Any alternatives to oscillating fans to cool led qb ?

cannabineer

cannabineer

Ursus marijanus
Hiddengems said:
His main issue is he's mixed up on the first law of thermodynamics.
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You do realize that, if both emit 300 watts of energy, it all ends up as heat? (I’m stipulating no plants in the room. They will siphon off a small percentage of photon energy into chemical potential.) Photons in a room without light leaks are converted losslessly to heat.
 
Billy the Mountain

Billy the Mountain

Well-Known Member
The textbook example I recall was that a big Zenith console TV pulling 500w would heat the room exactly the same as a 500w space heater

A watt is a watt is a watt = 3.41 BTU

As @cannabineer said, every watt ultimately ends up as heat.
 
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1212ham

Well-Known Member
ilovereggae said:
this is not 100% accurate. as I understand, using active cooling keeps the heat from building up, which keeps the overall heatsink cooler. otherwise the buildup of heat can cause the led to draw more current resulting in even more heat. I'm not sure that's 100% accurate either, but I know from experience if I blow a fan on my sinks and externally mounted drivers, they stay cool to the touch, and my temps in my tent and driver closet barely move. if I don't use active cooling in the tent, I can expect about a 3-5F degree temp increase per 250W of lights.
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A fan will increase heat transfer from the heat sink to the air around it.
It will also increase heat transfer from the air to the tent.
An increase in tent temperature would increase heat transfer from the tent to the air around it.
 
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1212ham

Well-Known Member
cannabineer said:
Watts are a measure of power.
BTU is a measure of energy which = power x time.
Surprised nobody caught this.
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You're just getting technical. ;-)

1 watt-hour = 3.4121416331 British Thermal Units.

1 watt-hour also 0.8598452279 Calories or 0.0013410221 horsepower-hour!

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Hiddengems

Well-Known Member
All the energy from the fixture isnt converted to heat. Some is converted to plant mass. E=mc^2

conservation of energy is absolute. But a tent isn't a perfectly insulated box.
 
ilovereggae

ilovereggae

Well-Known Member
Just finishing up work. I did some Google searches trying to find an answer. Maybe I'm imagining there is some difference, but I swear I can measure it.

For instance I have all my remote drivers mounted in my walk in closet right now. 2 circuits, 480W of drivers to each. If I don't run fans that blow air at the drivers, they are hot to the touch, and the tenps in the closet hit 85. if I run the fans, they stay cool and the temps never get above 80. I don't have time to do it rn but give me a few days and I can use my Sensor Plus and plot it across time for a day each way.

or @Smokeytit90 if you have a way to record your temps would you mind showing us how using the PC fans drops your tent temps? I know I am not crazy ;)
 
Billy the Mountain

Billy the Mountain

Well-Known Member
ilovereggae said:
Just finishing up work. I did some Google searches trying to find an answer. Maybe I'm imagining there is some difference, but I swear I can measure it.

For instance I have all my remote drivers mounted in my walk in closet right now. 2 circuits, 480W of drivers to each. If I don't run fans that blow air at the drivers, they are hot to the touch, and the tenps in the closet hit 85. if I run the fans, they stay cool and the temps never get above 80. I don't have time to do it rn but give me a few days and I can use my Sensor Plus and plot it across time for a day each way.

or @Smokeytit90 if you have a way to record your temps would you mind showing us how using the PC fans drops your tent temps? I know I am not crazy ;)
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Perhaps the fan is creating enough airflow for some exchange with the outside air?
If you measurements are correct, where do you suppose the heat went?
 
ilovereggae

ilovereggae

Well-Known Member
Billy the Mountain said:
Perhaps the fan is creating enough airflow for some exchange with the outside air?
If you measurements are correct, where do you suppose the heat went?
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not sure. maybe wherever missing socks end up?

are you saying that you do not think adding active cooling has any effect on the temps of a tent?

you are probably right, extra airflow is causing more air exchange or something. but in that closet in particular, there's no exhaust fan just a vent that dumps to outside.

how do you explain Smokeytits90 example of the PC fans dropping his temps by 5C?

the only thing I can think is that the thermometers we are using are sitting close enough to the heatsink that without active cooling its radiating heat that creates a small microclimate of warmer air. when hitting w a fan it never let's that build up. maybe the overall total heat produced remains the same if u measure what is pulled out of the exhaust. but inside of a tent, if it changes the canopy temp by adding active cooling, I would say you are getting caught up in the math and ignoring the actual effect.
 
Billy the Mountain

Billy the Mountain

Well-Known Member
ilovereggae said:
not sure. maybe wherever missing socks end up?

are you saying that you do not think adding active cooling has any effect on the temps of a tent?

you are probably right, extra airflow is causing more air exchange or something. but in that closet in particular, there's no exhaust fan just a vent that dumps to outside.

how do you explain Smokeytits90 example of the PC fans dropping his temps by 5C?

the only thing I can think is that the thermometers we are using are sitting close enough to the heatsink that without active cooling its radiating heat that creates a small microclimate of warmer air. when hitting w a fan it never let's that build up. maybe the overall total heat produced remains the same if u measure what is pulled out of the exhaust. but inside of a tent, if it changes the canopy temp by adding active cooling, I would say you are getting caught up in the math and ignoring the actual effect.
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A fan on a driver will increase the rate that it dissipates heat from the case into the air. The heat is simply moved. It's really that simple.
 
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Hiddengems

Well-Known Member
Stick a power meter on the light and run it from dead cold to as hot as it gets with no fan. Then put a fan on it.
That will give you your answer.
 
Billy the Mountain

Billy the Mountain

Well-Known Member
As mentioned before, the wattage as displayed by a kill-a-watt does not change regardless of whether the driver was in or outside the tent.

Have you tried it yourself?

What change would you expect to see?
 
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Hiddengems

Well-Known Member
Billy the Mountain said:
As mentioned before, the wattage as displayed by a kill-a-watt does not change regardless of whether the driver was in or outside the tent.

Have you tried it yourself?

What change would you expect to see?
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I didn't see that part. If the unit isn't drawing more power when hot, it's a air exchange happening.
 
madvillian420

madvillian420

Well-Known Member
1212ham said:
A fan will increase heat transfer from the heat sink to the air around it.
It will also increase heat transfer from the air to the tent.
An increase in tent temperature would increase heat transfer from the tent to the air around it.
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assuming you have adequate or even surplus negative pressure wouldnt that extra heat just be cycled out? and dissipate after that?
 
Syntax747

Syntax747

Well-Known Member
I run a 6" AC Infinity and it stays relatively quiet.
Quiet enough to run your grow in your toddlers room if you wanted.
 
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