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315 CMH distances
- Thread starter Spaventa
- Start date
Natural high
Member
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.
I run Jack Herer within 12 inches of a 600w hps without dramas so i think you would be fine.
Shooter350
Member
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. 
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.
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
Active member
I've been running about 12" from canopy, FWIW, with those 150 degree wide spread reflectors.
Natural high
Member
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
Member
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
Active member
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:
Plants are a little over 3 weeks old now and I just moved them up to 36" and they seem to be pretty happy:
The distances people are reporting for a 315 are crazy! anything from 6" to 48"!
Im not calling anyone a liar - Im amazed at how wide the range of usable distances is! I know myself, as others have said, that even at greater distances of more than 2 ft you don't get any stretch. I also noted better development of lower bud sites, despite my expectation.
Ive not pushed the other end of the range. I haven't ever run the light closer than 18".
I find 2 ft gives me all the penetration and power I want with the spread I need to cover the area perfectly. I don't have a plant directly below it and never had any hot spot issues at all.
Im not calling anyone a liar - Im amazed at how wide the range of usable distances is! I know myself, as others have said, that even at greater distances of more than 2 ft you don't get any stretch. I also noted better development of lower bud sites, despite my expectation.
Ive not pushed the other end of the range. I haven't ever run the light closer than 18".
I find 2 ft gives me all the penetration and power I want with the spread I need to cover the area perfectly. I don't have a plant directly below it and never had any hot spot issues at all.
J
jaded1
For me the perfect height is 15in from top of plants,any nearer and the footprint they cover is too small.
I also believe that going closer than 18" exceeds the rate at which the plant can photosynthesise so its wasted light over a certain level of intensity.
CO2 rooms could logically run closer but only by as much as the metabolic rates rise in the plant, maybe 20% at 1000ppm? I don't know but in a vented room at atmospheric co2 levels I doubt many genetics will make use of being closer than 18". These are just my observations.
CO2 rooms could logically run closer but only by as much as the metabolic rates rise in the plant, maybe 20% at 1000ppm? I don't know but in a vented room at atmospheric co2 levels I doubt many genetics will make use of being closer than 18". These are just my observations.
J
jaded1
I feel it's a bit strain dependant,have been running a lot of sats lately and they seem to be able to take that intensity with no issues
Yes this is one example of what I was talking about when I mentioned genetics. Some use more light than others. I think we only differ in our conclusions on this by a few inches and genetics account for that
M
moose eater
I have several of the 315cmh's. I tend to maintain 14" - 20", and assert that Natural High's statements are fairly solid with my experiences thus far..
i got my 315 today and set it up- since my ladies have been veggin under 8bulb 4ft fluor, i have it about 2+ feet about them- givin them a bit of time to adjust... i did the hand test... man they run cool... i can put my hand 2-3inches from the bulb with no heat problem... my temps this morn in the tent were 64/65f... with the 315 on... maybe 2degrees warmer... so far pretty impressed...
I'm willing to participate.
Let's see what happens.
Let's see what happens.
senor coconut
Active member
Thanks for starting this thread because after the first experience with this lamps I'm a bit confused too...
I run a single 315 on a D-Papillon type reflector, only for flowering... for vegging I use PLLs.
I found that the hand test is not so significative with these kind of lamp, I used to start flowering with a distance of 12 inches from the canopy then progressively arriving at 8.
I did not get a real burn of the tips, no curling signs but I've noted that the leafs on top were more pale/yellowish than the ones in the lower branches... next cycle I'll try to start flowering from 18 or even more.
I run a single 315 on a D-Papillon type reflector, only for flowering... for vegging I use PLLs.
I found that the hand test is not so significative with these kind of lamp, I used to start flowering with a distance of 12 inches from the canopy then progressively arriving at 8.
I did not get a real burn of the tips, no curling signs but I've noted that the leafs on top were more pale/yellowish than the ones in the lower branches... next cycle I'll try to start flowering from 18 or even more.
