LED question...

Discussion in 'Hydroponic Growing' started by birddog1971, Mar 3, 2015.

  1. I've tried to decypher all there is about LED and it has left my brain fried. Simply put, I have a 3' x 2' x 1.5' grow box. What size LED should I use? ImageUploadedByGrasscity Forum1425414075.891978.jpg ImageUploadedByGrasscity Forum1425414144.061914.jpg


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  2. No, that was just a pic of the box. I am currently using 2 100w CFL's.


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  3. It's doing well under the 2 CFL's in a DWC. Had some problems early that I rectified.


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  4. #5 DazedAndStoned, Mar 4, 2015
    Last edited by a moderator: Mar 4, 2015
    You want about 50+ actual watts per square foot for flowering and about 30+ for veg for optimal results using LEDs. Most lights will draw about half to 60% of advertised wattage, so adjust accordingly

    You have 6'² so you want around 300W pull if you have the ventilation to do so

    My LED flower cab is around 5'² and I have 540W of UFOs in there, and they draw about 300W. The more light the better, I run 1W diodes so I don't have to worry about bleaching unless the plant gets out of control and touches the lenses


    My other cab is around the same size, just taller and I run a 400W HPS under the same ventilation system and my temps are stable at 78. More light the better in most cases :)
     
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  5. Personally, I don't understand the concept of less wattage / square ft for veg than for flowering.
     
    In nature, plants get more light intensity during veg months when the angle of the sun is more perpendicular than during flowering when the angle of the sun is more shallow (less intensity).
     
    Plants are a lot smaller in veg than they are when they finish flowering, so vegging plants can be put closer together and grown in less space.
     
    Just as a general example (not saying that this is THE combination/ratio to use), lets say you vegged in a 2x2 space with a 250w MH and then moved them to a 3x3 space to flower with a 400w HPS.
     
    That would be more than 50w/sq ft for veg and less than 50w/sq ft for flowering.
     
    So, doing split cycle harvesting using 250w / 2x2 for veg and two 3x3 tables with 400w HPS for flowering. Veg each batch of clones for 3-4 weeks then move into one of the flowering tables (taking clones during veg for the next batch). The tables are staggered 4 - 4 1/2 weeks apart (for 8-9 week flowering cycle).
     
    That's using 250w for veg and 800w for flowering, and still having more watts/sq ft in veg than in flowering, and 4 sq feet for veg and 18 square feet for for flowering.
     
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  6. Not to argue, but to point out my personal experience.
     
    True: Cool spectrums (typically used in veg) are more intense.
     
    I have vegged strong and healthy plants with < 25w/sft, but I mix 3500/5000 ~ 1:2
     
    Currently, I am wondering if I need 300 flowering watts (strong reds) for the final 3-4 weeks in a 19 x 19 x 19 space, or will 150w be more than sufficient?
     
    If yes, I could move one SS 150 over my babies, which are currently under 2 ufos (~80w) in a 2 x 2 space
     
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  7. #8 DazedAndStoned, Mar 4, 2015
    Last edited by a moderator: Mar 4, 2015
    I'm trying to follow along with what you said. But I honestly have no idea how you went from a 2x2 room with 250W and a 3x3 room with a 400W to 18'² and 800W. What!? Did I miss something?

    If you go by your original statement, there is
    62.5W a square foot for veg
    44.4W a square foot for flower
    That is a flawed system design, and I know most if not all growers would catch onto that, and up the lighting.

    The whole point of growing indoors is to grow the biggest bud you can which is why we typically give more light during the flowering period, because more light will equal more sugars for the plant to use when producing her buds. We can't use the sun indoors so we give as much light as possible without bleaching. The first two weeks of flowering is some of the most important growth because she will go from growing roots and stretching like a bitch, to only worrying about producing flowers and seed if she was pollinated, and starts producing sugar leaves all around the bud sites.

    Here is a better ratio for the same sized cabs, so wattage per foot is higher than the veg cab:

    In a 2x2 veg room, 150-200W would be 30+W would be sufficient for veg, and in a 3x3 room a 450W would give you 50+W for flowering. Again, the higher those numbers, generally the bigger the plants and the more buds you get to smoke


    My next lighting upgrade will allow for 60+W for veg, and 100+W for flower to see how much more I can get from my cabs, but if you can reach half of that, you should be able to see some good results. As long as you can get 40-50% more light in your flowering cab than the veg cab, your girls will will be thanking you by growing like a weed. I've noticed that with slightly more light your plants will go from growing at a decent rate, to holy crap this plant has grown a couple inches in a day! Combine with a perpetual type setup and you can be harvesting every two weeks if you have the space
     
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  8.  
    I apologize. Some how I got this thread mixed up with another one, and I was thinking that this was about a veg cabinet. I realize now that it's about full cycle growing in a small space.
     
    Anyway, the way I got from one 3x3 with one 400 to tow 3x6 with two 400's is that one 2x2 veg area can provide plants for a 3x6 flowering area if you split the 3x6 into two split cycle grows and veg for half the flowering cycle. With 250w for the veg, you can veg clones for 3-4 weeks in 2x2 and they'll be big enough to fill out a 3x3 area during 12/12 (in my experience).
     
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  9.  
    I agree. Vegging plants can be kept healthy with lower light levels, but you get slower growth rate. Sometimes that's what you want if you have to keep plants in veg for an extended time without them over growing the veg area. That's why people usually use low watts/sq ft to keep mother plants.
     
    If you think about it, plants grown outdoors don't get as much light intensity during the early spring months but they are still healthy. They grow more vigorously though in mid summer when the light is the most intense.
     
    I like to use more than 50w / sq ft for veg so they grow faster so I can supply two flowering tables from a small veg area.
     
  10. If you can control temps (5 watt led bulbs get hotter than the 3 watt versions) then put as many as you can man.
     
  11. #12 GoldGrower, Mar 6, 2015
    Last edited by a moderator: Mar 6, 2015
    That low height is something to consider so I would use a unit with 3w diodes because for the same overall wattage you get a better spread compared to a 5w.
     
    For a 2'x1.5' area I'd be looking at about 200 actual used watts, but with the low height you probably don't want to go much higher than that.
     
    As always I recommend mars-hydro because they are pretty much the best value and I use 3 of them and they work great.
     
    I would choose one of these...
     
    http://www.mars-hydro.com/led-grow-light-100-3w.html
    http://www.mars-hydro.com/reflector-led-grow-light-96-3w-99.html
     
    the reflector version has a vegging switch so you can cut out many of the red diodes when vegging. Plants don't need as much light when small so having all the diodes lit can be a bit of a waste. Plus LEDs can knock a seedling and clone over if the light is too intense. I prefer to start seedlings with a small CFL for the first week anyway 
     
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  12.  
    He has 3 square feet, not 6. 
     
  13. #14 DazedAndStoned, Mar 6, 2015
    Last edited by a moderator: Mar 6, 2015
    OP's cab is 3' x 2' x 1.5' which is 6 square feet, please recheck your math lol, can't have just as many square feet as it is wide unless length is 1'. Unless the original post the dimensions are different? I'm just going by then original statement of 3x2x1.5 lol. Then again I'm stoned

    Length x width= square footage
    2x3=6:²
     
  14.  
    Height=3'
     
    Footprint is 2x1.5
     
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  15. Ahh my apologies

    So for meeting basic requirements 90W will give ya 30W a foot for veg and 150W for 50W a foot but I personally would double that in such a small space if you have a 4" fan cooling it or something
     
  16. Keehs, you gave me the answer I was looking for. I am going with the 96 x 3w. Spoke with Forrest @ Mars Hydro, he is giving me the best price. The ole girl is looking great under just the two 100w CFL's.


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  17.  
    Good choice, its what I would have gone for too. You should get a few oz of that. The plant is looking good man, what strain is it? 
     
  18. Caboose! I just topped it. Beginning stages of Scrog. Almost killed her early. Learned some valuable lessons from some experienced growers here.


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  19.  
    Daaaam, you did well to pull it back from that man. I would have recommended to start again lol 
     

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