How far away should my light be

A

ap25

Active Member
Hey guys, I just planted my first seeds and I was going to put them under a 400 watt mh light. I was wondering how far away from the lights the plants should be. Any help would be awesome.
 
platypusmann

platypusmann

Well-Known Member
Everyone will tell you one basic rule......if it feels hot on your hand, it is hot on the plant. This is mostly true, but I learned the hard way that it is best to start farther away and lower it daily to the optimal range. I have attatched a lumemns chart that will show at what bulb distance the optimal growth occurs. I personally started my 400w MH at 21" above top of plants and after 3 weeks of regular lowering and at 13" with no heat stress at all. Hope it helps!
 

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noturbo

noturbo

Well-Known Member
N.Lights x nightshade said:
2-3 inches
Click to expand...
Are you serious? lol

Id have it about 3ft for seedlings and gradually move it a few inches closer every day untill you are about 12" away and stick to that distance from then on

And please please dont do what N.Lights x nightshade said as you will kill your plants lol
 
dilbo99

dilbo99

Active Member
I'm no expert but i would say 2-3 inches might be a little close using a 400w mh, i would say more like 1 -1 + 1/2 ft but I'm sure someone with more knowledge than me will be along soon to give you some more advice.:peace:
 
A

ap25

Active Member
thanks for the help guys, I had it at about 12 inches away but I thought that might be too close, so Ill move the light highter. Thanks again
 
mrskitz

mrskitz

Well-Known Member
22" above seedlings,,,lower it bit by bit as the days go by,,when there about 2-3 weeks old 12" above um will be fine,a little lower if you have a oscilating fan blowing over the tops of ya plants,,,,,,,,,,,,,,peace
 
DrWatson

DrWatson

Well-Known Member
yea I gotta 1000 watt and it has to be 1.5 to 2 ft away from my plants so I would say at least a foot away probly more like 1.5 to 2 for babies... when mine were little I used cfls for the first week and a half which I think may not be a bad idea at least it seemed to work well for me. Then put the 400w on it that way you dont kill the little things HIDs can be a lot for seedlings maybe, so If you can I'd start em with flourescents especially if your new to the growing thing.
 
timsatx1

timsatx1

Well-Known Member
2 foot should be adequite. look for streching and if you see any sign of it move them closer
 
joker152

joker152

Well-Known Member
depending on the temp of your room i would put them a little closer. the closer they are the more light they get so as long as they arent gettin your plant your all good
 
J

jollytime

Well-Known Member
i thought i was burning them but it was the nutrients i am growing 3 types, some are not as tall as the others, how do i judge hight
 
daz321

daz321

Active Member
hi, how can i lower the temp in my room?
i have a 400w hps about 15" from my plants,
i have a 4" fan extracting hot air through the roof,
i have another 4" fan bringing coldair in from outside,
and another 4" fan just blowing air round my room plus a fan heater blowing cold air at my light,
it is 92.3f at the moment and my lights go off in 40 mins.
any ideas would be great!
 
Sheepdog420

Sheepdog420

Well-Known Member
The rule of thumb is to put your hand at the plant's canopy for 30 seconds and if it's not uncomfortable, it's fine for your plants.

Daz321, My urge is to not comment, since you should have started your own thread...

My advice is to make sure you're not taking temp readings in direct light. Look up Ambient heat vs radiant heat. That may be your issue since your ventilation sounds good.

Sheepdog
 
AcidBurn901

AcidBurn901

Well-Known Member
noturbo said:
Are you serious? lol

Id have it about 3ft for seedlings and gradually move it a few inches closer every day untill you are about 12" away and stick to that distance from then on

And please please dont do what N.Lights x nightshade said as you will kill your plants lol
Click to expand...
I have to agree, a MH light, 2-3 inches?
your asking for burnt plants.
 
daz321

daz321

Active Member
thanks sheepdog, i've took your advice and im gonna read up on my temps now and sorry guys for butting in on this thread i did look for how to start my own thread i did it the other day but cant rememeber how i did it,
 
miko

miko

Well-Known Member
On a further note, every inch you move your light away decreases lumens. So remember,keep those lights close.
 
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