What is an LED?
LED is an abbreviation for a light-emitting diode. An LED consists of a semiconductor diode that emits light when a voltage is applied to the diode. LED technology is new to the outdoor decorative market however they have been used in the electronic industry for several decades.
Have LEDs been used in other lighting applications?
LEDs are commonly used in applications such as accent and effect lighting, traffic lights, exit signs and many other areas.
What are the advantages to using LED lights?
LEDs provide many advantages over traditional options. They are very efficient, and durable, and have a great lifespan compared to other lamp sources, reducing maintenance costs.
What is efficacy?
Efficacy is used in situations where the output and input units differ. This term is used in the lighting market because we are interested in amount of light measured in lumens produced by a certain amount of watts of electricity.
Efficiency is a term usually dimensionless.
How are LEDs evaluated?
A complete evaluation of an LED product must review the entire systems efficiency, optical control, thermal management of the LEDs and at what point the fixture will reach 30 percent lumen depreciation. Fixtures that have good optical efficiency and practical thermal management system will be able to deliver more lumens, on average, than a HID product.
“Heat management and an awareness of the operating environment are critical considerations to the design and application of LED luminaires for general illumination. Successful products will use superior heat sink designs to dissipate heat, and minimize Junction Temperature. Keeping the junction temperature as low as possible and within a manufacturer specification is necessary in order to maximize the performance potential of LEDs.” US Department of Energy
What is junction temperature?
Junction temperature is the temperature at the point where an individual diode connects to its base. Maintaining a low junction temperature increases output and slows LED lumen depreciation. Junction temperature is a key metric for evaluating an LED product's quality and ability to deliver long life.
The three things affecting junction temperature are: drive current, thermal path, and ambient temperature. In general, the higher the drive current, the greater the heat generated at the die. Heat must be moved away from the die in order to maintain expected light output, life, and color. The amount of heat that can be removed depends upon the ambient temperature and the design of the thermal path from the die to the surroundings. [Source: DOE]
Will I have to replace LED diodes?
A LED does not burn out like a standard lamp. Diodes gradually produce lower output levels over its lifetime. If one LED fails, the fixture will not have a complete outage.
Why is the life span of an LED measured as lumen depreciation?
A LED never burns out but the lumens gradually depreciate. The lifespan of traditional lamp sources is significantly less compared to an LED.
The Illuminating Engineering Society's (IES) current standard for calculating the life of an LED as the point at which the LED reaches 30 percent lumen depreciation.
Please note that a 100,000-hour rating is not comparable to lamp life rating. LED life is rated when it reached 30 percent lumen depreciation. At 100,000 hours an LED would be still operating but at a decreased lumen output.
How long is 100,000 hours?
Based on how long a fixture is illuminated per day, here is what 100,000 hours works out to be:
Hours of Operation = 100,000 hours
24 hours a day 11.4 years
18 hours per day 14.8 years
12 hours per day 22.8 years
8 hours per day 34.2 years
What should I know about optical performance?
Many manufacturers imply that their luminaire will optically perform equal or better than the existing HID fixture it is replacing. Ask for an independently tested IES file showing the optical performance in the designed luminaire you requested. A lot of companies are just showing the “bench test performance” and not providing the actual optical performance of the LED system inside the actual fixture! Most units, especially the Retrofit Kits, lose more than 50% of their performance when the photometry is measured with the Retrofit Kit inside the luminaire! A far cry from the output that is claimed outside of the luminaire!
Why is Color temperature and aesthetics important?
Many manufacturers provide the luminaires with “forced optical systems”. These forced optical systems take away the genuine look of the luminaire. Multiple points of LEDs are noticeable as we refer to as a “field of dots”. Areas of the fixture are darkened or skewed with unnatural tones of light, giving the fixture an abnormal “space age” appearance. Spring City decorative period luminaires are made to look just as they are supposed to be supplied. To create the sense of place and provide the history of the city, town, college or park, the way it was originally designed. Our CROSSFIRETM OPTICS were specifically designed to provide the same warm blanket of light you’re accustomed to seeing from a traditional sources. This single source of light gives the appearance of a standard source of light, not a “field of dots or abnormal tones”. Spring City also offers multiple color temperatures from 2700K to 6000K, giving the customer the option to choose a color temperature of their preference.