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Old 10-12-2012, 03:27 AM   #1
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How much heat do LED's actually put off?

I have read some people say they don't put off much heat, and others say they put off a lot of heat.

Watt for Watt, say 400w LED vs 400w HPS, does LED produce less heat?
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Old 10-12-2012, 03:59 AM   #2
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Watt for watt, significantly less heat. Panel dependent though - some run cooler than others due to efficiency and design given the same wattage. My veg led throws off a good bit more heat watt for watt than the Kessil leds I use in my plasma/led flowering tent for example.

Major difference in how the heat is distributed though - a lot of it goes straight up via the heatsink, and what does go down is spread out. The heat is so diffused that the issue with how close the plant can get is never about heat - you hit the light intensity barrier way before that with even the least efficient panels. Downside of this approach is the built-in fans get loud, especially on the bigger panels.

Listen to this 800w (620w draw) panel kick on -

http://www.youtube.com/watch?feature...nRaUoUs#t=184s

You may as well have a 1k in there with a nice 6'' canmax fan/filter and a muffler, would prolly be about the same noise level if not less.

Here's the LumiGrow es330 kicking on -

http://www.youtube.com/watch?feature...GAU0R3L0#t=25s

Pretty loud, so yeah, just gotta keep in mind how this kind of light achieves its "low heat" status.
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Old 10-12-2012, 08:12 AM   #3
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The LEDs must stay cool for maximum efficiency. And when I say cool I mean no more than 30-35 degrees Celsius ( 95F).

In addition, a led efficiency is calculated as the ratio between the emitted light (measured in lumens) and the total power consumption (measured in watts).

The power that in not converted in light is lost as heat. This heat must be dissipated quickly or the LED will fail. This is why so many LED grow lights incorporate fans for active cooling.

Speaking in terms of 'watt per watt', the head produced by a LED panel is much lower than the heat produced by a HPS lamp, but in the same time the LED panel does not emit IR or UV .

To avoid using noisy fans, the LED grow lights can have sometimes over-sized hetsinks to be able to dissipate the heat in the surrounding air.

And the conclusion :
Quote:
Watt for Watt, say 400w LED vs 400w HPS, does LED produce less heat?
Yes, LED produce less heat than HPS !
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Old 10-12-2012, 07:55 PM   #4
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Old 10-12-2012, 10:14 PM   #5
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my led lamps raise the temps in the cabinets about 3-5 degrees. my hps would raise the temps by 30-50 degrees.
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Old 10-12-2012, 10:35 PM   #6
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I have 500W units which draw 295W.. if you want, I can take pictures with my hand right on the glass....little warm but if you need to see it...no problem...that alone should say something about how much heat they give off....Even on a 60W regular incandescent light it's impossible to do that unless you're a psycho and like the pain and burns that is..

Like the rest of the gang says,,they raise the temps a bit but no where near the temp rise of an HID...

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Okay okay....a few people were requesting this info:

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Old 10-13-2012, 12:49 AM   #7
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touch an hps bulb then touch a led panel, it is like touching boiling water and ice in my opinion lol. Maybe its just me and had too many bad "hps on skin" experiences in my day and am biased a bit.
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Old 10-13-2012, 11:51 AM   #8
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I had buds developed around LEDs (sticked to them) and nothing happent to them (just a little light bleaching). Try to wrap a plant around a HPS bulb and you will get a nice fire !
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Old 10-14-2012, 10:54 AM   #9
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If one unit draws 400w of power and puts out x amount of light. Second unit draws same 400w of power and puts out same x amount of light. They both will produce same amount of heat. No matter what you think, or how it heats your hand/plants. The amount of heat produced will be same. Leds wont produce much more light than hps, if any. Maybe better PAR. What makes many people think they produce less heat is that leds need heatsinks and active cooling to work properly. So that heat is transferred away and not heating the leds, like with hps light.
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Old 10-14-2012, 11:29 AM   #10
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Surprisingly, watt for watt commercial LEDs actually produce more heat than HPS. 600 and 1000 watt HPS is about 40% efficient converting electricity into visible light. Commercial LEDs are only 15-20% efficient.

So if you had 600 watts of actual commercial LED dissipation in your growroom it will emit more heat than a 600 HPS will.

If you can get your hands on top bin cree or osram LEDs they can be up to 40-50% efficient. This is where the heat savings can come into play. Because LEDs can provide a more efficient spectrum than HPS, do not require reflectors or glass shields and spread light more evenly, they can produce more grams per watt of production. So 300 dissipation watts of top quality LED can do the job of a 600 HPS and that will definitely eliminate your AC bill.
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Old 10-14-2012, 11:30 AM   #11
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The heat produced by an HPS is from photons of light and is directed to wherever the light touches. LED has the same thing, but with a much smaller radiation area. a bulb radiates light 360º whereas LED has a small footprint. The majority of the heat produced by the LED is in the heat sink, which is then vented away.

The light that is not used but absorbed turns directly into heat. The light itself is a heat source, the concept of LED is that you match the spectrum that is used by the plant without adding any light that is not used. The light that hits a surface is harder to cool because the light is continuously bombarding it with photons. The heat from an LED goes out the top an can be vented before it heats the entire room and plants.

LED allows you to minimize the photon heat that is otherwise inescapable. You will still need to manage the hot air coming out of the top.
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Old 10-14-2012, 11:34 AM   #12
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Also many commercial LEDs hugely overstate their actual dissipation wattage. As the earlier poster mentioned his 500 watt LED is actually consuming 295 watts. Because of the fans and drivers, this means actual LED dissipation is closer to 250 watts or less.
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Old 10-15-2012, 10:44 PM   #13
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Quote:
Originally Posted by Its_a_hobby View Post
If one unit draws 400w of power and puts out x amount of light. Second unit draws same 400w of power and puts out same x amount of light. They both will produce same amount of heat. No matter what you think, or how it heats your hand/plants. The amount of heat produced will be same. Leds wont produce much more light than hps, if any. Maybe better PAR. What makes many people think they produce less heat is that leds need heatsinks and active cooling to work properly. So that heat is transferred away and not heating the leds, like with hps light.

if this is the true case, then i should be able to touch my 150 hps bulbs with no burns. i can touch and keep hold of the led lamps that draw 195 watts. i can determine the amount of heat in a cabinet simply by testing the temps. also, if the heat is drawn away from the led motherboard, then the led case would be hot. again, no heat on my led cases.
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Old 10-19-2012, 12:19 PM   #14
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If your LED actually draws 195 watts there will be more heat in the room than the 150 HPS. Have you put it on an AC power meter. They sell them at Walmart for $15 in the light bulb isle if you are curious to test it.

I had a small box with 160 LED dissipation watts using passive cooling from huge heat spreaders and they were about 95f.
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Old 10-19-2012, 10:16 PM   #15
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SupraSPL (and Phychotron) nailed it in his above posts, regardless of however much someone determined his post to be "helpful". It is all about the efficiency of the conversion of electricity to useable light. There are HID lamps that are more efficient at that process than many LEDs. The heat generated by either is a result of the inefficiencies of the conversion process - the current not being transformed to light is converted to heat.

The problem in comparing them is because they are so radically different in the way that they function. If you were to hold a LED in your hand that didn't have the heat sink attached, it would burn the shit out of you just shortly before it burned itself out. LED's, because they are wavelength specific, don't generate IR and consequently don't "throw" heat like HID's do. This is what heats up the surrounding area. HID lamp's arc tube is largely a point source of heat, and runs somewhere around 1600 degrees. LEDs move the majority of the heat that they generate into the heat sink, which while it may look small, has a tremendous amount of surface area to dissipate the heat over and results in a much lower heat rise over it's area. It is like trying to compare a woodstove to hydronic heat in your floor - they may both generate the same number of btu's, but your body is going to tell you that they do not.
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