315w CMH 4x4 tent 5 plants ok??

Aviatorshades

Aviatorshades

Well-Known Member
Would 5 strains in 5 gal fabric pots work? I have one 315w can for the grow. I plan on using two cmh for a total of 630w for the lastmonth. To help keep costs down. I was just wondering two things


1. Will a single 315 cmh grow five just fine? What kind of yield can I expect
2. Using another 315 cm h for last 4 weeks will that make a big difference in yield or just stick to my single?

Tried searching but couldn't find anything
 
DesertPlants

DesertPlants

Well-Known Member
From my testing, they really work best in a max coverage of 2.5' x 2.5' in flower and 3.5'x3.5' in veg. For a 4x4, I would run two in veg if your room will be packed, if not, center them and just use one. when you get to flower, again, it will depend on the size of the plants. I would run Three of them if wall to wall or two of them if centered. Just be weary of heat. I know a lot of Hydro/grow stores claim CMH is not an HID, but it is. It comes with all the same fire hazards that MH and HPS have.

Back to your setup... five strains in a 4x4 is going to be pushing it unless you don't veg for long. Last one I did, each bush got to about 2.5' x 2.5'. Regardless of what you end up doing, let us know how it works out.
 
M

MedN00b

New Member
Sun systems diamond 630w fixture seems to be a nice compact unit for a 4x4 tent. Has a 4x5 coverage

(apparently I don't meet the criteria to post links but look it up)

Just need to see if you can aquately cool it.
 
DesertPlants

DesertPlants

Well-Known Member
Just be careful accepting vendors specs on flow and veg footprint... almost nothing is ever 100% what they claim.
 
DesertPlants

DesertPlants

Well-Known Member
Yes, I don’t use CMH anymore because I have no way to properly v by heat. It was getting over 90F. Now I use COBs and it stays between 77-79
 
Yodaweed

Yodaweed

Well-Known Member
DesertPlants said:
Yes, I don’t use CMH anymore because I have no way to properly v by heat. It was getting over 90F. Now I use COBs and it stays between 77-79
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watts generate heat not the type of light you use, 315w of cmh is the same heat load as 315w of leds. it's the first law of thermodynamics.
 
DesertPlants

DesertPlants

Well-Known Member
Yodaweed said:
watts generate heat not the type of light you use, 315w of cmh is the same heat load as 315w of leds. it's the first law of thermodynamics.
Click to expand...
Oh god... this BS is why I hate these forums. Everyone thinks they are physicists. BTUs are measurement of heat energy. Watts are a unit of power equal to one joul per second. It has nothing to do with heat until you convert it to BTUs, which ARE a measurement of heat.

Energy can be neither created or destroyed.. yes, but you are not converting 100% of it to heat in either case. The conversion from electricity to photons has an efficiency percentage. An HID has a lower efficiency than an LED. No system is 100% efficient and the loss in conversion is what you are getting as heat. Photonic energy, thermal energy, chemical energy, and electrical energy are all types of energy, but are not converted at 100%.

Photonic energy gets converted to chemical energy during photosynthesis. More usable photons means less heat and more chemical energy. You can’t convert 100% electrical energy to photonic energy, which is where a big portion of the heat comes from. Then you don’t convert 100% of photonic energy to chemical energy, most is lost as heat after exciting surfaces and converting to thermal energy, but that which does get absorbed and converted to chemical energy does NOT get converted to heat. More usable photonic energy results in more chemical energy and because no system can be equal to or greater than 100%, that means less heat is generated.

People spouting things as fact is why there is a LOT of misinformation on this forum and in the cannabis community.
 
Yodaweed

Yodaweed

Well-Known Member
DesertPlants said:
Oh god... this BS is why I hate these forums. Everyone thinks they are physicists. BTUs are measurement of heat energy. Watts are a unit of power equal to one joul per second. It has nothing to do with heat until you convert it to BTUs, which ARE a measurement of heat.

Energy can be neither created or destroyed.. yes, but you are not converting 100% of it to heat in either case. The conversion from electricity to photons has an efficiency percentage. An HID has a lower efficiency than an LED. No system is 100% efficient and the loss in conversion is what you are getting as heat. Photonic energy, thermal energy, chemical energy, and electrical energy are all types of energy, but are not converted at 100%.

Photonic energy gets converted to chemical energy during photosynthesis. More usable photons means less heat and more chemical energy. You can’t convert 100% electrical energy to photonic energy, which is where a big portion of the heat comes from. Then you don’t convert 100% of photonic energy to chemical energy, most is lost as heat after exciting surfaces and converting to thermal energy, but that which does get absorbed and converted to chemical energy does NOT get converted to heat. More usable photonic energy results in more chemical energy and because no system can be equal to or greater than 100%, that means less heat is generated.

People spouting things as fact is why there is a LOT of misinformation on this forum and in the cannabis community.
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1 watt = 3.14 btu, there's direct conversions i'd look into more to get some knowledge, 100% of lighting gets converted to heat, plants don't absorb heat and photon absorption is so low it's negligible. ....600w of one lighting source = 600w of another it's basic science .


read this thread to get a better understanding.

https://www.rollitup.org/t/heat-from-1200w-of-1212s-vero-29s-cxm-22-cxb3590-compared-to-2x-600w.936071/


frica said:
Because the light will also turn into heat eventually, and since that light stays in your room it becomes heat in your room.

Photosynthesis stores some energy inside the plant (doesn't become heat), but photosynthesis is rather inefficienct so you can safely ignore it.
So 1200W will always be 1200W.
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CobKits said:
in a room 1200W of anything is 1200W

will produce the same amount of heat

cobs will give you more usable light for that same 1200W, or an equal amount of light for a lesser wattage, like 800W
Click to expand...
 
J

jayblaze710

Well-Known Member
DesertPlants said:
Oh god... this BS is why I hate these forums. Everyone thinks they are physicists. BTUs are measurement of heat energy. Watts are a unit of power equal to one joul per second. It has nothing to do with heat until you convert it to BTUs, which ARE a measurement of heat.

Energy can be neither created or destroyed.. yes, but you are not converting 100% of it to heat in either case. The conversion from electricity to photons has an efficiency percentage. An HID has a lower efficiency than an LED. No system is 100% efficient and the loss in conversion is what you are getting as heat. Photonic energy, thermal energy, chemical energy, and electrical energy are all types of energy, but are not converted at 100%.

Photonic energy gets converted to chemical energy during photosynthesis. More usable photons means less heat and more chemical energy. You can’t convert 100% electrical energy to photonic energy, which is where a big portion of the heat comes from. Then you don’t convert 100% of photonic energy to chemical energy, most is lost as heat after exciting surfaces and converting to thermal energy, but that which does get absorbed and converted to chemical energy does NOT get converted to heat. More usable photonic energy results in more chemical energy and because no system can be equal to or greater than 100%, that means less heat is generated.

People spouting things as fact is why there is a LOT of misinformation on this forum and in the cannabis community.
Click to expand...
Dude, joule can be converted to heat. Because all energy eventually is dissipated as heat. Yes, a small amount of the energy will be stored in the plant, but the vast majority won’t. For all intents and purposes, 315W LEDs, 315W HID, or a 315W space heater will have similar results.
 
DesertPlants

DesertPlants

Well-Known Member
jayblaze710 said:
Dude, joule can be converted to heat. Because all energy eventually is dissipated as heat. Yes, a small amount of the energy will be stored in the plant, but the vast majority won’t. For all intents and purposes, 315W LEDs, 315W HID, or a 315W space heater will have similar results.
Click to expand...
You guys are completely missing the point of the whole thing... A light that puts out the same Photons at a lower wattage will ALWAYS produce less heat. More usable photons means more efficiency. These are not real numbers, but here is an example: HPS puts out 750 PAR at 18" drawing ~600 watts. LED puts out closer to 1950-2150 PAR at 600 watts. That means the efficiency gain in photon conversion results in a lower wattage requirement to get the same PAR. So to go from 600 watts of HPS, you would only need 200-250 watts of LED. Again, not real numbers exactly, but I hope you get the point. That difference is due to efficiency. This means you need less power and in turn, less heat. When I stopped using 315W CMH lights, I didn't go to 315W of LEDs... I went to 220W.
 
Lucky Luke

Lucky Luke

Well-Known Member
Could we get back to the topic please. CMH has other advantages that some of us are interested in.
So one 315 is not large enough for a 4 x 4. I get two may be better that a solo 630w but as a single light it would have to be close to 800 or so W of HPS (or more) wouldn't it? Without the 1000w's heat generation and running costs.

Im seriously considering going from 600w of HPS for my flowering tent to 630 CMH.
 
DesertPlants

DesertPlants

Well-Known Member
I would use both for all of flowering, but it’s really up to you. Yield will really depend on the strain/pheno.
 
Aviatorshades

Aviatorshades

Well-Known Member
when they say 1g per 1w do they mean each plant or all combined? if its overall that might mean each 5 plants would be tiny yielders? would suck i would do 5 different strains and see what one is better.. also would 5 plants smell more than 1 plant or will the carbon scrubber take care of that regardless
 
Lucky Luke

Lucky Luke

Well-Known Member
Aviatorshades said:
when they say 1g per 1w do they mean each plant or all combined? if its overall that might mean each 5 plants would be tiny yielders? would suck i would do 5 different strains and see what one is better.. also would 5 plants smell more than 1 plant or will the carbon scrubber take care of that regardless
Click to expand...
all plants. 1 gpw is not a bad number anything over is a good yield. Keep in mind different strains will yield better than others so its not the be all and end all.
Using multiple lights will give you a higher gpw in general due to the overlaps
 
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