2 x 240w HTG LED Cabinet - Minimum height of LED above seedlings?

Hi all, and thanks in advance for any advice. I am currently running a single 240w LED over 4 seedlings. I plan to add a second identical light in my cab once I'm sure it's gonna do the job.


Transplanted these into 1 gal pots a few days ago. They are doing well, but I have one that is a lighter shade of green... doesn't look unhealthy, just that pheno's normal color I think. Anyway, I'm wondering how close you would recommend that I get the light to the plants. I have researched extensively on this forum (and others) and have seen opinions vary from 4" to 24". I started at 12" for a day, but dropped down to 8" yesterday and plan to go to 6 if I don't see problems. Can I assume that if I get too close that I will be able to tell within a day or so?


Pics are of 303Seeds' Snow Goddess (looking for the CBD pheno) and Dank#5. The natural light pics were taken on transplant day, the LED lit pics were taken 2 days later. They are clearly loving the light, I just wonder where the sweet spot is?


Much Karma flows to those who help noobs....


Bubba

Thanks for the non help guys lol. Have a nice day.

Even though you guys weren't able to help me, I will leave a nugget of experience for folks researching this LED. I went out and bought a meter and the light pulls exactly 130 watts at the plug, 54% duty cycle, I had hoped for 60 or 65%. At 130w per light, that only gives me 37w/sqft, not enough with just 2 lights, I could add another 240w LED, this would give me one light per plant and 56w/sqft, but that's another outlay of $550 for both.

I'd wait to lower it until you see how the distance between nodes is. I'd even consider backing it off to +12 at least. 8 just seems way to close at this stage.

Thanks, I backed it off to 12.

Distance from plants varies from light to light due to plant age/size, drivers/leds, lens angles, environment and spectrums.
12" seems way too close for that light over a seedling.
24" at minimum I would think. 30" might be better.
How large is your space?

Thanks for the reply. The cabinet is 2x4x6h (but top foot lost mostly to filter & fan).

2 lamps will work. Just keep them short (24"). Scrog or LST. I've gotten just over 1g/w with about 30wpsf.
You've got some time before you need a second light.

8" is way too close, more for flowering. 18" seems to be my sweet spot.

Id say 16-24" would be great.

Node spacing isnt going to tell you a whole lot if you do not have prior LED exp.

Much thanks to all. I pulled it up to 18". I had a couple of grow 32w CFLs, so I stuck them in there also. i also have some 2' T5s that I can put in the corners if needed.

I keep my lights at about 36'' from seedlings and let the plants grow to them, I never move my lights, that's the beauty of LEDs, I never touch my lights!!

Thanks again for advice. 18" seems perfect. They like it.
p

GreenSanta said:

I keep my lights at about 36'' from seedlings and let the plants grow to them, I never move my lights, that's the beauty of LEDs, I never touch my lights!!

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Cool. Do you mind if I ask what size light you are running? Are they 3w or 5w diodes?

Scotch089 said:

8" is way too close, more for flowering. 18" seems to be my sweet spot.

Id say 16-24" would be great.

Node spacing isnt going to tell you a whole lot if you do not have prior LED exp.

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Thanks for the advice. I have been at 18" for a week or so, the sprouts will be 3 weeks old from germination tomorrow. They are growing well, but I'm worried that they aren't stretching much. Should I raise the light further?

Just out of curiosity, it that 240w light, the 7-band? or the 3-band?

7- band. I'm liking it so far and will most likely go ahead and pick up 2 more. Then I would have one light per plant scrogged with a total watt (at plug) per sqft of 56 w/sqft.

Sweet! I'm thinking about getting one just like it. I also see that you're using blumats. How do you like them?
And don't worry about them not stretching man; keep them nodes nice and tight!

You really do not want your plant to stretch tall... the taller it becomes, the harder time it will have holding itself up when the extra weight in flower... check out my grow 780watts of LED's... and you will see at 4weeks my plants are all nice and short and fat

pacificarage said:

Sweet! I'm thinking about getting one just like it. I also see that you're using blumats. How do you like them?
And don't worry about them not stretching man; keep them nodes nice and tight!

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Yes, so far the Blumats are the bees knees. Just a hardly imperceptible drip rate keeps everything perfect. The top 2" of soil stays pretty dry but the roots seem to stay at perfect moisture level, and no excess water has made it out into the tray... Which worries me some, but they are growing well so must be ok. I think I lose more water to evaporation out of the res than the Blumats are currently drawing. It will be interesting to see how they work with the 5 gal fabric pots and thirsty gurls.

509Zman420 said:

You really do not want your plant to stretch tall... the taller it becomes, the harder time it will have holding itself up when the extra weight in flower... check out my grow 780watts of LED's... and you will see at 4weeks my plants are all nice and short and fat

Click to expand...

Thanks for the input. They are starting to stretch some now they just kicked into gear, but I think nodes are still tight.