400w users, how far from tops is your light?

18"-24" is what I shoot for but every strain is different. I have had a couple tops on the perimeter grow right up to the edge of the reflector and it took two days before damage. I also have a floor based voranado fan set back enough so the whole plant and hood get a gentle breeze.

 

Mines around 13-15" away. No negative effects so far

 

I find that while there young I like to keep it 20-24" from plants, as they get older I reduce it down to 16" and of course near the end usually I'm down to 8-10", closer than that and the buds start showing heat stress. Of course its just fan cooled.

 

Rule of thumb is to find the right temp from the bottom of light to the top of plant.....The right temp is '80 F or 27-28 'C find that and you will have no prob..
good luck....

As long as you have a breaze going across you plant tops you will be fine...

 

14"-18" is about right any closer could start to give stress or burn. A 400w is enough for 4 flowering plants. Anything smaller you want to stay away from as you are having the problem keeping both plants under full light. Keep Air flowing in the room and check room temp.

 

Dr pot, how long you been growing indoors? I sounds like your spewing out dribble that you have read. Its real simple, seaofgreen is right, also good rule of thumb is if it not uncomfortable when you place the back of your hand just above the top of your plants for 30 seconds, then it is ok. As for how many plants you can grow under a specific light, it is determined by the growing method. Truth is if you grow one big enough 400watts will not suffice for even one plant.

 

I grow 3 very well and 4 in a tight squeeze under a 250w HID, so 400 is good for 5-6 plants in general. Agree it does depend on the strain, trimming/training, room conditions, veg time, etc.

 

hahahhha, i have 8 under a 400 watt. we'll see how it goes and ill let u know. strain is 99.9% feminized white widow.

 

The ammount of plants has to do with their size. If they are bigger you can bud out less, but if they are real small you can do more than 8 under 400 watts. As far as how far the light goes, to me it depends on what stage. When I first pull them out of the cloning room (under flourescents), I put them under a 400 hps (son-t-agro) to get bigger and give the other crop time to finish. When they first go in the 400 room I keep the light a good distance away. Slowly they get closer and can handle more intense light. Then they go in the room with the 600 (again hps son-t), where they bud. They are about 3 feet away from the light at first, but when they are done, they are only about a foot and a half away (sometimes even closer). I use strong fans so the tops dont burn.

This is how my system works: First I have 4 mommies under a 150 hps (just a standard regular store bought thing - It has a built in grow type ballast and hangs horizontally, but the bulb is nothing fancy). From there I cut clones and move them under this fluorescent light that I have had for years. It has 2 of the circular types on it and is about 2 and a half feet long. I root the little girls under that for a couple of weeks. From there they go to the room with the 400 for about a month of veg. They are solid stocky little bushes then and I move them into the room with the 600 when that crop is done. Then it is around 60 days under the 600 (I used to add the 400 in there for the very end - but I found that the heat kills me, and that I do better when I leave the 400 on the ones that are about to be budded, instead of bringing them under the 600 straight from the flourescent room). I have a never ending grow this way and it pretty much stays this way unless it is late winter/early spring - that is when I get the ladys ready that are going outdoors, so the indoor budding stops for a few months. I have 2 different strains that I have used for the last few years and they keep getting stockier and stronger. (I only use clones now - no more seed steps at all). Every once and a while I trade some clones with buddies and bud some other stuff but usually I just grow their stuff outside. I like my strains (a berry cross and the other is a hash/widow type (I say type because although they were started from real seeds they have been mixed quite a bit, especially at first). I think because the mommies have been under the same hps for so long that the plant responds to hps better, and that is why I dont use mh for vegging (I used to have a conversion set up instead). I do use son-t so there is blue given to the plants, but I for one have used plain 600 hps from start to finish before, and had the same or better plants then when I switched to mh for vegging. So to all the people that think that you cant only use hps, do whatever works for you, cause this works for me. And one last thing, I always am buying new bulbs, especially for the 2 bigger lights, because that is the key. Lights lose their brightness very quickly (especially when they turn on and off - faster then just running them 24). Oh yah and everything is on 24 except the bud room (12/12 and I switch to 10 on/14 off for the last 3 or 4 days). And I stop watering for at least a week before I pick, because I have found that they are like a sponge, the more water you give them before harvest, the more weight they lose - where if you dont give them water before harvest, they lose very little weight. (The same goes outdoors, try to harvest after a dry/warm period - you avoid mold this way too - better to pick them after a warm/dry period and lose a few days of growing, than to let them go a few more days and get soaked with rain).

 

My 400watt is 12 inches from the top of my plants now. And I can tell a huge difference in growth compared to when it was 18 inches away. If yo ucan keep your light/top of your plants cool, then I recommend 12 inches.

 

i have 1 400HPS and a 400MH under the same hood....
the glass under the lights is 1/2 inch thick tempered glass this keeps the temps around 76 degrees 5 inches below the glass..... thats where the tops sit in my closet...