In the center we ve got 2 views of a typical 2 foot by 4 foot fluorescent light fixture, or ceiling troffer. The upper photo shows it in the ceiling,

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Henry Conley
5 years ago
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4 In the center we ve got 2 views of a typical 2 foot by 4 foot fluorescent light fixture, or ceiling troffer. The upper photo shows it in the ceiling, and the lower photo shows it out of the ceiling, standing up on one end with the lens off, and three 4- foot fluorescent lamps inside, plus 2 electronic ballasts. When an existing building already has a bunch of these in place, there are 2 ways to convert these troffers to LED lighting. First, there are linear replacement lamps, shown on the left. These are shaped just like 4-foot linear fluorescent lamps, and they use the same lamp holders as the old fluorescent lamps that they replace. Most LED lamps like this have the LED s all on one side, that look like rows of little yellow dots. A few of the newer LED lamps have a translucent cover so you don t actually see the LED s, and a few lamps even send light out in all directions, instead of just one direction. Besides Lamps, there are also Kits. Most kits replace or modify the old lens, and they re designed to get the best light distribution from the LED s. Ballpark prices for lamps are over $50 for each lamp, and for kits, over $150 per kit. But those are rough numbers and they re changing every month, so it s worth checking your actual prices. 4

5 There are hundreds of different LED lamps available. They fall into 3 main categories, based on where the driver is. As you know, a fluorescent lamp needs a ballast to convert line voltage into the right voltage and current to drive the lamp. An LED lamp has a similar little transformer box, but it s called a driver instead of a ballast. Some manufacturers of LED lamps provide an external driver, that looks just like a ballast. Others put the driver inside the lamp, so then the AC line voltage gets wired directly to the lamp holders. A third option is that some manufacturers actually reuse the existing fluorescent ballast, so in that case there s no energy savings. 5

6 Here are pictures of a few Kits. There are more and more products like this available, where the retrofitted troffer looks like a brand-new LED troffer, but the back of the troffer is the old one that was already in the ceiling. 6

Back in March 2013, there were 5 manufacturers of these kits on the DesignLights Consortium list. That s the main list of LED lighting fixtures, that I ll talk about more later.

7 Back in March 2013, there were 5 manufacturers of these kits on the DesignLights Consortium list. That s the main list of LED lighting fixtures, that I ll talk about more later. Now, in early July there are 10 manufacturers, and 80 products, so it s growing fast. Most of these kits use a new lens, but some re-use the old lens. And, some re-use the old lens but also add a diffuser so the combined lens plus diffuser works better with LED, provided that the diffuser fits right and is installed right. 7

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9 Here are a few things that many LED lights are good at. You ve probably heard that they last a long time. Nobody s quite sure how long, but there are credible claims for 100,000 hours and higher. It seems likely that in many cases, the LED driver electronics will burn out long before the LED light source dies. Recently, some manufacturers have gotten really good at rendering colors the way people like them. For instance a retail store might sell more products if their lighting provides bright, deep saturated colors that LED does well. Also, if somebody wants advanced controls such as dimming, bi-level lighting and daylight harvesting, LED lights might work really well, and be comparable in price to fluorescent lights with dimming ballasts. Unlike fluorescents, LED lights do not mind being switched on and off frequently, and when they re dimmed then their already long life gets even longer. 9

10 A few years ago, it was hard to find products that had good color rendering, a choice of color temperature, and were bright enough. That s no longer the case, there s a broad selection of products now, although you might still find inferior junk if you re not careful. You can pick a product that delivers the brightness you need, and you can probably find a product to deliver that brightness with a relatively low wattage, to save energy. 10

There are still some concerns with safety. The Pacific Northwest National Lab recently completed a report on LED troffers and troffer retrofits, as a Caliper report for the Department of Energy.

11 There are still some concerns with safety. The Pacific Northwest National Lab recently completed a report on LED troffers and troffer retrofits, as a Caliper report for the Department of Energy. Of all the lamps and kits they tested for retrofits, half would have failed a safety inspection, mainly because of poor instructions and labels. So if you start selling these things, please make sure you pick a product where the instructions are clear, so you don t create safety hazards without knowing it. 11

12 For linear LED lamps, there are some safety concerns about the lamp holders. Most linear LED lamps are designed for power at either one end, or both ends, with either shunted holders or non-shunted holders. If you install the wrong lamp with the wrong lamp holders, it might not light or it might burn out, and the instructions might not necessarily be clear about that. LED lamps are typically heavier than fluorescents, and that s especially true for LED s with internal drivers. Lamp holders are designed to hold the weight of fluorescent lamps. Some were probably overdesigned, so they ll manage the extra weight ok, but others might not. The easiest way to avoid these concerns is to use kits when you can. That way, you don t need to worry about old lamp holders, or mess with installing and wiring new lamp holders. 12

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14 Now, you might not have complete control over the maintenance procedures that will be used 10 or 20 years from now to replace these things. You can not necessarily prevent all the things that might go wrong. But, if you apply the right labels, then at least you re giving somebody a chance to do maintenance properly, if they want to. In addition, if you pick a product that does not need line voltage at both ends of the lamp, then you reduce the risk that somebody could get electrocuted by touching both lamp holders at once, when the switch is energized. 14

Here s a summary of product selection, in terms of safety and energy savings. At the top of the list, Kits are best, because they re safer to wire, and you don t mess with lamp holders.

15 Here s a summary of product selection, in terms of safety and energy savings. At the top of the list, Kits are best, because they re safer to wire, and you don t mess with lamp holders. After that, lamps with separate drivers are pretty good, because they re safe to wire, and the lamp holders are not expected to do much that they were not designed for. After that, there s single-ended lamps with integrated drivers, because at least you can not touch the 2 energized lamp holders with your two hands. After that, there s double-ended lamps with integrated drivers. The only good thing about them is that, like all the other ones I ve mentioned, if you pick a good product with a low wattage, then they save energy. If an LED lamp re-uses the existing ballast, then it s probably safe, but it probably does not save any energy, so there s no incentive for energy savings. I should mention that at the moment, in the present BPA lighting calculator these are all non-standards. The new lighting calculator that comes out this Fall will have them more integrated in the calculator, so you probably will not need a nonstandard incentive, with the new calculator. 15

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17 Fluorescent troffers are designed for fluorescent lamps, that put out light in all directions. Over the years, some troffer manufacturers have gotten pretty good at redirecting the light that goes up, so there s lots of light coming down in a nice batwing pattern of light levels, like the one shown in black. This pattern means that you can space the troffers farther apart, and they still provide uniform light. LED lights are very directional, and most linear LED lamps only have LED s on one side. That means they point straight down, and the fancy reflector above the lamp is useless. So the light level under a troffer with new LED lamps looks more like the blue circle. That s great if you ve got a workbench directly underneath the troffer and you want all the light right there. It s not so good for creating a uniformly lit area, because the troffers need to be close together. Of course, if the existing troffers are already installed close together, then LED lamps are probably ok. Again, most LED Kitsaddress this challenge better than most LED Lamps, because the optics of the kits are designed around LEDs. Still, some of the newer lamp designs are pretty good, where the designers really took the time to make a product that spreads out the light for a more even distribution. 17

If an old acrylic diffusing lens is reused with LED lamps or with a few of the LED kits that do not provide a new lens, then the light distribution is likely to be uneven.

18 If an old acrylic diffusing lens is reused with LED lamps or with a few of the LED kits that do not provide a new lens, then the light distribution is likely to be uneven. You get a bright stripe of white light under each row of LED s, with stripes of gray between the rows. When a multi-lamp troffer has been delamped, then you really notice the gray stripes. Here are some examples from the Caliper Troffer study. These uneven patterns in the lenses tended to feel less comfortable and more glarey to people. 18

19 On the left, here s an example where an old 3-lamp fluorescent fixture was delampeddown to two LED lamps. You can see where each row of LED s points down really bright, but the spaces between LED s are gray. On the right, here s an example where an old parabolic louver was reused with bare lamps. This painted white stripes of light and weird shadows on the walls, as shown on these cupboard doors. 19

20 If you need to add LED s to old parabolic louvers, the best choice is a kit that replaces the louvers. Short of that, you could choose a kit or lamp with new diffusers, so the diffusers spread out light from the LED s before it hits the louvers. Otherwise you get glare, and stripes and sharp shadows. 20

21 The Caliper study on LED Troffers concluded that for visual appeal, people preferred a light source with a good diffuser, or else a combination of a lens plus a reflector. Smooth white panels with uniform brightness were also ok, but less exciting. 21

22 The losers were the ones with contrasty patterns between bright spots and dark spots 22

23 Continuing on our overview of quality in LED troffer retrofits, we come to flicker. You may recall that old, magnetic ballast T12 lamps flicker at 120 Hz. Some people notice this more than others, and some people get headaches with long exposure. A few people can actually get seizures that are dangerous, and there can also be danger around machinery if a moving part appears to be moving more slowly than it really is, or appears to be standing still. This problem with early fluorescent lighting was solved when electronic ballasts came along, with a flicker rate that s well over 10,000 Hz. From what I ve heard, anything above 1000 Hz is probably safe in terms of health. For lower frequencies there s some concern, so then it depends on more details besides just the frequency. Some LED lights flicker all the time, some only flicker when they re dimmed, and some LEDs do not flicker at all. There is no standard test yet for flicker, and there is no standard measurement to report on the product labels. 23

24 In the meantime, until they get a standardized measurement on the labels, here are some different ways you can check for flicker. First, make sure that the only light source is the one you want to check. If there s daylight or incandescent or other light sources in the area, then you might not see the flicker even if it s there. One way is to wave your finger and hand back and forth beside your head, and notice if there s any stop-action artifact like a strobe light. Another way is to point your cellphone camera at the light source. If there s flicker, then you ll probably get strange-looking bars of light that are not really there, like the 2 photos on the left. If there are no stripes, and you only see the light itself, then there is probably no flicker. Probably the best way to check is to use a flicker checker, which is a little spinning top. Sylvania makes them, as a way to find old magnetic ballasts. You spin it, and if you get a smooth gray pattern, then there s not much flicker. If you see any strange unexpected patterns, then you ve got flicker. 24

These charts show some examples of flicker. The vertical axis of each chart shows light output from each light, from 0 near the bottom to 1 near the top.

25 These charts show some examples of flicker. The vertical axis of each chart shows light output from each light, from 0 near the bottom to 1 near the top. All charts were normalized to 1 as the maximum output of that light. The horizontal axis shows time in milliseconds, from 0 to 100. The 3 columns show the performance when the light is switched on, when it s turned on 100% using a dimmer, and when the dimmer is set to 25%. The top row V shows great performance. There is constant light output, so there s no flicker, and the 25% dimmer setting produces light output of 20% (which is pretty close to 25%, in the world of LED dimming). The middle row W has no flicker, but the 25% dim setting only delivers 10% light. That s still pretty good, but not quite as great as V. Row X flickers when it s dimmed to 25%, but it does not flicker at full power. 25

Row L has 120Hz flicker comparable to an old magnetic ballast T12, or worse. It flickers all the time, whether it s dimmed or on full power. Row M only flickers when it s dimmed.

26 Row L has 120Hz flicker comparable to an old magnetic ballast T12, or worse. It flickers all the time, whether it s dimmed or on full power. Row M only flickers when it s dimmed. At 460 Hz it s not as bad as a lower frequency, but not quite as safe as 1000 Hz. I showed these charts as illustrations, but not as particular warnings about particular products. Before you go find this study to help choose products without flicker, please consider that the products in the study were purchased a year ago. New products from the same manufacturers might not behave the same way, since designs are constantly changing. And you can bet that if DOE singled out any manufacturers for poor performance, they re probably already updating their products to perform better. 26

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28 Linear fluorescent lighting with high performance T8 s is still hard to beat, for cost and for energy savings. While LED s have longer lives than typical HPT8 s, there are extended-life fluorescents available with lifetimes of 50,000 hours, 80,000 hours, and even 100,000 hours, that s competitive with LED. Still, keep in mind that the definition of lifetime for HPT8 is that 50% are dead. That s different than the definition of lifetime for LED, where the light output has dimmed to 70% So, installations are more likely to use LED s over their full rated lifetime, rather than relamping fluorescents early because 30% or 40% of thelamps have burned out. 28

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33 At present, the DLC Qualified Product List is a big spreadsheet with tens of thousands of rows for each product. 33

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35 At present, some lamps are listed on DLC as kits, which is confusing. These categories will eventually go away, so then lamps and kits will be easier to tell apart. 35

36 Within a few weeks, the DLC website will get a major upgrade, that will be easier to search than a huge spreadsheet. 36

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