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LED parking lot replacement corn cobb style bulbs ( FYI )

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    #16
    Originally posted by tom baker View Post
    i agree 100%. I was a member of the IES and attended the Street and Area Lighting conferences for many years and saw the beginnings of LED in 2008. An HPS or MH lamp is a point source and putting in a corn cob LED lamp yields poor photmetrics. Most failures in LED sources are the driver, and in a cord cob they are in the lamp. One big issue with LEDs is heat and a new fixture will be designed for that

    Replace the entire fixture, there are many quality mfgs now, GE, Hubble, etc. Your local wholesale house will have lighting department who can assist with meeting the IES requirements. Also look for POCO rebates.
    I would also suggest a 7 pin PE socket instead of a 3 pin, the 7 pin allows monitoring and control, but a 3 pin PE can be used
    Replace the entire fixture and it should be good for 20 years.
    I don't understand the poor photometry with a cob lamp. If you leave the reflector in the HID fixture I would think that is would be similar, ( other the light cannot pass from the reflector through the lamp like in a HID)

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      #17
      We didn't measure the light output but it looks brighter with the LED's . For what a new fixture would cost it was well worth it to retrofit the lights with the LED's if we get the life expectancy out of them . Replaced some 250 watt fixtures at our gate and on the side of the building and are happy with how those turned out too ...

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        #18
        Originally posted by Sierrasparky View Post
        I don't understand the poor photometry with a cob lamp. If you leave the reflector in the HID fixture I would think that is would be similar, ( other the light cannot pass from the reflector through the lamp like in a HID)
        Poor photometry would be a relative term here as it's all on what you're evaluating; HID is notorious for bright spots beneath the pole and less light further from it with traditional optics which can yield to poor site uniformity (max/min ratios) so sites with better uniformity may actually have lower light levels because your eye perceives it as being brighter than when a site has a really bright spot, and then dark spots between poles. Corn Cobs can be an appropriate solution for cost depending on the application (ie, parking garage retrofit with high ceilings) versus a roadway light with a corncob style that utilizes the traditional reflector.

        LED's can still be glary across multiple manufacturers and there is more to evaluate than just lumens and optics; the amount of lumens measured across certain angles cause nuisance glare (60 - 80 degrees). The benefits and why sales people tout certain fixtures is they may have a higher amount of lumens coming at a higher angle and then saying they can space their pole XX feet further than traditional source. Many times we ignore this glare component, but I'd argue that this factor should be just as important, especially for municipalities evaluating their lighting standards.

        We should think what the purpose of the light is for in each application and then design around those parameters in determining visual comfort as well and if it's even a factor.

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          #19
          Originally posted by Sierrasparky View Post
          I don't understand the poor photometry with a cob lamp. If you leave the reflector in the HID fixture I would think that is would be similar, ( other the light cannot pass from the reflector through the lamp like in a HID)
          The reflector is designed (focused) for the, relatively speaking, point-source of the light at the center of the bulb. Some applications will be more noticeable than others.

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