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Advise for adding co2 to a grow box

Discussion in 'Grow Room Design/Setup' started by RobsGreen, Jan 15, 2008.

  1. Well the time has come to build box #2, I'm hoping to have it complete and fine tuned before I start my next grow in about month. The current box is nice but just not big enough, my goal is to get close to a pound per harvest with the new box.

    The new box will be 6' wide and 7' high, it will have 3 chambers, 1 for growing, 1 for a mom and 1 to start clones. To help achieve that one pound I plan to add co2 for the main grow chamber during flowering, whatever it takes. ;)

    I'm hoping some of you co2 users can help me out. Here's my plan, let me know if its a good one and what I should re-think.

    The box will be completely sealed and the light reflector will be cooled without affecting the air flow in the box. The intake will come from the mother chamber and the air will blow throw the light and exhaust out the box. Having it that way I'm assuming my temps will be around the 85 degrees, thats without exhausting the box. I read that higher temp is what you want when applying co2 so that should work out nicely if true. I'll have another exhaust for the main chamber attached to a carbon scrubber which will run a couple times a day, possibly being triggered when humidity gets too high. I think I'll be getting a controller for the co2 to monitor the levels.

    Here's a few questions.

    When you start flowering do you use co2 for the full 12 hours of light, as in keeping a 1500 ppm during the whole period?

    I'm thinking you don't need fresh air in the box when co2 is being used as in no intake period? Of course it would be there during veg.

    What equipment is good for co2 as in regulator and controller, any brands to look for?

    How much co2 is normally used for 2 plants during a grow? Just looking for ballpark figures.

    Thanks for any advice you can pass along.

    Here's how it will basically be setup.

  2. ive got a similer setup, was gonna make a post too.

    i have a big co2 canister from paintballing which i was thinking of putting extra co2 in my grow cupboard. i didnt have amazing airflow in my last grow, but still got couple of decent ounces of 'oasis' from 2 plants.
    I heard co2 could double the growth rate, dont know if that means it grows faster or yeilds more. hmmm. was thinking of putting a set amount of co2 in each day and opening cupboard to get fresh air in every day probably. anyone know what volume co2 gas i would need to put in a 30cm by 70cm cupboard?
    ime getting 4 seeds going at mo, thinking if its going to get too humid i can put a little dehumidifier that ive got in there. should i put the co2 in before the light cycle do you recon and air it out just before i do that?

    appreciate the help
  3. Hey Willcarr60, welcome to grasscity. :wave: It seems like co2 really does help increase yield during the grow, it won't get you a harvest any quicker but will get you a bigger one. Here's how I understand the way it works, I could be wrong on some of this.

    You only need to use the co2 when you start harvesting, the goal is to keep the cab at a certain level, I think 1500ppm. This is where it makes the big difference. Apparently the plant can use more light when the co2 level is higher. The co2 is only helpful when lights are on, save it when lights are off. You also don't want to exhaust the air out of your cab very often when co2 is on, if it does exhaust often the co2 won't do anything really. For maximum results you need a sealed cab without air coming from the outside, a fan blowing the air around in the cab is needed of course. I think the plant can also handle more heat when the co2 level is high, 85f should be ok even 90f. It may need to be that hot in order to be effective, not really sure yet. Without high co2 levels you want around 75f.

    Good chance you will need that dehumidifier if you don't exhaust, I'm having a hard time keeping mine down with the exhaust running lots.

    I don't know how much co2 you will need for a grow, its probably different for everyone. I'm hoping to get away with 10pounds per grow, 20 should do it for sure.

    If any of this is wrong someone please correct me. :smoking:
  4. Sounds good but it wont work. How do I know? I did that same thing:D.

    Even if you blast cold air through the cool-tube, the radiant heat from the bulb will still build in your grow. It wont build up as fast but it will build and get over 100 if not vented. Even when its freezing outside and my cool-tube is frosted up, the heat kicks my thrmostat two or three times an hour. It does not cycle for long on cold days, but it still needs to cycle.

    It is weird but you can grab the cool-tube and the glass will be cold, but put your hand an inch away and it will start warming up your palm.

    I'm not here with all bad news. It can still work, just not they way you think. The simple answer is an AC unit. It will cool and dehumidify at the same time without ever allowing air to excape your grow room. No need to carbon filter. Or do what I do and deal with your grow cycling a few times an hour. It will use up more CO2 then the AC grow, but will work never the less.

    You will need a thermostat if you plan to vent like me. I use up about 20 pounds of CO2 during the cold months and twice as much during the summer. So two tanks handy will make it simple to run in the hot months.

    I tried going without a CO2 controller/monitor. It is very hard to do. You won't know what your levels (PPMs) are and will burn up tanks for no reason. If you have a free supply of tanks, then you will be ok, but if you have to pay to fill them.... Sorry, the damn monitors cost an arm and a leg. I tried the 15 minute timer method with the bubble counter, not very good results at all.

    You only run CO2 when the lights are on.

    Welding supply is the best place to exchange your tanks. Beer makers want top dollar. I would buy your tanks from the same place you plan on exchanging/filling with. If you go out and buy real nice tanks and find out that most places will only exchange not fill, then your give your real nice tanks for some old beat up ones. Best to pay for the old beat up ones from the start.

    I shit your not, I tell them I use the CO2 for SCUBA because the cost of compressed air is too much.:D
  5. Thanks for the heads up, I figured heat would still get a bit high but thought 2 or 3 exhausts during lights on would do it, 2 times an hour is definitely to much. My main goal with the co2 is to be as conservative with it as possible, I'm not looking forward to getting it refilled a lot, I'm hoping 1 tank a grow. That's funny you can say its for scuba diving, I don't think I'll try that, it would suck if the guy knew and said it wouldn't work.

    I really like the idea of having an AC in the box, I'm going to look around and see what I can find. Then I definitely won't need another fan, my current fan will blow through the light and exhaust the mom and clone box. Getting away without a carbon filter would be nice as well, my current grow is just starting to smell every so often, I'm lucky what I have is low odor. On that topic how strong does your WW smell? I might go with that as it seems high yield and sounds like its quite strong.

    I plan on getting a controller/monitor, I realize its really the only way. Hopefully I can find a good deal somewhere.

    What temp do you have your closet at when you use the co2?

    I'm guessing you use it as soon as you start flowering and try and keep the level up during the whole lights on period?

    Well time to get at her. :D
  6. I run my CO2 the whole grow. But I only veg ten days. In the winter I have the fan come on at 80 and off at 75. I played with it for months to find the right temp so it would not cycle much. I have to adjust it up for the summer 90 to 85.
  7. So you still prefer to keep lower temps with high co2 levels? Do you yield more in the winter or just save co2?
  8. Oh yeah, the winter yeilds are about 2oz more then summer. CO2 does not make the plant want higher temps. It allows them to grow in spite of higher temps. If you can grow them in optimum temps while keeping a CO2 enriched environment, you will get in increase in growth rate and yeild.
  9. ive decided that as it costs so much to get a co2 monitor to just keep my exhaust fans on for a while, then when its budding maybe turn off the exhaust fan and put some co2 in somedays.

    does it matter if you have more than optimal amount of co2, does the plant still need some oxygen, am i right in saying that the plant needs some oxygen when its dark and breaths co2 in the light. i dont want to keep buying co2 and i wont be able to tell exactly how much ime putting in so guess its a bit of a waste of some co2, but its still worth it i imagine.

    ive just got one co2 canister like 1m20cm high so guess i wait till theyre are budding well, before i use the co2? or do they use more when they are growing to full size.

    thanks for your help people
  10. I would way rather have optimal temps then CO2 enrichment. Keep your fan on a thermostat and let it maintain your temps.
  11. Unless you can do the co2 properly its probably not worth messing with. I've decided to put it off for at least another grow. I can see the system costing me over $1000 and I don't want to even attempt it until I have everything needed and a monitor is necessary.
  12. From what I have read its not good to add co2 during flowering. You should discontinue 2 weeks before harvest. It supposebly makes the plant loose its potency.
  13. That is my understanding too, mr.piffy87. :)

    CO2 should only be used during the vegetative stage of the plant's lifecycle, not during the flowering stage. And yes, stopping 2 weeks prior to budding.

    I also understand that between 1500 - 1700 ppm is the ideal concentration range.
  14. I dont agree at all. If I had to pick a cycle to use CO2, it would be during flowering. I use it during both cycles and leave it on to harvest day. It's not like nutrients that need to be flushed.
  15. #15 Dr.HydroThumb, Mar 24, 2010
    Last edited by a moderator: Mar 24, 2010
    Hey there guys. I am a local grower here at GC. I too wanted to implement a co2 systerm. However I was going about it a total different way. I have my co2 setup almost complete using this idea in mind. theorethicly you shouldnt need a monitor using this. Anyone have any experience using it?


  16. If that site is legit thats a huge money saver..
  17. Any time I've grown it's been in mine, or someone elses house. Controllers and meters for parts per million all seems a little complicated to me. So if you have a smallish cabinet here's my recipe to supplement co2 a little bit, maybe with 2 of em you could do the space you have.

    Get a 5 gallon bucket and fill it 2/3 with water. Add a cup or two of sugar. Add in a handful of brewers yeast. Put it in your cabinet. Ever week or so pour about 1/3 off and add some fresh water and a few tablespoons more sugar.

    The yeast eats the sugar and the plants oxygen and produces alcohol,and CO2.

  18. i went to my local hydro store and asked a couple of people that hang out up there

    they all said it would work. one said 'how do you think old schoolers did it til the digital stuff came out' the store owner actually suggested using the chart instead of buying the 500+ meter.
  19. where do you run the co2 hose from the bucket?
  20. I believe the bucket stays open to the air and the CO2 is naturally released through that reaction, into the air. If you were to go this route, I would put a small fan above the bucket blowing it toward the desired direction.

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