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/aquarium/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.

[lastlight]

Will you remove the fixture and work with the bulbs away from the tank? How do you do regular maintenance for that matter? Just put an arm in and swing the fixture out? Off topic questions but I'm curious. Looking forward to seeing your results.

[Stones]

All I do to remove the bulbs is to lift the fixture using the adjustable cable hangers. Then I tilt the fixture by sliding the 2 front portions of the ^ shaped cable that attaches the fixture to the cable hanger through the hook of the cable hanger. The fixture then hangs at an angle that allows access to all of the bulbs. Takes about 10 minutes to slide out the glass covers, lift, tilt, and switch out the bulbs. No need to take the fixture down thanks to the slick hanging system.

[parkinsn]

The general idea of that artical is correct and what you are saying makes sense. However that article was printed in 2000, the tecnology has changed a fair bit since then. For a standard F54T5HO @ 32 degrees (ambient temp in degrees C) you will get 100% relative light output, @ 45 degrees (ambient) you will get 96% relative light output. You will not be able to see a 20% change in relative light output untill you hit on the low end of 22 degrees (ambient) and the high end of 57 degrees (ambient). They have designed T5's now for replacement's of 400W metal halide in warehouse applications, (if you have ever changed a lamp in a homedepot type warehouse it is hot as heck at the top of the roof usually 45-50 degrees C in the summer)

If its a 20% increase in lighting your looking for i dont think your going to see it without a PAR meter or even get more that about 2-4% increase by droping the temp a few degrees. As for the temp going up in your canopy, i would say that is due to the fact that you are creating more heat with your fan motor in turn blowing warmer air into your canopy

In summery the new style ballasts and lamps are all designed for higher temp's, but it still remains true that T5's do not like cold. On that note you can buy "extreme tempature rated lamps" which will get 100% relative light output @ 32 degrees C to 60 degrees C (ambient temp). Although im not sure if they are available in the color temps that aquarium lamps come in.

[Stones]

If its a 20% increase in lighting your looking for i dont think your going to see it without a PAR meter or even get more that about 2-4% increase by droping the temp a few degrees.

I wish I had a PAR meter to see what the results will be like for my fixture as you are correct, any difference in light intensity will likely be undetectible to the naked eye. I do have results that TheGrimReefer posted on RC shortly after T5s were introduced to the aqurium trade.

http://www.reefcentral.com/forums/showthread.php?s=&threadid=933795

He saw an increase in PAR over 20% from using fans to not using fans in his retro canopy when taking PAR measurements on his sandbed.

I'm not too sure where the 2-4% increase in intensity figure came from but Grim's tests with a PAR meter in an aquarium setting clearly indicate that using active cooling increases light output much more significantly than that.

[parkinsn]

I would like to see the results of this test you should get some good before and after pics. I am building a new canopy now and would like to finish it sometime soon with 6 T5HO's and 2 MH's.... I was going to put 2 4" fans on it, it will be interesting to see what happens. Might have to go with 3. What do you have for fans/cooling on your tank now and what type of fixture is it?

[Stones]

The fixture that I am using is an 8 x 54 watt Sfiligoi Stealth. It uses 4 fans that are each ~2" in diameter and are mounted at the left most end of the fixture, just behind the endcaps. In this way, one fans blows along the length of a pair of bulbs. The fans are also wired to a variable voltage DC converter so that depending on the temperature of your house, you can run the fans at anywhere from 3V to 12V in order to have greater control over the temperature inside of the fixture.

http://i53.photobucket.com/albums/g47/prestieb/DSCN0230.jpg

I took some before shots of the tank but it is hard to capture the acutal light intensity. Once I finish swapping bulbs and setting the fans to the correct voltage, I'll snap an after pic and see if I can notice a difference. Most likely, it will be negligible without the aid of a PAR meter, but here's to hoping:biggrin:

[parkinsn]

Those are sweet lights :biggrin:, looks like a nice tank as well.

[dreef]

Yes those sure are sweet lights,i seen them in person a few times.As for the tank..well..if you like your tank crammed full of acros,i guess it's pretty nice... sry had to bud (<: