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HPS Distance from Plant

Discussion in 'Newbie Central' started by Lestat2888, Mar 6, 2008.


    Lestat2888 Active Member

    Hey, i was wondering how far the distance of HPS lamps, 400 watt, should be from plants throughout the grow process. I am just starting now, what should my seedling distance be, vegetative and flowering distance. i am going to use the hps light the entire time.

    willRavage Well-Known Member

    I was told always 12 inches but no further than 16

    johndoh610 Active Member

    I'm using a HPS for my whole grow, and my light is about 16 inches from the plants. They are currently in the seedling stage and looking very good. Just put your hand under the light if it's too hot for you, it's too hot for the plants. As far as the vegetative, and flowering I don't have an answer yet. Good luck.

    KAOSOWNER Well-Known Member

    Best rule of thumb for lighting is to put the back of your hand above the tallest part of the plant for a minute or so if your hand gets hot the light is to close. Also remember that your plants can grow several inches in a day

    smokee Active Member

    my husband and I are using a 400 hps for our first grow also. we have two that are 2wks and 11 that r 1 wk we had the lamp to close at first n sort of scorch the leaves, when we realize this we moved it up to about 10 ins to see if that help, yes it did. they began to grow again n open up whew they survived. now the lamp is about 12ins from 2wk olds and 15ins from seedlings. just watch ur plants, they will tell u when something is wrong remember the light is a good one, so keep it high.:weed:

    stickyicky77 Well-Known Member

    According to Jorge Cervantes a 400W HPS puts out 50,000 lumens at one foot and at two feet it puts out 12,500 lumens. He recommends between 12 and 24 inches. In his newest grow DVD he was saying 18" and all of the gardens he showed looked like they were doing well at 18 inches above the plants. I have been keeping mine at 18 inches and my plants have been doing well. I guess the size of space you have and how well ventilated it is will be a factor as well.
    AutoNorCal likes this.

    Lestat2888 Active Member

    So is the heat from the lamp more important than the intensity of the light when it comes to burning up plants?

    firebrand18rjr Well-Known Member

    keeping a room/closet at a steady 73-80 degrees with a lamp a foot away is ideal . and a must is good humidity. spray the plants but careful not to hit the bulb.

    bigbrew Well-Known Member

    yes but dont ever ever spray while the lights r on. I did and burned my shit.

    ~MacLee~ Member

    Yea thats what i do, i got some rhino's going at the moment, and my 4 double o is right at 9 inches from the tops of my gurls with no stress what so ever. I keep a fan like 3 inches away from the bottom of the bulb blowing the heat up and away from the tops of my gurls...

    mjr99 Well-Known Member

    wouldnt you want the light as close as possible as long as it doesnt burn the leaves? I keep my air-cooled light about 7-8 inch's from the tops and my girls are blowin up.

    LUDACRIS New Member

    h.p.s. Lamp height guide.

    dont burn them


    tusseltussel Well-Known Member

    ive been useind a 400w hps for about5 years and i keep it 12" away, i usually will move it up to 16 and let the plant grow til its no closer than 8.
    sixe of the room matters too. if your covering a 3x3 room and your light is 8" away from tops chances are the tops toward the outer edges are in the dark and if you rais the light a few inches the lights foorprint will cover the even canopy you should have

    immaking3 Well-Known Member

    ya right now i got them at 15"
    new guy25

    new guy25 Well-Known Member

    I got my 400 hps light at 8inch from mine no cooltube and no sign of stress and growing fine I go by this tabe So why is everybody saying a 12" to 18"???? Its my first grow and now wondering if its to close and could be growing faster grrrrrrrrrr

    smallclosetgrowr Well-Known Member

    30 cms , 1 foot

    riddleme Well-Known Member

    Well I just started a new grow (Balls to the Wall sig link) using a 400 watt CMH and currently it is 4 and 1/2 feet above my seedlings (which are starting to pop) you will see in the pics that they are getting 5000 lumens, the light meter only cost $29 and is one of the best tools you can have to truely understand lights

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    NBKA Active Member

    10-12" away, use a high volumn fan to cool.

    dirtyoldbastard Member

    I put my 400 W HPS to close I got great looking buds but they had no THC keep your lights 18 inches away even if you have a cool tube like me

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