Iluvtomatoes
Member
Hello my fellow CannabiNoid’s!
I thought I’d help share some of my hard-earned knowledge about some of the pitfalls and limitations of setting up CO2 in both semi-closed and open environments. At the start of this project, I was a complete novice and have learned through others, but mostly through a time-consuming process of trial-and-error.
Over the last year I’ve spent countless hours tweaking the room adding and removing equipment in hopes of finding the optimal and most efficient setup, a quest that we all share. Likewise, I found a CO2 generator in my hands and I wanted to implement the ultimate grow room accessory. Unfortunately, I found that CO2 was something more easily implemented in greenhouses or a large room. I, however, wanted to use CO2 in a small space and design a room that was similar to the larger closed-environment grow rooms.
The results of my exploration lend some insight into partitioning a single room into multiple chambers (lung rooms) and how air can be circulated, scrubbed, cooled, enriched, and exhausted in a small, semi-closed environment.
*IMPORTANT NOTE*
* This article is for people that are using non-traditional setups for CO2 environments such as: intake/exhaust fans, portable-single and dual hose a/c units. If you have a 5 ton chiller, split-level a/c unit, window box a/c unit, swamp/evaporative cooler, or a complete HVAC system for your room then you’re all set and are truly running a closed system; so let the rest of us be envious until we can outfit ourselves with closed system equipment. Likewise, this is for folks that don’t necessarily have a window, so extra long duct runs are normal
Also, I use a propane generator, so there’s not much on tanks, dry ice, and other methods here. Propane costs about $16.50 a tank and can last from anywhere to 1 to 4 weeks, so in the long run it’s the cheapest. However, a CO2 tank is much easier to implement than a generator, which produces additional heat and humidity that the tank does not. Initial costs for a refillable CO2 tank and regulator package are about $150-$300, while a fuel burning generator with a propane tank runs $300-$600 (more if you buy an air-cooled model $800-1400).
Even though the CO2 tank is cheaper on the initial outlay, refilling CO2 tanks will cost 2x-4x when compared to propane or natural gas. Purchasing these items will add CO2, but this does not include any CO2 measuring meters ($350-$550) or light-activated timers/controllers/relays ($80-$1200) which will be needed to make your garden run more efficiently. $Buyer Beware$ should be placed on all related CO2 systems because in order to use it efficiently requires the purchase of both controllers and meters. You may rely upon the charts that give approximate fill times for the rooms, but the only mention of loss rate is, “you may need to recharge your room with CO2 every 1 to 2 hours.” Yes, CO2 is great, but approach CO2 generators with caution.
Before I begin, I copied some background information on CO2 and optimal environment conditions.-Please read the cut/paste article by G.A.P. below. After that, I’ve included my experience with “effectively implementing co2,” which is not easier than it sounds, particularly if you use a generator. I will say right off the bat that the temperature range here states 80-85F (27-29C), but many experts suggest 72-78F (22.2-25.5C) as a much better range. Scientific evidence shows that plants grown at a steady 75F (23.8C) day and night have the highest THC concentrations. I have a tendency to go with that knowledge and aim for 72-78F when the lights are on with CO2. Also some people recommend a max of 1800ppm over 1500ppm. This is an unlikely scenario for people working with portable a/c units or fans.
Effectively Implementing CO2
Submitted by Green Air Products
First a little Plant Science 101 - For a successful, productive garden, hydroponic, indoor and greenhouse growers must control six "essential elements" - air, light, nutrients, water, humidity and temperature. Remove or alter the ratio of only one of these elements, growth will slow, and plants could eventually die. In this article, we will review the air element, specifically carbon dioxide (CO2), it's role in the most vital plant process - photosynthesis - and how to effectively implement CO2 systems.
Photosynthesis begins when stomata, pore-like openings on the undersides of leaves, are activated by light and begin breathing in carbon dioxide (CO2) from the air. This CO2 is broken down into carbon (C) and oxygen (O). Some of the O is used for other plants processes, but most is expelled back into the air. The C is combined with water to form sugar molecules, which are then converted into carbohydrates. These carbohydrates (starches) combine with nutrients, such as nitrogen, to produce new plant tissues. CO2 is vital to plant growth and development, and yet is often the most overlooked element in indoor gardening.
Successful indoor growers implement methods to increase CO2 concentrations in their enclosure. The typical outdoor air we breathe contains 0.03 - 0.045% (300 - 450 ppm) CO2. Research demonstrates that optimum growth and production for most plants occur between 1200 - 1500 ppm CO2. These optimum CO2 levels can boost plant metabolism, growth and yield by 25 - 60%.
Plants under effective CO2 enrichment and management display thicker, lush green leaves, an abundance of fragrant fruit and flowers, and stronger, more vigorous roots. CO2 enriched plants grow rapidly and must also be supplied with the other five "essential elements" to ensure proper development and a plentiful harvest.
Commercially available CO2 generators offer the most economical, practical and consistent method of enriching indoor gardens. Using atmospheric control systems in conjunction with CO2 generators ensure the most effective production and use of CO2.
Atmospheric control systems with automatic override or defeat, and CO2 monitoring logic, enrich and maintain optimum levels in the environment during the photo (light) periods, when most plants can absorb CO2; and they defeat CO2 production during dark periods. Automating your CO2 enrichment system pays for itself quickly with shorter crop cycles, improved quality and higher yields.
When enriching an indoor garden with CO2, proper light is essential for effective assimilation. For plants to use CO2 efficiently, light spectrum and intensity should be appropriate for the plant species in your garden. Remember - CO2 enriched plants under intensified lighting demand higher levels of nutrients, water, space and room temperatures of 80-85 F. (27 - 29 C.).
As CO2 is a critical component of growth, plants in environments with inadequate CO2 levels - below 200 ppm - will cease to grow or produce. And, growers should be cautious when experimenting with CO2 levels above 2000 ppm. CO2 is heavier than oxygen and will displace the O2 required by both plants and human to function and live. (FYI: OSHA max allowable for human exposure is 5000 PPM). So, air circulation and ventilation is critical to profitable CO2 enrichment.
Plants use all of the CO2 around their leaves within a few minutes leaving the air around them CO2 deficient. Without air circulation and ventilation, the plants' stomata are stifled and plant growth is stunted.
Proper air circulation with oscillating fans and in-line blowers will eliminate potential stagnation problems and ensure efficient CO2 enrichment.
If you have never enriched your garden with CO2, start with 700 - 900 ppm (double the normal atmospheric levels). If yields improve, increase CO2 enrichment to 1200 - 1500 ppm. If there is no response to the CO2 enrichment, double-check your other five "essential elements" to ensure they are not limiting factors.
This chart will give you the minutes of operation required for the areas and models shown. Top row of the chart represents cubic feet of area in the enclosure (LxWxH) The left column is the model size. Model numbers represent maximum CO2 output per hour in cubic feet (CD-3 = 3 cuft/hr CO2)
Example: A CD-6 will take 10 minutes to produce a CO2 level of 1000 ppm in a 1000 cu. ft. enclosure. The area should be charged as quickly as possible for maximum advantage. Charging the atmosphere quickly insures that the rapid photosynthesis process will not be interrupted and the plants growth rate reduced. Five to ten minutes is a good charge time. Try not to exceed twenty minutes. Your microclimate will need to be recharged every 1 to 4 hours depending on how much CO2 is lost due to plant usage or drafts (leaks). Large greenhouses logically require longer charge times and multiple units may be necessary. The CD-36 takes 1.66 minutes per 1000 cu.ft. area to charge to 1000 ppm. Therefore a 20,000 cu. ft. area would be 20 X 1.66 which is 33.2 minutes. For this application that may be an acceptable charge time.
I presume the run times here are for the pilot light only, It does not include ON times for the burner.
Alrighty Then!!!
Now that some of the basic groundwork for environmental conditions has been described, how do we go about getting them without some of the high-end cooling/ventilation systems that commercial growers have? Well, short of dropping $2,000-$5,000 on a 5 ton water chiller or a $120 window-shaker a/c, you don’t!!! I’m going to tell you right off the bat, that running CO2 generator (not tank) will increase the overall load on your system. In other words, the more you try to get that meter to 1200-1800 ppm, the more you’re exhaust fans and/or air-conditioning unit will work-usually taking CO2 with it.
The smallest generators Green Air Products CD-3 (3.2cuft/hr) or CAP 1 will produce as much heat as a 100-watt incandescent bulb with the pilot light. Fully active it generates approximately 2300 Btu-the same amount of heat as a 1,000 watt HID. Larger units can generate anywhere from 6-36cuft/hr with a complimentary amount of fuel consumption and other by-products. Considering the additional heat/humidity produced by burning propane, it is difficult to find the “sweet-spot” for rooms that rely upon traditional intake/exhaust fans or portable a/c units that inevitably pull air from the room—usually unfiltered for odor when a/c is involved. Since we’re not working with closed system cooling equipment, every gardener has to find an sustainable level of CO2 with an optimal amount of exhaust and cooling. Before we address the primary ventilation system in our room, heat from the bulbs needs to be removed via air-cooled hoods. What types of hoods, fans, and ducting are required for cooling various bulbs?
The bulbs are the primary source of heat for any indoor garden. In an effort to remove that heat from the garden we employ air-cooled shades that run on an independent ducting system preferably in a series (aka one after the other) when using multiple lights.
Parallel-ducting setups can be difficult to properly construct, it is often better to make two more holes in the ceiling/wall than trying to tie your room exhaust system to your air cooled shades. However, if you do go this route, invest in one-way duct dampers and larger fans to push the dampers open. So how much ventilation is required to cool my lamp? Here’s a rough estimate-Half the wattage of the bulb=recommended cfms. Some might say that is overkill but is it really?
*DUCTING TIP: Air is like electricity--It will take the path of least resistance! If you split intakes and exhausts, it is imperative that you place a fan pulling on the primary vent that all secondary vents are dumping into; otherwise the backpressure of multiples feeding into a non-power, ventilated exhaust stack will just cause inefficiencies. Look at some pictures of industrial ducting at warehouse facilities to see where inline fans have been properly placed at each workstation with a large workhorse fan exhausting all the merged workstations.
Likewise as you move up in duct size, you almost double the area that the air has to flow through. This allows larger fans to move more air while spinning at lower rpm’s or an exceptionally larger amount of air for HO fans at slightly higher rpm’s. I’d recommend the Fantech XL, Vortex, Can High-Output models over a lower wattage rpm standard. Below are some examples of fans and filters for hobby growers.
FAN/FILTER COMBOS for exhaust applications-for recycling room air go up to the next fan size.
Can Filter 33 w/ 6” Can-Fan - true CFM 168
Can Filter 50 w/ 6” High Output Can-Fan - true CFM 300
Can Filter 66 w/ 8” Can-Fan - true CFM 350
Can Filter 50 w/ 10” HO Can-Fan - true CFM 484
Can Filter 75 w/8” HO Can-Fan - true CFM 559
Can Filter 100 w/ 8” HO Can-Fan - true CFM 621
Can Filter 150 w/ 12” HO Can-Fan - true CFM 898
CAN FANS
Can Fan 4” – 142 CFM/3200 RPM/61w
Can Fan 4” High Output – 178 CFM/3260 RPM/70w
Can Fan 6” – 270 CFM/3240 RPM/73w
Can Fan 6” HO – 440CFM/3246 RPM/136w
Can Fan 8” – 493CFM/3215 RPM/125w
Can Fan 8” HO – 737CFM/3310 RPM/253w
Can Fan 10” HO – 781CFM/3290 RPM/251w
Can Fan 12” HO – 971CFM/3365 RPM/331w
CAN FILTERS
Can Filter 150 - 1260 CFM/123lbs of carbon weight
Can Filter 125 – 1110 CFM/103lbs of carbon weight
Can Filter 100 – 840 CFM/82lbs of carbon weight
Can Filter 75 - 600 CFM/62lbs of carbon weight
Can Filter 66 - 412 CFM/42lbs of carbon weight
Can Filter 50 – 420 CFM/31lbs of carbon weight
Can Filter 33 – 200 CFM/16lbs of carbon weight
VORTEX FANS
Specifications
12 inch - 1140 CFM - 2400 RPM - 3.2 Amps - 400 watts
10 inch - 790 CFM - 2510 RPM - 2.00 Amps - 224 watts
8 inch - 747 CFM - 2550 RPM - 1.60 Amps - 185 watts
6 inch - 449 CFM - 2600 RPM - 0.80 Amps - 100 watts
4 inch - 172 CFM - 2500 RPM - 0.65 Amps - 80 watts
Fantech Fans
Quick Specs:
• Model FX 4: 117 cfm, 2950 rpm, 44 watts, for 4 inch duct
• Model FX 4XL: 148 cfm, 2800 rpm, 83 watts, for 4 inch duct
• Model FX 5: 132 cfm, 2950 rpm, 42 watts, for 5 inch duct
• Model FX 5XL: 191 cfm, 2650 rpm, 87 watts, for 5 inch duct
• Model FX 6: 257 cfm, 2700 rpm, 84 watts, for 6 inch duct
• Model FX 6XL: 392 cfm, 2950 rpm, 147 watts, for 6 inch duct
• Model FX 8: 481 cfm, 2600 rpm, 119 watts, for 8 inch duct
• Model FX 8XL: 521 cfm, 2950 rpm, 152 watts, for 8 inch duct
• Model FX 10: 521 cfm, 3000 rpm, 147 watts, for 10 inch duct
• Model FX 10 XL: 590 cfm, 3000 rpm, 242 watts, for 10 inch duct
• Model FX 12: 711 cfm, 2450 rpm, 196 watts, for 12 inch duct
• Model FX 12 XL: 801 cfm, 3250 rpm, 411 watts, for 12 inch duct
If you look around the internet you’ll find some approximations on how much air flow is required to bring room temperatures within 3-8 degrees F of ambient air temperatures (see Fig. 1). While these charts are fairly accurate, they do not take into account the length of duct runs, number of turns, type of ducting, et cetera. Likewise this is a chart for open air-cooling of a grow room, not inline cooling of bulbs—so there is some disparity there, but the chart is close enough in my opinion.
In my experience, I’ve found that it’s better to go one or two sizes up from the diameter of ventilation you think you need. I’m cooling 1600 watts with one 6-inch Vortex 449cfm (100w) mated with SunSystem 2 air-cooled shades with 6-inch flanges and I would prefer 10-inch (780cfm) to 12-inch (900-1100cfm) High-Output (HO) inline fans considering the length of ducting (50 ft/15.2m).
Fig. 1—Thanks to Caligrower on CC
This setup allows room temps to come within 5-8 degrees F of ambient air temps, but will gradually keep rising well above safe temperatures if no additional venting or cooling is provided. This is not enough to maintain acceptable room temperatures for more than an hour, especially since I have a pilot light burning in the CO2 generator constantly. If, intake temperatures for the air-cooled hoods are below freezing you can maintain CO2 concentrations for several hours before the exhaust turns on; usually for humidity buildup. Likewise, if your fans CFM rating is more than 50% of your lights wattage number (i.e. 1000watts/500CFM+), you’ll be able to prevent frequent exhaust cycles. Warmer temps will eventually require a/c, if CO2 supplementation is going to be used.
According to the chart, you will only cool your light by a few degrees before you hit a point of diminishing returns on fan size. In Figure 1, you can see that the lower left-hand corner shows air flow targets that exceed most single pieces of equipment especially those used by hobby growers. If you can get half the cfms to lamp watts you’ll be in a good place for maintaining room air temps. If you can match the cfms to the lamp wattage then you will have maximized air-cooling especially when limited by the flanges on air-cooled hoods (4, 6, or 8 inches).
Unfortunately, most of us want more wattage while cooling with only 4 to 6 inch fans and ducting. If you’re running 1kw purchase an 8 to 12inch inline fan and use reducers to an 8 or 6inch air cooled hood you won’t be disappointed-especially in the summertime. So where do the ducts go?
Ultimately, you’ll want the coolest air you can find to cool your lamps and you’ll want to dump that air outdoors. You can either pull air from another room or run ductwork to the outside; I’ve tried recycling the indoor air to heat my house and it made the house too hot! I’ve found that an exterior intake and exhaust is best for air-cooling lights. You’ll notice more particulate matter in the hoods so you will need to clean the glass more often (between cycles is adequate) or add a small filter to keep debris out, but it is decidedly better than creating the negative pressure in your home.
*HOOD TIP: Match the wattage to the diameter of the air-hoods flange. 4inch=400watts or less, 6inch=600watts/1000watt, 8in=1000watts. In general, go with the 6 or 8 inch if possible.
* FAN TIP: When trying to judge the true power of a fan-look at the wattage of the motor and the size of the fan! Higher wattage=airflow with decent static pressure. A low watt computer fan may move 100cfm’s but only a few inches beyond the blades. We need more powerful air pressure and higher air flow capacities for lamps over 400 watts.
*A/C TIP: Higher wattage also applies to a/c units. Less wattage/power consumption is not better in these scenarios. The wattage is directly indicative of the size of the motor or compressor. The larger those items are the less they will have to work!
Now that we’ve got our lights air-cooled, we’re ready to exhaust the radiant heat produced by the electrical components, plants, and CO2 generator. In the typical grow room, a controller or device senses that the temperature/humidity are elevated (didn’t want to use the phrase “too high”), thereby triggering the exhaust fans.
At the minimum, you want the air to be exhausted in less than 5 minutes with 1-3 minutes being ideal. However, along with the hot and humid air, you’ve just exhausted all of the CO2. As a result, your CO2 ppm’s are probably back down to the 250-550 ppm range. If you have a controller or a timer on your CO2 (i.e. 6mON/30mOFF or 8mON/60mOFF) the controller will reactivate the generator and burn for the preset amount of time in an attempt to raise the CO2 (if you have a ppm meter it will try to reach whatever you’ve set the room at 600-1500ppms but it will be overridden with the time limitations/release schedule set by your controller).
Unfortunately, regenerating the CO2 causes the room temps to go beyond optimal conditions once again and our generator hasn’t even gotten us to 1000 ppm much less the 1200-1800 ppm range before the fans have been triggered again. Basically, the only remedy to this situation, is to have “super-cooled” lights with super-cool air actually turning the light into a sealed air cooling unit for the room. However, this isn’t really feasible because it requires large inline fans, short duct runs, 6in or 8in air cooled hoods (maybe 10in but the market doesn’t have these yet), and Siberian cold air.
So, if you maintain this setup you can burn a lot of fuel/CO2 tanks shooting for the moon in terms of 1200-1800ppm. Instead of continually engaging your exhaust system and then trying to refill the room with CO2, lower the setting on your ppm meter or CO2 burn timer. In this scenario, it’s easy to see that it might be better to run shorter bursts more frequently versus one long burn every 1-2 hours. If you run shorter bursts, you will keep the CO2 generator from directly engaging the exhaust fans thereby allowing a steadier level of CO2 in the garden, and more efficient use of resources.
Most manufacturers recommend that your CO2 burner run for approximately 4-10 minutes for a room fill, if it takes longer, they recommend a larger unit. This is misleading because a larger unit will fill the room faster, but it will also burn fuel faster and engage the exhaust fans sooner than a smaller unit, basically quickening the burn/exhaust cycle. Do not make this mistake. In this situation, it is much better to work with CO2 enrichment at the 600-900 ppm range. Often times this is complimentary with the amount of light that most home growers maintain. If you have a 600 to 1kw lamp, plants will be able to utilize concentrations above 1000, but how do we get there, when it is going to activate the exhaust more frequently while consuming more fuel to no avail?
In that case, I’d tell you that we can start edging a bit closer but like all things in life, nothing’s free. At this stage, you’ll need some form of a/c unless you’ve got the Siberian setup mentioned earlier. But before we buy any portable a/c here’s my story.
Before I ever purchased portable a/c units and a CO2 generator, I bought a CAP CGC-1 high-end controller and three 6-inch vortex fans, thinking that the more economical and ventilated approach would be the most efficient setup. While it’s true, that energy consumption is lower with the old in-and-out ventilation of fans, it’s neither conducive nor cost-effective when trying to enrich with CO2.
In the warmer months, the exhaust fans were running constantly; thereby wasting any attempt to raise CO2 significantly. It didn’t take long for me to realize that additional cooling would be needed for me to maintain CO2 temps of 72-78F (25.5C) so I bought an air conditioner. If you want 80-85F, an over-powered air-cooled light with standard intake/exhaust fans will usually be adequate, especially during the winter. However, many people find that during warmer temperatures additional cooling with more exhaust or a/c units will be required.
A/C TIP #2: If you have to buy one for the purpose of CO2 and you can’t do a window shaker; purchase a single-hose unit if you’re not using CO2, buy a double hose if you are going to use CO2. BEWARE all portables exhaust the room air, dual hose units to a lesser extent.
Ventilation TIP: Place all exhaust vents and filters up high to pull hot air out of the room (usually 5-10degrees warmer up there). Likewise, place your portable a/c unit on a chained platform or at least table height so that you may drain the runoff into a resevoir or a drain.
Originally, I opted for a low-powered (685w) single-hose, 9000 btu unit (once again, less watts is not a good thing in a motor/compressor). I installed it on a platform up high so that the drain line could go to my reservoir or sink. It worked great but was working most of the time and was sucking the CO2 out of the room keeping it from getting above 700ppm. On top of that, the vortex 449cfm and can 50 carbon filter combo (true cfm=300cfm) recycling room air was NOT effective in removing odors (600 cu/ft bathroom) before being sucked out of the room. I needed a more powerful fan for my filter to work in that manner.
Carbon-Filter TIP: If you need to use carbon filters for recirculation of room-air only, then go 1.5x the recommended fan for exhaust applications (0.1 sec contact time). Otherwise, the room air will only be reduced of odors by 60-80%. Either way, for recirculating applications you need a larger fan w/ the larger flange/adapter, a larger filter, or both. If you’re using it strictly for exhaust applications, you should know that a carbon filter will reduce a fan’s cfm rating by 30-40%.
A carbon sheet over the exhaust helped, but I was exhausting cooled, enriched, semi-stinky air because a single-hose unit cools the condenser coils with room air before exhausting out the hose. I knew that it was only a matter of time before the paranoia about the smell would get to me. At one point, I even installed a Carbon filter on the exhaust hose in the attic; till I realized that the carbon was being rendered useless by all the humidity. In addition to this, humidity levels will rise if you only have an air conditioner in a closed system. So, I bought a 40-pint dehumidifier 650 watts. Unfortunately, the dehumidifier puts out as much hot air as small CO2 burner in full tilt (approx 2k-3kbtu). The heating action of the dehumidifier further engaged the single hose portable a/c into cooling/sucking the now cooled/heated/enriched/semi-stinky/dehumidified air out the exhaust. In addition, the dehumidifier was noisy at 57db (sounds like a 18kbtu a/c running) because of the condenser.
After doing more research, I was incorrectly told that a dual-hose a/c unit would solve all my problems or at least minimize them. So, I found a 53db 85lb 12,000 Btu unit 1485 watts that actually had all the features: ionizer, dehumidifier, heater, air conditioner. It also had auto mode which would activate heat below 68F, dehumidify above 55%, a/c above 80F. I braced a couple of boards above the bathroom sink and cut two holes in the attic to run venting lines (longer, but larger diameter +2 inches, than the 9 foot, 4-inch PVC extension recommended by manufacturers). I added a double stack of rubber feet (circle fits into the square) to aid in dampening noise while installing closed cell foam (camping sleep pad) between the mounting boards and the wall.
I thought I would boost the air exhaust using a parallel run from my air-cooled lights. Unfortunately, this caused backpressure in the system and I had to give it an independent exhaust, but still managed to tie the intake to a larger 8x6x6 that also fed the intake to the air-cooled lights.
. It seemed to run just great, but once again, it was sucking cooled, enriched, stinky air out of the room. After doing some research, I found an article on sealing up the a/c unit. I disassembled the unit, and I could see where the gaps were, but it was a difficult and dirty job that would probably turn out poorly due to the tight spaces. As a result, I ended up sealing the lower edge near the wheels with liquid foam and a couple of spots where the a/c cabinet was vibrating when the compressor was on. This stopped some of the negative pressure in those areas and I didn’t want to modify the unit any further at the time.
I didn’t seal the whole interior cavities from one another because I believe the design is meant to be semi-open due to backpressure, particularly if you have a long duct run. I mention this because the back of the a/c unit has a 3 inch square (not the washable filtered intake) that clearly allows room air into the in/out chamber. Initially, I covered this up but with the long intake (28 feet) and exhaust run (25 feet) it would cause the compressor to overheat and fail after 10-15 minutes of operation.
At first, I kept the unit in auto-mode, but it had to run the dehumidifier during night time which would drop the temperature down below 68F. So I went to regular air conditioner mode, but this meant my environment was being completely regulated by the a/c unit. This mode is great, but the swing is generally only 1 or 2 degrees before the compressor engages. Of course, this doesn’t provide enough “swing” range for a CO2 generator to fill the room beyond 800 ppm.
Ultimately I had to dampen the a/c’s ability to read the temperature/humidity directly. I could change the thermistors to adjust the “swing” of the unit, but I really wanted to find something easier. I chose to create a b/w poly wall, while allowing the a/c unit to be on the other side closer to the passive air intakes and door. The output from the a/c was then ducted through a hole in the b/w poly, creating positive pressure in the sealed CO2 chamber and pushing out stinky air. The lung room where the a/c unit lies has a fan/scrubber that air-cools a MH light for vegetative. The hose has an external exhaust port or can be permitted to recycle and scrub air in the lung room.
In addition to this lung room, there is a b/w poly curtain near the entrance door that has a time-mist on low (air freshener) to help with any additional odors. This area has incoming ducting from both the central air system, and a dummy vent to the next room, it also has a storage/drying closet. This setup allows the air that escapes the main flowering chamber to be scrubbed and time-misted while minimizing odors while the a/c is in operation. Let’s not forget that we still have an exhaust fan in the flowering room in addition to the one in the lung room.
Finally some positive results, creating a partition and dampening that overflow temp from the flower chamber allows the a/c to be set at 75F(23.8C) which maintains 72F(22.2C)-78F(25.5C) or set at 78F(25.5C) which gives 75F(23.8C)-82F(27.7C) temperatures. It also allows the room to reach levels of 900-1300ppm without over engaging the equipment. Likewise, it keeps the lung/vegetative chamber partially enriched with CO2 but several degrees cooler. Air is getting filtered and freshened, so odors are reduced to “something green” or nothing at all before getting pulled into the a/c exhaust system.
By the way, it's a good idea to place all of your ballasts in the lung room that holds the a/c and vegetative stage fan/filter/lights.
After being somewhat satisfied with the situation, I noticed I had to configure some form of exhaust for the night time humidity. I set the CGC-1 at 58% humidity. This provided enough backup ventilation through a carbon filter to allow the a/c to free flow without activating the compressor. I then had an idea about an additional bathroom fan 83cfm that was not being utilized. I moved the CD-3 CO2 generator under the bathroom fan (factory recommends 18-inches from the ceiling), attached a cord and connected it to CO2 controller outlet, so that they would activate simultaneously. I was hoping that the weaker bathroom fan would provide enough exhaust to remove excess heat and humidity during generation. At first it seems to do the trick, but as CO2 concentrations get higher (above 1000ppm) the exhaust seems to outrun the generators ability to raise it any further. Additionally, it increased the overall burn time to fill the room or sometimes never reaching it, but it did reduce the rise in temperatures and humidity allowing the CO2 dispensed to stay in the room an additional 10-15minutes before the ventilation engaged. It may be possible to go with a somewhat larger model that can overcome the barrier at the expense of more fuel. I may investigate this option in the future, considering that the CD-3 is appropriate for 300 cu ft space and I’m utilizing it for around 700 cu ft. Until then, I’ve relegated the bathroom fan as a secondary exhaust controlled by the CGC-1.
On a side note, I have utilized the unfiltered bathroom exhaust in the night time ON position of the controller. It would run only during nighttime hours exhausting excess humidity. However, within 1 hour it reduces the night time CO2 concentrations from 800ppm to 450ppm, not that the plant is transpiring much-but I prefer the higher concentration. I prefer to use the controller’s humidistat unless I’m getting excessive humidity in late flowering, at which point I’ll plug it back into the NIGHT ON position.
CO2 generator TIP: I have high CO2 concentrations at night because the pilot light on my burner causes the room to rise approximately 1ppm/sec. It also makes it warm and moist like a greenhouse, sometimes it’s too much, not to mention the plants aren’t really using excess CO2 at night. Oh yeah, it’s burning fuel and has an open flame inside the box, occasionally I wonder about that! So, if you want more control over these things, purchase a newer ELECTRONIC ignition model made by companies like CAP. This allows the unit to save fuel and turn on only when you want it to operate. In addition, these generators use glow plugs (flameless) instead of a burner. They cost about $60 more than the old standard. Likewise, solatel and megagarden (formerly blu-ox) have units that have two 4-inch flanges that air-cool a metal plate that conducts heat from the glow-plugs WITHOUT removing room air. Unfortunately, these units cost $800-$1400.
Before purchasing the PPM meter that controls the CO2 generator, I allowed the CGC-1 to activate the burner for a 5 minute interval every 60 minutes. This provided one months usage of a standard propane tank ($16.50). After getting the meter, I realized that I should try to find the sweet spot for how long the burner is on and how long before it is exhausted from heat/humidity buildup. I soon figured out that it is actually better for me to let the burn cycles come on for shorter intervals more frequently than to have a long interval infrequently. With that in mind, I reset the CO2 for up to 5 minutes every 30 minutes while trying to attain 800ppm set on the PPM-1c. It worked! It was maintaining that level hour to hour with a 5 minute burn allowance every 30 minutes. Now I wanted to see if it would perform well at 1300 ppm. Unfortunately, It needed more than a 5 minute burn allowance to even get to that level. I increased the burn allowance on the controller. Once again, before it could reach 1300ppm the humidistat would activate. So I’ve found that 900-1200ppm’s are manageable with a 6 minute burn time every 30 minutes. Occasionally, the a/c is running during that time in the lung room slowly exhausting some of the positive pressure, but CO2 concentrations in the flower chamber will stay 30-50% higher than in the lung room. A result of the increased burn times, means I use a propane tank now every 2.5 weeks. It would seem that my system is near approached it’s limit with current equipment.
CO2 PPM Meter TIP: CO2 meters are great, but expensive! The standard controllers let you set a preset limit and then set the amount that it’ll let the ppm’s drop before activating the generator again. In addition, meters will show low ppm numbers if your propane tank is empty or leaky ducting is exhausting room air.
Many people say that fuzzy logic controllers will cycle you’re generator on/off too much, but it figures out what your “sweet-spot” is and prevents the ventilation from engaging while keeping moderate CO2 levels. If this is the case, these advanced controllers can be overridden to operate in standard mode.
After all of this tinkering, I’ve managed to set the a/c in the lung room to a 72-76F depending on outside temperatures, which results in 74-79F inside the chamber. I let the CGC-1 controller exhaust humidity with fans above 60% and temps above 86F/30C as a safeguard. If I turn off the a/c unit during winter, the air-cooled lights allow room temps to be at 80-85F while maintaining 900-1200ppms for a longer duration while relying upon the exhaust fans for cooling. I usually prefer to let the a/c run and maintain cooler overall temps. It seems to work fine, but it should after all the time and money I’ve invested. I wish everyone the best of luck with their setups and hopefully, the inordinate amount of time and money I’ve spent on this project can benefit you in your mini-version of a commercial grow room.
I thought I’d help share some of my hard-earned knowledge about some of the pitfalls and limitations of setting up CO2 in both semi-closed and open environments. At the start of this project, I was a complete novice and have learned through others, but mostly through a time-consuming process of trial-and-error.
Over the last year I’ve spent countless hours tweaking the room adding and removing equipment in hopes of finding the optimal and most efficient setup, a quest that we all share. Likewise, I found a CO2 generator in my hands and I wanted to implement the ultimate grow room accessory. Unfortunately, I found that CO2 was something more easily implemented in greenhouses or a large room. I, however, wanted to use CO2 in a small space and design a room that was similar to the larger closed-environment grow rooms.
The results of my exploration lend some insight into partitioning a single room into multiple chambers (lung rooms) and how air can be circulated, scrubbed, cooled, enriched, and exhausted in a small, semi-closed environment.
*IMPORTANT NOTE*
* This article is for people that are using non-traditional setups for CO2 environments such as: intake/exhaust fans, portable-single and dual hose a/c units. If you have a 5 ton chiller, split-level a/c unit, window box a/c unit, swamp/evaporative cooler, or a complete HVAC system for your room then you’re all set and are truly running a closed system; so let the rest of us be envious until we can outfit ourselves with closed system equipment. Likewise, this is for folks that don’t necessarily have a window, so extra long duct runs are normal
Also, I use a propane generator, so there’s not much on tanks, dry ice, and other methods here. Propane costs about $16.50 a tank and can last from anywhere to 1 to 4 weeks, so in the long run it’s the cheapest. However, a CO2 tank is much easier to implement than a generator, which produces additional heat and humidity that the tank does not. Initial costs for a refillable CO2 tank and regulator package are about $150-$300, while a fuel burning generator with a propane tank runs $300-$600 (more if you buy an air-cooled model $800-1400).
Even though the CO2 tank is cheaper on the initial outlay, refilling CO2 tanks will cost 2x-4x when compared to propane or natural gas. Purchasing these items will add CO2, but this does not include any CO2 measuring meters ($350-$550) or light-activated timers/controllers/relays ($80-$1200) which will be needed to make your garden run more efficiently. $Buyer Beware$ should be placed on all related CO2 systems because in order to use it efficiently requires the purchase of both controllers and meters. You may rely upon the charts that give approximate fill times for the rooms, but the only mention of loss rate is, “you may need to recharge your room with CO2 every 1 to 2 hours.” Yes, CO2 is great, but approach CO2 generators with caution.
Before I begin, I copied some background information on CO2 and optimal environment conditions.-Please read the cut/paste article by G.A.P. below. After that, I’ve included my experience with “effectively implementing co2,” which is not easier than it sounds, particularly if you use a generator. I will say right off the bat that the temperature range here states 80-85F (27-29C), but many experts suggest 72-78F (22.2-25.5C) as a much better range. Scientific evidence shows that plants grown at a steady 75F (23.8C) day and night have the highest THC concentrations. I have a tendency to go with that knowledge and aim for 72-78F when the lights are on with CO2. Also some people recommend a max of 1800ppm over 1500ppm. This is an unlikely scenario for people working with portable a/c units or fans.
Effectively Implementing CO2
Submitted by Green Air Products
First a little Plant Science 101 - For a successful, productive garden, hydroponic, indoor and greenhouse growers must control six "essential elements" - air, light, nutrients, water, humidity and temperature. Remove or alter the ratio of only one of these elements, growth will slow, and plants could eventually die. In this article, we will review the air element, specifically carbon dioxide (CO2), it's role in the most vital plant process - photosynthesis - and how to effectively implement CO2 systems.
Photosynthesis begins when stomata, pore-like openings on the undersides of leaves, are activated by light and begin breathing in carbon dioxide (CO2) from the air. This CO2 is broken down into carbon (C) and oxygen (O). Some of the O is used for other plants processes, but most is expelled back into the air. The C is combined with water to form sugar molecules, which are then converted into carbohydrates. These carbohydrates (starches) combine with nutrients, such as nitrogen, to produce new plant tissues. CO2 is vital to plant growth and development, and yet is often the most overlooked element in indoor gardening.
Successful indoor growers implement methods to increase CO2 concentrations in their enclosure. The typical outdoor air we breathe contains 0.03 - 0.045% (300 - 450 ppm) CO2. Research demonstrates that optimum growth and production for most plants occur between 1200 - 1500 ppm CO2. These optimum CO2 levels can boost plant metabolism, growth and yield by 25 - 60%.
Plants under effective CO2 enrichment and management display thicker, lush green leaves, an abundance of fragrant fruit and flowers, and stronger, more vigorous roots. CO2 enriched plants grow rapidly and must also be supplied with the other five "essential elements" to ensure proper development and a plentiful harvest.
Commercially available CO2 generators offer the most economical, practical and consistent method of enriching indoor gardens. Using atmospheric control systems in conjunction with CO2 generators ensure the most effective production and use of CO2.
Atmospheric control systems with automatic override or defeat, and CO2 monitoring logic, enrich and maintain optimum levels in the environment during the photo (light) periods, when most plants can absorb CO2; and they defeat CO2 production during dark periods. Automating your CO2 enrichment system pays for itself quickly with shorter crop cycles, improved quality and higher yields.
When enriching an indoor garden with CO2, proper light is essential for effective assimilation. For plants to use CO2 efficiently, light spectrum and intensity should be appropriate for the plant species in your garden. Remember - CO2 enriched plants under intensified lighting demand higher levels of nutrients, water, space and room temperatures of 80-85 F. (27 - 29 C.).
As CO2 is a critical component of growth, plants in environments with inadequate CO2 levels - below 200 ppm - will cease to grow or produce. And, growers should be cautious when experimenting with CO2 levels above 2000 ppm. CO2 is heavier than oxygen and will displace the O2 required by both plants and human to function and live. (FYI: OSHA max allowable for human exposure is 5000 PPM). So, air circulation and ventilation is critical to profitable CO2 enrichment.
Plants use all of the CO2 around their leaves within a few minutes leaving the air around them CO2 deficient. Without air circulation and ventilation, the plants' stomata are stifled and plant growth is stunted.
Proper air circulation with oscillating fans and in-line blowers will eliminate potential stagnation problems and ensure efficient CO2 enrichment.
If you have never enriched your garden with CO2, start with 700 - 900 ppm (double the normal atmospheric levels). If yields improve, increase CO2 enrichment to 1200 - 1500 ppm. If there is no response to the CO2 enrichment, double-check your other five "essential elements" to ensure they are not limiting factors.
This chart will give you the minutes of operation required for the areas and models shown. Top row of the chart represents cubic feet of area in the enclosure (LxWxH) The left column is the model size. Model numbers represent maximum CO2 output per hour in cubic feet (CD-3 = 3 cuft/hr CO2)
Example: A CD-6 will take 10 minutes to produce a CO2 level of 1000 ppm in a 1000 cu. ft. enclosure. The area should be charged as quickly as possible for maximum advantage. Charging the atmosphere quickly insures that the rapid photosynthesis process will not be interrupted and the plants growth rate reduced. Five to ten minutes is a good charge time. Try not to exceed twenty minutes. Your microclimate will need to be recharged every 1 to 4 hours depending on how much CO2 is lost due to plant usage or drafts (leaks). Large greenhouses logically require longer charge times and multiple units may be necessary. The CD-36 takes 1.66 minutes per 1000 cu.ft. area to charge to 1000 ppm. Therefore a 20,000 cu. ft. area would be 20 X 1.66 which is 33.2 minutes. For this application that may be an acceptable charge time.
I presume the run times here are for the pilot light only, It does not include ON times for the burner.
Alrighty Then!!!
Now that some of the basic groundwork for environmental conditions has been described, how do we go about getting them without some of the high-end cooling/ventilation systems that commercial growers have? Well, short of dropping $2,000-$5,000 on a 5 ton water chiller or a $120 window-shaker a/c, you don’t!!! I’m going to tell you right off the bat, that running CO2 generator (not tank) will increase the overall load on your system. In other words, the more you try to get that meter to 1200-1800 ppm, the more you’re exhaust fans and/or air-conditioning unit will work-usually taking CO2 with it.
The smallest generators Green Air Products CD-3 (3.2cuft/hr) or CAP 1 will produce as much heat as a 100-watt incandescent bulb with the pilot light. Fully active it generates approximately 2300 Btu-the same amount of heat as a 1,000 watt HID. Larger units can generate anywhere from 6-36cuft/hr with a complimentary amount of fuel consumption and other by-products. Considering the additional heat/humidity produced by burning propane, it is difficult to find the “sweet-spot” for rooms that rely upon traditional intake/exhaust fans or portable a/c units that inevitably pull air from the room—usually unfiltered for odor when a/c is involved. Since we’re not working with closed system cooling equipment, every gardener has to find an sustainable level of CO2 with an optimal amount of exhaust and cooling. Before we address the primary ventilation system in our room, heat from the bulbs needs to be removed via air-cooled hoods. What types of hoods, fans, and ducting are required for cooling various bulbs?
The bulbs are the primary source of heat for any indoor garden. In an effort to remove that heat from the garden we employ air-cooled shades that run on an independent ducting system preferably in a series (aka one after the other) when using multiple lights.
Parallel-ducting setups can be difficult to properly construct, it is often better to make two more holes in the ceiling/wall than trying to tie your room exhaust system to your air cooled shades. However, if you do go this route, invest in one-way duct dampers and larger fans to push the dampers open. So how much ventilation is required to cool my lamp? Here’s a rough estimate-Half the wattage of the bulb=recommended cfms. Some might say that is overkill but is it really?
*DUCTING TIP: Air is like electricity--It will take the path of least resistance! If you split intakes and exhausts, it is imperative that you place a fan pulling on the primary vent that all secondary vents are dumping into; otherwise the backpressure of multiples feeding into a non-power, ventilated exhaust stack will just cause inefficiencies. Look at some pictures of industrial ducting at warehouse facilities to see where inline fans have been properly placed at each workstation with a large workhorse fan exhausting all the merged workstations.
Likewise as you move up in duct size, you almost double the area that the air has to flow through. This allows larger fans to move more air while spinning at lower rpm’s or an exceptionally larger amount of air for HO fans at slightly higher rpm’s. I’d recommend the Fantech XL, Vortex, Can High-Output models over a lower wattage rpm standard. Below are some examples of fans and filters for hobby growers.
FAN/FILTER COMBOS for exhaust applications-for recycling room air go up to the next fan size.
Can Filter 33 w/ 6” Can-Fan - true CFM 168
Can Filter 50 w/ 6” High Output Can-Fan - true CFM 300
Can Filter 66 w/ 8” Can-Fan - true CFM 350
Can Filter 50 w/ 10” HO Can-Fan - true CFM 484
Can Filter 75 w/8” HO Can-Fan - true CFM 559
Can Filter 100 w/ 8” HO Can-Fan - true CFM 621
Can Filter 150 w/ 12” HO Can-Fan - true CFM 898
CAN FANS
Can Fan 4” – 142 CFM/3200 RPM/61w
Can Fan 4” High Output – 178 CFM/3260 RPM/70w
Can Fan 6” – 270 CFM/3240 RPM/73w
Can Fan 6” HO – 440CFM/3246 RPM/136w
Can Fan 8” – 493CFM/3215 RPM/125w
Can Fan 8” HO – 737CFM/3310 RPM/253w
Can Fan 10” HO – 781CFM/3290 RPM/251w
Can Fan 12” HO – 971CFM/3365 RPM/331w
CAN FILTERS
Can Filter 150 - 1260 CFM/123lbs of carbon weight
Can Filter 125 – 1110 CFM/103lbs of carbon weight
Can Filter 100 – 840 CFM/82lbs of carbon weight
Can Filter 75 - 600 CFM/62lbs of carbon weight
Can Filter 66 - 412 CFM/42lbs of carbon weight
Can Filter 50 – 420 CFM/31lbs of carbon weight
Can Filter 33 – 200 CFM/16lbs of carbon weight
VORTEX FANS
Specifications
12 inch - 1140 CFM - 2400 RPM - 3.2 Amps - 400 watts
10 inch - 790 CFM - 2510 RPM - 2.00 Amps - 224 watts
8 inch - 747 CFM - 2550 RPM - 1.60 Amps - 185 watts
6 inch - 449 CFM - 2600 RPM - 0.80 Amps - 100 watts
4 inch - 172 CFM - 2500 RPM - 0.65 Amps - 80 watts
Fantech Fans
Quick Specs:
• Model FX 4: 117 cfm, 2950 rpm, 44 watts, for 4 inch duct
• Model FX 4XL: 148 cfm, 2800 rpm, 83 watts, for 4 inch duct
• Model FX 5: 132 cfm, 2950 rpm, 42 watts, for 5 inch duct
• Model FX 5XL: 191 cfm, 2650 rpm, 87 watts, for 5 inch duct
• Model FX 6: 257 cfm, 2700 rpm, 84 watts, for 6 inch duct
• Model FX 6XL: 392 cfm, 2950 rpm, 147 watts, for 6 inch duct
• Model FX 8: 481 cfm, 2600 rpm, 119 watts, for 8 inch duct
• Model FX 8XL: 521 cfm, 2950 rpm, 152 watts, for 8 inch duct
• Model FX 10: 521 cfm, 3000 rpm, 147 watts, for 10 inch duct
• Model FX 10 XL: 590 cfm, 3000 rpm, 242 watts, for 10 inch duct
• Model FX 12: 711 cfm, 2450 rpm, 196 watts, for 12 inch duct
• Model FX 12 XL: 801 cfm, 3250 rpm, 411 watts, for 12 inch duct
If you look around the internet you’ll find some approximations on how much air flow is required to bring room temperatures within 3-8 degrees F of ambient air temperatures (see Fig. 1). While these charts are fairly accurate, they do not take into account the length of duct runs, number of turns, type of ducting, et cetera. Likewise this is a chart for open air-cooling of a grow room, not inline cooling of bulbs—so there is some disparity there, but the chart is close enough in my opinion.
In my experience, I’ve found that it’s better to go one or two sizes up from the diameter of ventilation you think you need. I’m cooling 1600 watts with one 6-inch Vortex 449cfm (100w) mated with SunSystem 2 air-cooled shades with 6-inch flanges and I would prefer 10-inch (780cfm) to 12-inch (900-1100cfm) High-Output (HO) inline fans considering the length of ducting (50 ft/15.2m).
Fig. 1—Thanks to Caligrower on CC
This setup allows room temps to come within 5-8 degrees F of ambient air temps, but will gradually keep rising well above safe temperatures if no additional venting or cooling is provided. This is not enough to maintain acceptable room temperatures for more than an hour, especially since I have a pilot light burning in the CO2 generator constantly. If, intake temperatures for the air-cooled hoods are below freezing you can maintain CO2 concentrations for several hours before the exhaust turns on; usually for humidity buildup. Likewise, if your fans CFM rating is more than 50% of your lights wattage number (i.e. 1000watts/500CFM+), you’ll be able to prevent frequent exhaust cycles. Warmer temps will eventually require a/c, if CO2 supplementation is going to be used.
According to the chart, you will only cool your light by a few degrees before you hit a point of diminishing returns on fan size. In Figure 1, you can see that the lower left-hand corner shows air flow targets that exceed most single pieces of equipment especially those used by hobby growers. If you can get half the cfms to lamp watts you’ll be in a good place for maintaining room air temps. If you can match the cfms to the lamp wattage then you will have maximized air-cooling especially when limited by the flanges on air-cooled hoods (4, 6, or 8 inches).
Unfortunately, most of us want more wattage while cooling with only 4 to 6 inch fans and ducting. If you’re running 1kw purchase an 8 to 12inch inline fan and use reducers to an 8 or 6inch air cooled hood you won’t be disappointed-especially in the summertime. So where do the ducts go?
Ultimately, you’ll want the coolest air you can find to cool your lamps and you’ll want to dump that air outdoors. You can either pull air from another room or run ductwork to the outside; I’ve tried recycling the indoor air to heat my house and it made the house too hot! I’ve found that an exterior intake and exhaust is best for air-cooling lights. You’ll notice more particulate matter in the hoods so you will need to clean the glass more often (between cycles is adequate) or add a small filter to keep debris out, but it is decidedly better than creating the negative pressure in your home.
*HOOD TIP: Match the wattage to the diameter of the air-hoods flange. 4inch=400watts or less, 6inch=600watts/1000watt, 8in=1000watts. In general, go with the 6 or 8 inch if possible.
* FAN TIP: When trying to judge the true power of a fan-look at the wattage of the motor and the size of the fan! Higher wattage=airflow with decent static pressure. A low watt computer fan may move 100cfm’s but only a few inches beyond the blades. We need more powerful air pressure and higher air flow capacities for lamps over 400 watts.
*A/C TIP: Higher wattage also applies to a/c units. Less wattage/power consumption is not better in these scenarios. The wattage is directly indicative of the size of the motor or compressor. The larger those items are the less they will have to work!
Now that we’ve got our lights air-cooled, we’re ready to exhaust the radiant heat produced by the electrical components, plants, and CO2 generator. In the typical grow room, a controller or device senses that the temperature/humidity are elevated (didn’t want to use the phrase “too high”), thereby triggering the exhaust fans.
At the minimum, you want the air to be exhausted in less than 5 minutes with 1-3 minutes being ideal. However, along with the hot and humid air, you’ve just exhausted all of the CO2. As a result, your CO2 ppm’s are probably back down to the 250-550 ppm range. If you have a controller or a timer on your CO2 (i.e. 6mON/30mOFF or 8mON/60mOFF) the controller will reactivate the generator and burn for the preset amount of time in an attempt to raise the CO2 (if you have a ppm meter it will try to reach whatever you’ve set the room at 600-1500ppms but it will be overridden with the time limitations/release schedule set by your controller).
Unfortunately, regenerating the CO2 causes the room temps to go beyond optimal conditions once again and our generator hasn’t even gotten us to 1000 ppm much less the 1200-1800 ppm range before the fans have been triggered again. Basically, the only remedy to this situation, is to have “super-cooled” lights with super-cool air actually turning the light into a sealed air cooling unit for the room. However, this isn’t really feasible because it requires large inline fans, short duct runs, 6in or 8in air cooled hoods (maybe 10in but the market doesn’t have these yet), and Siberian cold air.
So, if you maintain this setup you can burn a lot of fuel/CO2 tanks shooting for the moon in terms of 1200-1800ppm. Instead of continually engaging your exhaust system and then trying to refill the room with CO2, lower the setting on your ppm meter or CO2 burn timer. In this scenario, it’s easy to see that it might be better to run shorter bursts more frequently versus one long burn every 1-2 hours. If you run shorter bursts, you will keep the CO2 generator from directly engaging the exhaust fans thereby allowing a steadier level of CO2 in the garden, and more efficient use of resources.
Most manufacturers recommend that your CO2 burner run for approximately 4-10 minutes for a room fill, if it takes longer, they recommend a larger unit. This is misleading because a larger unit will fill the room faster, but it will also burn fuel faster and engage the exhaust fans sooner than a smaller unit, basically quickening the burn/exhaust cycle. Do not make this mistake. In this situation, it is much better to work with CO2 enrichment at the 600-900 ppm range. Often times this is complimentary with the amount of light that most home growers maintain. If you have a 600 to 1kw lamp, plants will be able to utilize concentrations above 1000, but how do we get there, when it is going to activate the exhaust more frequently while consuming more fuel to no avail?
In that case, I’d tell you that we can start edging a bit closer but like all things in life, nothing’s free. At this stage, you’ll need some form of a/c unless you’ve got the Siberian setup mentioned earlier. But before we buy any portable a/c here’s my story.
Before I ever purchased portable a/c units and a CO2 generator, I bought a CAP CGC-1 high-end controller and three 6-inch vortex fans, thinking that the more economical and ventilated approach would be the most efficient setup. While it’s true, that energy consumption is lower with the old in-and-out ventilation of fans, it’s neither conducive nor cost-effective when trying to enrich with CO2.
In the warmer months, the exhaust fans were running constantly; thereby wasting any attempt to raise CO2 significantly. It didn’t take long for me to realize that additional cooling would be needed for me to maintain CO2 temps of 72-78F (25.5C) so I bought an air conditioner. If you want 80-85F, an over-powered air-cooled light with standard intake/exhaust fans will usually be adequate, especially during the winter. However, many people find that during warmer temperatures additional cooling with more exhaust or a/c units will be required.
A/C TIP #2: If you have to buy one for the purpose of CO2 and you can’t do a window shaker; purchase a single-hose unit if you’re not using CO2, buy a double hose if you are going to use CO2. BEWARE all portables exhaust the room air, dual hose units to a lesser extent.
Ventilation TIP: Place all exhaust vents and filters up high to pull hot air out of the room (usually 5-10degrees warmer up there). Likewise, place your portable a/c unit on a chained platform or at least table height so that you may drain the runoff into a resevoir or a drain.
Originally, I opted for a low-powered (685w) single-hose, 9000 btu unit (once again, less watts is not a good thing in a motor/compressor). I installed it on a platform up high so that the drain line could go to my reservoir or sink. It worked great but was working most of the time and was sucking the CO2 out of the room keeping it from getting above 700ppm. On top of that, the vortex 449cfm and can 50 carbon filter combo (true cfm=300cfm) recycling room air was NOT effective in removing odors (600 cu/ft bathroom) before being sucked out of the room. I needed a more powerful fan for my filter to work in that manner.
Carbon-Filter TIP: If you need to use carbon filters for recirculation of room-air only, then go 1.5x the recommended fan for exhaust applications (0.1 sec contact time). Otherwise, the room air will only be reduced of odors by 60-80%. Either way, for recirculating applications you need a larger fan w/ the larger flange/adapter, a larger filter, or both. If you’re using it strictly for exhaust applications, you should know that a carbon filter will reduce a fan’s cfm rating by 30-40%.
A carbon sheet over the exhaust helped, but I was exhausting cooled, enriched, semi-stinky air because a single-hose unit cools the condenser coils with room air before exhausting out the hose. I knew that it was only a matter of time before the paranoia about the smell would get to me. At one point, I even installed a Carbon filter on the exhaust hose in the attic; till I realized that the carbon was being rendered useless by all the humidity. In addition to this, humidity levels will rise if you only have an air conditioner in a closed system. So, I bought a 40-pint dehumidifier 650 watts. Unfortunately, the dehumidifier puts out as much hot air as small CO2 burner in full tilt (approx 2k-3kbtu). The heating action of the dehumidifier further engaged the single hose portable a/c into cooling/sucking the now cooled/heated/enriched/semi-stinky/dehumidified air out the exhaust. In addition, the dehumidifier was noisy at 57db (sounds like a 18kbtu a/c running) because of the condenser.
After doing more research, I was incorrectly told that a dual-hose a/c unit would solve all my problems or at least minimize them. So, I found a 53db 85lb 12,000 Btu unit 1485 watts that actually had all the features: ionizer, dehumidifier, heater, air conditioner. It also had auto mode which would activate heat below 68F, dehumidify above 55%, a/c above 80F. I braced a couple of boards above the bathroom sink and cut two holes in the attic to run venting lines (longer, but larger diameter +2 inches, than the 9 foot, 4-inch PVC extension recommended by manufacturers). I added a double stack of rubber feet (circle fits into the square) to aid in dampening noise while installing closed cell foam (camping sleep pad) between the mounting boards and the wall.
I thought I would boost the air exhaust using a parallel run from my air-cooled lights. Unfortunately, this caused backpressure in the system and I had to give it an independent exhaust, but still managed to tie the intake to a larger 8x6x6 that also fed the intake to the air-cooled lights.
. It seemed to run just great, but once again, it was sucking cooled, enriched, stinky air out of the room. After doing some research, I found an article on sealing up the a/c unit. I disassembled the unit, and I could see where the gaps were, but it was a difficult and dirty job that would probably turn out poorly due to the tight spaces. As a result, I ended up sealing the lower edge near the wheels with liquid foam and a couple of spots where the a/c cabinet was vibrating when the compressor was on. This stopped some of the negative pressure in those areas and I didn’t want to modify the unit any further at the time.
I didn’t seal the whole interior cavities from one another because I believe the design is meant to be semi-open due to backpressure, particularly if you have a long duct run. I mention this because the back of the a/c unit has a 3 inch square (not the washable filtered intake) that clearly allows room air into the in/out chamber. Initially, I covered this up but with the long intake (28 feet) and exhaust run (25 feet) it would cause the compressor to overheat and fail after 10-15 minutes of operation.
At first, I kept the unit in auto-mode, but it had to run the dehumidifier during night time which would drop the temperature down below 68F. So I went to regular air conditioner mode, but this meant my environment was being completely regulated by the a/c unit. This mode is great, but the swing is generally only 1 or 2 degrees before the compressor engages. Of course, this doesn’t provide enough “swing” range for a CO2 generator to fill the room beyond 800 ppm.
Ultimately I had to dampen the a/c’s ability to read the temperature/humidity directly. I could change the thermistors to adjust the “swing” of the unit, but I really wanted to find something easier. I chose to create a b/w poly wall, while allowing the a/c unit to be on the other side closer to the passive air intakes and door. The output from the a/c was then ducted through a hole in the b/w poly, creating positive pressure in the sealed CO2 chamber and pushing out stinky air. The lung room where the a/c unit lies has a fan/scrubber that air-cools a MH light for vegetative. The hose has an external exhaust port or can be permitted to recycle and scrub air in the lung room.
In addition to this lung room, there is a b/w poly curtain near the entrance door that has a time-mist on low (air freshener) to help with any additional odors. This area has incoming ducting from both the central air system, and a dummy vent to the next room, it also has a storage/drying closet. This setup allows the air that escapes the main flowering chamber to be scrubbed and time-misted while minimizing odors while the a/c is in operation. Let’s not forget that we still have an exhaust fan in the flowering room in addition to the one in the lung room.
Finally some positive results, creating a partition and dampening that overflow temp from the flower chamber allows the a/c to be set at 75F(23.8C) which maintains 72F(22.2C)-78F(25.5C) or set at 78F(25.5C) which gives 75F(23.8C)-82F(27.7C) temperatures. It also allows the room to reach levels of 900-1300ppm without over engaging the equipment. Likewise, it keeps the lung/vegetative chamber partially enriched with CO2 but several degrees cooler. Air is getting filtered and freshened, so odors are reduced to “something green” or nothing at all before getting pulled into the a/c exhaust system.
By the way, it's a good idea to place all of your ballasts in the lung room that holds the a/c and vegetative stage fan/filter/lights.
After being somewhat satisfied with the situation, I noticed I had to configure some form of exhaust for the night time humidity. I set the CGC-1 at 58% humidity. This provided enough backup ventilation through a carbon filter to allow the a/c to free flow without activating the compressor. I then had an idea about an additional bathroom fan 83cfm that was not being utilized. I moved the CD-3 CO2 generator under the bathroom fan (factory recommends 18-inches from the ceiling), attached a cord and connected it to CO2 controller outlet, so that they would activate simultaneously. I was hoping that the weaker bathroom fan would provide enough exhaust to remove excess heat and humidity during generation. At first it seems to do the trick, but as CO2 concentrations get higher (above 1000ppm) the exhaust seems to outrun the generators ability to raise it any further. Additionally, it increased the overall burn time to fill the room or sometimes never reaching it, but it did reduce the rise in temperatures and humidity allowing the CO2 dispensed to stay in the room an additional 10-15minutes before the ventilation engaged. It may be possible to go with a somewhat larger model that can overcome the barrier at the expense of more fuel. I may investigate this option in the future, considering that the CD-3 is appropriate for 300 cu ft space and I’m utilizing it for around 700 cu ft. Until then, I’ve relegated the bathroom fan as a secondary exhaust controlled by the CGC-1.
On a side note, I have utilized the unfiltered bathroom exhaust in the night time ON position of the controller. It would run only during nighttime hours exhausting excess humidity. However, within 1 hour it reduces the night time CO2 concentrations from 800ppm to 450ppm, not that the plant is transpiring much-but I prefer the higher concentration. I prefer to use the controller’s humidistat unless I’m getting excessive humidity in late flowering, at which point I’ll plug it back into the NIGHT ON position.
CO2 generator TIP: I have high CO2 concentrations at night because the pilot light on my burner causes the room to rise approximately 1ppm/sec. It also makes it warm and moist like a greenhouse, sometimes it’s too much, not to mention the plants aren’t really using excess CO2 at night. Oh yeah, it’s burning fuel and has an open flame inside the box, occasionally I wonder about that! So, if you want more control over these things, purchase a newer ELECTRONIC ignition model made by companies like CAP. This allows the unit to save fuel and turn on only when you want it to operate. In addition, these generators use glow plugs (flameless) instead of a burner. They cost about $60 more than the old standard. Likewise, solatel and megagarden (formerly blu-ox) have units that have two 4-inch flanges that air-cool a metal plate that conducts heat from the glow-plugs WITHOUT removing room air. Unfortunately, these units cost $800-$1400.
Before purchasing the PPM meter that controls the CO2 generator, I allowed the CGC-1 to activate the burner for a 5 minute interval every 60 minutes. This provided one months usage of a standard propane tank ($16.50). After getting the meter, I realized that I should try to find the sweet spot for how long the burner is on and how long before it is exhausted from heat/humidity buildup. I soon figured out that it is actually better for me to let the burn cycles come on for shorter intervals more frequently than to have a long interval infrequently. With that in mind, I reset the CO2 for up to 5 minutes every 30 minutes while trying to attain 800ppm set on the PPM-1c. It worked! It was maintaining that level hour to hour with a 5 minute burn allowance every 30 minutes. Now I wanted to see if it would perform well at 1300 ppm. Unfortunately, It needed more than a 5 minute burn allowance to even get to that level. I increased the burn allowance on the controller. Once again, before it could reach 1300ppm the humidistat would activate. So I’ve found that 900-1200ppm’s are manageable with a 6 minute burn time every 30 minutes. Occasionally, the a/c is running during that time in the lung room slowly exhausting some of the positive pressure, but CO2 concentrations in the flower chamber will stay 30-50% higher than in the lung room. A result of the increased burn times, means I use a propane tank now every 2.5 weeks. It would seem that my system is near approached it’s limit with current equipment.
CO2 PPM Meter TIP: CO2 meters are great, but expensive! The standard controllers let you set a preset limit and then set the amount that it’ll let the ppm’s drop before activating the generator again. In addition, meters will show low ppm numbers if your propane tank is empty or leaky ducting is exhausting room air.
Many people say that fuzzy logic controllers will cycle you’re generator on/off too much, but it figures out what your “sweet-spot” is and prevents the ventilation from engaging while keeping moderate CO2 levels. If this is the case, these advanced controllers can be overridden to operate in standard mode.
After all of this tinkering, I’ve managed to set the a/c in the lung room to a 72-76F depending on outside temperatures, which results in 74-79F inside the chamber. I let the CGC-1 controller exhaust humidity with fans above 60% and temps above 86F/30C as a safeguard. If I turn off the a/c unit during winter, the air-cooled lights allow room temps to be at 80-85F while maintaining 900-1200ppms for a longer duration while relying upon the exhaust fans for cooling. I usually prefer to let the a/c run and maintain cooler overall temps. It seems to work fine, but it should after all the time and money I’ve invested. I wish everyone the best of luck with their setups and hopefully, the inordinate amount of time and money I’ve spent on this project can benefit you in your mini-version of a commercial grow room.
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