FREQUENTLY ASKED LED QUESTIONS

What are some Advantages of LED Lighting?

Energy efficiency is of the utmost importance in every industry, and LED lighting is the clear winner in this category. With LEDs, up to 80 percent of electrical energy is converted to light energy; compare that to incandescent bulbs, which operate at about 20 percent efficiency. For this reason, lower-wattage LED lights may replace comparable light fixtures. For example, a 90 w LED street light may replace a 200W metal halide street light.

Rated lifetime use for LED lights is often eight times longer than alternative lighting choices, leading to drastically reduced maintenance costs. This is especially true where scores of bulbs are installed, such as in an office building, arena or city skyscraper.

The initial cost of LED lights may be offset by tax credits for those who are eligible, and all customers will realize a recovery of the purchase price over time in the form of energy cost and maintenance savings

What is LED Lighting?

LED is an abbreviation for Light Emitting Diode.  Put simply, LEDs are small pieces of material (called diodes) that emit light when voltage is applied to them.  Voltage is applied to LEDs via electrical circuits, or circuit boards similar to those used in computers.  Unlike many conventional light fixtures, LED fixtures do not contain bulbs with filaments or tubes; the components of an LED fixture are an LED (or LEDs), a circuit board, optics (optics direct the light emitted from the LED), a power supply, a fixture or housing and a lens.  LED light engines can often replace conventional light bulbs using the conventional fixtures.

How long have LEDs been used in lighting?

LED lighting started in the early 1960s.  General Electric, RCA, and Texas Instruments discovered that miniature crystals emitted infrared radiation when electric current was applied; this turned out to be the first light emitting diode, or LED.  Shortly thereafter, the first visible (red-colored) LED was developed.  In the 1970’s, additional colors and wavelengths for LEDs were discovered, and LEDs were utilized commercially in calculators, digital watches, and test equipment.   Attempts to expand into other markets were hindered by high failure rates…. unproven manual component assembly methods, and epoxy, crystal and substrate defects lead to short life cycles, thus limiting LED applications.

The 1980s brought improved LED materials, which meant improved efficacy and brighter, longer-lasting LEDs.  LEDs were incorporated into message boards; outdoor signs, barcoding and medical equipment, but end users still saw a noticeable decrease in light output after several years.

During the 1990s, LED efficacy increased further and more colors were developed.  A major breakthrough in LED lighting came in 1995 with the development of the white LED.  If designed and manufactured properly, white LEDs could be used not only for special commercial applications, but for general illumination as well.

Why is LED lighting appropriate for general lighting applications?

There are a number of other benefits discussed below, but the main reason LED lighting will work for general lighting applications is efficacy.  As the chart below illustrates, technology has now advanced to the point where using LEDs for general illumination is not only viable, but makes good business sense for many applications.  A properly designed and manufactured LED fixture can meet output and color requirements while providing significant energy savings.

What are the advantages of using LEDs compared to traditional light sources?

Efficacy: As mentioned above, efficacy is the first advantage of LEDs compared to traditional light sources. Efficacy is a metric used to compare light output to energy consumption, usually measured in lumens per watt.  LEDs use 50% to 90% less energy to produce the same amount of light than traditional light sources, which results in cost savings.  What’s more, LED fixtures do not require ballasts.  Ballasts require an additional 15% to 20% electricity.

Durability: LEDs, being solid state components, are unlike incandescent and fluorescent bulbs as they contain no tubes or filaments.  Therefore, they are much less prone to damage from external shock.

Long life: LED lights average 50,000 hours of life.   Some LED lights last 30,000 hours while others last over 100,000 hours, depending upon the application.  Fluorescent tubes are rated at an average of 30,000 hours, and incandescent and HID bulbs are rated at 1,000 – 5,000 hours.  Long LED life means far lower maintenance and replacement costs when comparing LEDs to traditional light sources.

Environmental: LED lights contain no mercury or chlorofluorocarbons (CFCs), last longer and produce less waste, and are made from fully recyclable materials.  Even aluminum fixtures and housings for LEDs can be made from post-industrial recycled material.  Thus, recycling costs are minimal when compared to traditional light sources.

Full Range of Colors:  LEDs are available in a full range of colors, and color is easily controlled.

Design Flexibility: Because LEDs themselves are very small, they can be designed for many applications where traditional light sources are impractical.
Instant On:  LEDs light up very quickly.  A typical LED will achieve full brightness in less than a second.  LEDs are ideal for use in frequent on-off applications.

Silent operation:  There is no flicker or buzzing with LED lighting.

Low Heat:  LED lights produce much less heat than traditional sources, which means confined areas requiring many lights won’t require as much ventilation when compared to traditional light sources.

Cold Temperatures:  Unlike fluorescent light sources, cold temperatures do not impact performance of LEDs.

Dimming:  Most LEDs can be very easily dimmed. Solar Power: Because LEDs draw significantly less electricity than most traditional light sources, powering an LED fixture with solar panels is now viable in many applications.

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.

How should LED products be evaluated?

There are all kinds of LED lighting products on the market today, and not all LED lighting products are created equal, sometimes by a wide margin.   When evaluating any LED lighting product, it is important to consider the following:

Thermal Management:  Some LED lights last longer than others.  LED light service life is primarily a function of operating temperature.  Operating, or junction temperature, is the temperature the LED operates at while in service, measured at the junction between the circuit board and the LED.   As a general rule, the lower the operating temperature, the longer the service life, as measured by light output depreciation.   LED service life is considered compromised when an LED fixture light output depreciates 30% (measured in foot-candles or lumens).    Maximum operating temperature for most LEDs is 110°C.  At an operating temperature of 100°C, the average rated life of an LED is typically 30,000 hours.  At an operating temperature of 65°, the average rated life of the same LED typically increases to over 100,000 hours.   A typical long-term LED output projection looks like this:

Manufacturers use several methods to manage operating temperature, and which method/methods a manufacturer will use is application-dependent.

Circuit Board Technology:  A key component for controlling operating temperature and providing long lasting, quality LED light is the circuit board.  Many manufacturers build LED light engines with “off-the-shelf”, “one size fits all” circuit boards, and will often weld several circuit boards together to come up with a finished light engine.    Such methods can greatly compromise light quality and service life, especially if an LED light is to be used outdoors or in a challenging environment.    A purpose-designed and built circuit board for a specific LED lighting application will most often provide better light and extend service life.

Light Quality: Light quality is usually assessed in several ways – light output in terms of the amount of light produced, the color of light produced, and pattern/distribution.

Light produced is measured by the amount of light on a surface at a particular distance from a light source, measured in Footcandles (English), or Lux (metric). Light color is measured by Color Temperature, a specification of the color appearance of a light source, where color is related to a reference source heated to a particular temperature, measure by thermal units called Kelvin(“K”).  Color Temperature is often described as “warm”, “neutral”, and “cool”, with “warm” considered to be below 3500K, “neutral” between 3500K and 5000K, and “cool” above 5000K. Light pattern or distribution specifications should be readily available from the manufacturer for standard products.   For custom or retrofit applications, customers will often request a manufacturer to meet application-specific requirements.

What are the best applications for LED lights?

The possible applications for LED lights are endless.  Cost savings will most often determine what applications will favor the use of LED lights the most.  The longer a light fixture is in service on a monthly or annual basis, the sooner an LED light will yield a “payback”, or cost savings.   Other factors that weigh into cost savings are frequency and cost of traditional bulb/ballast replacement and energy cost. For example, a consumer in a remote location who pays $0.45 per Kilowatt hour for electricity will see a more rapid payback or cost savings than a consumer living in a populated area paying $0.10 per Kilowatt hour.

Another consideration relative to LED light applications is that LED lights tend to be much more directional in operation…they light areas required without needlessly illuminating surrounding areas.  And when durability is an issue, very few light sources are as durable as LEDs.

Lumens to watt ratio compared to current HID bulbs?

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 color band. 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.

Lumens to watt ratio compared to current HID bulbs?

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 color band. 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.

What is color temperature?

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.

What are the drawbacks to the new fluorescent lamps?

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.

Mercury toxicity of fluorescent 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 erythematous; 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.

Non-compact light source

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.Ordinary people have better reading performance using high-frequency (20–60 kHz) electronic ballasts than magnetic ballasts.

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. However, these studies had interpretive problems and have not been replicated.

Color rendition of fluorescent lamps

The issues with color faithfulness of some tube types are discussed above.

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