Electrical & Lighting
Five tips for choosing LEDs for exterior lamping applications
The use of light emitting diodes, or LEDs, for exterior lamping applications has become a viable option for parking lot and street lighting over the past couple of years. The energy savings possible for municipalities and businesses can be remarkable, but to get full value from the adoption of LEDs, it’s important to use the right approach. Bryan Charlebois, Director of Technical Sales for Ruud Lighting Canada offers these tips to anyone considering replacing older luminaires with LED technology.
November 26, 2009 By Robert Colman
1. Look for a complete solution
“You can retrofit an existing HID (High Intensity Discharge) luminaire with an LED lamp module, but that’s not your complete solution — that’s maybe a 5,000 hour solution a highly compromised solution on many levels: lumen output, distribution patterns and longevity,” says Charlebois. “The problem is, the LED lamp module hasn’t been designed to function in that environment because LEDs give off a lot of back heat created at the junction, so the luminaire itself should be designed around the LED’s requirements.”
You also can’t expect that light levels will be the same with a direct swap either, notes Charlebois. “You can’t say ‘oh, I have a 70 watt high-pressure sodium cobra head right now, what is your LED equal to that.’ Some manufacturers will say, ‘here’s one that saves you 50 per cent on your energy bills, just swap it out.’ You can do that, but you don’t know what sort of light levels you’re going to get, or what sort of distribution is going to hit the ground and light up the area that you want to light. So when people ask us that question, we always say it depends on their specific application (pole height and spacing, light level required, etc.). We complete a design in AGi32 based on their application to show light level values and renderings if needed.
2. Understand the lighting standards for your application
“There are standards in lighting, and the Illuminating Engineering Society (IES) has their Recommended Practice 8 (RP8) for roadway lighting,” explains Charlebois. “Depending on whether it’s classified as local, collector, major or expressway and the pedestrian conflict rating, there are different light levels and uniformity ratios we have to design to. And typically there is basic safety criteria. For example, in a street lighting project we did in Penetanguishene, we took the town’s average pole spacing and their average mounting heights and we satisfied their light level requirements based on that.”
The Town of Penetanguishene is saving 63.8 per cent on energy by replacing legacy mercury vapor cobra heads with RuudLED’s The Edge area luminaire.
Lighting levels for parking lots don’t have the same requirements as roadways, but there are still minimum safety standards there as well. For instance, Simcoe County District School Board chose The Edge, a RuudLED product, to light their newly constructed parking lot at Bradford District High School. The original design called for 32 light assemblies. RuudLED was able to remove two poles and four fixtures while increasing minimum light levels from 0.2 to 0.3 to footcandles and improving uniformity.
“When we do a parking lot, we usually try to do a half a footcandle average, and that’s for basic security lighting,” says Charlebois. “For Bradford District High School it was higher – just over 2 foot candles on average. This is even higher than enhanced security requirements.”
The school achieved over 70 per cent energy savings and uncompromised performance with virtually no maintenance up to 100,000+ hours.
3. Understand your minimum light levels
“A few years ago, big box retailers were aiming for a 5 footcandle average in their parking lots,” says Charlebois. “They needed that because HID luminaires typically had a hot spot right underneath the pole and levels quickly fell off between poles. As a result the minimum light levels between poles would measure in at 0.3 or 0.4 footcandles. We can now do that with LEDs having a lower average and actually bring up the minimum light levels, so you’re not wasting light to get your minimum higher. We can achieve a more even distribution, which translates into better visibility for their customers. Performance will vary between LED manufacturers depending on how they engineer their optics. For example, each one of our LEDs has its own nano-optics, and that nano-optic refracts the light from the LED and creates this distribution pattern. Each single LED has the same optics, so regardless of conditions you still have the same distribution on the ground. Some manufacturers might have four or 5 different optic configurations in the same luminaire to create a pattern, and in that case some of the patterns might failing and affect the light quality.”
4. Make sure the lighting design will last
“Customers should also be asking manufacturers for a design that is many thousands of hours out,” says Charlebois. “If I do a lighting layout, for example, I could create that lighting layout with the light levels the customer asks for in place for the first day I turn the fixture on, but that’s not realistic or sustainable. If we’re doing a lighting layout for someone for street lighting specifically, we’ll aim for 50,000 hours — meaning your light levels at 50,000 hours will meet your criteria.
“And that’s a good segue into what the industry calls L70. That refers to a 30 per cent lumen depreciation. When you plug in your system the first day, you have 100 per cent lumen output. After a 30 per cent loss, you’re at L70, and that’s where the IES has determined the end of life for an LED luminaire. To make it a little more complicated, the L70 is never the same for two fixtures. Even our products – we have two main product lines, the Edge (our architectural fixture), and the LEDway, which is our streetlight fixture. The streetlight fixture has slightly better thermal properties for removing heat from the LED, so it lasts longer, therefore the L70 is longer. Any reputable LED manufacturer will provide all this data in their spec sheets.”
5. Find relevant data that reflects your needs
“For towns or businesses that want to go ahead with their own testing programs to confirm the savings or lighting qualities in an LED system, it’s worthwhile but it’s not necessary to do those tests,” Charlebois offers. “Major cities and U.S. federal government departments have gone through enough testing that relevant data is available that anyone can apply it to their own situations. For example, in Los Angeles we already have over 4,000 fixtures installed, and those decisions aren’t made overnight.”
LEDs offer a viable, energy-saving alternative to traditional exterior lighting. Following these tips can help you make an investment that will last a long time and save on maintenance.
For more information, you can reach Bryan Charlebois at email@example.com, or check out the Ruud Lighting Canada website at www.ruud.ca.
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