Ventilation for Co2 question

First my specs:

4'W x 8'L x 7'H
2 x 600w phantom
2 x plantmax mh
2 x ushio hps
2 x raptor 6
9500 btu portable ac
orbital wall mount xtreme 16"

2 phantom 600w


A little bud porn from my last harvest.. La Confidential and Lavender, both were under a single 1000w, I have since moved to 2 600w, and adding in supplemental light where it may be needed



2 raptor 6"
both hoods and the ac are ducted through the ceiling. I pull air from in my house, carbon scrubbed during flower,




9500 btu portable ac
last grow was under a single 1000w, I live in a very hot dry climate. So cooling was an issue. So i ended up with this ac unit which was bought off craigslist for $100. A steal if you ask me. but It has brought its challenges as well. I bought a square duct work that goes to an 8" then reduced to a 6" into my flower room. atleast thats the idea



I have an idea of how am I am going to make this work with a single hose portable ac unit but I wanted to bounce the idea around a few experts. I have been on this forum for awhile now but im not really one to make small talk online. But with the direction I'm heading I sure could use some help.


co2 : I think I understand the concept of ventilation for co2... there needs to be an exhaust for heat exchange and an intake for fresh air to start the process over again.. my question is can I use my Portable ac outside my grow room and custom make ducting similar what an inline fan would be doing..using the C.A.P TMP-DnE controller to control both when my ac outside my room kicks on and my exhaust fan kick on. both of which could be controlled via a co2 shutoff? so something like this...sorry for the rough sketch..its all I could think of. but hopefully you get the idea.

its rough, I know.

the day and night temperature controller * tmp-dne * will control both the ac and the exhaust fan. the exhuast fan is on a speed control to match the intake from the Ac. I should probably keep a slight neutral to positive pressure in my flower room? [ edit ] Im thinking of putting backdraft dampers on both intake and exahaust. are they needed? they make sense to me

^ And those controllers would be controlled by the CO2 controller, so it will shut the exhaust system down, to add co2. Once maximum temp/1500 ppm has been reached the co2 controller kicks on the * tmp-dne * which in turn switches on the cooling/exhaust. then the cycle continues.

Should the cycle be continuous during lights on?
The flow meter, which setting should it be set at? should it be set to coexist with how long the flower room can stay under 85? *example* if I set the flow meter to 1 it takes 16 mins to fill the room to 1500 ppm, if im starting with a 200ppm room currently. so if I up the flow meter setting to 2, which in turn should fill the room in half the time.



Or ---- should i scratch the ac unit and just go with 2 x 4" or 6" inlines? intake exhaust..

I like the idea of the ac, especially if you are in a hot area. As for the co2, I have a rather large setup so for me I just run the co2 at night (lights off) because my exhaust stays off 60% of the time at night. In my experience more co2 is not needed (keeping it constantly at 1500ppm) but thats me. As for temp 85 is optimal but as long as you below 90 you should be ok especially if you have co2 levels above 900ppm. IMHO

Wow. First of all, don't run CO2 at night, it's pointless. Second, you don't have to vent fresh air in or bad air out, CO2 is best used in a COMPLETELY sealed environment.

The best advice I can give you is to score a C02 monitor, hydrofarm makes a cheap unit brand new to the market. Use that monitor to see what your AC does to the CO2. Nobodies room is the same.

Sencha said:

Wow. First of all, don't run CO2 at night, it's pointless. Second, you don't have to vent fresh air in or bad air out, CO2 is best used in a COMPLETELY sealed environment.

The best advice I can give you is to score a C02 monitor, hydrofarm makes a cheap unit brand new to the market. Use that monitor to see what your AC does to the CO2. Nobodies room is the same.

Click to expand...

good advice

^^^^^ exactly what he said.
2 types of rooms

sealed or not
supply supplemental c02 if you can't do air exchanges. one or the other. and only run it with lights on. a monitor is needed for c02 enrichment to work properly.
haven't seen the monitor from hydrofarm, b ut this is a plug and play with a built in photocell.http://www.sunlightsupply.com/p-14371-titan-controls-atlas-2.aspx

The purpose of co2 enrichment/ac is to eleminate exhaust/intake and to increase production. Your lights should be on their own isolated system unless your ac can handle the heat output. In that case, open hoods are fine. The room should be as close to 100% sealed as possible for co2 efficiency.

Respiration rates of plants are sensitive to temperature changes. Plants take in carbon dioxide during photosynthesis in the day, and release it during respiration at night. But they don't necessarily photosynthesize and respire at the same rates. Eventually half of the CO2 they use in photosynthesis is released back to the atmosphere by plant respiration
As long as there is no water, CO2 or nitrogen limits warmer summer temperatures will require more dark respiration to deal with the photosynthates produced during the long summer days. Several factors affect dark respiration. Light intensity & duration, water, nutrients, [CO2], and temperature all work together.
Once the temperature goes over 30C dark respiration increases sharply releasing a maximal [CO2].
[h=3]Source(s):[/h]http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=157143
http://books.google.com/books?id=MUS7BCmAPHcC&pg=PA708&lpg=PA708&dq=plants+nocturnal+respiration+temperature&source=web&ots=TXCKLatqGx&sig=Y8wN_2kbEPaS3Zgufp1Z1Y0kprY#PPA708,M1

So Ive decided to X out the ac. I added 2 inline fans, 1 for intake 1 for exhaust. both of which will be connected to the same speed control unit and also being controlled by an C.A.P air 3. CAP --> speed control --> inline fans * intake and exhaust * . The inlines are rated much higher than I need for my space which is why the speed control was needed. Thanks for all the replys Hoping to set up a grow journal on my next grow.

the room is sealed, except for zippers. will this be an issue? My reflectors are raptor 6" ducted with a 6" inline fan 400cfm.

IrishDoc said:

I like the idea of the ac, especially if you are in a hot area. As for the co2, I have a rather large setup so for me I just run the co2 at night (lights off) because my exhaust stays off 60% of the time at night. In my experience more co2 is not needed (keeping it constantly at 1500ppm) but thats me. As for temp 85 is optimal but as long as you below 90 you should be ok especially if you have co2 levels above 900ppm. IMHO

Click to expand...

LOL @ you for running CO2 at night

VICTORYGARDENSHYDRO said:

^^^^^ exactly what he said.
2 types of rooms

sealed or not
supply supplemental c02 if you can't do air exchanges. one or the other. and only run it with lights on. a monitor is needed for c02 enrichment to work properly.
haven't seen the monitor from hydrofarm, b ut this is a plug and play with a built in photocell.http://www.sunlightsupply.com/p-14371-titan-controls-atlas-2.aspx

Click to expand...

Agree with this! And your portable AC is probably sucking out your Co2.

Sencha said:

Wow. First of all, don't run CO2 at night, it's pointless. Second, you don't have to vent fresh air in or bad air out, CO2 is best used in a COMPLETELY sealed environment.

The best advice I can give you is to score a C02 monitor, hydrofarm makes a cheap unit brand new to the market. Use that monitor to see what your AC does to the CO2. Nobodies room is the same.

Click to expand...

I used black and white poly. Wrapped around a wood frame sealed every hole with gorilla duct tape. room is completely sealed. My hoods are 6" ducted from out of the room. I am timing my system now to see how long I can keep temps and humidity within the range.

The idea is to keep the co2 on the plants as long as possible, without the need to exhaust the room due to high temps or high humidity?

Should I expect high humidity while using co2 and temps above 82? therefore picking up a dehumidifier now.

chllnvlln28 said:

I used black and white poly. Wrapped around a wood frame sealed every hole with gorilla duct tape. room is completely sealed. My hoods are 6" ducted from out of the room. I am timing my system now to see how long I can keep temps and humidity within the range.

The idea is to keep the co2 on the plants as long as possible, without the need to exhaust the room due to high temps or high humidity?

Should I expect high humidity while using co2 and temps above 82? therefore picking up a dehumidifier now.

Click to expand...

Your idea is wrong though! Thats why he's telling you to get a co2 monitor. You only need 1500 PPM of Co2 during lights on. Anything more than that is just wasting it. A controller and regulator will allow you to constantly give your plants 1500 PPM of co2 during lights on. When levels reach 1500PPM the controller stops the regulator and when levels drop below 1500PPM the regulator starts filling the room up with co2. Co2 has nothing to do with humidity. Co2 is best used in sealed rooms and best used for temps over 85. Co2 @ 1500 PPM basically allows you to run hotter temps in your grow space.

BeaverHuntr said:

Agree with this! And your portable AC is probably sucking out your Co2.

Click to expand...

The portable ac was outside the room. the ac system had a single exhaust hose which i ducted into the ceiling. the blower part of the ac was covered with duct work. A retangle aluminum piece with an 8" port that was connected to an intake into my flower room. then I was going to exhaust with a 6" inline fan 435 cfm on a speed controller, to keep the exhaust at the same level as the blower from my ac. I needed the ac to blow the COOL air in cause the Ambient temperature in my house was not cool enough during the summer months. In which now I dont need the ac. So ive turned to adding another 6" inline fan to the mix for intake and problem solved.

BeaverHuntr said:

Your idea is wrong though! Thats why he's telling you to get a co2 monitor. You only need 1500 PPM of Co2 during lights on. Anything more than that is just wasting it. A controller and regulator will allow you to constantly give your plants 1500 PPM of co2 during lights on. When levels reach 1500PPM the controller stops the regulator and when levels drop below 1500PPM the regulator starts filling the room up with co2. Co2 has nothing to do with humidity. Co2 is best used in sealed rooms and best used for temps over 85. Co2 @ 1500 PPM basically allows you to run hotter temps in your grow space.

Click to expand...

Perfect thankyou!

YES, sealing your room will raise your humidity.