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Is there any method, table, equation, mathematical procedure, computer algorithm, or data base to convert lamp data such as a Philips PAR30L flood lamp or LED Par38L flood lamp to minimum housing size? Simplified, what do PAR30L or PAR38L mean? I believe the 'L' is for long neck. Also is there any table to calculate the housing, for Halo 6 inch new construction fixture, heat rise knowing the lamps dissipation in watts for a kitchen housing installed in the ceiling between the kitchen and attic. Typically on hot days the attic will see temperatures of about 120 degrees F.

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There are several questions here. Split them up and ask them separately, please. See stackoverflow.com/questions/how-to-ask –  Brock Adams Apr 21 '12 at 7:48
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2 Answers

Here's a quick breakdown of the most common residential lamps here in the US.

  • "A" lamps are mostly used in table lamps or maybe outside wall fixtures. If the lamp is a 60A19 then it is 60 watts, "A" shaped and is 19/8 wide, or 2-1/8 inch. Divide the number after the style by 8 and you will get the width.
  • "R" or "BR" lamps are reflector lamps, thin glass. If the lamps is a 75R30FL then it is a 75 watt "R" style, 30/8 wide or 3-3/4 inches.
  • "Par" lamps or Parabolic aluminized reflectors is a hard glass reflector lamp, where the lens of the lamp is a separate he piece from the rest of the lamp but not removable. Because of the different type of lenses this style offers more directional control of the beam spread. Everything measures up the same as the other lamps, the difference is that the part number will usually give you the degree of the beam spread like a 50PAR20/HAL/NFL30 except the HAL is halogen or capsylite, the NFL is narrow flood and the 30 is the 30 degree beam spread.

I cannot answer the question about the thermocouple that protects the fixture from over heating. I don't know what my attic temperature is, mostly because in the summer time the ambient outside temperature floats between 110 and 120 most of the day and about 2 months of night time temperatures in the high 90's at midnight. It's the same can as what you buy.

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lqlarry, Thank you for your reply. It is most helpful and clearly fulfills my need. The heat rise problem, I will pursue. I believe that an adaption to heat sink formulas found in one of my transistor design books holds the answer. Robz –  Robz Apr 22 '12 at 15:09
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Doesn't answer all of your question but try checking out Harrington lights page on identifying lights or the PDF with pictures and descriptions of light shapes and wattages.

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UNECS, Thank you for your reply. The PDF will help get the data needed for lamp dimensions. –  Robz Apr 21 '12 at 17:00
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