COB distance

Megalomando

Well-Known Member
How far from the tips should COBs at 50W each be placed from the tips in both veg & bloom? 4 COBs are on one heatsink for 200W total.

In Veg, the COBs are four all 5000K and in Bloom, they're placed as 3000K - 3500K - 3000K - 3500K

Also, how far should the cobs be kept above clones and newly rooted cuttings?

Thanks.
 

dandyrandy

Well-Known Member
I run 100w per. See the avatar? 6 to 8". Just me. I run a hood which helps with heat. Pretty much all of mine is radiant from the cob. The 2 things hanging down are remote thermometers. Never above 82.
 

Humanrob

Well-Known Member
I doubt there is a single definitive answer to your question. I'm relatively new to this, but I'll share my experience and what I've read. First, different plants "like" or in other cases can handle, different light intensity. So right from the start you need to figure out how the strains you are growing responds to your lights.

Another aspect seems to be that the hotter/more intense/closer you put the lights, the more cal-mag and other nutes you'll need, and the faster nute imbalances will show up and progress. By keeping them a little further away, it seems like it slows things down more -- it slows growth slightly, and slows the progression if issues. In that regard, whether you are growing in soil or hydro impacts your ability to (or at least the speed with which you can) respond to those issues.

I'm running at 50watts each, and 12" was way too close for my plants, they started to bleach. Dandyrandy is running 100w @6-8", based on my experience so far I truly believe that would kill my plants within days. But it works for him, so that's all that matters.

Bottom line is you may need to experiment and find out what works for you. I would start nice and far with the young ones, if they are babies, 36", teens, 24", and then slowly work your way closer. I'm sure others will have other advice. Good luck to you.

Edit: and just to make sure we are comparing apples to apples -- I'm using Cree cxa/cxb-3070 COBs.
 
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Humanrob

Well-Known Member
...also, personally, I prefer to root cutting under CFLs, you just can't go wrong with those. I wait until they are well established before I put them under my COBs.
 

GreenSanta

Well-Known Member
For clones u can keep super far like 3 feet until they start growing, then 2 feet for a while. Later in flower I try to keep the tops around 12-16 inches from the cobs. I am still trying to figure out the best distances....
 

JimmyIndica

Well-Known Member
How far from the tips should COBs at 50W each be placed from the tips in both veg & bloom? 4 COBs are on one heatsink for 200W total.

In Veg, the COBs are four all 5000K and in Bloom, they're placed as 3000K - 3500K - 3000K - 3500K

Also, how far should the cobs be kept above clones and newly rooted cuttings?

Thanks.
I keep 60watt vero18s 18 to24in veg and flower 12 to 14inches from canopy with lenses on and no problems.
I rec to start at 24in and move down
 

Metacanna

Well-Known Member
Hey.
This topic is old but it's the subject that matters.

My plants are suffering from light bleaching. What would be preferable, increasing the distance of the Cob fixture or dimming the lights?

By dimming the lights I would keep total coverage since my space is small and save on the electrical bill. Do you see any cons by doing this?

My space is 38" x 18". 5x Citizen 1212, MW 240H C1400B.
Right now plants seem to be recovering since I increased height to 14" and dimmed to approx 350mA, pulling 65W from wall. In theory this set up right now put 375 PPFD. I was expecting to be able to give my plants double or triple that.
 

Metacanna

Well-Known Member
It is for sure, but from what I read in this forum it seems people prefer to play with the distance. I'm trying to figure out why people don't just dim the lights.
 

Walterwhiter

Well-Known Member
It is for sure, but from what I read in this forum it seems people prefer to play with the distance. I'm trying to figure out why people don't just dim the lights.
How big are your plants? This is one convoy I haven't seen much is how much par and or ppfd a plant can handle as per it's relative size? I'm sure peeps would be quick to say by the sq' of the canopy....Idk
 

CobKits

Well-Known Member
Hey.
This topic is old but it's the subject that matters.

My plants are suffering from light bleaching. What would be preferable, increasing the distance of the Cob fixture or dimming the lights?

By dimming the lights I would keep total coverage since my space is small and save on the electrical bill. Do you see any cons by doing this?

My space is 38" x 18". 5x Citizen 1212, MW 240H C1400B.
Right now plants seem to be recovering since I increased height to 14" and dimmed to approx 350mA, pulling 65W from wall. In theory this set up right now put 375 PPFD. I was expecting to be able to give my plants double or triple that.
usually when i have unhealthy tips its because the roots cant keep up. with a big rootmass the tops are lush and can take tons of light
 

Metacanna

Well-Known Member
A study someone published here before stated cannabis maximum photosynthesising at 1500 PPFD with temp 30° C.
In practice I guess growers have problems with that amount of light. Concerning plant size and the ideal PPFD, good question...
 

Kush_Dabz

Member
boom.

I cut those tops back they dont seem to recover as quick as the green stuff underneath. usually they stunt, branch, and taco.

go easy on it for a bit
Hey Cobby! I bleached the tops of my plants with my cxm22s in veg day 55. Bottom of plants are green and happy I was wondering if i should cut the bleached tops or let them recover? Some plants are bleached quite alot some other only bleached tips.
Cheers!
 

DesertHydro

Well-Known Member
My shit is just inches away on my flowering colas. Like 3-4" on a couple lol. No damage or bleaching yet but I am only running 37.5w on each citi 1212. On my veg I am about a foot away and all is well.
 

ttystikk

Well-Known Member
My shit is just inches away on my flowering colas. Like 3-4" on a couple lol. No damage or bleaching yet but I am only running 37.5w on each citi 1212. On my veg I am about a foot away and all is well.
Low watts and no lenses.

Higher watts per chip and/or lenses to concentrate output can cause problems quickly.

Quantum Boards spread the light emission out so much bleaching is all but a ring of the past unless your plants are nearly touching them.
 

KonopCh

Well-Known Member
I bought LUX meter... I don't have money for PAR meter. Anyway, how much lux is good for seedling, veg and flower?
 

HydoDan

Well-Known Member
Right now I have my seedlings 10" away from a Citizen 1812 5000k cob @ 54 watts.. So far all is well..
I plan to let them grow too the light and see where bleaching begins.. 24/0 photo period..
 
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