CO calculation without controller - please help!

[invi]

Hey!

If anyone could tell me whether my thinking is correct it would be great. I plan to introduce CO to my garden - but would be nice to know if it's of any use in my situation, and if my plan regarding control can work.

The girls are in soil. I have a small hot place in the attic, temps reach 90F, or go up till maybe 95F - i measured that when the thermometer got direct light, and with door closed. I measured 81-88F at canopy level in shade, and near the vents that circulate inside air. There are 2 HPS for a 12 square feet area with ~90k lumens (7450 lumen/sqfeet). Humidity can reach 60-70 when the lights are off on a rainy day, but the HPSs reduce this to 50 or below usually. Since proper ventillation would cost about as much as a CO2 tank with a solenoid valve i thought it might bring better yield then just fixing ventillation.
Hope this is correct so far.

I could not find a CO2 controller around here for less than a $1000 (there are cheaper 'CO controllers', those only have a timer and maybe a light detector to disable CO2 in the dark, but no actual ppm meter). A few hundred bucks would be fine for this, but found nothing near that price so far.

So my plan is to measure how long it takes to fill a 1L bag with CO2, calculate my grow space in cubic decimeters, multiply it with 0.0012 (for a 1200 ppm increase for ex.) to get the needed volume of CO2, then multiply this with the time it takes to fill a 1L bag.

So with numbers,
Time to fill 1L bag = X (guess maybe more than 5 secs if i set the pressure really low - the regulator is for fish tank CO2 supply and can be fine tuned)
Grow space = 8 cubic meters ~= 280 cubic feet
Needed amount of CO2 in liter = grow space * ppm to raise = 8000 * 0.0012 = 9.6

To enrich the room from 300 to 1500 ppm, the valve needs to stay open for 9.6 * X.
Let's say 8 * X to make sure it will stay below 2000 ppm.

Since the room is not sealed, and i might need to leave the door open a bit to keep temps around 93F i should probably repeat this every 2-3 hours. I could maybe exchange the air completely before each cycle to reset to 300 ppm. not sure if this is needed though, since the room is not sealed.
Also dont know what is the max acceptable temp with 1000-1500 ppm CO2.

Please let me know if you see any errors in this - or if you have experience with such things!
Thanks!

 

[invi]

Hmm just a second thought - this way a 5L co tank will be depleted in 5 days or so if i calculate correctly (5L @ 5 bar = 250L on 1 bar theoretically). Is that fine? Maybe 2x a day would be enough to enrich the area? There is only a 6" diameter vent duct open, walls and door are not airtight of course.
I kept the door closed the whole day cycle now, temps went up till 93F in shade - was really weid to see how good they looked, at this temp i was expecting a minor catastrophe after 16 hours.

I found a gadget for $200 that can display CO2 levels - it's not a controller, but can activate an output connector depending on ppm. Just need a switch that terminates the power for the valve when this output has a current in it.

 

[invi]

Got the meter finally, just for the record this worked more or less - i filled the room to 1700 ppm with this calculation, and base co2 level was 1-200 ppm higher then i thought so error was less around 100 ppm.

 

[Lester Freeman]

You first started off telling me you were going to add "Carbon Monoxide"

I laughed.

 

[Lester Freeman]

Nice analysis, glad it worked. I'd just say to becareful to not fry and over-work them. But it's assumed , you know the limits of your plants. Heat stresses are always a possibility.

 

[invi]

Nice analysis, glad it worked. I'd just say to becareful to not fry and over-work them. But it's assumed , you know the limits of your plants. Heat stresses are always a possibility.

Thanks!
I dont know their limits, all new strains for me but they are alive!
They can spend quite a few hours in 90F without looking sad so i guess co2 does its job.

There was one thing i miscalculated - the time it takes to deplete the tank. The 5L is still kicking after 3 weeks. Its stored as liquid probably hence the error.