315 CMH and seedlings, I asked last year, anymore input

[pointer80]

Hello everyone, I asked this question last year and was curious if any else since then have been sprouting and raising seedlings under 315 cmh light? If so how far do you place the light above the seedlings? what kind of results are you getting? Thanks all.

 

[Pbass]

Hiya @pointer80 I don't grow under CMH but I did some poking around and I'd guess you want that thing higher than the 18" it suggests, I'd guess 2' or more to start is plenty of light for seedlings. Yield is not determined by light alone! CHeers mate, gl to your grow!

 

[Captain goodvibes]

Ive raised seedlings under 315 cmh, the key is to have the light far enough to eliminate heat stress as the CMH also gives out more heat than leds. Generally around 18 inches I think but Ive never measured. Put your hand where the top of the seedlings are for 30 seconds if it feels too hot its too close. Thats how Ive been doing it.

 

[Slicknick909]

I ditched the CMH for the QB lights for heat reasons (CMH will turn a tent to an oven quick if your fan fails when you're not home, ask me how I know). But I ran from seed to harvest under them, kept them about 30" away from the seedlings, with a oscillating fan blowing above the plant but below the light to prevent heat build up.

 

[cr8grow]

I am 4 weeks into my second grow, both under CMH 315 from seed to harvest. I started seedlings at 4.5 ft. above, then dropped to 24” for the grow at around the end of week 2 from sprout. If my second grow stretches to the point I need more headroom I figure I could go as close as 18”, but, havent tried that close. The light is very intense and my Corleone Kush girls are squat fat bushes...taking very well to LST. Picture from mid week 4.

 

[pointer80]

I am 4 weeks into my second grow, both under CMH 315 from seed to harvest. I started seedlings at 4.5 ft. above, then dropped to 24” for the grow at around the end of week 2 from sprout. If my second grow stretches to the point I need more headroom I figure I could go as close as 18”, but, havent tried that close. The light is very intense and my Corleone Kush girls are squat fat bushes...taking very well to LST. Picture from mid week 4.

did you have any issues with getting too hot? I have my tent in a 60 degree room and I have two 315 cmh lights in one half of a 4x8 tent (basically two in a 4x4) and it gets around 80 degrees or a little warmer and thats with the lights at 3 feet high and a fan going. Thanks.

 

[cr8grow]

I run fan/filter and clip fans 24/7. I needed some heat as unfinished part of basement averages 60-65F, a big consideration when I selected the CMH 315w. Temp at canopy runs 81F and top of cabinet is 71F. I have one clip fan above pushing cooler air down and one lower to circulate air.

 

[ThaTinMan]

Woa! Does anyone own a LUX meter, they're cheap. Magic yellow brick road will show a much better path to the wiz. Pull the straw out of ya head...

4K. Using 315 cmh gives incredibly darker green, what everyone wishes for. Spectacular instant changes to the most woeful looking babies you have ever seen!

Get a clue, buy a 315cmh light with a LUX meter and you are set. So easy now it's kinda stupid.....

ThaTinMan

 

[Fuzzy Duck]

I'm reasonable sure you are confusing the basic meaning of lux - The lux (symbol: lx) is the SI derived unit of illuminance, measuring luminous flux per unit area. ... It is equal to one lumen per square metre. In photometry, this is used as a measure of the intensity, as perceived by the human eye.

As it is by the human eye it is not much use to the plant it self !