Cooling MH Fixtures, the Why

[ataller]

I have a 60" metal halide fixture with 3 250w 14k phoenix DE bulbs over my 120G.

There are two computer fans built into the fixture. With the fans on, or with the fans off, I do not notice any increase/decrease in performance from the fixture.

My question is, why do we cool our metal halide bulbs? Is it to reduce the amount of heat they contribute to our water temperature? Or does cooling the bulbs also increase their longevity?

Thank you

[thegrun]

Both, but the fans built into the fixture are primarily to cool the bulb and fixture itself to prevent fire and extend bulb life.

[ataller]

Great to know.

Thanks

[stanlalee]

fans arent there to increase life or performance of the bulb what so ever. Ambient temps have virtually no effect on metal halides. the bulbs are under aluminum reflectors and sometimes a glass panel and the fixtures themselves are usually aluminum as well so there is little to no threat of fire related to heat created by the bulbs. 90% of the reason cooling fans are there is to prevent heat tranfer into the tank. the only other reason is to keep internal ballast from overheating. Most fixtures that use higher wattage than 150w use external ballast so this is usually not an issue either.

[brubinfeld]

and also for the fixture itself that shouldnt melt on u

[spleify]

Originally Posted by thegrun

Both, but the fans built into the fixture are primarily to cool the bulb and fixture itself to prevent fire and extend bulb life.

+1, good accurate info!!

[stanlalee]

Originally Posted by spleify

+1, good accurate info!!

its not accurate. halides became partly popular in industrial lighting because of the immunity to ambient temps on performance and the aluminum fixtures arent susceptable to fire from halide heat. the bulbs need NO cooling what so ever.

[thegrun]

Originally Posted by stanlalee

its not accurate. halides became partly popular in industrial lighting because of the immunity to ambient temps on performance and the aluminum fixtures arent susceptable to fire from halide heat. the bulbs need NO cooling what so ever.

Then we are going to disagree here. I could have been a little more clear, but the fan is to cool the fixture, not as you stated the water. Industrial fixtures are not designed to sit on top of a marine environment as aquarium fixtures are. I can absolutely state that if I disconnected the fan and thermal protection on my MH fixture, it will melt, as it has several plastic components.

[radicaltimes]

Turn off the fans for 6 hours and put your hand on top of the fixture and try to hold it there. You will then know why you need to run cooling fans in the fixture. The fan is going to cost a few cents a month to run.

[stanlalee]

Originally Posted by thegrun

Then we are going to disagree here. I could have been a little more clear, but the fan is to cool the fixture, not as you stated the water. Industrial fixtures are not designed to sit on top of a marine environment as aquarium fixtures are. I can absolutely state that if I disconnected the fan and thermal protection on my MH fixture, it will melt, as it has several plastic components.

I do agree cooling may be neccessary to prevent thermal protection of internal ballast which I made reference to as well as fixtures that have supplemental flourescent lighting that benefit from cooling but thats it.

as for the industrial fixture reference, the point was made cooling was there to: cool the bulb and extend the life. this is FALSE. there is no bulb life or performance to be gained from cooling the ambient air around the bulb like T5s. this is what I was addressing and this info is easier found searching industrial/horticulture sources than aquarium industry sources. the application is irrelavent, the advantage remains the same but it does eliminate one rationale for cooling leaving only two left (spontanious combustion and heat transfer to the water)


let me be clear I agree the cooling may be there to cool the fixture but NONE of it is related to the halides or the need to prevent fire. if there is plastic it doesn't have to be there as virtually ALL halide only pendants have no plastic (or active cooling) nor would appropriate plastic melt without direct exposure to the bulb. ever pop open your hood and see all the plastic clips and parts mounted directly to hot engine components and even cooling parts themselves like many radiators are now made from plastic. the diverter valve on my car is made of all plastic and is mounted DIRECTLY to the turbo which glows orange on the hot side in hard use so use of plastic itself is not a problem. IF its a halide ONLY fixture with external ballast the cooling can ONLY be there to reduce heat transfer to the water. If the fixture has supplemental flourescent lighting or internal ballast the cooling may be there to cool the fixture but it is NOT halide related.

[thegrun]

Originally Posted by stanlalee

I do agree cooling may be neccessary to prevent thermal protection of internal ballast which I made reference to as well as fixtures that have supplemental flourescent lighting that benefit from cooling but thats it.

as for the industrial fixture reference, the point was made cooling was there to: cool the bulb and extend the life. this is FALSE. there is no bulb life or performance to be gained from cooling the ambient air around the bulb like T5s. this is what I was addressing and this info is easier found searching industrial/horticulture sources than aquarium industry sources. the application is irrelavent, the advantage remains the same but it does eliminate one rationale for cooling leaving only two left (spontanious combustion and heat transfer to the water)


let me be clear I agree the cooling may be there to cool the fixture but NONE of it is related to the halides or the need to prevent fire. if there is plastic it doesn't have to be there as virtually ALL halide only pendants have no plastic (or active cooling) nor would appropriate plastic melt without direct exposure to the bulb. ever pop open your hood and see all the plastic clips and parts mounted directly to hot engine components and even cooling parts themselves like many radiators are now made from plastic. the diverter valve on my car is made of all plastic and is mounted DIRECTLY to the turbo which glows orange on the hot side in hard use so use of plastic itself is not a problem. IF its a halide ONLY fixture with external ballast the cooling can ONLY be there to reduce heat transfer to the water. If the fixture has supplemental flourescent lighting or internal ballast the cooling may be there to cool the fixture but it is NOT halide related.

Peace, we are on the same page.

[Slim_jim989]

ever pop open your hood and see all the plastic clips and parts mounted directly to hot engine components and even cooling parts themselves like many radiators are now made from plastic. the diverter valve on my car is made of all plastic and is mounted DIRECTLY to the turbo which glows orange on the hot side in hard use so use of plastic itself is not a problem.


What type of car do you have? And the radiators are made of aluminum core with plastic end caps. On your turbo that's the cold side which draws in cold air and there's almost always a silicon boot to connect the two. Don't reference things that are irrelevant to the questions above.

[stanlalee]

Originally Posted by Slim_jim989

What type of car do you have? And the radiators are made of aluminum core with plastic end caps. On your turbo that's the cold side which draws in cold air and there's almost always a silicon boot to connect the two. Don't reference things that are irrelevant to the questions above.

wrong. I have removed, replaced and installed the diverter valve 3 times and there is no silicon boot that connects the two (MKV GTI). it bolts STRAIGHT to the turbo:


and YES it is relavent because the cold side of a turbo is cold compared to the hot side but certaintly NOT cold compared to plastic somewhere in a halide fixture unless its where it doesn't belong like between the bulb and reflector.

and what is your point with end caps regarding heat? are plastic end caps not exposed to the same heat as the core? does the hot water not go thru one of the end caps BEFORE the core?

[brubinfeld]

who cares about the car engine bottom line is cooling with a fan is benefical

[lostanime]

My fixture (aquamedic) has no internal ballasts, and no supplemental lighting beyond the halides. It's running over a thousand watts of metal halides closed in with reflectors and glass shields, and does NOT have any fans whatsoever.

I would tend to agree with others that the fans would be great if there are internal ballasts and/or other lighting incorporated in the fixture and/or plastic stuff. The bulbs don't need fans.

The flipside is, my coralife fixture had a fan in it (despite no internal ballasts or additional lighting components). The previous owner didn't run the fan, and the majority of plastic stuff in that fixture was melted and/or deformed. I practically gave that fixture away. If a fixture is designed to run with a fan, I'd strongly recommend running it for safety reasons.