Tutorial Ventilation 101

[nepalnt21]

not a sticky? how's that work???

good thread

 

[Amstel Light]

bump

 

[Black Sheep]

well iv put my cab on the back burner for a while. i ran across a 4.4 cubic foot mini fridge and cant decide on the ventilation. would 2 41cfm fans side by side be suffecient enough 2 keep the temps down? i stil havnt decided if im going with a 150 watt hps or 200 watt cfl. so temps could become an issue as far as the hps goes. not realy sure how much heat the 200 watt cfl puts out and id rather over do the ventilation than not enough. i should have some pics posted of the mini fride with in a couple weeks when i start the demo and reconstruction. this will be my first build so keep your fingers crossed.

 

[Black Sheep]

if anyone thinks that another cfm rateing would work other than the 41 cfm feel free to educate me. the intake will most likely be an 8"x8" darkroom vent and the air will be scrubbed thru a 12"x12"x2" square scrubber. if this info even helps to help determine.

 

[phr3d0m2gr0]

Black Sheep: Are the fans PC fans? could possibly post a drawing or link to the style of scrubber your going to use? Most likely the two fans side by side won't have enough "sucking" power to pull through a darkroom vent AND scrubber and still be able to keep temps down.

I'm not totally sure, but the CFL's might be cooler and a better option if your concerned about keeping temps down. Plus you could always reduce the CFL wattage if the temps do become too much of a problem, whereas you are stuck with what you have with the HPS.

 

[Black Sheep]

thanks for responding phr3d0m. the fans that im thinking of useing are the dayton axial 115 volt. i cant seem to find the scrubber that i spoke of earlier. i thought that i originally seen it on Anti's grow cab 3000 thread. Hydro-Soil posted about the panisonic whisper fan and i could swear that he posted pics of the scrubber that he used with it.

i would post a drawing but unfortunately im a complete noob and i dont know how to.

the reason i was thinking of such a high wattage for the cfl is that il be scrogging and i want to make sure that i get plenty of penetraton into the canopy. iyo do you think that im makeing a mistake going with such a high wattage in the small area?

hopefully il be able to begin working on the fridge next week. il be takeing pics through out the construction and i will figure out how to post them. iv got so many differrent ideas for it and could definitely use the advice from the pros.

 

[phr3d0m2gr0]

I don't think the CFL wattage would be too high as long as you can ventilate it properly. If you take a look at some of the CFL grows on here you can see people running fairly high CFL wattage's with a surprisingly low amount of ventilation. Also, if possible try to put the fridge in the coolest part of your house. This will help reduce the amount of ventilation you will need.

 

[guest 77721]

Hey guys, it's been a while since I checked out my thread. It seems to have a life of it's own!!!

Black Sheep - take a good look at Freezer Boy's fridge cab. He's done an awesome build. Anti has a good NGB multichamber design.

There are three basic cab designs in use on this forum. Each has their own characteristics. Make a good choice and run with it.

1. Simple Cab - one chamber, no scrubbers or restrictions to airflow.
CFM = 3.16*Watts/deltaT
Intake Area = 2 x Exhaust Area
Fans - Axial/Computer Fans due to minimal pressure loss

2. One Pass Scrubber - may incoporate cooltube and multi chambers
CFM = 3.16*(Total Watts)/deltaT
Intake Area = 2 x Exhaust Area
Fans - Blower or Inline for high pressure drop across scrubber
Pros: single fan design less equipment to purchase
cooltube allows for lower CFM operation as exhaust deltaT
can run 30-40 *F as heat is concentrated in tube.
Cons: fan operates at 50% or less airflow due to pressure drops
2x or more oversize to get base airflow
many restrictions in multi chamber designs
scrubber/fan combo usually undersized
high airflow for lights creates stress on plants
high airflow through scrubber reduces effectiveness
Blower and Axial fans are noisy 60-70 db

3. Two Stage Cooling/Ventilation with cooltube and scrubber
LIGHTING CFM = 3.16*(Total Watts)/deltaT
VENTILATION = 1 - 0.2 ACM ( Air Changes per minute)
Intake Area = 2 x Exhaust Area for EACH section
Fans - Axial for Lighting maximum airflow, minimal pressure loss
Small blower, inline or axial for scrubber

Pros: unrestricted airflow through lighting allows fan to operate at
maximum rated flow
low air flow rates allow for small scrubber
use of less expensive fans as design is more efficient
Lighting exhaust deltaT can be 30-40*F while maintaining grow
chamber temps
Much quieter as axial fans operate at 30-40 db
Cons: more equipment
more intake and exhausts require more light proofing
ventilation design is more complex with ducting (R2D2)

well iv put my cab on the back burner for a while. i ran across a 4.4 cubic foot mini fridge and cant decide on the ventilation. would 2 41cfm fans side by side be suffecient enough 2 keep the temps down? i stil havnt decided if im going with a 150 watt hps or 200 watt cfl. so temps could become an issue as far as the hps goes. not realy sure how much heat the 200 watt cfl puts out and id rather over do the ventilation than not enough. i should have some pics posted of the mini fride with in a couple weeks when i start the demo and reconstruction. this will be my first build so keep your fingers crossed.

 

[phr3d0m2gr0]

redgreenry: With the two stage design do you mean to say that each chamber would be vented separately and the lights would also be vented separately?

So for example, say you have a cooltube in a single chamber for flowering. That would mean the entire ventilation of the cabinet would contain:

• A single fan would ventilate the light. It would be a flow through system with no scrubber
• A single fan would ventilate the grow chamber. This would have a carbon filter, but it would be divided into two stages to allow for minimal pressure loss.

Is that correct?

-Phr3

 

[Black Sheep]

phr3d0m: ok thanx for that info. il try the 200 watt and see how that works out. i think that im going with 2- 70 cfm 115 volt ac axial fans for the ventilation to help with goin thru the dark room vent. the location of the fridge will be in the basement so it should have plenty of cool air.

redgreenry: freezerboys set up is nice but il be useing a mini fridge with 4.4 cubic feet and will have 2 deal with space constaints. its the 1st mini fridge that iv seen with a seperate freezer. i cant decide on wether or not i want to use the freezer as the utility room or if i should make it a mother and clone room. decisoins decisions. im working on trying to figure out how to get the pics from my camera to my laptop and then posted here. but when i do i think everyone will have a better idea of what im trying to do.

 

[Black Sheep]

o ya one more thing thanx for the thread on the google sketch up. as you can prolly tell im a noob. i downloaded sketch up a while ago to help aid in the design of the cab im going to build and was completely lost. iv got a killer idea for a cab and when i get done with the mini fridge i plan on getting back on the it. so again thanx for the guide and the advice earlier.

 

[phr3d0m2gr0]

No prob Black Sheep. I'm just trying to help fellow growers out there!

Also as far as the separate freezer in your mini fridge I almost want to suggesting using it for utilities. I grow in an NGB, but i'm starting to believe that separating chambers is a better way in growing for multiple reasons. One reason is that I think it's easier to make several small chambers stealthy rather than one huge cabinet with multiple chambers. Also it helps isolate the plants more and makes it less likely for contamination from pest etc.

Just something to think about.

-Phr3

 

[Black Sheep]

definitely food for thought. i will keep that in mind. that was my first thought when i seen it.

 

[guest 77721]

Yes, that's the basic design. The lights get the full unrestricted airflow of a axial fan. Size the scrubber to the number of air changes/ minute to keep the plants happy. Scrubbers block airflow so they don't belong on the duct connected to the lights.

This is the most efficienct way to ventilate your air box. Requires two fans and a way of isolating the lights from the grow chamber but makes the fans much smaller, cheaper and quiet.

Check out my R2D2 and 150HPS cab designs which use 2 stage cooling. I get the maximum performance out of computer fans.

redgreenry: With the two stage design do you mean to say that each chamber would be vented separately and the lights would also be vented separately?


So for example, say you have a cooltube in a single chamber for flowering. That would mean the entire ventilation of the cabinet would contain:

• A single fan would ventilate the light. It would be a flow through system with no scrubber
• A single fan would ventilate the grow chamber. This would have a carbon filter, but it would be divided into two stages to allow for minimal pressure loss.

Is that correct?

-Phr3

 

[Black Sheep]

ok so would 3 fans @ 40 cfm be better than 2 fans @50 cfm? and so on

 

[phr3d0m2gr0]

Yes, that's the basic design. The lights get the full unrestricted airflow of a axial fan. Size the scrubber to the number of air changes/ minute to keep the plants happy. Scrubbers block airflow so they don't belong on the duct connected to the lights.

This is the most efficienct way to ventilate your air box. Requires two fans and a way of isolating the lights from the grow chamber but makes the fans much smaller, cheaper and quiet.

Check out my R2D2 and 150HPS cab designs which use 2 stage cooling. I get the maximum performance out of computer fans.

Yeah definitely sounds good. I have some major remodeling to do when I get back to growing. I'm gonna try to grow the DrBud style and try to set up some ventilation using your ideas redgreenry, hopefully I can build a nice stealth cabinet. If I can get everything dialed in then I'll probably try to help several friends build small stealth cabinets for personal meds. Thanks for posting this thread up, it's giving my lots of ideas.

Black Sheep: Maybe. If you only needed two 50cfm fans to get everything properly then it might be better choice if they aren't much louder then the 40cfm fans. Sounds add together so three 40cfm fans at 30dB each might be louder than two 50cfm fans at 34dB each. Of course those are just figures i made up, it actually depends on the real fans. If your cabinet doesn't need to be really quite then maybe the 40cfm's would be better. I actually don't quite remember how sounds add together, so if someone could chime in that would be nice.

-Phr3

 

[Black Sheep]

thats what i was thinking. iv started a new thread on the mini fridge if you want to check it out. it should give you a better understanding of what im trying to do. i accidentaly posted it on the growers forum instead of micro grows. is there any way that i could change that around? i think it would be noticed a lil bit easier on the micro grow anyways thanx for all the advice and i hope you will have more once you see it.

 

[lysol]

Two fans in Series increases the Pressure. Two fans in Parallel increases the Flow. The actual increase depends on the fan curve and the system resistance curve. Most guys think doubling up will give double results but becuase the ventilation calculations have squares and square roots in them the results are 1.4 not 2.0 times at best.


Thanks to everyone for dropping by. If anyone has a ventilation problem or a system that needs to be tinkered with don't be afraid to drop by. I've already fixed a couple of guys up already.

Earlier in the thread I believe you said in parallel obtains 200% cfm but no increase in pressure. Just confirming this with you, and lets say both fans are 6" centrifugal, how would I have to configure my ducting to maximize the cfm? 6" to 8" adapters and a 8" Y to a 8" exhaust? Could I just run two 6" blowers to a Y leading to a single 6" exhaust without killing cfm too badly? Already cut a 6" hole in my attic itd take a while to re-do, I ordered 2 fans when I needed only 1 I guess but if I can put it to good use, then hey.. why not. ( Keep cfm the same and be able to turn the fans down ). Would this work? Sorry for lack of grammar, too high to think

My scrubber is 6" so I guess 8" ducting wouldnt help since it has that bottleneck?

Basically can I run a 6" duct from my 6" 50lb scrubber, run it to a Y or T, have a fan on each leg of that split, then merge the ducts again and exhaust thru the hole I cut, or would I need a 2nd or larger scrubber?

Or I could put the 2nd fan to use scrubbing my living ( read smoking ) area, eliminating the need for me to re-up on incense every few days and look suspicous

 

[lysol]

Turns out my problem was I didn't connect the CORE duct ( well not reading the instructions on the box was the cause of that ), still looking to see exact details on how I can use a 2nd fan to increase cfm.

 

[guest 77721]

Running the two 6" fans Y'd into a 6" duct would nearly double the airflow in the 6" ducts. The velocity would be nearly doubled as well so would the duct noise. The reason I'm saying nearly doubled is that the duct losses would be more with a 6" duct than an 8" duct.

I don't know your ducting configuration to say what would be the best solution to go with. My designs break the lighting and scrubbing into two sections. You could do somthing similar with two fans and a common exhaust.

Earlier in the thread I believe you said in parallel obtains 200% cfm but no increase in pressure. Just confirming this with you, and lets say both fans are 6" centrifugal, how would I have to configure my ducting to maximize the cfm? 6" to 8" adapters and a 8" Y to a 8" exhaust? Could I just run two 6" blowers to a Y leading to a single 6" exhaust without killing cfm too badly? Already cut a 6" hole in my attic itd take a while to re-do, I ordered 2 fans when I needed only 1 I guess but if I can put it to good use, then hey.. why not. ( Keep cfm the same and be able to turn the fans down ). Would this work? Sorry for lack of grammar, too high to think

My scrubber is 6" so I guess 8" ducting wouldnt help since it has that bottleneck?

Basically can I run a 6" duct from my 6" 50lb scrubber, run it to a Y or T, have a fan on each leg of that split, then merge the ducts again and exhaust thru the hole I cut, or would I need a 2nd or larger scrubber?

Or I could put the 2nd fan to use scrubbing my living ( read smoking ) area, eliminating the need for me to re-up on incense every few days and look suspicous