I have a grow room that measures 3.5’x3.5’. I have two 700w Mars Hydro LEDs. The manufacturer says that this light will cover 3’x3’ during flower. I have relective mylar on the walls, a 6" exhaust fan pulling air out.
I know that putting any light too close can cause light burn but my question is this: If I put two 700w lights in a 3.5’ square room can I prevent light burn by raising the lights? If I keep them at 20" +/- and control the heat with fans, will I need to worry about light burn?
Or would you just use one light hoping the reflective walls will help with the 6" area that won’t be getting the light?
Thanks you guys for all your great help!
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Hey brother. Light burn is not from the heat but the UV rays being too intense. What are the true wattage ratings of those lights? @Tarzan
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I can tell you there are 140, 5w diodes. These lights DO have UV and IR
diodes. I am running with both the grow and bloom diodes on.
I think part of the calculations have the recommended distance from the
plant included. Since they recommend the light, during flower, be like 16"
from the plant, that would reduce the 3.5’x3.5’ coverage at 20-24" to the
3’x3’ coverage during flower the manufacturer indicates in their literature.
Forgive me if this is a dumb question but…If I run 2, 700w lights in a
3.5’ square room and keep the recommended distance from the plants and
control the heat will I burn my plants?
I want to give them ALL the light they can stand but obviously want to
avoid burning the plants.
HEY, thanks for your input!!!
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@Tarzan; you are on the right track but have no worries. The actual wattage is FAR less than 700 watts per fixture. Probably more like 130. You can probably run your plants within 8 inches of the lights if you wish. I have a 4’ X 6’ box with 3,600 watts of led’s in it and it’s nowhere near too much.
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Wow, that is alot! With no sign of burn?
How far from your plants?
I am hearing you say that my 2 700w fixtures will not overload my 3.5’x3.5’
room.
If you are right about the actual wattage per fixture being 130w then two
would be 260w / 12.5 sf = 20w per sf. Not nearly enough, huh?
I will check with the manufacturer to see if I can determine what they say
about actual wattage output.
I do appreciate your time and response.
I will get back to you!
So the manufacturers website says that these lights are equivalent to 350w
HID light. If that is true then it seems two will work just fine.
Since I am dealing with seedlings right now I will keep them 24 to 30" away
and see what happens. This additional light will also solve the coverage
problem I am anticipating with just the one light.
Thanks again for your input, I really appreciate it.
The light burn that you read about comes from the actual heat of HPS and HID lights. With LEDS the heat is so low that you shouldn’t have to worry about burn. I have never heard of anyone running LEDS having light burn. I am running a 1200w LED (actual wattage 200w) 14" away from my seedlings and they love it. Just spray the top of the dirt once a day and water as usual. And remember no nutes till bottom round leaves fall off. Happy growing
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2 of those lights is just about perfect for your space.
They run about 260W true. A little less in veg and a little more in bloom. So, 2 of them is about 520W which, at 50w PSF, covers about 10.5 SF. You have a little over 12 SF, so again, just about perfect.
Follow the manufacturer’s recommended height. You can absolutely burn/bleach your buds if the light is too close due to the intensity of light (as others have said).
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I agree with @MAXHeadRoom and @Matthew420. I love the led’s and have never had a stretching issue nor a burning issue. I think you are right in the sweet spot with your lights.
Man, thanks for the input. Last year was my first grow, wish I had taken
heed to the folks on here raving about LEDs. Had
a decent crop but I bet this year will be alot better.
Thanks again!!
Thanks for the response!
Do you differentiate between light burn and light bleaching?
Obviously I am on a learning curve and want to be careful, as we all do.
I’m on day three with LEDs and so far I am very pleased.
Thanks again!
I searched the forums and it looks like when you burn your plants they will turn white and look like they are bleached. That is where that term came from. So bleaching is the effect of light burn.
This is only my second grow and in fairness I give my girls sunshine whenever I can but they have lived the majority of their lives under lights. That said: my entire experience has been with led’s. It has also been a case of playing catch up with what I felt was adequate light. I believe I’m there.
This is a top from one of my plants, now hanging upside down, on the evening of harvest. That’s about 8" of it.
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No, picture was cropped. 4 inches maybe.
I’d say you are there!!
Very nice. How many watts per square foot are you getting under your LEDs.
Ever think you can get too much light?
Yeah, I have enough light, and heat is much less of a problem than with HID lighting. As far as rated versus actual wattage per square foot? Rated, about 150. Actual about 50. The thing is if you put a meter on your indoor setup it will be equal to a cloudy day outside.