# CO2 Question



## Killertea08 (Jul 2, 2011)

My question is what would be the better choice.  CO2 in a bottle or a generator?  My grow space is going to be a 4x8 hydrohut with 3 aircooled  600w HPS lamps.  I'm going to fill out the space with 4 plants with a SCROG  set up.  Plants are going to be in soil all organic for this run.  any suggestions?


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## Herm (Jul 2, 2011)

Do you have monitoring equipment to keep track of the CO2's ppm?


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## Killertea08 (Jul 2, 2011)

No I don't have anything that will do that.  I have a regulator by green air products that connects co2 and my exhaust fan together so when my fans go on the c02 shuts off.  Connected to this is a cycle timer.


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## Locked (Jul 2, 2011)

I think you need to be able to monitor the ppm...something like 1500ppm is needed....? Not sure.


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## WoodyPheonix (Jul 3, 2011)

To get the best from CO2, you need a sealed room with AC running the CO2 at 1500 as HL said.
If not, It can be used by having it run for 15 mins, 3x per lights on. During this time, your exhaust fans need to be turned off and the CO2 should be pumped from tubing at leaf level.
I see the latter method as a complete waste of resources, ie, time and money. The only sure way to know if it makes a difference is if you already have a perfectly dialled in room and have explored all the alternatives to improving yield, such as air exchange, lighting etc. Remember, it is photosynthesis that makes any part of a plant grow and CO2 is only part of that, light, nutrition and water being the others.
JMO W


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## Killertea08 (Jul 5, 2011)

Woodypheonix thanks very much for the info   Question for you then, what size a/c do you recommend for a 4x8 room.  I was looking at portable a/c the other day and I'm thinking of just getting the biggest one they had which was 11,000 btu's.  Seems over kill but I remember in the past I had one that was only 7,000 btu's and I had to max it out with just one 1000w HPS lamp!  Considering the fact that I will be using 3-600w lamps now this leaves me scratching my head a lot as to what size i'm going to need.  I could of course rig up a window a/c, but then I would have to cut a hole into the fabric of the hydrohut?


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## Killertea08 (Jul 5, 2011)

whats the better choice, bottle co2 or generator?  I found out that burning NG or LP creates a lot of water vapor as well as heat in the space which requires more ventilation.  With 3 lamps in there the last thing I need is more heat, but then again LP tanks are cheaper and then I don't have to go fill up co2 tanks and raise suspicion as to why i'm going to often.


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## Herm (Jul 5, 2011)

I have seen posted on this site that you want to be running hotter with CO2 but I have zero experience with it.  I just knew one of the first questions was going to be about your monitoring set up.


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## Locked (Jul 5, 2011)

Found this online....take from it what you will.


*A good grow room will have good temperature and humidity control with different settings for day and night and a gradual change over between. Night temperatures should normally be about 5oC below day temperatures whereas night humidity should be well below that of day time (perhaps around 50%).  An exception to the 5oC night drop may be for short periods  when you are trying to reduce spindly growth.  Good interaction between CO2 enrichment and ventilation is vital to ensure that no precious CO2 is wasted.  The system must be easy to use and provide simple data logging to show you what the temperature, humidity, CO2 and light levels have been doing while you werent there. 



Good fail safes are essential.  What happens if the air-con fails, what if the dehumidifier fails?  or if the power fails when the lights are on? (when power resumes we need to bring the lights back on methodically, taking into account minimum cooling periods and time delays between banks switching on in order to avoid power surges).  An alarm system that will text or phone you if something goes wrong or if an intruder is detected.  All of these things come to mind.



If you are looking for ultimate growth then CO2 injection must be considered but it does bring with it a further difficulty.  When injecting CO2 you need to keep the growing area closed with fans off.  If using ordinary lights the temperature will quickly rise and soon you will need to switch on fans to cool the room down.   This limits the time that you are able to inject CO2 and it also increases CO2 wastage (although a good controller will minimise this by stopping CO2 injection well before venting is required). 

Hint 1.   Use air cooled lights if you intend using CO2 enrichment.  This allows longer periods of injection before venting is required.



Even so, the crop under lights and with CO2 enrichment will be growing vigorously and will transpire heavily.  This will raise the humidity and again it will become necessary to turn on the fans to reduce this.  A better option is to use a dehumidifier to keep the humidity at an acceptable level without the need for frequent ventilation. 

Remember also, that the desired humidity varies depending on the stage of growth starting from a very high level for cuttings/seedlings and reducing considerably when flowering.  Good controllers now offer automatic scheduling of all important growroom variables, changing these automatically as the crop grows.

Hint 2.  Use a dehumidifier to extend the CO2 injection period to the maximum possible.  




If you have decided to use CO2 then be aware that the rate of injection must match the growth stage of the crop.  For example, if you inject high levels of CO2 at the cutting stage, the roots will not be able to cope with the attempted growth rate and the cuttings may be damaged. 

Hint 3.  Start with CO2 of 600ppm and increase it gradually as the plants develop.  You should be able to increase by about 100ppm every four days days until you reach your target CO2 level for the mature crop.  This is typically 1100 to 1500ppm.





Now were really cooking with gas!  Growth rates will be high and we need to ensure that the crop gets adequate lighting for high growth.  With two banks of lights you have an ideal situation. During vegetative stage of growth you require a lower intensity of light but for a longer period (say one bank of lights for 18 hours per day).   During this period the controller should be set so that only one bank of lights is used at a time and the two banks are switched on alternately each day.  This ensures that the crop receives light on both sides.  During flowing, more light is required for a shorter period (eg 12 Hours) and for this stage both banks of light will be used.  Modern controllers can be scheduled to do all of the above automatically.  It will even switch banks if the light sensor detects low light (such as for a bulb failure) and will recover lighting correctly after a power failure ensuring that cool down periods are observed.  When both banks of lights are programmed to be on together the controller will enforce a minimum gap between each bank switching on to allow the power surge from the first to die down before the second starts.

Hint 4.  Use two banks of lights and program them to alternate during vegetative phase and for both to be on together during flowing stage.



In warmer climates or to ensure growing is possible during the warmer months of summer, an air conditioner may be used to keep the room cool and thus allow long CO2 injection periods.   One disadvantage is that air-con tends to dry the air and to correct this some form of humidification is required. 

Low humidity will also be a problem when regular lights are used (ie not air cooled) as the fans will be on most of the time and the combination of heating (from the lights) and fan ventilation is very drying.

Humidification can be achieved by using either a humidifier or a fogging nozzle.  These both need a slightly different control as the humidifier can normally be switched on when the humidity is low and switched off when it is high.  Fogging, on the other hand, tends to be more effective and needs to be pulsed on for short bursts to avoid putting too much water into the air.  Fogging is the lower cost option if mains water pressure is available together with low pressure fogging nozzles.  Ensure the nozzles are classified as foggers rather than misters.  Droplet size should be below 80microns. 

Of-course, your climate controller must have the intelligence not to humidify the grow room just before the lights turn off as leaving the crop damp and cool will lead to fungal disease problems.

Hint 5.  If an air-conditioner or regular lights (non cooled) are used then humidification will be required.  Use either a humidifier unit or pulsed fogging nozzles. The finer the droplet size the better.



Humidity must be carefully controlled especially during flowering as air filters become ineffective at high humidities.

Hint 6.  Ensure that maximum humidity is programmed to be below 70% during flowering stage



Things do go wrong (bulbs fail, circuit breakers trip, CO2 runs out, intruders detected) and you need to know about these events as soon as possible.  A good control system will have flexible alarms including dial out to a remote telephone or  mobile phone.

Hint 7.  Ensure that you have a good alarm system to warn you if anything should go wrong.



Lighting, CO2 and humidity all require frequent settings changes during the overall grow period.  A good controller such as those made by Autogrow allow these changes to be pre-programmed so that you cant forget to do them.  Of-course, growth rates are never the same and so changes to the schedule must be easily made.  With a telephone or internet link to your PC you can even make these changes remotely.*


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## Killertea08 (Jul 5, 2011)

WOW Hamster Lewis that was a great read!  Thanks very much for that.


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## WoodyPheonix (Jul 6, 2011)

The size of AC unit you would need all comes back to the science and lots of details needed.
What volume space are you talking about, what are the ambient temps throughout the year and day/night differrentials, how much heat do the lights generate, will the ballasts be housed in the same space, thereby increasing the temps. These are just off the top of my head but there are other factors too.

From what I have seen a 12ton unit will cope with most domestic situations of growing, remembering you should never run equipment such as an ac unit on full power all the time, there should be room to spare. Also, what is good for somewhere such as where I live (Scotland) will be different from Florida for example.

You really need to do a lot more research before spending money on an AC unit and CO2 ammendments and as I said previously, for 2 or 3 lights I just dont see the point until you have ran several grows in the space and got the space totally dialled in. Only once this happens can you quantify the value of adding expensive AC & CO2.

Heres an example of what I am talking about, a dialled in room can produce say 1g/W, a high tec room with ac & CO2 and top end nutes with all the add ons will produce, for arguments sake, 1.5g/w. Lets say you have 2x1000W. Room a costs $150 per month, room b $250. Now do the math,
a 2000g/$150 = 13g/$
b 3000g/$250 = 12g/$

My friend spends £30 per month on CO2 and I call him an idiot, for the same cost he could run an extra 4x 1000W lights. He doesnt understand my argument, he just sees the bigger yield. Maybe a degree in business management is my problem that I understand getting value from each £or$.

The downside, for those who cant see it, is this is all dependant on maximising yield per $, not yield per m2. CO2 with AC will give more yield for the available space when set up correctly but there are a lot of factors to take into account.

In short, get a 12T BTU unit, CO2 generator (not bottles) and computer monitoring/control. If I had unlimited space & £ its what I would do.

Peace W


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## Killertea08 (Jul 6, 2011)

Hey Woody thanks very much, I understand your idea and will take it into consideration.  I'm doing a lot of planning on this one well before i put any girls in the room.  I have 3 600w HPS lamps right now all with digital ballasts.  The 4x8 hydrohut is coming soon.  Once everything is in place i will be posting this up so everyone can watch.  Would you suggest that I just run the 3 600w lamps?  I can get 1000w easy fyi


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## WoodyPheonix (Jul 6, 2011)

I had that size space and got good results from 2x600W so 3 should get super result. You will have 9,000 lumens per sq ft which is excellent.
I would suggest getting cool tubes though for cooling with a dedicated fan drawing in cold air and a separate fan for air exchange otherwise it will get very hot in there. In my space it would hit 100 in 20 mins with the fans off.

Looking forwards to seeing a gj and some pics. W


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## Killertea08 (Jul 6, 2011)

Thanks again Woody, I can't wait to start!  I will be running a 6in vortex for the lamps, another 6in vortex for exhaust and maby a 4in for intake.  My plan is 4 plants utilizing the SCROG mindset to maximize yields.  I would like to set up CO2 in there as an experiment to see the yields, but then i would have to get a/c and a co2 monitor so i'm not wasting.


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## greenmentat (Jul 7, 2011)

Here in CA I saw a CAP environmental controller with CO2 monitoring on craigslist for $120.  An used window mounted 11kBTU AC can be had for under $200 and a portable one shouldn't be much more.  Just saying.  I didn't have much luck with cool tubes, they had more of a hot spot than my regular reflectors.  If you aren't getting an AC you might want to go with an 8" valuline fan(750cfm) ($99), instead of a 6" vortec(450cfm) to reach the optimum rate of 150cfm per light you will lose cfms with distance and corners in your ducting.  Are you planning on doing 4 plants per light or 4 plants for the whole room? That would take a lot of vegging


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## WoodyPheonix (Jul 7, 2011)

I love your enthusiasm KT, getting a new room going is great, watching plans come together and actually doing what you hoped for takes some beating.

If I had the cash, space, privacy I would go with CO2 but until a room is dialled in, I dont see how you can quantify if it is worth it. Especially if your botanical skills are not properly honed (like mine). Short cuts such as expensive nutrients dont make up for skill shortages such as mine.

I do think however that concentrating on developing a plants roots and getting the environment correct will yield better results than CO2 and expensive flowering boosters. Yet something like michorise and trachoderma (sorry about spelling) cast very little in comparison.
W


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## greenmentat (Jul 7, 2011)

Thanks for the reminder, Woody.... I need to go hit up my plants with some MycorRhize(sp?)...... If you have roots taken care of, watering/feeding schedule down, then it seems like it would be wise to integrate things like CO2 and bloom accelerators... after every harvest I take a look at the root structure of the plants and it's always the the plants with the best root systems that are the biggest, healthiest, and my highest yielding..


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## WoodyPheonix (Jul 8, 2011)

You can be sure the weakest, poorest plants will have the weakest and poorest root structures.
On old guy I know who grows just about everything told me what he sees above ground tells him how his roots are and it is those he cares about. He says he is a root gardener, the flowers, veg & other plants look after themselves as long as he looks after their roots!
A good ethos I think. W


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## Killertea08 (Jul 8, 2011)

I agree 100% Woody, I always learned from my mother when gardening.  She always said "Feed the soil not the plant".  I have a few grows under me, so I think i will be ok.  I never buy that expensive stuff, there are a few brands I like that are in the mid range of prices, but I like to stick to compost teas "killertea" and such.  I will dial in my grow space and run a course without additional c02 and see how it goes.


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