standards. The data required to complete
an LM-80 test report can take up to 6,000 hours (or 8+ months) to generate. This data will become increasingly available
over the next several months, at which time Relume Technologies will be able to obtain the appropriate test reports.

Our LED suppliers, Cree, OSRAM and Seoul, have been using the ASSIST lifetime projection method for more than
decade. All three manufacturers have a high degree of confidence in the ASSIST testing methods and their published
lifetime projections. They do not expect there to be any significant differences between current lifetime projections and
future LM-80 lifetime projections.

3) What is the operating temperature range specification and what is the maximum junction temperature (Tj) of the LED lamps over that operating range?

Relume Technologies designs each fixture to keep LED junction temperatures [Tj] below ~ 60 C [140 F] for 70,000 hours
of usable life [L70]. Adequate heat rejection [heat dissipation] from the lamp is essential.

4) What is the expected L70 lifetime of your fixture? How did you calculate it?

The useful life of a LED is a function of junction [die] temperature. Base on the performance of the Cree XRE white LED
(measuring 70% of initial output) the following equation derived by Relume Technologies from data supplied by Cree
Research, Durham, NC on 1/12/2007 to assign junction temperature as a measure of life span.

Log t [hrs.] = 23.4 (eKT)⁻¹

Where: e = 2.718 [base of natural logs.]                         k = 4.70 x 10⁻3 [dimensionless thermal activation coefficient]

T = Junction temperature in ⁰K

Using the above equation Relume has generated the following chart to show how many hours of functional (useful) life
will be achieved at different Junction Temperatures:

Judging by the above, it would make sense that practical heat management is a must when designing a light fixture. A
fixture must keep LED junction temperatures [Tj] below ~ 60 C [140 F] for 70,000 hours of usable life [L70]. Adequate
heat rejection [heat dissipation] from the lamp is essential. Passive heat sinks that reject heat to ambient air by convective
cooling are the only real, acceptable solution that cannot be achieved using active fans.

The first step to a proper heat dissipating design starts with how the LED is attached to a circuit board and/or heat sink.
Some manufacturers solder LEDs to a metal core circuit board. Some attempt to clip to cabling. The net result is the the
inability to shed the significant heat generated by the diode.

Relume has developed and patented a process called Silver Circuitry™. This Silver Circuitry is 95.5% pure silver, plated
onto an aluminum heat-sinking substrate. LEDs are bonded to it using the same silver epoxy that LED manufacturers
have used to bond the LED diode to the LED leads. These designs maximizes the extraction of heat from the diode
through the leads or mount then through the circuit to the aluminum substrate, through the back of the housing and into
the outside air, which supplies the convective cooling. Relume’s patented Silver Circuitry design minimizes the heat
retained by the diode. No other LED light engine provider can make that statement.

The second step involves the actual design of the heat sink and the amount of area required to properly dissipate heat
away from the LED. Relume uses a LED Heat Sink Temperature Rise Calculation Summary derived from empirical tests
performed by Relume in still ambient air. The general form of the equation is:

ΔT [⁰F] = 200.5 x W x Mf x Tf x Cf x A⁻ ¹

Where:
• ΔT = Temperature rise in ⁰F above ambient
• A = Substrate fin area in square inches [not double sided]
• W = Input power in Watts
• Mf = Material coefficient
• Tf = Thickness coefficient
• Cf = Convective cooling coefficient

The bottom line, in order to limit the Tj rise to under 40 C [72 F] in actual operating conditions [20 C / 68 F] we need
about 4 -5 square inches of heat sink fin area per input Watt, exposed to convective air flow. For a 150 Watt LED
fixture, that amounts to a minimum 600 square inches of heat sink area! Other manufacturers use much less heat sink area
… bending to design cues over function.

Relume actually designs fixtures “backwards” from a thermal management perspective allowing their LED fixtures to
typically provide 3 to 4 times more heat dissipating area than other competitive products - assuring the lowest temperature
rise and best lumen maintenance over time. To effectively project a Relume LED light fixtures life span in your area of
the world please refer to the LED life vs., Operating temperature chart below. We have taken all the above calculations
above and crunched the numbers so that by referencing your areas average night time temperature during the warmest part of the year, the
lifespan of the fixture can be calculated.

7) What Is the chromaticity of the fixture in the ANSI C78.377A color space and is it stable over time? How
do you know?

This is especially important for indoor luminaires. Relume Technologies focuses in mostly outdoor applications. If it is
not in the ANSI color space, then the color of the luminaire could be pinkish or greenish in hue. Color point stability is a
common problem in lower quality fixtures. It can be a result of poor LED selection, poor thermal management, or both.

Relume Technologies works closely with the LED manufacture carefully selecting LEDs from a narrow bin to assure
common color correlated temperatures. This along with proper thermal management allows Relume to actively manage
and maintain correlated color temperature ensuring that each fixture’s chromaticity is stable across time.

8) Does the color of the light output vary from fixture to fixture or in different spatial locations for a single
fixture?

Relume Technologies LED selection process and consistent thermal design and operation ensure consistent chromaticity
between fixtures.

9) What is the power factor of your fixture? How much power does it consume in the “off” state?

All Relume Technologies Products are engineered to have a Power factor in excess of 0.9. Power factor should be at least
0.7 for residential applications, 0.9 for commercial, according to Department of Energy’s pending Energy Star criteria. In
addition Relume Technologies products do not consume power in the “off” state.

10) Have you applied for the DOE Energy Star?

On September 30, 2008, the ENERGY STAR Solid-State Lighting (SSL) Program went into effect for residential and
indoor LED lighting. As a result, manufacturers who are ENERGY STAR partners can begin submitting products for
qualification, retailers can begin promoting these qualified products in their stores and showrooms, utilities and energy
efficiency organizations can begin implementing incentive programs for these efficient products, and consumers can start
looking for the ENERGY STAR on quality SSL products. The ENERGY STAR label on SSL luminaires provides
consumers with the confidence that these products meet efficiency and performance criteria established by DOE in
collaboration with industry stakeholders.

Currently Relume Technologies is awaiting finalization of the DOE Energy Star outdoor SSL Program. Relume is
confident once the final criteria is set each one of Relume’s products will meet or exceed DOE criteria. Each product will
be submitted when appropriate.

11) Is your fixture lead-free, mercury-free and RoHS compliant?

Yes, all Relume Technologies products are lead free, mercury-free and RoHS compliant. RoHS is the acronym for
Restriction of Hazardous Substances. RoHS, also known as Directive 2002/95/EC, originated in the European Union and
restricts the use of specific hazardous materials found in electrical and electronic products. All applicable products in the
EU market after July 1, 2006 must pass RoHS compliance. For the complete directive, see Directive 2002/95/EC of the
European Parliament. The substances banned under RoHS are lead (Pb), mercury (Hg), cadmium (Cd), hexavalent
chromium (CrVI), polybrominated biphenyls (PBB) and polybrominated diphenyl ethers (PBDE).

12) What is your warranty and do you have the means to stand behind it?

Relume Technologies offers a solid 7 year warranty on all LED light engines and a 5 year warranty on all drivers.

Q: How does heat affect the life and output of LED’s? How can one manufacturer's management of heat differ from others?

A: Heat lowers the light intensity of an LED and shortens its useful life.

Conventional high output LED arrays are particularly vulnerable to degradation, as it becomes increasingly difficult to shed heat from such arrays. Without aggressive cooling means, high output LED arrays will degrade rapidly because of the significant amount of heat that these LED arrays produce.

LED dies are designed to perform optimally at 77˚F (25˚ Celsius) or lower, and by most measures, each 1.8˚F (1˚ C) rise above the level reduces the lumen output of a white LED by .5%. Over time, high heat levels also dramatically shorten an LED’s useful life. Each 30˚F (17˚C) rise in temperature halves the useful service life of most LEDs. Unlike traditional bulbs, LEDs generally do not fail catastrophically, but diminish in intensity over time. Relume Technology addresses this issue with every step of its luminaire fixture design process. To better understand this process we address each issue in depth below.

First we must understand the how the LED functions so we may understand how heat affects it. Let’s begin with the amount of light generated is a direct function of the current forced through the LED. Watts per LED equals the forward voltage of the particular LED being used x the current being forced through it.  [W = Volts x Amps]. Heat developed in the lamp [Watts] equals power per LED in Watts X the number of LEDs in the lamp. [Plus power supply losses].

Secondly we need to understand is that not all LEDs are created equal. LEDs are available in various configurations and will generate different amounts of light and heat. Premium white LEDs [Cree XRE] can develop over 100 lumens / Watt while less costly, smaller die LEDs are less efficient.  Note that a white XRE LED develops about 2 Watts of heat while a neutral white XRC with a smaller die generates 30% more heat while delivering approximately 40% less light!

The most effective measure of the actual heat rise of the LED is to monitor the LEDs “junction temperature” (where the LED die bonds to the heat sink slug or mounting base). The LED junction temperature at the LED die is a function of the intrinsic heat rise of the LED itself … typically 8 degrees C / Watt [for most common packages] plus the aggregate thermal resistances of the mounting medium and the heat sink itself. So it becomes very important how the LED is mounted to a circuit board and/or heat sink because all three have a direct effect on the junction temperature of the LED.

Now that we have covered that let’s talk about how heat affects the LED life and light output. The useful life of a LED is a function of junction [die] temperature. Base on the performance of the Cree XRE white LED and assuming that useful life of a LED is the measured light depreciation to 70% of initial output uses the following equation derived by Relume Technologies from data supplied by Cree Research, Durham, NC on 1/12/2007 to assign junction temperature as a measure of life span.

Using the above equation Relume has generated the following chart to show how many hours of useful life will be achieved at different Junction Temperatures:

Judging by the above, it would make sense that practical heat management would be a must when designing a light fixture we have to keep LED junction temperatures [Tj]  below ~ 60 C [140 F] for 70,000 hours of usable life [L70]. Adequate heat rejection [heat dissipation] from the lamp is essential. Passive heat sinks that reject heat to ambient air by convective cooling are the only real, acceptable solution [no fans].

The first step to a proper heat dissipating design starts with how the LED is attached to a circuit board and/or heat sink. Some competitors solder their LEDs to a metal circuit board or clip to cabling thereby retaining the significant heat generated by the diode. Relume has developed and patented a process called Silver Circuitry™. This Silver Circuitry is 95.5% pure silver, plated onto an aluminum heat-sinking substrate.  LEDs are bonded to it using the same silver epoxy that LED manufacturers have used to bond the LED diode to the LED leads.  These designs maximizes the extraction of heat from the diode through the leads or mount then through the circuit to the aluminum substrate, through the back of the housing and into the outside air, which supplies the convective cooling.  Relume’s patented Silver Circuitry design minimizes the heat retained by the diode.  No other LED light engine provider can make that statement.

The second step involves the actual design of the heat sink and the amount of area required to properly dissipate heat away from the LED. Relume uses a LED Heat Sink Temperature Rise Calculation Summary derived from empirical tests performed by Relume in still ambient air. The general form of the equation is:

Q: Why are the lumens to watt ratio so much lower in LED fixtures compared to current HID bulbs?

A: Comparing the Lumen output of LEDs to that of a discharge source is not an accurate way of measuring effective light output of a Luminaire.

High intensity discharge lamp Lumens are measured spherically, counting all the lumens being produced over 360 degrees.  The discharge arc tube is NOT a point source and is difficult to optimize optically, making for poor light collection efficiency and utilization.  Many light fixtures, especially type 2 and 3 with a cutoff rating have to redirect most of the lumens produced by a bulb, losing as much as 50% of the output.

LEDs on the other hand are directional; essentially point sources and have practically no wasted lumens. Virtually every LED Lumen is directed and placed to maximize efficiency. A better and more accurate evaluation is to measure actual foot candles or LUX on the ground. One last note that needs to be considered is the considerable initial light output loss of HPS or MH within the first 6 months. LEDs have no such drop and will deliver useful light [with only 30% depreciation] for 12 to 15 years before needing replacement.

Photopic lumens refer to the amount of light emitted from a light source as measured by a light meter. The typical light meter is most sensitive to the yellow-green part of the colorband. This is the light that is seen by the cone receptors in the eye and is called the "photopic lumens". However, the rod receptors in the eye also receive light but it is the light rich in the blue portion of the spectrum. This light isn't measured by the typical light meter. The combination of the light received by the rods and cones is called the "seeable lumens". Therefore, the photopic lumens could be misleading when comparing different colors of light. Even though a lower lumen reading is obtained with a LED vs. HPS or Metal Halide, the LED will produce more seeable light.

Q: What is color temperature?

A: Color temperature is a description of the warmth or coolness of a light source.

When a piece of metal is heated, the color of light it emits will change with temperature.  This color begins as red in appearance and graduates to orange, yellow, white and then blue-white at the highest temperature.   The temperature of this metal and therefore its color is measured in degrees Kelvin or absolute temperature. While lamps other than incandescent do not exactly mimic the output of this piece of metal, we utilize the correlated color temperature (or Kelvins) to describe the appearance of that source as it relates to the appearance of the piece of metal (specifically a black body radiator)

By convention, yellow-red colors (like flames of a fire) are considered warm, and blue-green colors (like light from an overcast sky) are considered cool. Confusingly, higher Kelvin temperatures (4000-6500 K) are considered cool while lower color temperatures (2700-3000K) are considered warm. Cool light is preferred for visual tasks because it produces higher contrast than warm light. Color temperature is not an indicator of lamp heat in anything but an incandescent bulb.

Q: Why is the color range so large 5,500K - 7,000K?

A: The color temp is that large due to (a) it is very difficult to visually discern a difference between a 5,500K LED and a 7,000K LED, and (b) if we were to narrow that color temp range, and request LEDs from Cree that are only between 6,000 and 6,500K color temperature (for example), then the cost of our LEDs would soar, perhaps by as much as 200-300% of our current purchase price.  This is because binning and sorting is an expensive process, and Cree prefers to bin their LEDs within specific bands of color temps to keep their costs down.  Again, visually there is very little noticeable difference.

Q: What is color rendition or visual acuity and why is it important when discussing lighting options?

A: The lighting effect of different kinds of lights may be due to more factors than the foot candles produced (1).

"Visibility, task, performance, mood and atmosphere, visual comfort, aesthetic discrimination, health, safety and well being, and social communication are all human needs served by light" (2). The color of the light can have a great impact on how much light is necessary and the additional effects resulting from lighting. A light meter can read the intensity of a lamp light in foot candles or lux, but it cannot measure clarity of vision as a result of using colored or non white light. This is an important consideration because LED lights are considered Spectrally Enhanced Lighting (SEL).  Such SEL sources appear brighter because of their color characteristics but may not measure [photometrically] as bright (2). Evidence from studies have shown that when color temperature is cut in half (CCL 7500 to CCL 3500 it takes 4 times the foot candles to get the same functional light. The higher the color temperature is, the closer it is to natural sunlight.  This is important because human eyes use color as part of their perception and visibility which is optimized for natural sunlight (2).

(1) Comparative Analysis of LED Lights for Street Lighting by Patrick I Rigg, MPA Spring 2007
(2) Hung, Eugene, Louise Conroy and Michael Scholand (Navigant Consulting, Inc) "US Lighting Market Characterization, Volume ii: Energy Efficient Lighting Technology Options" Washington DC, 2005.

Download: An Energy-Efficient Street Lighting Demonstration Based Upon the Unified System of Photometry
Download: U.S. Environmental Protection Agency Demonstration
Download: International Dark-Sky Association - Some Issues in Low Light Level Vision
Download: The Re-engineering of Lighting Photometery by Sam Berman

Q: My light meter is not registering any light output from LED lighting fixtures?

A: The sensor used in most light meters is partially color blind to certain wavelengths or colors of light.LED makers create white light by mixing blue and yellow. Relume has found that very few light meters are either calibrated correctly or are suitable for measuring a wide range (color and type) of light sources. For example; if the light meter is not sufficiently sensitive to blue light it will not measure white LEDs correctly. This is why Relume recommends several different light meters. There are a couple of meters Relume uses that seem to have the correct sensitivity to metal halide, HPS and LED sources.  These include: Extech Model 407026 for about $ 175 available from Grainger, Extech Model 401036 – with a data logger,  and a lab standard Yokogowa 51002 luminance meter ($1,133 from Byram Labs) that Relume had certified by N.I.S.T. (the certification alone was over $2,000) This meter is now used as a transfer standard to check other meters.

Q: Why do the Relume Fixtures use less LEDs than anybody else, yet give the same light output?

A: LED technology is more than sufficient to meet today's lighting requirements, the issue is whether thermal dissipation technology is ready for today's applications. As you may or may not be aware, conventional arrays of high output LEDs are particularly vulnerable to degradation as it becomes increasingly difficult to shed heat from such arrays.  Without aggressive cooling means, LED arrays will degrade rapidly as the operating temperature of the system increases. This is why many Lighting companies use many more LEDs than Relume in order to compensate for their lack of thermal dissipation.

Relume Technologies has developed and patented technologies that increase the light output, the useful life, and the reliability of LEDs through aggressive thermal management. Our proprietary high performance adhesive to insulated metal substrate process for LED arrays has been able to demonstrate a two to four fold increase in luminous output over conventional approaches with a dramatic improvement in life.  Our technologies also reduce production costs and increase reliability. The most expensive portion of an LED fixture is the LEDs themselves so this is not a bonus to have them be replaceable, the bonus is to have our whole fixture be less expensive than 100 LED replacements.

Q: What LED do you currently use and what is the Lumen per watt rating?

A: Relume currently is using the Cree XRE in all Luminaire products. According to Cree's Flux Characteristics Specification the Typical Luminous Flux is 80 lm @ 350mA, 136 lm @ 700mA and 176 lm @ 1000mA. But that is not the whole story, with Relume's patented thermal dissipation technology we are able to run each LED between 2 to 3 watts each (700-1000mA) and produce over 200 Lumens per LED. It is a classic case of more watts create more heat and if this heat can be rejected than more lumens will be produced. This is why we can give the same light out but at 24 LEDs that it takes our competition 66 to achieve.

Q: What is your recommendation for current technology replacement with LEDs?

A: Each situation is completely different, we suggest contacting us or one of our representatives for a recommendation on a given project. Remember that all the LEDs are directional lumens pointing exactly where they need to be with no reflective loss. Standard HPS or MH are spherical balls that can lose up to 50% of their initial lumens through reflective material redirecting the light typically straight down into a hot spot. The object of LEDs is to eliminate all wasted lumens and maximize efficiency. Contact us today for our recommendations.

Q: What are the drawbacks to the new fluorescent lamps I've heard so much about?

A: One need look no further than good ole Wikipedia for your answers, you know the benefits of LEDs and that they will last 5-7 times longer than Fluorescent but here is the rest of the story:

A fluorescent lamp is a gas-discharge lamp that uses electricity to excite mercury vapor in argon or neon gas, resulting in a plasma that produces short-wave ultraviolet light. This light then causes a phosphor to fluoresce, producing visible light.
Unlike incandescent lamps, fluorescent lamps always require a ballast to regulate the flow of power through the lamp. In common tube fixtures (typically 4 ft (120 cm) or 8 ft (240 cm) in length), the ballast is enclosed in the fixture. Compact fluorescent light bulbs may have conventional ballast located in the fixture or they may have ballasts integrated in the bulbs, allowing them to be used in lamp holders normally used for incandescent lamps.

Because fluorescent lamps contain mercury, a toxic heavy metal, governmental regulations in many areas require special disposal of fluorescent lamps separate from general and household wastes. Mercury poses the greatest hazard to pregnant women, infants, and children.

Landfills often refuse fluorescent lamps due to their high mercury content. Households and commercial waste sources are often treated differently.
The amount of mercury in a standard lamp can vary dramatically, from 3 to 46 mg. [1] Newer lamps contain less mercury and the 3-4 mg versions are sold as low-mercury types. (A typical 2006-era 4 ft (120 cm) T-12 fluorescent lamp (i.e., F32T12) contains about 12 milligrams of mercury [2].)

In early 2007, the National Electrical Manufacturers Association in the US announced that "Under the voluntary commitment, effective April 15, 2007, participating manufacturers will cap the total mercury content in CFLs under 25 watts at 5 milligrams (mg) per unit. CFLs that use 25 to 40 watts of electricity will have total mercury content capped at 6 mg per unit."NEMA Voluntary Commitment on Mercury in CFLs.

Cleanup of broken fluorescent lamps

A broken fluorescent tube is more hazardous than a broken conventional incandescent bulb due to the mercury content. Because of this, the safe cleanup of broken fluorescent bulbs differs from cleanup of conventional broken glass or incandescent bulbs. 99% of the mercury is typically contained in the phosphor, especially on lamps that are near their end of life [3]. Therefore, a typical safe cleanup usually involves first opening a window and then leaving the room (restricting access) for at least 15 minutes, wearing gloves carefully dispose of any broken glass, as well as any loose white powder (fluorescent glass coating). You can use sticky tape to pick up small pieces... double bag any waste. Dispose of waste in accordance with local hazardous waste laws. Finally a wet paper towel should be used instead of a vacuum cleaner for cleanup of glass and powder, to reduce the vaporization of the mercury into the air.
The first time you vacuum the area where the bulb was broken, remove the vacuum bag once done cleaning the area (or empty and wipe the canister) and put the bag and/or vacuum debris, as well as the cleaning materials, in two sealed plastic bags in the outdoor trash or protected outdoor location for normal disposal [6]
It would be safer to use a vacuum cleaner with a HEPA filter, because older-type vacuum cleaners don't trap really-fine dust. That dust is exhausted into the room, which spreads it.

Fluorescent lamps manufactured many decades ago had phosphors that contained beryllium, which is toxic. One is not likely to encounter lamps this old.

Ultraviolet light from fluorescent lamps

Fluorescent lamps can cause problems among individuals with pathological sensitivity to ultraviolet light. They can induce disease activity in photosensitive individuals with Systemic lupus erythematosus; standard acrylic diffusers absorb UV-B radiation and appear to protect against this.[4] In rare cases individuals with solar urticaria (allergy to sunlight) can get a rash from fluorescent lighting.[5

Ballasts and fluorescent lamps
Fluorescent lamps require a ballast to stabilize the lamp and to provide the initial striking voltage required to start the arc discharge. This increases the cost of fluorescent luminaires, though often one ballast is shared between two or more lamps. Electromagnetic ballasts with a minor fault can produce an audible humming or buzzing noise.

Conventional lamp ballasts do not operate on direct current. If a direct current supply with a high enough voltage to strike the arc is available, a resistor can be used to ballast the lamp but this leads to low efficiency because of the power lost in the resistor. Also, the mercury tends to migrate to one end of the tube leading to only one end of the lamp producing most of the light. Because of this effect, the lamps (or the polarity of the current) must be reversed at regular intervals.

Power factor of fluorescent lamp ballasts

Fluorescent lamp ballasts have a power factor of less than unity. For large installations, this makes the provision of electrical power more expensive as special measures need to be taken to bring the power factor closer to unity.

Power harmonics of fluorescent lamps

Fluorescent lamps are a non-linear load and generate harmonics on the 50 Hz or 60 Hz sinusoidal waveform of the electrical power supply. This can generate radio frequency noise in some cases. Suppression of harmonic generation is standard practice, but imperfect. Very good suppression is possible, but adds to the cost of the fluorescent fixtures.

Optimum operating temperature of fluorescent lamps

Fluorescent lamps operate best around room temperature (say, 20 C or 68 F). At much lower or higher temperatures, efficiency decreases and at low temperatures (below freezing) standard lamps may not start. Special lamps may be needed for reliable service outdoors in cold weather. A "cold start" electrical circuit was also developed in the mid-1970s.

Because the arc is quite long relative to higher-pressure discharge lamps, the amount of light emitted per unit of surface of the lamps is low, so tube lamps were large compared with incandescent sources. However, in many cases low luminous intensity of the emitting surface was useful because it reduced glare. The bulk created by this lamp affected the design of fixtures since light must be directed from long tubes instead of a compact source.

Recently, a new type of fluorescent lamp, the CFL, has been introduced to address this issue and allow regular incandescent sockets to be fitted with this type of lamp, thereby negating the need to mount it on special fixtures. However, some CFLs intended to replace incandescent will not fit some desk lamps, because the harp (heavy wire shade support bracket) is shaped for the narrow neck of an incandescent lamp. CFLs tend to have a wide housing for their electronic ballast close to the lamp's base, too wide to fit.

Flicker problems of fluorescent lamps

Fluorescent fittings using a magnetic mains frequency ballast do not give out a steady light; instead, they flicker (fluctuate in intensity) at twice the supply frequency. While this is not easily discernible by the human eye, it can cause a strobe effect posing a safety hazard in a workshop for example, where something spinning at just the right speed may appear stationary if illuminated solely by a fluorescent lamp. It also causes problems for video recording as there can be a 'beat effect' between the periodic readings of a camera's sensor and the fluctuations in intensity of the fluorescent lamp.

Incandescent lamps, due to the thermal inertia of their element, fluctuate to a lesser extent. This is also less of a problem with compact fluorescents, since they multiply the line frequency to levels that are not visible. Installations can reduce the stroboscope effect by using lead-lag ballasts, by operating the lamps on different phases of a polyphase power supply, or by use of electronic ballasts.
Electronic ballasts do not produce light flicker, since the phosphor persistence is longer than a half cycle of the higher operation frequency.

The non-visible 100–120 Hz flicker from fluorescent tubes powered by magnetic ballasts is associated with headaches and eyestrain. Individuals with high flicker fusion threshold are particularly affected by magnetic ballasts: their EEG alpha waves are markedly attenuated and they perform office tasks with greater speed and decreased accuracy. The problems are not observed with electronic ballasts.[6] Ordinary people have better reading performance using high-frequency (20–60 kHz) electronic ballasts than magnetic ballasts.[7]

The flicker of fluorescent lamps, even with magnetic ballasts, is so rapid that it is unlikely to present a hazard to individuals with epilepsy.[8] Early studies suspected a relationship between the flickering of fluorescent lamps with magnetic ballasts and repetitive movement in autistic children.[9] However, these studies had interpretive problems[10] and have not been replicated.

Dimming of fluorescent lamps

Unless specifically designed and approved to accommodate dimming, most fluorescent light fixtures cannot be connected to a standard dimmer switch used for incandescent lamps. Two effects are responsible for this: the waveshape of the voltage emitted by a standard phase-control dimmer interacts badly with many ballasts and it becomes difficult to sustain an arc in the fluorescent tube at low power levels. Many installations require 4-pin fluorescent lamps and compatible controllers for successful fluorescent dimming; these systems tend to keep the cathodes of the fluorescent tube fully heated even as the arc current is reduced, promoting easy thermionic emission of electrons into the arc stream.

Disposal and recycling of fluorescent lamps

The disposal of phosphor and particularly the mercury in the tubes is an environmental issue. (Incandescent lamps do not contain mercury.)

For large commercial or industrial users of fluorescent lights, recycling services are available in many nations, and may be required by regulation. In some areas, recycling is also available to consumers. The need for a recycling infrastructure is an issue with instituting proposed bans of incandescent bulbs.

Q: Are LED Lights more or less likely to attract bugs?

A: Virtually all lights attract bugs!

That said, it should be noted that the DEGREE by which flying insects are attracted to light varies with the wavelength [color] of the lamp spectrum.

1) Bugs use light to navigate. The moon is a very long way from us by normal standards and the light rays which reach the earth are virtually parallel. By flying at a constant angle to these rays it is possible over a short period of time to fly in a straight line. When an insect is close to a lamp the rays are not parallel, but divergent. The effect of keeping the rays at a constant angle will be to fly round the light source.

2) Many bugs see ultraviolet light and may be attracted to flowers at night which reflect ultraviolet patterns using moonlight. Lights which emit UV rays may therefore attract such insects. As you already know there are no UV rays emitted by LEDs.

3) Some insects are attracted by the heat that some incandescent bulbs produce at night (infrared radiation). Again LEDs used in lighting emit no infrared radiation.

4) 'Bug zappers' commonly use long wave ultraviolet lamps [black light] to attract flying insects.   That's because insects have heightened vision in the long wave u.v.. spectrum ... centered around 365 nm.    Common metal halide lamps,  fluorescent and older mercury lamps have significant long wave u.v. output so they attract insects very effectively.   High pressure sodium lamps have an attenuated blue / violet / u.v.  output spectrum and while they can  attract flying insects, they aren't nearly as bad as M.H. or fluorescent lamps in this regard.

5) Yellow LEDs and  low pressure sodium lamps are much like common, yellow 'bug lamps'  and are essentially invisible to flying insects.

In conclusion, white LEDs  are similar to HPS lamps  as far as insect visibility, since there's a distinct, broad  blue emission [470 nm] that is combined with yellow from the phosphor ... to create  white light.  White LEDs do NOT emit long wave ultraviolet  so they aren't nearly as effective in attracting flying insects as are MH, fluorescent or mercury lamps.

Q: I'm curious about the power factor related to LED lighting versus HID lighting?  We have a parking deck application using HID lighting now.  Their utility rate structure has a power factor component to it.  It's not just a penalty if you drop below 85%, it actually works like a credit if you are anywhere above 85%.  I thought that HID lighting ballasts had low power factors, and I'm curious if an LED installation would save energy and help with the power factor?

A: The power factor of all discharge lamp fixtures [including fluorescents] has been notoriously bad.

In fact, the PF of supposedly efficient compact fluorescent lamps is often around .40 !   The simplest explanation of the importance of power factor is that the utility has to provide MORE power than the nameplate wattage to operate the device.  That is,  if the lamp is rated 100 Watts but exhibits a PF of .40,  the power company has to supply 160 Watts to the fixture ... negating many of the supposed savings.  

This reactive power isn't well understood outside the power distribution community,  but is very significant as it has a direct effect on required generation capacity.  That's why utilities often impose a PF penalty.

In recent years, some states  [CA]  have imposed minimum power factor standards of at  least a 0.85 PF  for lamp ballasts.  These  high PF ballasts command a premium.  Fortunately, most of major LED power supply manufacturers have followed IEEE and IEC recommendations and have designed in power factor correction circuitry right from the start.  We have yet to measure a LED power supply with a PF of less than 0.91  and many of the latest models from Advance operate in the 0.95 PF range  - or higher.

In fact,  there's another parameter that's equally important in power supply performance:  Net efficiency.   

Reactive ballasts are often not terribly efficient [85 %  on a Watts in / Watts out basis].  Even for high PF magnetic ballasts, the internal Ohmic losses result is self generated  heat.  That's why the primary ballast failure mechanism is thermally induced deterioration.

On the other hand, newer  switch mode power supplies  for LEDs like the ones we purchase from Philips / Advance,  exhibit a measured efficiency in excess of 93% !  The immediate benefit is less heat and much more reliable operation.

Q: We had a slide from Ann Arbor that showed that each 1 LED Light fixtures saves 2 tons of CO2 what was the source of this stat?

A: This stat was a quote from Energy Director David Konkle from the city of Ann Arbor. He is sighting the formula provided by the US EPA. I have provided the link below.

http://www.epa.gov/cleanenergy/energy-resources/calculator.html

Q: CRI Index comparisons...they commented that the reference to a Metal Halide being 65 is not accurate. They say that modern Metal Halides are at 85-90? Please explain slide difference.

A: They are correct in the fact that quality metal halide lamps do range from 85CRI (4200K MH) to 93CRI (5400K) unfortunately CRI merely measures the faithfulness of any illuminant to an ideal source with the same CCT, but the ideal source itself may not render colors well if it has an extreme color temperature, due to a lack of energy at either short or long wavelengths (i.e., it may be excessively blue or red). This is common in lower end Metal Halide lamps which are often chosen by contractors and installers for cost reasons.

Q: Condensation on the lens.....do we get condensation on the lens due to cold outside and hot inside? Do we have any testing?

A: Our Lenses are completely sealed thus preventing condensation from ever forming.

Q: Lumen deprecation and LLF...we advised that the industry norm is 0.95 (they advised that they use 0.65 for MH that includes a factor or the light and a factor for the "stuff" that builds up on top. Please confirm how we publish 0.95 and what it is made up of.

A: With current HID sources there is a number of operating and environmental conditions interfere with the transmission of light, resulting in wasted lumens that do not apply or affect LEDs. First let’s look at Non-recoverable Light Loss Factors.  Some light loss factors are called "non-recoverable" because preventative maintenance generally does not affect the extent of the light loss. These include ballast factor, ambient fixture temperature, supply voltage variation, optical factor and fixture surface depreciation.

Now let’s look at Recoverable Light Loss Factors. Some light loss factors are called "recoverable" because preventative maintenance can reduce the extent of the light loss. These include lamp burnouts, lamp lumen depreciation (LLD), fixture (luminaire) dirt depreciation (LLD) and room surface dirt depreciation (RSDD)

Lamp Burnouts

When a lamp expires, it becomes a "burnout." Lighting designers usually assume that the burnout will be replaced immediately. However, if it is known that a percentage of the lamps are burnouts at any given time, then a light loss factor must be reckoned with. For example, if 5% of the lamps are burnouts at any given time, then this light loss factor would be 0.95. Remember that 100% rated life is defined when 50% of the lamps in a large sample of lamps have failed. To this point LEDs do not catastrophically fail. The Relume LEDs rated life is to 70,000 hours to 30% deprecation from 100%. 70% of rated light output still remains but should be changed as the luminous depreciation begins to accelerate after this threshold.

Lamp Lumen Depreciation

As a lamp ages and nears end of life, it produces less and less light on a predictable curve, the extent of which depending on the type of lamp. If group relamping is employed as a planned maintenance strategy, then take the LLD factor for the point in life at which the lamps are replaced en masse. Unfortunately group relamping is rarely employed by today’s cash strapped municipalities and utilities. Most take a full failure replacement only strategy. Another plus for Relume LEDs rated life of 70,000 hours to 30% deprecation from 100%.

Fixture (Luminaire) Dirt Depreciation

Dirt and dust present in all ambient environments are ultimately attracted to and trapped in electrical equipment. The extent of dust collecting on the lamps depends on the environment, what type of fixture is in use, whether it is ventilated or not, and the type of work performed in the area. The extent of LDD depends on these conditions and also how often the fixtures will be cleaned. Relume LED Fixture are not immune to dirt but are completely sealed to avoid dust, dirt and insect intrusion into the lens area. This coupled with no UV degradation leaves little room for interfering with the luminous output.
When all light loss factors are determined and multiplied one against the next 65% percent seems rational for existing HID lamps, but as stated above most of these factors do not apply to Relume LED fixtures and that is why we stand behind using only a 95% LLF.