4X4 LED question yet again. How much is enough?

Discussion in 'LED and other Lighting' started by MLS007, Feb 26, 2013.


    MLS007 Member

    I need to ask a question and I have searched all over the net and can't find a definite answer. I have a 4x4 grow tent. I am using LEDs but I am not sure if I have enough lights. For right now its okay as I am just in the seedling phase. I am growing 15 seedlings. My expectations are that a few will die along the way and then 1/2 will be males leaving with me about 5/6 plants. I am currently using a 200W LED (3w x 90 something) and a 90W LED (1w x 90). I have ordered another 200W LED. These are all no name using BridgeLux. So far the 200W + 90W seems enough for now. As these seedlings go into veg state do I need to add in the additional 200W and how much do I need for flowering stage?

    Any advice you have is greatly appreciated. I do not have access where I am to any namebrand LEDs. I have access only to the no name LEDs.

    509Zman420 Active Member

    It really depends on how may plants you plan to have in there... If you plan to fill it up then I would recommend no more than 40watts per sq ft (4x4 16sq ft time 40 w=640 watts) I run 780 watts in a 21 sq ft area... Any more than 40 and you are diminishing production. There is only so much light a girl can take ya know. Hope this helps

    Snafu1236 Active Member

    Disagreed. Load em up. Invest 50$ in a simple lumen meter. Though not accurate in reading LED, it will give you a fair judgement in light intensity and will allow you to be able to 'back off' the lights if ti proves to be too much. This is not a professional way of doing things, but a very simplistic method that works.

    With LEDs my concern would not be as how much wattage is enough (though of course this is an important factor), but more so that your LEDs are providing a proper coverage of your canopy.

    jcmjrt likes this.

    jcmjrt Active Member

    You need 40 and preferably 50 watt/ft2 to bloom. You could use more than that (up to 70) but 50 is good.

    I wonder though what you actually have. It sounds like you are stating the wattage the same as the manufacturers do - theoretical watts - and not real watts. When I am talking 40 - 50 watts/ft2, I am talking real watts. For example, you say 90 X 3w but I'm guessing that the LEDs are being driven at 50 - 60% (may be more or less this is my guess but the cheaper the lesser) so real wattage would be 90 x 3 x (.5 or .6) = 135 or 162W and the other would be 90 x 1 x (.5 or.6) = 45 or 54 W so you have a total watts in your tent now of probably 180 Watts. 180/16ft2 = 11.25 W/ft2 so maybe OK for a seedling. When you add the other "200W" unit, it will be about 315 W or 315/16ft2 = about 20W per ft2sq maybe enough to veg for a while. You really should have about 16 X (40 or 50) = 640 or 800 W so you should look at adding about 300 - 500 W of lighting to your space for adequate lighting for bloom. This extra lighting could be fluorescent (CFL or T5, etc). Of course, you could also just grow fewer plants this time around. You'll tend to yield higher quality with less space for the light.

    I also agree with Snafu though, the coverage of the canopy is important. LEDs work like fluorescent lighting in that they grow well what is directly beneath them and a few inches to the side (maybe 6 inches to the side). So look at your lights and judge that too. I'd say that if your canopy is well covered, that you could probably do well with 40 watts/ft2. Of course, if it isn't well covered then more watts/ft2 would be needed.

    You should look at diying LED lights, It's really not that difficult and the lights will be superior. That's the biggest benefit. If you can go know brand, top bin LED then you go less wattage per ft2 because you are producing more light per watt....and the fixtures might actually last unlike so many of these cheap e-bay lights which burn out in a few months. ledgroupbuy.com stevesleds.com and there are more....

    MLS007 Member

    Thank you so much for these comments. You cannot imagine the pains I have searched the internet for these answers. Hope it goes good.

    I talked to the LED factory and they told me that the 200w is the adjusted real 200w

    I plan on getting some of the Apollo either of the two below:

    The Output power of 315w is 567w. The lumen is 2509lm. The actually percentage of Led is 55.6%
    The Output power of 280w is 504w. The lumen is 2327.1lm. The actually percentage is 41.3%.

    I am currently at 490w with two rectangles and one UFO. I figure with one more of these rectangles I will be close too 800w.

    My question is how much do I actually need for my seedlings. I feel that the 490w is border line too much. I have raised them over 16" because the light meter is close to 2000 at certain places. I have included a pic of very newb basic setup.

    View attachment 2544379

    ic0n Member

    Good thread, dont mean to hijack so I hope this stays on topic. Why is the assumption that 90 x 3W LEDs would only be driven at 50-60%? Are all LED fixtures manufactured this way? I wouldn't think there would be much cost savings in having a half wattage power supply. Im switching over from a 150W HPS and 4 CLFs to a 300w triband LED panel for two plants tonight and just curious.

    jcmjrt Active Member

    It is possible that the unit is actually 200W but if it is then the LEDs are being driven at about 75%...which is possible...but I hope the heatsink is good so your light lasts/is on spectrum. The 90 X 1 W is no way making 90W because it is not being driven at 100%.

    The better fixtures tend to be driven at a higher percentage. I'm driving Cree XMLs with a max of 3000mA with an inventronics driver at 2100 mA. I might drive it at a little more but more than 70% tends to start creating heat/longevity issues. 50% is more like what the cheaper e-bay LEDs are driven at with no heat sink and some cheap fans for heat management.

    Snafu really did have a good point.... canopy coverage is important. You will only grow excellent bud directly under the light and a few inches to the side...a foot away and it's fluffy stuff maybe good for making hash. I really try to keep a coverage which is almost complete...maybe 3 inches to the sides. If your LED doesn't cover your space completely, keep the CFLs in the equation for coverage.

    MLS007 Member

    The cheap ones work just fine. No need to shell out3 times the price. The LED life, fan effectiveness and drivers are just fine.

    slitherlygrow Member

    I don't want to hijack either, but I too have a 4 by 4 grow tent. I want to use my 400 watt HPS with two 180 watt LED's. Gotham hydro (an online hydro shop on Ebay) told me that the two 180 watt led's would not be enough for my tent, but in conjunction with my 400 watt will do the job. I am unsure how far my lights should be....Not the hps, I use the back of the hand method there, but how far away do I have my led's? I know they have better light penetration than cfl's or hps, but.........

    mtlhaze Active Member

    Even the Cree unit I have is driven at about 60%. All chips will start burning off the extra electricity as heat and they will burn out much quicker. Forget using them for 10 years, you would be lucky if you get 10 months if they are pushed at 80% or more.

    The bigger and stronger the led's get the more power we will eventually get out of them but the field of high output led's is till evolving.

    I cant wait to see the single chip 5watt leds start taking over.

    PetFlora Well-Known Member

    So much misinfo here. All of you need to stop regurgitating crap (of course you wouldn't know that) and actually study leds from a DIYers point of view as well as investing in LED magazine (available on line). The tech is developing faster than computers. Yesterday's truths are so... yesterday
    Lemon Sour

    Lemon Sour Active Member

    Yeah as soon as we start seeing a wide enough wavelength choice!

    jcmjrt Active Member

    Maybe you should enlighten us with your version of today's truth as I'm not sure what crap you are talking about.

    Snafu1236 Active Member

    So are you trying to help this thread or just troll it?

    Because comments such as these certainly do not help the cause, PetFlora.


    slitherlygrow Member

    So, Mr. PetFlora, kind knowledgable master of LED technology that you are, would you please inpart to this lowly groveling supplicant just how far to hang a led 180watt light from the top of my marijuana plant. I will worship at the altar of your "Tomorrow" Truths..............May your grows be stupendous!:-P

    Beefbisquit Well-Known Member

    ONE BILLION DOLLARS.... er... WATTS.... yes...

Share This Page