All about Co2

Ahh yes, this is why I am an engineer.
OK, evrything you ever will need to know about CO2 usage/consumption.
Its kinda long, but well worth it.
It is eaasiest to make a spread sheet with three columns, and 25 rows long. Then, just fill in the information. There is a little math here, so don't be afraid to grab a calculator, thats what they are made for!
Ok the formula:
a) Enter Length of the ENCLOSED room.
b) Enter Width of the ENCLOSED room.
c) Enter Height of the ENCLOSED room.
d) Multiply A x B x C = D (the volume of the enclosed grow area)
e) Enter existing CO2 levels. (350 ppm is almost a universal average)
f) Enter the desired CO2 ppm.
g) Subtract E from F. This is how much CO2 you need to supplement.
h) Multiply answer (G x 0.000001) x answer D [ex: g=1650; d=500 - therefore 1650 x 0.000001 x 500 = 0.825 (answer H)]
i) Enter Light cycle hours. How long are the lights on?
j) Enter Overall cycle time. How long from the time the CO2 goes on, sits, fans extract etc. until the next cycle starts?
k) Enter Exhaust duration. How long are the fans on, exhausting the air?
l) Enter the injection duration. How long are you wanting to inject the CO2 for?
m) Enter the injection frequency. How long do you want the CO2 OFF in between injections?
n) Add L + M to get the total injection cycle time.
o) Divide J by N (J/N) to get the scheduled injection periods per cycle.
p) Round O down to the nearest full number to get the actual injection periods per cycle.
q) Divide H by L (H/L) to determine the flow rate (CFM) to set your flowmeter to.
r) Mulitply Q x 60 to determine flow rate in CFH. (Depending on your flowmeter)
s) Add J + K. This is the Overall Cycle time. This is the CO2 cycle time + the exhaust cycle time.
t) Multiply I x 60, then divide by S (Ix60/S). This determines the scheduled injection cycles per day, and should be as close to a whole number as possible for best efficiency.
u) Round T down to a full number. This is the actual number of injection cycles per day.
v) Multiply P x U. This is the actual number of injection periods per day.
w) Multiply H x V. This is the actual CO2 usage per day.
x) Enter the bottle size in cubic feet. Small 20 lbs. tank = 172.8 cu. ft. , Large 50 lbs. tank = 432 cu. ft.
y) Divide X by W. This is how long the tank of CO2 will last.


Well, that should be a healthy homework assignment for you. Remember, it is most benficial to leave the CO2 for up to three hours before exhausting. You can always adjust cyle times etc. to get the most from your CO2. You just have to figure out what suits your grow room the best.
As a side note, a 20 lbs. tank of CO2 costs about $13-$20 to fill.


*Note* - all measurements are in calculated in feet.
Metric to Standard conversion factor:
25.4mm = 1 inch; 2.54 cm = 1 inch; 12 inches = one foot; 3 feet = 1 yard; 1 meter = 39.3 inches


(Edited by Herbsparky at 1:26 pm on July 14, 2003)