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??? watts per sq feet

Discussion in 'Indoor Growing' started by healthy_ganjaForest, Apr 3, 2007.

  1. healthy_ganjaForest

    healthy_ganjaForest Registered+

    I use to know this but lost my knowlegde of growing for sometime now. thats why Im back in here! :D If anyone knows could you pls tell me? this is for veg stage
  2. xcrispi

    xcrispi Registered+

    50 if im not mistaken = use the search function of the site
    Crispi :jointsmile:
  3. bongerstonerd00d

    bongerstonerd00d Registered+

    I veg under 2 T5 4 bulb flouro's, and they are ummm......52 watts a bulb I think so thats 208 watts per light, and my veg area is 4x4 so thats uhhhhh.......416/16=26 watts sq/ft and my plants are happy.

  4. postmandave

    postmandave Registered+

    A general rule of thumb is 50 watts per sq ft with a minimum of 25 .i also use 6x58 wat T12 fluoresant tubes for early stage of veg and clones in a 5ftby3ft area works out around 23 watts per square feet and these work fine up to 3 week veg then struggle after that.the postman.
  5. BlazeIdo

    BlazeIdo Registered+

    I would think the answer would be different for flouros and hid.
  6. Deejay2163

    Deejay2163 Registered+

    Nice avatar Blaze.
  7. Dr.Hashman

    Dr.Hashman Registered+

    I just caught myself staring at his avatar for like 30 seconds...
  8. faithlessxxx

    faithlessxxx Registered+

    That seems strange...4*6ft makes 24sqf, right? and that would need 1200w???
  9. postmandave

    postmandave Registered+

    Strange but the average can be done with less but if you want the buds then give em the light when flowering i use 1600 in an area that size
    A very general rule of thumb is that your garden needs 50 watts of HID lighting per square foot of illuminated area. This rule ignores the shape of your garden, so the following is really a better guide:

    A 250 watt HID will illuminate a 2' x 2' garden.
    A 400 watt HID will illuminate a 3' x 3' garden.
    A 600 watt HID will illuminate a 3.5' x 3.5' garden.
    A 1000 watt HID will illuminate a 4' x 4' garden.

    From Jackerspackle, here's a different take on watts-per-square-foot/meter (WPSF).

    WPSF assumes that the bulb's intensity is equal over the entire grow area.. in other words each square foot/meter receives the same number of lumens. But in reality light diminishes rapidly the farther you go from the bulb (1/4 the intensity for each doubling of the distance). So each bulb has a limited range, beyond which you do not have good growth.

    For example, a growspace that's 2 x 10 feet would require 1000 watts if you go by the 50 WPSF guideline that's commonly mentioned.. But a 1000 watt bulb only covers an area about 5 feet across - meaning the edges of your garden will be dark.. A better choice in this case would be three 400s or two 600s.

    Another problem with WPSF is it assumes all bulbs have the same intensity. But 1000 watts of HPS is not the same as 1000 watts of fluorescents or (yuk) incandescents. Fluorescents have their lumens spread out over a long tube and are therefore dim.. incandescents have the wrong color spectrum and are also dim.

    Nor is a 1000 HPS the same as four 250 HPSs.. 250s don't have anywhere near the intensity needed to penetrate thick canopy or tall, bushy plants. (Don't even think about growing meter-tall plants with a 250.)

    I could go on, but here's a basic guideline for lighting a growspace for good growth using common HIDs:

    1000 watt - 4 to 5 feet across (1.3 to 1.5 meters)
    600 watt - 3.5 feet (1 meter)
    400 watt - 2.5 possibly 3 feet (.8 to .9 m)
    250 watt - 2 feet (.6-.7 m)
    175 watt - small, less than 2 feet

    These numbers assume you have a good reflector around your bulb and also reflective wall coverings. You can increase the figures a bit if using multiple bulbs, due to their overlapping effect. You can also increase coverage using a light mover...

    I know this won't put to rest the old WPSF idea, but i hope it shed some light on the subject. the postman.capj
    Last edited: Apr 5, 2007

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