Why are the fans in LED's backwards?

[Remystemple]

I was shocked to realize that all the fans in all my LED lights suck air in from the top and push it out the side. I've always just assumed the air was pulled in through the sides and pushed out the top.

especially with heat sinks involved this goes against everything and every other heat sink ever lol.
fans generally pull the air from a heat sink rather than blowing on it.

the other thing that bugs me is that since the lights are sucking in air from the top means they are pulling in air that's already warmer than the air would be coming into the lights from the side then being blasted up toward the tent exhaust.

the way i see it, all the lights are really doing is mixing warm air around more than they have to.

Maybe im' wrong and probably am, but like i say, this push instead of pull goes against the way a heat sink traditionally works.

 

[Marzbadrock]

Huh! Only reason I can think is to keep from pulling heat through the fans but it seems bass ackwards to me

 

[TurboBucket]

That's interesting. All three brands I had used the fans in your preferred orientation. I'm surprised to hear that yours do not.

 

[Remystemple]

That's interesting. All three brands I had used the fans in your preferred orientation. I'm surprised to hear that yours do not.

damn, i'm really thinking about opening one up and seeing about turning them around.

 

[Remystemple]

@fanleaf I'm curious what direction you chose for your cob heat sink fans. do they blow upward or inward?

 

[fanleaf]

@fanleaf I'm curious what direction you chose for your cob heat sink fans. do they blow upward or inward?

Mine all suck air from the top and push out the side of the heatsink. It makes perfect sense to me though because let's say these small (honestly weak but important) fans were reversed...The air the fans suck in would almost all be air closest to the tips of the pin fins on the heatsinks. They wouldnt suck enough air hard enough and fast enough to suck air all the way down to the base of the heatsink. I believe if they were reversed the fans would only primarily be cooling the top half of the fins. Sucking air from the top and blowing towards the base of the heat sink Gets the air moving all the way down to the base. I could see reversing them but only if the fans we use were 5 to 10 times stronger than the fans currently used. Even if so, I still wouldn't reverse them. If I turn my lights all the way up to the max and I put my finger on the chip side of the heat sink after about 15 minutes of running on high the heat sink closest to the chips mounting location is still barely over room temperature. Lots of electronics blow air over a heat sink. the air moving over the aluminum still draws a ton of heat out of the metal.
I have $4,000 amplifiers that operate in the same manner with three fans blowing across the heatsink.

 

[Remystemple]

Mine all suck air from the top and push out the side of the heatsink. It makes perfect sense to me though because let's say these small (honestly weak but important) fans were reversed...The air the fans suck in would almost all be air closest to the tips of the pin fins on the heatsinks. They wouldnt suck enough air hard enough and fast enough to suck air all the way down to the base of the heatsink. I believe if they were reversed the fans would only primarily be cooling the top half of the fins. Sucking air from the top and blowing towards the base of the heat sink Gets the air moving all the way down to the base. I could see reversing them but only if the fans we use were 5 to 10 times stronger than the fans currently used. Even if so, I still wouldn't reverse them. If I turn my lights all the way up to the max and I put my finger on the chip side of the heat sink after about 15 minutes of running on high the heat sink closest to the chips mounting location is still barely over room temperature. Lots of electronics blow air over a heat sink. the air moving over the aluminum still draws a ton of heat out of the metal.
I have $4,000 amplifiers that operate in the same manner with three fans blowing across the heatsink.

Hey thanks a lot man. I figured there must be something i'm not understanding about how they're built. and obviously they're not computers but just expected them to work the same way.

thanks for the detailed feedback. i won't be opening up my lights any time soon now lol.

 

[TurboBucket]

The fans are typically just little case fans. The cheap lights I had were anyways. The only difficulty in flipping them over: the mounting points are drilled larger on one side of the fan. Presumably to insure proper installation at the factory. Drilling out the other side allowed me to flip the fans over. Two different brands same design. I have seen some lights that use a frameless motor in the heatsink though.