I’m confused over light height can you advise ?

skullcandy

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Okay I have got two small led grow lights and another one on the way they are 250 watt 100 watt and 145 watt all led grow lights my concern is at what height above the top of the plant should I place the light ? The info in here says 18” the light info said 24-36” just for the 100 watt so that being said I’m considering hanging two off the lights so the point side ways and one on top do you know if this would work? If not what do you suggest?
 

zem

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I am no expert in leds but i feel like 18 inches is too close for 250w LED. Anyway it seems like light is not as straightforward as we might think. I the old days we were always told to place HPS and fluros as close as we can without burning plants, however, i saw some videos of commercial grows who have great grows while the lights seem to be placed much higher than that. I would like to try a light meter to determine this but i don't have one.
 

WeedHopper

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With HPS and HOT5s it's all about heat. My HOT5s could be right in top of the canopy and my plants loved it. The 6500k you could put your hand on and it wouldn't burn you. The 2700k for flowering would get warm so I would back them off to 4" and I was fine
HPS will burn the fk out of them if they are too close. Most used 12 to 18" on HPS especially with a cool tube.
LEDs bleach the crap outta them if to close. I would follow manufacturer specs and work your way from there. I don't use LEDs but it's seems to me most use 18 to 24 inches from canopy .
 

SubmarineGirl

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I run LEDs and they are pretty easy on the plants. Depending on the size of your plants. If they are seedlings like my current tent, I run my lights about 18” away from plants at 40%. If you have no dimmer to reduce it, I would say farther away at this age. If your plants are in Veg, you can run the lights much closer as LEDs do not produce heat and the plants love the light in veg. I turn my lights up to 100% as soon as my plants start taking off.
 

T_Dub

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Here are the recommendations from my 130 watt LED based on the stage of life. Gives you the option of adjusting the dimmer or adjusting the height to achieve the proper amount of lighting. Your lights should hopefully come with recommended distances.

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sharonp

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Okay I have got two small led grow lights and another one on the way they are 250 watt 100 watt and 145 watt all led grow lights my concern is at what height above the top of the plant should I place the light ? The info in here says 18” the light info said 24-36” just for the 100 watt so that being said I’m considering hanging two off the lights so the point side ways and one on top do you know if this would work? If not what do you suggest?
I have some LED light bulbs that I hang on the side during flowering. I have used one during the seedling stage too. I put them fairly close like 12 " to 18 " during those stages. You can use them farther away during the vegetative stage as long as they don't start stretching. You're going to have to play around with them like somebody else suggested until you find what works best.
 

oldfogey8

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The rule of thumb used to be to put the back of your hand under your lighting and if it is too hot at a certain height for your hand, it is too hot for your plants. I think LED tech has changed though with some manufacturers adding UV LEDs to the array. As we all know, you get a sunburn(from the UV) long before you feel the burn. As hopper said, HO T5’s can get really close to the plants without burning them. I have had my HO T5’s a few inches from the tops without hurting the plants. I have had my sh!tty LEDs about a foot above my plants without burning them(and they have a UV LED in them). Just keep in mind, the closer the LED is to the plants, the smaller the spread of the light(smaller sweet spot footprint). Many LED manufacturers have specs with a grid layout showing PPFD values over the grid based on fly-height. I would use those as a guide for height above your plants. Smart phone apps are now available to give your a relative idea of the light spread and uniformity as well but they should probably only be used for reference.
 

oldfogey8

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I push the spider farmer lights and the mars hydro lights a bit over the manufactures requirements I gotta admit. My plants seem to like the extra light they provide…
From what I have read in your posts, you adjust both height and intensity so I think you are essentially ‘hardening off’ your plants. Getting them used to more light gradually(as you do) and pushing the envelope so to speak has yielded your excellent results.
 

SubmarineGirl

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Yes but in the auto tent I turned them up to 100% at the seedling stage based on Cartys page and comments. Didn’t hurt them at all. My lights have no heat but I understand that some lights do. I’m not pushing the light in my current photo seedling tent I’m only at 40%. Watching node growth now but will pump up the volume soon. I never use to put my plants in the tent so early but noticed after the auto tent that they do much better there with nice even node growth and very little stretching. I didn’t start my seeds this time in the tent tho as I did in the seed to harvest spider light tent but the took off after I put them under the LED even after an early transplant
 

RosterMan

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Okay I have got two small led grow lights and another one on the way they are 250 watt 100 watt and 145 watt all led grow lights my concern is at what height above the top of the plant should I place the light ? The info in here says 18” the light info said 24-36” just for the 100 watt so that being said I’m considering hanging two off the lights so the point side ways and one on top do you know if this would work? If not what do you suggest?
Welcome Back
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skullcandy

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What LED'S do you have?
LED'S are not created equal
I go
Go 20 inch watch the plant how it responds drop it down another 2 if it responds good until you find that sweet spot leds you don't have to worry about heat like hps. Actually I'd start at 18in
Go 20 inch watch the plant how it responds drop it down another 2 if it responds good until you find that sweet spot leds you don't have to worry about heat like hps. Actually I'd start at 18in
I started the canopy @ 36” now it’s around 18 “ because she grow
 

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