Need help with 400W MH Height for seedlings and temp control.

I have my 400w MH 4 feet from my 1 day old seedlings and they seem to be streching pretty fast. In a few hours it has sprouted and grew 2 inches. Should I move the light closer?

I have a fan in there right on the bulb but the room/soil temp is about 85 with my closet door open...obviously I cant keep it open all the time. I really wanna stay with the 400w but I have to lose the heat soon. Any ideas? Is 85-95 too hot?

I plan on doing a journal on this once I have more pics and info to share.

Thanks
DBB

Staying awake watchin temps... I need some help.

I had the same issue, i got a 400 watt mh thats vertical hanging lamp. Im not no expert,but if u have a small space hang it 4 feet above and use mylar on everything and itll work, if u look at my post in the hydro section..first...all my seeds r growing under a 24 hour mh 2 feet away i can do this cuz my space is 8x10 and alot of free moving air..MH makes alot of heat,which im sure u know,and i use to have it in a closet but either they stretched or fell over dead from the heat or moving it to close. Were i am which is midwest close to you i use my light for the heat too and it keeps my room at 71 degrees.

i think 85-95 is too hot. 4 feet with a 400 will make em stretch. you gotta get a fan to pull the heat out of the closet.i made a hood for my 400 just for that reason and once i put it in my box,it was a 2'wx4'hx4'l , i was able to get it very close to the plants at 78f the plant in my avitar was under a 400 for all but the first few weeks. and at the end it was about 4" from the tops. good luck

yes..above 87degrees you start to loose... my care giver thinks close lights makes herms .... i dont know about that, but what I have read is close is good as long as they dont burn... its the heat thats kills, if you hold your hand under the light and it dosnt burn after a minute, then thats how close you can place your pants... if you feel a burn/to hot, to close...

funk ya said:

yes..above 87degrees you start to loose... my care giver thinks close lights makes herms .... i dont know about that, but what I have read is close is good as long as they dont burn... its the heat thats kills, if you hold your hand under the light and it dosnt burn after a minute, then thats how close you can place your pants... if you feel a burn/to hot, to close...

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Perfect advice, back of the hand test is perfect to tell you if its too close.

4 feet from a 400 watt is way way to far away.

My flower room atm is 400 watt HPS, with an air cooled hood, and my 5 flowering ladies are less than 1 inch from the glass.

I use flouros for the first couple weeks and then to the metal halide. I start 2' away with the MH and slowly move it closer as the plants adjust. My fixture has tempered glass and really helps cut down on the heat. I eventually get the light within 12" of the canopy and about 10" when they are mature and well adjusted.

Dirt Bikin Buds said:

I have my 400w MH 4 feet from my 1 day old seedlings and they seem to be streching pretty fast. In a few hours it has sprouted and grew 2 inches. Should I move the light closer?

I have a fan in there right on the bulb but the room/soil temp is about 85 with my closet door open...obviously I cant keep it open all the time. I really wanna stay with the 400w but I have to lose the heat soon. Any ideas? Is 85-95 too hot?

I plan on doing a journal on this once I have more pics and info to share.

Thanks
DBB

Click to expand...

Dirt,

My seedlings spend the first two weeks of their life close up under (2 to 4 inches) a standard fluorescent shop light fixture before they get moved under my 400W MH. And I like to keep the temps between 65 to 75. At the higher temps you're talking about under a 400W MH that's 4' above them you're going to get some really stretched out lanky seedlings.

And you're going to have to figure out something to get the heat vented out of your space. Even when they're bigger and stronger I never like to let my plants see anything over 80 degrees. I don't know your situation (apartment/house, rent/own) but until you get something figured out to deal with the excessive heat a 400W MH generates your best bet might be growing with some flourescents (because they generate less heat).

I had the very same problem with my 400W MH light when I started out. My solution ended up consisting of moving my ballast to the attic (I've got an 8' cord between ballast and light), installing a bathroom vent fan in the ceiling of the closet ($110 from Home Depot) and modifying my light fixture's enclosuer to except a 4" flexible drier vent hose on either side that's run up thru the ceiling. I've got a 4" inline duct fan that sucks air thru the light fixture and exhausts it up into the attic.

But still, even though I can keep my temps under control in my grow space I still like to have my seedlings under flourescents for the first two weeks. I end up with shorter, stockier, healthier plants that have way closer inter-node spacing than if I just put them under the 400W MH from the beginning.

Jack

kato420 said:

I had the same issue, i got a 400 watt mh thats vertical hanging lamp. Im not no expert,but if u have a small space hang it 4 feet above and use mylar on everything and itll work, if u look at my post in the hydro section..first...all my seeds r growing under a 24 hour mh 2 feet away i can do this cuz my space is 8x10 and alot of free moving air..MH makes alot of heat,which im sure u know,and i use to have it in a closet but either they stretched or fell over dead from the heat or moving it to close. Were i am which is midwest close to you i use my light for the heat too and it keeps my room at 71 degrees.

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kato,

Back 7 or 8 years a go when I first started out I was doing my veg under 24/0 lighting. I did a couple of crops this way and was kind of proud of myself for being able to do a grow in around 110 days (from seed in dirt). I was getting some fairly good smoke and thought I was getting everything pretty well dialed in as far as growing goes.

But then I got talking to a more experienced grower who recomended either 20/4 or 18/6 as a better light cycle for veg. I tried it on a crop and the results were indeed much better. I'm getting a lot better root system and a lot shorter, stockier plants that have much closer inter-node spacing. The final yield has been significantly increased also.

You might want to consider trying this out.

Jack

Thanks for all the replies!

Here is my light and ballast. I want to get a cooltube with a fan and vent duct but my ballast has no plug for it. Can I just hard wire it myself?




As for FL I only have a few 24" 5.0 UVB reptisun 17w. Will 2 of these be ok for a few days until I get some ventilation for my MH?

Thanks
DBB

If anyone was wondering I changed the 400w MH to my 400w HPS. It made a huge difference in the temps. I have the light about 2 feet from the tops now, I think they are done stretching. I will keep everyone updated!

I don't think a 24" 17w tube would have done much good.

Once I get my seedlings are growing right I will start a journal to try and help spread what I learn and experience as I go.


Thanks
DBB

I am stumped... they seem to have all stopped growing since the HPS. WTF Im switching back to MH and messing with an exhaust but IDK if I can cool it.

Will a 17w 5.0 UVB hold me over a couple of days?

Do cooltubes make a big difference with an exhaust fan?

Well I found a partial solution! If I keep my window open and let the cold in my light fights it off and the plants are at 75-80 with the light 2' from the tops.

Dirt Bikin Buds said:

I am stumped... they seem to have all stopped growing since the HPS. WTF Im switching back to MH and messing with an exhaust but IDK if I can cool it.

Will a 17w 5.0 UVB hold me over a couple of days?

Do cooltubes make a big difference with an exhaust fan?

Click to expand...

Dirt,

Good Lord man, take a deep breath (hold it, hold it) now exhale slowly. You've got to get yourself out of panic mode. There's only been around 5 hours between your last two posts and that's not enough time to base any decisions concerning different lighting on a plants growth on.

While HPS is not the prefered spectrum for young seedlings (or vegging in general) the fact that it's helped to lower the high temps in your space is what's most important right now.

Vegging is not all about what's happening with the above ground foliage. Your plant just might have shifted a little more of it's effort into root building. This is a good thing.

Jack

Hi dude, Was just browsing the new post and came across this one, it looks interesting I thought....Then I thought random! I've just talked to this dude lol Can you post some pics of your cupboard etc, I can help you out on stuff if you'd like - STELTHY

I'm also wondering the same question. I had my 400 watt mh 25" from the top of my babies ( working on third node) and it seemed to be too much. so I moved the light to 36" and dimmed the ballast to 360 watts. So what is the recommended height of the lights from the tops of babies?