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Thread: LED Light height in grow tent

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    Default LED Light height in grow tent

    Hey there,

    question is on lighting, LED height from top of plants..

    What height do you keep your LEDs while in Veg, and when they are in flower?
    Are they the same distance, and adjusted as the plant grows? Ex. Led is 22" from canopy top. No matter the stage.

    Thanks!

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    Wow! didnt even know that matters

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    It all depend on what kind of light and space you have?

    V8
    Mini veg tent grow: V8`s mini garden



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    Mine are ziptied to the roof bars at 7 foot and never move, just let the plants grow into them. But these are quantum board lights, bar lights will need to be lower etc etc.

    what style are your lights?

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    Like Mac, my lights, 2 x HLG 100, are fastened to the (8 foot) ceiling and don't move. The blurb says a minimum of 12" from the ceiling and the hanging cords supplied ensure that happens.

    No dimmers on my lights and even if there were, I wouldn't be able to access them without emptying the groom. Next grow onward, I'll be using a timer to act as a dimmer.

    Having the lights so high has made tending to the plants much easier. Well worth the extra leccy to me.

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    Quote Originally Posted by Mac View Post
    Mine are ziptied to the roof bars at 7 foot and never move, just let the plants grow into them. But these are quantum board lights, bar lights will need to be lower etc etc.

    what style are your lights?
    I have 2 lights in my 4x4 which are both Spider Farmer, but they're different wattage. SF2000 which is 200 Watts, the other is SF4000 which is 450 Watts.

    I start out at 36" from the tops - Seedling to midveg, then in late veg I lower it to 24" and in flower I start at 22" then down to 18". With earlier grows I was able to go lower than 18" but I'd watch for curling of leaves and possible burn marks.

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    I always wondered if the LED manual was "the guide" to follow. All the professional grow room tours show their LEDs fixed at ceiling height. Photos of grow closets and rooms seem to have their lights also at the ceiling, but those room appear to have 7' to 9' ceilings. Where as professional grow rooms are anywhere from 15' or higher.

    LED PAR tests on YouTube report on popular vendor LED par ratings, showing most put out more than enough par, some at higher than needed ratings, LED height never comes up as a topic with these tests so it got thinking should LEDs be managed at each phase, or just fix it to the safest height height (heat/fire risk) of your tent roof.

    Please share your thoughts and how you use your lights and if you adjust at different growth stages.

    Thanks,

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    I've done some reading - others with more grow experience may disagree.

    There's a number of factors that drive how you have your lights.

    1. Light PAR capability
    2. Length of time the light is on
    3. The size of the space you're lighting
    4. Your light spread
    5. The distance the light is from the camopy
    6. The plants

    So it's all a balance between all of those.

    Moving the Light
    As you raise your light, the inverse square law kicks in and your PAR decreases so you need the light stonger or the light on for longer so your plants get enough light. If you can't provide enough light this causes stretching and can cause "airy" bugs during flower.
    If you lower the light your PAR goes up provided you keep the light output the same. This can lead to too much light and you get light burn (very very easy with LED's)

    Changing the PAR of the light
    Exactly the same as moving the light, the higher the PAR, the further away you can have the light but high PAR runs the risk of light burn. Lower the PAR the closer you can have it without risking burn

    Spread of Light
    So every light and every manufacture publish PAR charts that map out the PAR ratings in the typical use case of the light in question. So if the light is sold as a 2*2 light, you'll generally get a chart that shows PAR testing in a 2*2 space. With a perfect light, you'd get an absolutely perfectly uniform PAR measurement for the entire area. This means all parts of the plant are getting exactly the same PAR. Very few lights provide this and generally, the cheaper the light, the more inconsistent the light uniformity is. Shane over at Mygro has a fantastic set of light comparisons where he's measured the PAR and shows how good/bad certain lights PAR uniformity is. That said, even though lights like the Mars TS1000 don't have a very uniform canopy, they are cheap and still grow some fantastic bud for many 1000's of people.

    The spread is also affected by the height of the light. Most lights have a 50 or 60 degree wide beam so ids the same is large and the light is low, it's not going to get out very far.

    Which leads to...

    Size of Space
    The smaller the light, the tighter the spread and the less light you'll get at the edge. You can run a 150W light in a 4*4 and right in the middle 1*1m you'll get great light, but at the tent walls you'll get very little light at all. So your light needs to have enough PAR and enough spread to ensure it reaches out to the edges of your space. The more uniformly, the better.

    Lastly

    The plants
    Every plant has a different capacity to deal with light and it also depends not only on the strain, but also the stage it's at in the grow.

    DLI
    The preferred way to measure lighting these days is DLI - Daily Light Integral. This is a number that is derived from the reading of the PAR at the canopy to and the length of time you have the light on. The "ideal" DLI changes through the grow (roughly 10-15 seedling, 25-40 veg, 35-45 flower) but it's VERY dependant on the plant as to how much light they can take. This should always be your preferred way of measuring your lights for your grow because it factors in how long you have light on for.

    Bringin it all together

    Everything is a balance. All that's really important is that your plants have enough light for the stage of grow they're at. I've not read anything about whether it matters whether you change the height or the intensity (dimming) accepting that your lights are appropriately sized for the space you have. I prefer to have the lights closer and the intensity lower as that saves me money. Depending on all the other factors YMMV though.

    MJ

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    Quote Originally Posted by ToughCall View Post
    Hey there,

    question is on lighting, LED height from top of plants..

    What height do you keep your LEDs while in Veg, and when they are in flower?
    Are they the same distance, and adjusted as the plant grows? Ex. Led is 22" from canopy top. No matter the stage.

    Thanks!
    I'm still learning about how to properly use LED's and light intensity in general, but in my current grow I'm following the DLI guidelines that MadJohn cited in his source. Seems to be working so far but i'm still experimenting

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    I'm still new to LED too so all info welcome. I'm still trying to judge distance and what percentage to put them on but I've seen that in early vege you have to have it at the highest and on low wattage setting I'm using a lumatek zeus 600w pro 2.9 but still unsure. I know v8 uses the spider farmer he's probably your best guy to ask

    Sent from my SM-F711B using Tapatalk

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