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- #41
I have a window ac unit thats always on, u think that brings enough fresh air in the room ?
Keeping the temperature down?
- Thread starter AZ007
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I have a window ac unit thats always on, u think that brings enough fresh air in the room ?
Hey A, I think Hiker's post above, where he talks about negitive pressure in the tent relates to the room and window as well. by opening up the tent to the room air, your exhust fan is what moves air past the plants. If you don't vent to the outside or into another /difernet air space your just move the same air around, heating and heating as time goes by. Vent out of that space and the cracks, and spaces around fixtures and opened windows become your source of fresh air, in old places like mine, all 400 cfm can be sucked with little or no notice. Find the air leaks and the openings can be restricted to create specific air flow patterens around the plants if that air pressure difference is big enough. If your fan is in the tent your opening and any cracks are the intake thereby the exhust fan is the intake fan. I don't know air conditioners but recon they either put moisture into the air or take it away and bet a hot area where you need air conditioning in April has stores that sell really nice air conditioners that cool the air, reduce its moisture or add to it, and give off a presence of a beautiful woman, would be idel for such indoor grows. How are your plants? do they sway in a tropical breeze or real from dirty urban air?
I have 4 A/C systems 3 window and 1 portable. Only 2 of those have the option to pull in fresh air. The newest one has NO OPTION to pull in fresh air.
If you have a switch (usually manual) that says recirc or exhaust or something like that, you might have one that allows fresh air in. If you do have one of those, it'll depend on the size of the A/C and the size of the room and the number of plants.
It's kinda funny that the old units allow fresh air and the newer digital one doesn't.
I just added a forced CO2 to the 2nd grow room yesterday to address the CO2 needs. It's 26 plants about 2' tall. As they grow, they need more CO2. Also, the amount of time the lights are on. Remember they make CO2 at lights off and use it at lights on.
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- #44
Well this is a pretty old unit, and its mounted on the wall, half of it its sitting outside, i thought thats where it pulled the air from..outside, no?
No. A window A/C is just like a two part central A/C, the difference is that it's contained on one box. There's the inside part and the outside part and they are kept separate from each other. Two of my units have a lever on them that opens a vent, the vent allows some of the outside air to mix with the inside air.
The vent is labels exhaust and has an open/closed setting.
If you don't have one, you can add a window fan. I have a window fan, it's two fans in a flat holder that goes in the window. It pushes air in or out or both in and out. The problem you'll face with these window fans is that they are not light tight. You'd have to cover it during lights out unless it dark outside.
Another option is to add a vent to the room. They make vents where you just cut a hole and install a duct, then route the duct somewhere outside or attic. Most attics are vented somehow. You can also add an inline booster fan, that's what I did to add CO2 to the room. I route CO2 from the gas furnace to the rooms. It's warm air that comes from the furnace and I have to run the furnace when I normally wouldn't, but I offset this with more A/C. It also has the upside of lowering the RH.
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- #46
Yea i dont have that option on my ac unit, but there is fan only, if i were to use the fan where is the fan bringing air from?
If it has fan only, it's just moving air over the coils without running the compressor. So it's just moving the same old air.
I don't know why they don't offer the fresh air option, probably because the fresh air is hotter than the indoor air and they are rated on how much cold air they provide.
If you're indoor air is 80 and you drop it to 70 that's easier than taking the outdoor air at 100 and dropping it down to 70. So that's probably why.
You should look into a window fan. I think they can sit directly on top of the window A/C unit. You'll just need to cover it when the lights are out and there is light outside. Also, they can let small bugs in I think.
Another option is to get a source of CO2, if you don't have a CO2 generator, it can be costly and I don't know is those CO2 booster boxes can provide enough to substitute for fresh air.
It's probably best to provide some source of fresh air.
I don't know why they don't offer the fresh air option, probably because the fresh air is hotter than the indoor air and they are rated on how much cold air they provide.
If you're indoor air is 80 and you drop it to 70 that's easier than taking the outdoor air at 100 and dropping it down to 70. So that's probably why.
You should look into a window fan. I think they can sit directly on top of the window A/C unit. You'll just need to cover it when the lights are out and there is light outside. Also, they can let small bugs in I think.
Another option is to get a source of CO2, if you don't have a CO2 generator, it can be costly and I don't know is those CO2 booster boxes can provide enough to substitute for fresh air.
It's probably best to provide some source of fresh air.
Be careful venting warm moist air directly into an attic. If the attic has a gable vent, try to run the ducting all the way too it. You do not want moisture inside your attic.
Karl, I'm not understanding what you're doing with the furnace to provide CO2... Are you venting the furnace's exhaust into the grow room? Yes, that will have a lot of CO2. My CO2 generator is simply a gas burner. I'd be worried that, if I used flexible ducting for that, it would cause too much resistance and cause the furnace problems. Also, that exhaust will not be dry air. It will add to the humidity in the room. When gas burns, you get CO2 as a by-product, but you also get H20.
Be careful venting warm moist air directly into an attic. If the attic has a gable vent, try to run the ducting all the way too it. You do not want moisture inside your attic.
Karl, I'm not understanding what you're doing with the furnace to provide CO2... Are you venting the furnace's exhaust into the grow room? Yes, that will have a lot of CO2. My CO2 generator is simply a gas burner. I'd be worried that, if I used flexible ducting for that, it would cause too much resistance and cause the furnace problems. Also, that exhaust will not be dry air. It will add to the humidity in the room. When gas burns, you get CO2 as a by-product, but you also get H20.
My house is in the processes of a remodel. The furnace is actually not installed. It had to be moved because it was burning the support beam. I vent from above the furnace exhaust. The RH in the 2nd grow room is 20% and I actually think it might be better if it were up a bit, but the plants look happy.
Once the furnace is properly hooked up, I'd have to figure out something else.
I'd really like to know what the PPM is, I wonder if I can rent a CO2 Meter. The reason I don't buy one is that I look at my TDS PPM meter, I tested the water, PH'd water, nute water, other than that... it just sits there. I know CO2 has value, but I don't know if I have to be that exact with it.
I wish I knew someone that had one I could borrow for a day.
What would it do for a day? I check mine everyday, and it took a couple weeks to dial in my CO2 where I want it. For $150 you also get another thermometer and rh meter as well. I'm glad I have mine. I suspect you will be glad you have it once you do. If you're trying to supplement CO2, I don't see any way to do it without some way to measure.
What would it do for a day? I check mine everyday, and it took a couple weeks to dial in my CO2 where I want it. For $150 you also get another thermometer and rh meter as well. I'm glad I have mine. I suspect you will be glad you have it once you do. If you're trying to supplement CO2, I don't see any way to do it without some way to measure.
My concern isn't in making it ideal, I'm actually happy with the growth rate and health of the plants. My concern is in my health. My house is under a remodel, so about 1/2 the house is pretty open (no walls) so the area where the grows are is near the area where I sleep.
CO2 can kill, and you can't smell it. You'll get headaches and other things, but you can actually die from it.
As far as what's best for the plants, it could be that I'm too high or too low, but I really don't have a precise adjustment for that. I could turn up the furnace or lower it, I guess, but I don't know that I'd gain a whole bunch. I actually think my best investment is in more lights.
I can get a 600W HPS for that amount of money and put it down in the center of the grow.
I don't know why I can get a CO meter for $30 and a CO2 meter is 5X that.
I'd probably do fine with one of those $16 test kits, just to see if I'm in the ball park.
I'm sure the reason I'm not hurt by the CO2 is that the whole roof is vented and open, once I have a full ceiling, it'll be different, but by then I'll have the HVAC setup properly.
I suspect the CO sensor is just cheaper to manufacture. I'm unsure how a CO detector works. My understanding of how the CO2 sensors work is they have an LED that emits a specific wavelength of light. CO2 must either absorb or diffract some of this light at varying levels based on concentration. There is a sensor reading the amount of that light being absorbed or diffracted and using that reading to calculate ppm.
How are you controlling temps in the room now? If you're venting the whole room every 5 minutes, then your ppm is probably somewhere around the 500-600ppm of normal air. If you're venting to control temps, then how will you keep your CO2 near the plants? It's much more efficient/effective to supplement CO2 in a sealed environment, but I've done it with fans and timers. If you can keep your room cool enough by only having your exhaust fan running part of the time (Mine had to run 24/7 before sealing the room), then you can set things up so the CO2 is injected right after the exhaust finishes. That's how I did it in the past with a CO2 tank that I could regulate very accurately.
You are absolutely right about the dangers of CO2. Remember that is it heavier than air though, so the open roof may not be helping as much as you think.
Good luck with the remodel btw. I've been there too. Boy is that stressful on a marriage, huh?
How are you controlling temps in the room now? If you're venting the whole room every 5 minutes, then your ppm is probably somewhere around the 500-600ppm of normal air. If you're venting to control temps, then how will you keep your CO2 near the plants? It's much more efficient/effective to supplement CO2 in a sealed environment, but I've done it with fans and timers. If you can keep your room cool enough by only having your exhaust fan running part of the time (Mine had to run 24/7 before sealing the room), then you can set things up so the CO2 is injected right after the exhaust finishes. That's how I did it in the past with a CO2 tank that I could regulate very accurately.
You are absolutely right about the dangers of CO2. Remember that is it heavier than air though, so the open roof may not be helping as much as you think.
Good luck with the remodel btw. I've been there too. Boy is that stressful on a marriage, huh?
The 1st grow has a window A/C and a fan on the floor. The CO2 comes from above. I haven't had a problem with temps yet, it's been mild weather so far.
The 2nd grow had no A/C and only one small fan on low. The temps have been good because of the mild weather, but that'll change soon.
The room isn't closed, I still need to put up one more wall and have no doors. I'm using a Panda sheet to close off the 2nd grow at night and it's still open at part of the ceiling.
Your right on the CO2! I've been paying attention to headaches, but that's a fool's game. I'll be changing that soon by putting in more vents and testing the CO2 level.
I don't know if I'm moving all the air from the room or how often, I'm just keeping an eye on how happy the plants are. The CO2 is free for me, so I just add it and it seems to be helping.
I think the CO vs CO2 costs are in part because of being mass produced. California now requires CO meters in every home. Just like a smoke detector. Someday, they'll probably require CO2 alarms as well. People can die from either one.
The 2nd grow had no A/C and only one small fan on low. The temps have been good because of the mild weather, but that'll change soon.
The room isn't closed, I still need to put up one more wall and have no doors. I'm using a Panda sheet to close off the 2nd grow at night and it's still open at part of the ceiling.
Your right on the CO2! I've been paying attention to headaches, but that's a fool's game. I'll be changing that soon by putting in more vents and testing the CO2 level.
I don't know if I'm moving all the air from the room or how often, I'm just keeping an eye on how happy the plants are. The CO2 is free for me, so I just add it and it seems to be helping.
I think the CO vs CO2 costs are in part because of being mass produced. California now requires CO meters in every home. Just like a smoke detector. Someday, they'll probably require CO2 alarms as well. People can die from either one.
Good point about why CO sensors are cheaper. I had not considered the increase in demand due to legal requirements. I know they sell a dozen different kinds of CO monitors/alarms at my local Wal-Mart. I suspect it's a combination of both effects.
Honestly, CO2 poisoning is a much smaller concern than CO poisoning due to the concentrations needed. It takes a level nearly 20 times normal to trigger symptoms in a healthy adult. CO requires much lower concentrations to be dangerous. This is due to it's mechanism. The CO is absorbed through the lungs as a replacement for O2. The CO's O molecule is able to bond to our blood cells, thereby replacing an O, but out bodies cannot use CO. If enough O gets replaced by CO, we can literally suffocate. CO2 is not absorbed into the blood, like CO, so it's less dangerous. The symptoms of high levels of CO2 are more likely related to it displacing the O2 concentration in the air.
I understand your concern, and you should at least check the levels, but I wouldn't be too worried.
I do have one question. How is it free CO2? Are you already running the furnace? What happens when it warms up? No more CO2?
Please don't take this as argumentative. I'm told I come across that way sometimes. It's just an important and interesting topic of discussion, so I did a little research and am sharing what I've found. You can see the info about CO2 at these links:
FactCheck.org misrepresents the dangers of carbon dioxide | Just Facts Daily
Carbon dioxide dangers
You can find hundreds of sites explaining the dangers of CO, so I'm not posting any.
I hope you do get a meter. I'm curious how much CO2 you get from the furnace.
Honestly, CO2 poisoning is a much smaller concern than CO poisoning due to the concentrations needed. It takes a level nearly 20 times normal to trigger symptoms in a healthy adult. CO requires much lower concentrations to be dangerous. This is due to it's mechanism. The CO is absorbed through the lungs as a replacement for O2. The CO's O molecule is able to bond to our blood cells, thereby replacing an O, but out bodies cannot use CO. If enough O gets replaced by CO, we can literally suffocate. CO2 is not absorbed into the blood, like CO, so it's less dangerous. The symptoms of high levels of CO2 are more likely related to it displacing the O2 concentration in the air.
I understand your concern, and you should at least check the levels, but I wouldn't be too worried.
I do have one question. How is it free CO2? Are you already running the furnace? What happens when it warms up? No more CO2?
Please don't take this as argumentative. I'm told I come across that way sometimes. It's just an important and interesting topic of discussion, so I did a little research and am sharing what I've found. You can see the info about CO2 at these links:
FactCheck.org misrepresents the dangers of carbon dioxide | Just Facts Daily
Carbon dioxide dangers
You can find hundreds of sites explaining the dangers of CO, so I'm not posting any.
I hope you do get a meter. I'm curious how much CO2 you get from the furnace.
Great info! Looks like CO2 has plenty of warning signs...
I guess 'free' isn't the best term. All the outside walls and 1 load bearing wall in my house are made of cinder block (concrete). The foundation is concrete as well. When I 1st got this house I was shocked how long it took to warm up and cool down. It takes MUCH longer to change the temp of this house compared to a stick frame house. It also has very heavy shading on the South side, so I tend to run the furnace until about the start of summer.
I too would like to know just how much CO2 is coming out. The furnace is very old, probably original to the house (1930's) and it's 55K BTU. My guess is that the CO2 burners are much less than this just based on the size.
I just noticed the 2nd grow seems to have much more aggressive growth where the duct fan is dumping the CO2 vs the areas that aren't in front of the CO2 fan.
I guess 'free' isn't the best term. All the outside walls and 1 load bearing wall in my house are made of cinder block (concrete). The foundation is concrete as well. When I 1st got this house I was shocked how long it took to warm up and cool down. It takes MUCH longer to change the temp of this house compared to a stick frame house. It also has very heavy shading on the South side, so I tend to run the furnace until about the start of summer.
I too would like to know just how much CO2 is coming out. The furnace is very old, probably original to the house (1930's) and it's 55K BTU. My guess is that the CO2 burners are much less than this just based on the size.
I just noticed the 2nd grow seems to have much more aggressive growth where the duct fan is dumping the CO2 vs the areas that aren't in front of the CO2 fan.
My CO2 gen is 15kBTU for comparison. 
Are you mixing the air in the grow space, ie lots of circulation fans and fans moving air from the ground to the ceiling? CO2 sinks, so the plants under the duct might be benefiting as it passed by, but it doesn't get high enough at the other end of the room. I don't know. Just an idea.
Are you mixing the air in the grow space, ie lots of circulation fans and fans moving air from the ground to the ceiling? CO2 sinks, so the plants under the duct might be benefiting as it passed by, but it doesn't get high enough at the other end of the room. I don't know. Just an idea.
The 1st grow room has a fan on the floor, but I haven't done that with the 2nd grow room. It's not a well sealed room, part of the ceiling is open and the 'door' is a Panda sheet that's open during the lights on. So I know I'm not getting the full effect of all that CO2.
If you were to look at the plants, you would notice two things: The T8's go over the top and the plants under the T8's and have the CFLs near them grow the most. The area where the CO2 is blowing down, has the best growth by a good amount. Easy to spot.
I should get a few more floor fans and move the plants around, but the problem is the space.
I have my hardwood flooring boards in that room waiting for install and I have 26 plants in there. Space is cramped. I can walk around the grow sides but that's about it.
Once I get more remodeling done, I'll have more space. Right now, I have 2 9X11 rooms going and they are both cramped a bit. Not only that, but I'm getting ready for more clones, this time might be close to 50, so I really need to get busy on the remodel stuff.
If you were to look at the plants, you would notice two things: The T8's go over the top and the plants under the T8's and have the CFLs near them grow the most. The area where the CO2 is blowing down, has the best growth by a good amount. Easy to spot.
I should get a few more floor fans and move the plants around, but the problem is the space.
I have my hardwood flooring boards in that room waiting for install and I have 26 plants in there. Space is cramped. I can walk around the grow sides but that's about it.
Once I get more remodeling done, I'll have more space. Right now, I have 2 9X11 rooms going and they are both cramped a bit. Not only that, but I'm getting ready for more clones, this time might be close to 50, so I really need to get busy on the remodel stuff.
Sounds a lot like my grow. I put my seeds in water the day I got them. There wasn't even a room built for them yet. They certainly were a strong motivator to get things done fast, but I wouldn't recommend it. 
Have you tried configuring both of your fans to push air out? Each with a separate exit? This would create a vacuum. This way you will push double the air out and the open vents at the bottom would suck in double the cool air. Having one fan as an intake and another as an exit moves the same amount of air as a single fan but at a higher velocity...I think.
That's actually a valid point. If you have 1 intake and 1 exhaust vs 2 exhaust that should see an improvement.
I think the fans CFM ratings are just a reference point. You have to consider things like where it's drawing air from and blowing it to. In a tent, you should see a nice improvement with your idea to make both exhaust fans.
In HVAC systems, most homes simple push air into a room without considering how to get the old air out. I've seen some homes where it's hard to open a door because it's a fairly sealed room with a heavy A/C compressing the air inside the room.
Giving the air an exit helps flow greatly.
Most homes don't have that.
Same kinda thing with the roof or a whole house fan. I installed a whole house fan years ago and it's HUGE, draws air like crazy if you open any door, doesn't do much with the doors closed.
