hahnmeister
In Memoriam
Well, all things considered, halides and T5s are very similar in heat output. A halide has a little over 12 square inches of surface to shed the heat, and T5s have about 40x the surface area to shed that heat. Now, according to thermaldynamics, what goes in must come out... what goes in is electricity, and what comes out is 75% heat, or more (tungstens for example, convert less than 10% to light)... well... where does the rest go? EM waves? Sure... some. Sound? Well, in the case of the noisy halide ballast, sure. Otherwise the majority of it is in heat. Now, being that your best with a halide is about 105 lumens/watt (HQI bulb, euro ballast at 3000K), and your best with T5s is about 85-90 lumens/watt (high-frequency ballast, and actually HO ballasts are only about 85% efficient, its the regular T5s that are 95% efficient), its safe to assume that T5s have a higher heat output when you take into account their total heat output across the entire surface. Now, for our tanks, we are talking about bulbs which are much less efficient than these ideals that mfg's websites give. A 10,000K halide is lucky to have half the output of a 3000K bulb... while for T5s, the blue bulbs are some of the strongest performers. So its arguable that T5s may make less heat, being that they seem to be much more efficient at making blue light than halides... but to argue it is kinda silly, because even if between the two there is some distinction in light efficiency, when you look at the overall heat efficiency of either lights it is a minute percentage because both are just plain horrible (kinda of like arguing over who is the king of losers or soemthing). What it really boils down to, as an example, would be that 250watts of halide might run at 70% efficiency, and 250watts of T5 might run at 70.5% thermal efficiency (or it could be the other way around but this argument isn't about light, its about heat, and comparing really is a mute point at that). Whoopie. Thats going to make a difference of what... .02 degrees?
Whats more important than comparing the two technologies here is how they are ventilated, or more, how the tanks are ventilated.
Last summer was my first with T5s going full tilt. On those two 40B comparison tanks I have, the one with the T5s overheated much faster than the one with the halide. Well, how could this be? Well, the halide lit tank has a fan that comes on with the light, and the top 40B has an open top with just a small pendant to block anything, so cooling through evaporation is very effective. I am able to keep the tank at 80 degrees even when the room is 90 and the halide is on.
The T5 lit tank HAD no such fan at the time... it was before Grim and I caught on to the whole 'T5s need active cooling' thing. So the T5s were cooking away, and covered almost the entire surface of the tank with reflectors that were 2-3" from the surface, while the halide was 8" from the surface... hmmm... but mostly, this pocket of air over the T5 lit tank was stagnant, and heating up very well.
As soon as I added the cross-flow fan to help the bulbs cool, the problem was solved. With either technology, and even more dated ones like VHOs and PCs, the thermal output is quite similar. Even LED's are pretty bad... actually they are slightly more horrible than the rest, its just that their design allows for attachment of heatsinks directly to the 'bulb' and that hot air is wicked away very fast.
Its not so much which light you chose as far as heat goes, but the ventilation you use. If you are switching from halides to T5s, thinking that that alone will solve your heating problems, you will be sorely mistaken. In fact, between the two, if given two tanks w/o any fans what so ever, the T5s will heat the water faster due to their closer proximity to the water, as well as the 'pocket' of stagnant air that they tend to create... a bit like putting a halide in a closed canopy over a tank.
Never underestimate the effects of evaporative cooling though. If you can have fans blowing not just into your canopy, but directly at the water surface, you will be amazed how much you wont need a chiller, but rather just a good auto-top-off.
Whats more important than comparing the two technologies here is how they are ventilated, or more, how the tanks are ventilated.
Last summer was my first with T5s going full tilt. On those two 40B comparison tanks I have, the one with the T5s overheated much faster than the one with the halide. Well, how could this be? Well, the halide lit tank has a fan that comes on with the light, and the top 40B has an open top with just a small pendant to block anything, so cooling through evaporation is very effective. I am able to keep the tank at 80 degrees even when the room is 90 and the halide is on.
The T5 lit tank HAD no such fan at the time... it was before Grim and I caught on to the whole 'T5s need active cooling' thing. So the T5s were cooking away, and covered almost the entire surface of the tank with reflectors that were 2-3" from the surface, while the halide was 8" from the surface... hmmm... but mostly, this pocket of air over the T5 lit tank was stagnant, and heating up very well.
As soon as I added the cross-flow fan to help the bulbs cool, the problem was solved. With either technology, and even more dated ones like VHOs and PCs, the thermal output is quite similar. Even LED's are pretty bad... actually they are slightly more horrible than the rest, its just that their design allows for attachment of heatsinks directly to the 'bulb' and that hot air is wicked away very fast.
Its not so much which light you chose as far as heat goes, but the ventilation you use. If you are switching from halides to T5s, thinking that that alone will solve your heating problems, you will be sorely mistaken. In fact, between the two, if given two tanks w/o any fans what so ever, the T5s will heat the water faster due to their closer proximity to the water, as well as the 'pocket' of stagnant air that they tend to create... a bit like putting a halide in a closed canopy over a tank.
Never underestimate the effects of evaporative cooling though. If you can have fans blowing not just into your canopy, but directly at the water surface, you will be amazed how much you wont need a chiller, but rather just a good auto-top-off.
