How much CMH wattage is reccomended for a 4x4 tent

overbudjet · Feb 16, 2021

zachrockbadenof said:
its all confusing... supposely a 315 is equal or exceeds a 400mh- so in my case (4x3.5ft tent), i'd be real close to a 1000watter

now i have grown with 1000wattter's , not in a tent but a small room , and the buds with the big-dog are bigger, and it seems more resin, and the penetration is def better...

if u should have a min of X watts... per sq ft, and a 315 is more powerful then a 400.... well i'm confused....

315 cmh have a better spectrum than a 400hps but lacking deep penetration of the hps ,so 3x315cmh will have better penetration (more light point /less hot spot)also better spectrum and will give you arm length bud than a 1000hps.
Also and old 1k hps user and 2x315cmh are not as good for a 4'x4', but 3 cmh are way better than a 1k hps

eyesdownchronic · Feb 17, 2021

Greenheart said:
This might help answer that. Ibechillin has an excellent sticky on lighting.

Post #5 has a chart at the bottom stating that a

"DLI of 43.2 mols/m2/d which is ideal for maximum yields according to NASA experiments"

That sounds about right... imagine they were using CO2.

43 DLI / 12 / .0036 = ~1000 u/mol/sec....
hmm... maybe 2 x 630 w ballasts set to about 75% capacity. ~450w each.
looks like zachrockbradenof was on to something...

Horselover Fat · Feb 17, 2021

A 315 cmh produces 50% of a 600w hps light output (550-600umol/s vs 1100umol/s). Two would be ok in 4x4, but three would be optimal.

Snook · Feb 17, 2021

zachrockbadenof said:
i have 2 315's (phillip bulbs) in a 4x3.5ft tent, and didn't think is was enough lite - i have some cheap led's (4) which i added for side light - maybe its overkill, but for sure the buds are not as large as when under a 1000w hps...

I too just dumped dual 315cmhs' for and back to the 1K HPS. :good:

Yes girls look more sexy half way thru the grow w the HPS. :dancer:

Horselover Fat · Feb 17, 2021

Snook said:
I too just dumped dual 315cmhs' for and back to the 1K HPS.
Yes girls look more sexy half way thru the grow w the HPS.

More light more plant. Could've added a 315 and gotten the same results.

eyesdownchronic · Feb 17, 2021

Horselover Fat said:
A 315 cmh produces 50% of a 600w hps light output (550-600umol/s vs 1100umol/s). Two would be ok in 4x4, but three would be optimal.

Strictly from a light output point of view that may be true, but CMH light is significantly more efficient than HPS lighting...

here is an interesting read i would suggest for those saying they prefer HPS...

https://www.icmag.com/ic/showthread.php?threadid=352859

Isaak had a side by side test of 630 wCMH v 1000 w HPS and CMH outprerfomed the HPS. I think after the thread he converted his whole grow to CHM.

Hammerhead · Feb 17, 2021

Ive been using CMH for years. I swapped out 4kw HPS to 4kw CMH and will never go back. There is no reason CMH will not out perform HPS. Currently testing CMH/LED..

Horselover Fat · Feb 17, 2021

eyesdownchronic said:
Strictly from a light output point of view that may be true, but CMH light is significantly more efficient than HPS lighting...

So you are saying cmh spectrum produces significantly more than hps spectrum? I doubt it.

overbudjet · Feb 17, 2021

If you compare 3 315cmh 945w to a 1k hps ,cmh will outperform hps in quantity and quality no doubt about it .More light=better cover over canope, less hotspot, better spectrum.

Horselover Fat · Feb 17, 2021

overbudjet said:
If you compare 3 315cmh 945w to a 1k hps ,cmh will outperform hps in quantity and quality no doubt about it .More light=better cover over canope, less hotspot, better spectrum.

Same ammount of light, but better spread for sure.

JKD · Feb 17, 2021

Match PAR, not watts for a more accurate side by side.

zachrockbadenof · Feb 17, 2021

3x 315 i would think gives a better coverage , but i use cmh as they throw out less heat (i think) then a 400, but 3x315's has to throw out at least...maybe more heat then a 1000- i don't know

eyesdownchronic · Feb 18, 2021

Horselover Fat said:
So you are saying cmh spectrum produces significantly more than hps spectrum? I doubt it.

Significantly more what?

"Light," in terms of like foot candles or whatever, no I dont think so.

"Photosynthesizable energy" , from what I understand yes, HPS is very heavy on infared (ie heat) which isnt used for PS... and this should correspond to yield.

In the thread I tagged, the guy yielded more from 630 w CMH over 1K HPS across like a 20x4 area for each, I think. hit about 1 gpw for the HPS. and 1.4-2GPW from the CMH. i wanna say

And same thing goes for LED's. those HLG 550's and other QB knockoffs, which really run on 480w, are rated for a 4x4. Can't imagine anyone running two of those things at full blast in a 4x4.

Snook · Feb 18, 2021

OK, I bought the 315cmh bit before and had 2, 315s in a 4x4 tent ina dual bulb hood. Ya'll saying I should have had 3 not 2. I went back to 1K HPS cause I had it on the shelf (although I now have 2 cmh ballasts and bulbs on the shelf). I would have to buy a third ballast and bulb. I stopped vertical, so how would I mount those '3' cmhs? 3 hoods in a 4x4? Can one of you put up a pic of 3 cmhs in a 4x4 please? I do have another small hood maybe put 1, 315 in there with the HPS? or run it vertical.

EDIT: Why not just dangle a 315 right now in this current run with the HPS and see how it goes.. thanks.. always better to talk it out.

Horselover Fat · Feb 18, 2021

eyesdownchronic said:
Significantly more what?

"Light," in terms of like foot candles or whatever, no I dont think so.

"Photosynthesizable energy" , from what I understand yes, HPS is very heavy on infared (ie heat) which isnt used for PS... and this should correspond to yield.

In the thread I tagged, the guy yielded more from 630 w CMH over 1K HPS across like a 20x4 area for each, I think. hit about 1 gpw for the HPS. and 1.4-2GPW from the CMH. i wanna say

And same thing goes for LED's. those HLG 550's and other QB knockoffs, which really run on 480w, are rated for a 4x4. Can't imagine anyone running two of those things at full blast in a 4x4.

More yield.

Photosyntetically active radiation is what I wrote about earlier: 315cmh 550-600 umol/s and 600w hps 1100 umols/s. HLG 550 produces 1300 umol/s. I agree cmh spectrum is better, but I don't think it will yield more.

Horselover Fat · Feb 18, 2021

^photons drive photosynthesis. The colour of the photons has an effect on cell expansion ie how big leaves grow and internodal length. More red equals more cell expansion and more blue reduces cell expansion.

eyesdownchronic · Feb 19, 2021

Horselover Fat said:
^photons drive photosynthesis. The colour of the photons has an effect on cell expansion ie how big leaves grow and internodal length. More red equals more cell expansion and more blue reduces cell expansion.

You're right. but theres also more to it than that, blue light reduces cekk expansion in favor of cuticle thickening (denser plans). also blue provides more light than does red. different wavelengths have varying levels of absorption which relates to efficiency.

eyesdownchronic · Feb 19, 2021

Horselover Fat said:
More yield.

Photosyntetically active radiation is what I wrote about earlier: 315cmh 550-600 umol/s and 600w hps 1100 umols/s. HLG 550 produces 1300 umol/s. I agree cmh spectrum is better, but I don't think it will yield more.

I'm going to quote Ibechillin's post in the thread "Do you measure PAR for your grows?" yesterday.
"[FONT=Arial, Helvetica, sans-serif] Bruce Bugbee mentioned in his lighting myths video cannabis can utilize more than 43.2 DLI typically regarded as most productive but spectral ratios have major influence on plant utilization....[/FONT][FONT=Arial, Helvetica, sans-serif]500 ppfd under 3500k led with minimal IR is roughly 30k lux and with adequate overhead diffusion to reach deeper into the canopy (or additional side lighting/under canopy lighting to stimulate lower leaf chloroplasts) people have claimed 2gpw. This is also approaching the "theoretical" max ppfd plants can tolerate at atmospheric ~400ppm CO2 availability."[/FONT]

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Greenheart · Feb 19, 2021

Snook said:
I went back to 1K HPS cause I had it on the shelf

You might try finding old stock of 860W cdm's. They run on 1k mag ballasts. They are vert though.

You might crush it with a vert 860 on the bottom and 2 x 315's up top?

Horselover Fat · Feb 19, 2021

eyesdownchronic said:
also blue provides more light than does red.

What do you mean?

How much CMH wattage is reccomended for a 4x4 tent

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