A
Anonymous
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I was one time told by a distributor that MH bulbs run better when they run hot, yet just about everyone with serious setups run fans through the hood to keep things cool. So what's the truth on this?
I don't think you could possibly blow enough room temperature air across a metal halide bulb to cool it down one little bit. You're just blowing hot air away from the tank.
I just bought Lumenarc III relflectors with built-in ducting vents and an in-line centrifugal fan to blow air though them and then out of the house through a vent in the wall. The fan will be ahead of the first reflector and will blow cool (room temperature) across and though the reflectors. The reflectors will be connected with insulated duct. So obviously I don't think it's going to hurt the bulbs one little bit.
Louey
I just bought Lumenarc III relflectors with built-in ducting vents and an in-line centrifugal fan to blow air though them and then out of the house through a vent in the wall. The fan will be ahead of the first reflector and will blow cool (room temperature) across and though the reflectors. The reflectors will be connected with insulated duct. So obviously I don't think it's going to hurt the bulbs one little bit.
Louey
Well I wouldn't say "thousands of degrees" but yes I agree really hot, I still have the scar on the back of my hand from when my hood got knocked off its "feet" and that was the longest 1 second in my life (and those were just 175w bulbs! )
Now from a thermodynamics perspective if you remove hot air and replace it with room temp air that would cool the bulb down.. maybe not in a noticable fashion (unless you have a few hundred cubic feet per second going across it). But I was just curious. Might have to cut a hole in a my custom wood pendant now.. since wood isn't exactly a good conductor of heat
So which leads to this question. Would you blow air in? or suck air out? And don't say both because that's not an option, I could have holes at the other end where air could blow out I guess.. but the point of the pendant is that I dont get blinded by the bulb when I view the tank so I'd rather not turn it from an opaque fixture to a semi-transparent one
Now from a thermodynamics perspective if you remove hot air and replace it with room temp air that would cool the bulb down.. maybe not in a noticable fashion (unless you have a few hundred cubic feet per second going across it). But I was just curious. Might have to cut a hole in a my custom wood pendant now.. since wood isn't exactly a good conductor of heat
So which leads to this question. Would you blow air in? or suck air out? And don't say both because that's not an option, I could have holes at the other end where air could blow out I guess.. but the point of the pendant is that I dont get blinded by the bulb when I view the tank so I'd rather not turn it from an opaque fixture to a semi-transparent one
In my case I have two 250watt bulbs approx. 12" off the top of a 3'x5' tank. I have a "ghetto" reflector which is very open. I have a box fan on top of a fridge sitting next to the tank which is blowing air away from the tank. When the fan is on the lowest setting it will drop the temp of the tank anywhere from 3 to 5 degrees. I have the fan hooked to the timer that runs the light and it has worked fairly well. BTW this setup is not in my house ;-)
sfsuphysics":w5vcwcna said:
The major effect of cooling the tank is from increasing water evap. Blow air across the water surface and not at the MH bulb. If you have flourescents near the MH then blowing air across the flourescents will increase their life span.
Evacuating the hot air in a canopy helps slightly with keeping the tank cooler but not nearly as much as you would think. The temp increase from lighting mostly comes from the light entering the water, very little comes from contact with the hot air.
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