Thursday - April 23, 2015

new work

Oh boy, I get to install an LED troffer.

A troffer is the generic name for those lighting fixtures you see built into the white textured fiberboard tile ceiling in most businesses and offices.  A classic unit takes 4 T12 F40CW fluorescent bulbs, which consumes about 160 watts for the bulbs and 15 watts for the ballasts. That’s rather old school, pre-1988, but the things often last 50 years. Newer ballasts, the “electronic” kind, that use the newer design slender T8 F32CW bulbs can get the power consumption down to 130 watts. The LED troffer uses 59 watts.

While it is really great to not have to use as much electricity, the main concern is providing adequate lighting. Generally the consumer thinks of this as the number of lumens a light produces. A 4 bulb T8 troffer makes around 11,400 lumens, whereas the LED troffer makes 5,000 lumens. But there is a lot more to it than that, and the bottom line is that the 4 bulb T8 has an Effective Lumens rating of 5,130 lumens, and the LED unit has an Effective Lumens rating of 3,850 lumens. So no, it isn’t as bright. BUT while the fluorescent bulbs make light in varying amounts across the whole spectrum, from ultraviolet to infrared and including some frequencies that the human eye isn’t very sensitive to, the LED bulbs make light only in several specific highly visible frequencies. So cut the T8’s Effective Lumens rating by a third and call that the Visually Effective Lumens. 3437 lumens. And now the LED unit pulls ahead, because all of it’s Effective Lumens are usable ones. So a 59 watt fixture that will run for 16 business years (6 days/wk @ 10hrs/day) appears brighter than a 175 watt fixture that will use 6 sets of bulbs in that same time period.

So they pay for themselves, even with installation labor, in under 4 years.

Sure, it’s grunt work to rip the old one out and put the new one in. And I’m expecting a face full of dust, and I’m expecting the ceiling tiles to be just a little bit off so that installation is a bitch. But hey, high output LEDs to play with. Kewl.  And I learned a new word: scotopic.

Here’s a neat little scientific paper on the subject. Visually Effective Lumens. This rocks. The lamp shops like to point out that a blue shifted 5000K bulb is good for reading, but they probably don’t know why. Rods baby. Scotopic illumination. Have you ever read a book under one of these OttLites? They’re awesome.

UPDATE - fuggit. Given the time constraints involved (get it done yesterday or before), and the not-quite-there-yet-ishness of LED fixtures, I’m going with 2 cheap-ass old school 4 bulb T8 fixtures. And even with the best of blue shifted “scotopic light”, a mail order only 6900 lumen 5000K LED unit just doesn’t deliver the same light punch. It needs to be about 8500 lumens. The best LED fixture I could find locally was 5000 lumens at 4000K, which is nearly even with a 2 bulb T8 fixture. Nice, but I’m replacing two 4 bulb units. So this wasn’t even half as bright as needed, and the light wasn’t color shifted at all, so the lumens were comparable one to one. 

Posted by Drew458     on 04/23/2015 at 01:47 PM   
Filed Under: • Miscellaneous •  
• Comments (4) • Trackbacks(0)  Permalink •  

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