How much space between crop and 400W HPS?

[forget]

i think i have been too agressive with lighting by putting my 400W hps 1ft or so from crop while vegging.

how much space is the norm?

 

[King Bud]

This recommends 1 foot. But I guess that didn't work

 

[Mr. Bubbles]

Is it enclosed? I to think I have been to aggressive with my HPS. I am playing it very safe with the latest grow. I can't make any recommendations here :/

 

[sweetnug]

The biggest ? is, is it air cooled?

 

[forget]

yes air cooled outtake. temp around 75-79.

 

[headband]

well is it burning the leaves? air cooled, whats the temp under the light, not the room temp... 1 ft seems a little close but its air cooled. i would try to lower your temps to 70-75 at the tops of the plants... i used a 400hps not air cooled and had to keep it 2 ft away at least.

 

[lowrydergrower775]

id try maybe two feet i keep my 250 watters a foot from the top of the plants so i think it would be almost double for a 400 watter just a guess

 

[Puffin Afatty]

a 400w is effective from about 8 inches to 22 inches, closer than that and you burn, and farther and it's of little value to the plant.

 

[headband]

farther and it's of little value to the plant.

i had mine farther than 22- and she soaked up the light and has dense insane nugs

 

[forget]

i had mine farther than 22- and she soaked up the light and has dense insane nugs

according to MP.com 400W should be set at the highest level in a closet. 8inches... didnt work for me, its burnt the baby.

 

[POTUS]

16-18 inches works perfect for me. Neither of my lights is vented. My grow room door is always fully open with a pedestal fan blowing in on high from about 3 feet away, pointed at the lights. The room stays at about 75-85.

I'm told by friends that my bud is always the best they've ever smoked. I agree.

Closer than 16 and I see damage starting on the leaves. Further than 18 and I notice a slowing in growth and the leaves start reaching.

You have to also consider that every grow room is different from every other grow room. Even in the same house, the rooms will have different characteristics.

Overall, the floor type, wall type, RH, fan pattern and speed, media type or mix, root health, heck, almost everything can affect how your plants will react to the conditions in your grow room.

There are boundaries. Over 90F or 33C degrees and more often than not, you're going to have problems.

Root Drowning. Everyone has done it.

Lights too close and plants turned into mummies.

It's an exact science in a laboratory, not someones house.

 

[BluntFullOfKush]

i have my 400 hps 8-12inches from the tops and mine not air cooled

 

[Mr. Bubbles]

A lot of different responses so I will chime in with what I have tried and am currently doing. The last grow 2 WW I ran close 4-8 inches with around 40 degree air through the hood. HUGE colas but the leaves are burnt and U curled. This grow I will not let anything get to 8 inches and want to average at least 12 - 14 inches away.

Here comes the crazy talk to be translated by someone less noobish. Ok I recall reading several articles in years past about what I think was radiant heat or energy that was omitted from the HID. I remember reading this existed no matter how well you cooled the hood and vented to room. This energy / heat will burn your plant, does this make sense to anyone ?

I have no doubt I could pull 65 degrees at four inches under the hood and it would still burn my plants. I ran the setup really hard during the WW to get the cola's as close as possible. I will not be as aggressive this time through.