[Spaventa]

I just switched from HPS/MH and can't find any consensus on how far it should hang over the plants. I found all kinds of numbers... what do you guys do?

Its sitting about 18" at the moment maybe 20, in flower.

[Natural high]

I'd say you can go as close as 12 inches but it would depend on your strain as well. If your light is too intense the top leaves will canoe (fold upward on the outer edge) and/or the buds will start to foxtail.

I run Jack Herer within 12 inches of a 600w hps without dramas so i think you would be fine.

[Shooter350]

18 - 24". At 24" you will be able to cover a 3-1/2' x 3-1/2' footprint in flower. 24" 4 x 4' for veg. They have a broad spectrum. Too close will stress the plants. Depend if you want coverage or penetration. I think the 630 will be the normal in 10 years. Time will tell. ✌️

[Raho]

What fixture are you using?
Some reflectors cause serious hot spots that can require a greater distance from the plant.

I don't understand how these fixture makers can get away with selling their product without supplying decent light pattern charts. Especially since there is what amounts to a "reference bulb" in the Phillips 930.
Output levels on a 6" or 12" grid over a 3' x 3' area (or 4' x 4') at 12", 24" and 36" height.
If they sell their own brand of bulb, show both charts. Its more about the consistency of light distribution than intensity.

You can increase intensity by changing distance from the plant, but you can't fix hot spots.

[clown baby]

I've been running about 12" from canopy, FWIW, with those 150 degree wide spread reflectors.

[Tipunch]

Bump

[Natural high]

I have one and it's possible to go as close as 10-12 inches. It is only a 315w we are talking about. A 630 would need more.

[Tipunch]

Originally Posted by Natural high

I have one and it's possible to go as close as 10-12 inches. It is only a 315w we are talking about. A 630 would need more.

Thanks mate 12' has A consensus apparently, maybe start at 14' and see if its ok then go down 2'.

[Natural high]

Originally Posted by Tipunch

Thanks mate 12' has A consensus apparently, maybe start at 14' and see if its ok then go down 2'.

Another factor to consider is the area you are trying to light up. If it's a 3 x 3 then adjust your shade so that there is a reasonable intensity of light out near the wall. It won't be as intense as the center unless you have the perfect shade, but you don't want too big a difference between the two or your central branches will leave the outside behind.

[IntotheGreen]

I would say it depends on a couple factors, such as the size/age of your plants, your ambient temps/airflow, and like NaturalHigh said, your desired area of coverage. Also I'm sure there are strain-specific tolerances as well. I think a good rule of thumb to judge minimum distance is to hold the back of your hand under the lamp; if it's uncomfortably warm to you, it's probably too hot for your plants. Based on that criterion, with the single 315 I have running now, that mark seems to be somewhere in the 6-12" range. I will have two 315s running in later veg and flower, but if temps are similar I don't think I would have a problem letting the top colas get 6 or 8 inches from the lamp. I am running the 4200K mogul bulb, which may have a slightly diff heat signature than the T9/12 based on the shape of the bulb but that is most likely negligible. I will say that on this grow, I started the seedlings out at 48" from the 315 and had almost zero stretch even at that distance - certainly less than I had with my old 250w MH. I mean I have plants that look like this lol:


Plants are a little over 3 weeks old now and I just moved them up to 36" and they seem to be pretty happy: