Active cooling and T5

[Stones]

Its been said countless times on just about every reef forum on the net that T5s operate more efficiently and bulbs last longer when used in conjunction with some form of active cooling. The general consensus is that bulbs ran with with active cooling typically achieve a 20% greater output in PAR values than bulbs ran without active cooling.

I've also read several articles which stated that overcooling T5s is also detrimental to bulb performance.

What I wanted to know was which part of the bulb should our fans be directed at in order to achieve this 20% increase in PAR values. I also wanted to know exactly what the ambient temperature inside of our T5 fixtures/retrofit canopies should be in order to see these results as well.

Then I stumbled upon this technical article put together by Philips:

http://home.versatel.nl/rsetteur/aqu...tl5_manual.pdf

Chapters 2.4 and 2.5 basically answered what I wanted to know about the temperature requirements of T5 lamps.

To sum up what was said, T5 lamps will operate at their maximum capacity when the cold spot (area of the bulb directly adjacent to the end cap on the side of the bulb where the company stamps their logo) has an internal temperature of 45 celcius. The article also stated that the cold spot has an internal temperature equivalent to the ambient temperature inside of the fixture + 10 degrees so the ambient temperature around the cold spot should be 35 celcius in order for the lamps to operate nominally.

The only way I was able to do this was to first check to see which way I had my bulbs mounted in my fixture. Sure enough, all of the cold spots were at the opposite end from where the fans are located. Checked the ambient temperature, 44 degrees. So before I flipped all the bulbs around, I thought I'd crank up the voltage for my fans from 4.5 to 6 V to see if that helped bring the temp down towards 35. Checked after 15 minutes and the temp was now up to 48 degrees. My last option was then to flip all the bulbs around so the cold spots were adjacent to the fans. I still haven't finished testing the ambient temp so that I can adjust the fan voltage, but I'm hoping that I should now be able to get the ambient temp around the cold spot down to 35 degrees. If I see a significant increase in light output, I'll post my results.