Tutorial Ventilation 101

Hey Baccusbud,

take a look at my air filter design using two Sterilite containers. The small one must fit inside the large one.

The bottom is cut out of the small tub, I left a small rib in the center to support the screening.
Glue the window screen in place with the epoxy.

The lid of the large box is cut so that the small box with fit into it.

Intake holes are cut into the large box and the dryer adapters are fitted onto it. You can just duct tape it to the side if you don't have the adapters. This is probably the first time that duct tape is actually used for it's intended purpose. The flap is removed from the dryer adapter and I use a hack saw to trim off the pipe on one side.

A computer fan and a dryer hose adapter is fitted onto the lid of the small box.

When the filter is all assembled, I take silicone caulking and seal up crack where the small box goes into the large box lid.

My setup uses 1/2 lb of activated charcoal for a filter depth of 1" that I buy at the pet store. The 1" layer is good for the whole grow.

Sounds like a real noisy fan. I'd stick it inside an old styrofoam cooler. You can buy those at the grocery store for a few bucks.

mayorofthdesert said:

if anyone has tips for combating noise in my system I'd love a few ideas. I have a multi-room cabinet with 2 cool tubed 150hps & 2 75Wcfls my exhaust is a 4"duct with an eco plus fan into a can type carbon filter. I've got way more airflow than I need with the cooltubes (they're on their own 3" computer style fans. My temps are fine & I could get by with less airflow but am too broke to spend anything on a different fan right now. I do actually have 4 120v 4" computer style fans not doing anything...

Originally the fan & filter were inside the cab but I moved them up into the attic and ran duct down to the cabinet. That helped some, but the vibration was worse, like through the whole house now. I took two pieces of plywood and a bicycle tube up to the attic and made a bike tube sandwich. i set that on the ceiling joists then set the fan on top. That helped also, but not enough. Now it just sounds like I have a fridge up in the attic. I hear that the speed controlers just trade air noise, vibration & efficiency for an increase in motor hum. I guess I'm going to build a box, line it with insulation (or some other cheap noise absorbing material if you have a suggestion) and put the fan and filter in there. Might hang it from the rafters to further isolate vibration. or what about setting the whole mess on a big box of sand? think that would that totally kill remaining vibration?

Click to expand...

Does the Styrofoam cooler not amplify the sound? If you scratch your finger nail on a Styrofoam cup or cooler, it is amplified. Bu then again I never have stuck a fan in a cooler before so I really do not know.

Dr. Conjuror

Yesterday I tried a quick idea with my noisy fan with good result. I lined a cardboard box with some old carpet and put the fan/filter combo in there. I set the box on that bicycle tube sandwich (tried it just setting on the rafters, but got a lot of house vibration back - my fan may have a tiny imbalance or something....) It's really very good now. It's not entirely silent, but you can be anywhere in my house except the bedroom & not notice it unless you were listening for it. The only real noise now is from the 4"duct running inside the wall. I'm thinking of dropping some loose insulation down the wall & seeing if that helps at all.

I just thought of something - my interior house walls are 1/4 plywood, not drywall or plaster. I think that's why the vibration seemed to travel through the whole house so bad. When I get the funds I may try a speed controller or a less powerful fan, between that & the loose fill insulation I may get it silent yet!

Dr. Conjuror said:

Does the Styrofoam cooler not amplify the sound? If you scratch your finger nail on a Styrofoam cup or cooler, it is amplified. Bu then again I never have stuck a fan in a cooler before so I really do not know.

Dr. Conjuror

Click to expand...

I think the open styrofoam cup in your scenario is acting like a vibrating loudspeaker due to it's shape. An open styrofoam cooler might give some of that same action, but with a lid on it I don't think it would be able to vibrate like the cup. foam definitely does muffle sound though.

mayorofthdesert - I thought that might be the case. I know it would provide great insulation as well. As far as acoustics, would a box be better? Have you tried making a muffler for you exhaust? And if you are using rigid duct work, hve you tried connecting it to the fan via a small piece of accordion to reduce the transfer of vibration?

Dr. Conjuror

I've seen guys suspend their fans using bungee cords to isolate the fan mechanically to cut down on vibrations. That's the same thing as putting it in a padded box.

So now you're ready to tackle the noise from the air rushing through the ductwork.

The noise is created from two souces that are linked together, Airspeed and Turbulence. An increase in duct size from 4" to 6" to 8" will drop the airspeed down by 50% for every 2" increase. Using insulated 6" ducting will make a big difference through the house.

A homemade muffler at the end of the duct will make a big difference. All you need is a big carboard box which will drop the airspeed down and a grill on the exit to make the airflow less turbulent. You can line the inside of the box with some foam or carpet to make it even more quieter.

mayorofthdesert said:

Yesterday I tried a quick idea with my noisy fan with good result. I lined a cardboard box with some old carpet and put the fan/filter combo in there. I set the box on that bicycle tube sandwich (tried it just setting on the rafters, but got a lot of house vibration back - my fan may have a tiny imbalance or something....) It's really very good now. It's not entirely silent, but you can be anywhere in my house except the bedroom & not notice it unless you were listening for it. The only real noise now is from the 4"duct running inside the wall. I'm thinking of dropping some loose insulation down the wall & seeing if that helps at all.

I just thought of something - my interior house walls are 1/4 plywood, not drywall or plaster. I think that's why the vibration seemed to travel through the whole house so bad. When I get the funds I may try a speed controller or a less powerful fan, between that & the loose fill insulation I may get it silent yet!

Click to expand...

Really great thread! I have learned a lot tonight and I wanted to see if I got a general idea of what I will need.

Grow space is 2'x4'x5' and I have a 400W MH/HPS air cooled reflector w/glass. If a good temp range for the box is 75-78F with controlled room temp of 70F, I would need roughly 250CFM to hold box temp at 75F and roughly 150CFM to hold box temp at 78F? I won't be able to provide unrestriced airflow as I need to vent out of the top of the cab. I will be able to exhaust directly out of the right side however as I plan to keep the light fixed. I planned to use an 6" S&P TD Series 293/218 CFM with speed controller for this application.

With my grow space being 2'x4'x5' (40 cubic ft), I would need 8CFM to cycle the cab air 5 times/min? I have read that the "wind tunnel" effect is bad, so would 5 times/min be acceptable? I don't quite catch how carbon filters decrease a fan's CFM rating, would a 4" S&P TD Series 101/97 CFM with speed controller and a 4" pre-fab carbon filter be overkill with this box?

I had planned to use the 90 degree PVC trick to light-proof. Will this setup be effective with the increases in static pressure? Any other tips to light-proof intake/exhaust?

Appericate any input. Once again fantastic thread!

Need Advice For Pulling Through 2 Seperate Carbon Filters With One Fan

Need Advice For Pulling Through 2 Seperate Carbon Filters With One Fan

I am trying to exhaust my veg tent and my flower tent with the same fan. Flower tent is 4 x 8 x 6 and veg tent is 2x4x5.

I have a S&P 6" fan pulling 300 cfm.

Best way to explain this is to work backwards from the exhaust outlet:

6" hard duct (6' run) . . . to

fan . . . to

6" hard duct (2' run) . . . to

6" Y connection

Veg branch from Y connector:

6" to 4" reducer ... to

4" hard duct (4' run) . . . to

Can 33 filter

Flower tent branch from Y connector:

6" Hard duct (8' run) . . . to

Can 33 filter

I am thinking that I need to reduce the short run to the veg filter to a 4" line to even out the vacumn so both filters are pulling the same?

So yeah, that's my question: how can I balance out this split exhaust system?

Thanks in advance.
Buddy

Sirus said:

Grow space is 2'x4'x5' and I have a 400W MH/HPS air cooled reflector w/glass. If a good temp range for the box is 75-78F with controlled room temp of 70F, I would need roughly 250CFM to hold box temp at 75F and roughly 150CFM to hold box temp at 78F?

Click to expand...

Yes, you got the math right.

Sirus said:

I won't be able to provide unrestriced airflow as I need to vent out of the top of the cab. I will be able to exhaust directly out of the right side however as I plan to keep the light fixed. I planned to use an 6" S&P TD Series 293/218 CFM with speed controller for this application.?

Click to expand...

I haven't looked at that fan, but it should not matter if you vent from the top or from a side hole at the top. You want to establish a clear path for the air from bottom floating up to the to exhaust. If you use the side vent, don't put your air intake on the same wall below the exhaust hole. Put it in the far side at the bottom, as much as possible. THis makes the air travel maximum distance through the box and gives a more even airflow across the growing survace.

Sirus said:

With my grow space being 2'x4'x5' (40 cubic ft), I would need 8CFM to cycle the cab air 5 times/min?

Click to expand...

No. You did the math wrong here. You would need 5x40=200 CFM to change the air 5 times per minute. 8 CFM would give you one air exchange every 5 minutes. The size of fan you talk about (150 to 250 CFM) will be just about right.

Sirus said:

I have read that the "wind tunnel" effect is bad, so would 5 times/min be acceptable?

Click to expand...

You don't have a choice. That size light needs a minimum cooling effect to remain stable in temperature. You have to provide the air flow or you will cook the girls.

150 to 250 CFM will be just fine. Make sure your intake holes are large enough area to avoid constricting the fan.

Sirus said:

I don't quite catch how carbon filters decrease a fan's CFM rating, would a 4" S&P TD Series 101/97 CFM with speed controller and a 4" pre-fab carbon filter be overkill with this box?

Click to expand...

Filters (or anything) act to constrict the airflow. all the air must pass through the filter. The filter has air resistance. This will rob some of the fan power.

I would say that if anything, a 4" filter will be too much constriction on the airflow and really kill it off. You want more surface area so the resistance of your filter to airflow is less. If you have a six inch fan intake, you need to make sure you use a six inch filter or it will throttle the fan even more than you would expect from just a filter alone.


That 100 CFM fan is not going to allow you to achieve your goals unless you can live with higher temps or can drop the intake temperature. You are going to need more like the 293/218 CFM fan you mentioned at first.

Then again, you mentioned you would be using a glass separation between the bulb and the growzone. Were you planning to vent each of these separately? If so, you might get away with two 100 CFM fans, one for the grow zone and one for the light itself. I don't really know your setup well enough to say for sure. It could work, it might not.

Sirus said:

I had planned to use the 90 degree PVC trick to light-proof. Will this setup be effective with the increases in static pressure? Any other tips to light-proof intake/exhaust?

Click to expand...

Put the intake and exhaust holes in the darker parts of your box, if possible. I have a plastic sheet the separates the box at the dirt line to keep light away from the roots. I also wrap the pots in thick black sheet plastic to stop light. The intake is located down there in that area. I use only 150W and that light is still the brightest thing I own. It's really hard to completely stop all light, if that is your goal. You can really knock it down but 100% stoppage is tough without killing the air flow. Use multiple solutions for light so that the PVC pipe trick is used, then black plastic blocks any direct line of sight from the entrance to the area.

The speed controller is a good idea if you want to really actively control the temps to get just the value you want. If possible, mount the temp sensor for the fan at the canopy and out of direct view of the light so you get a good ambient temp of the air at that level.

Get some cheapo digital thermometers and mount them at various spots around the canopy height so you can monitor for hot spots. I think they run about $8 or so, this is cheap. You can remount the temp sensor on the inside of the digital thermometer so it is on a wire and you get two probes for the price of one. I like to keep the digital thermometers outside the box so you can look at temps without opening the door and disturbing the running condition. Opening the box will totally destroy any temperature balance you have and it takes about 20 minutes for a box to stabilize thermally again after you close it up.

-SomeoneYouKnow

buddydro said:

I am trying to exhaust my veg tent and my flower tent with the same fan.

I have a S&P 6" fan pulling 300 cfm.


Veg branch from Y connector:

6" to 4" reducer ... to

4" hard duct (4' run) . . . to

Can 33 filter

Click to expand...

Buddy ,

You forgot the important parts.

What size lighting are in each tent?
What is your intake temperatures?
What problems (if any) are you having now?
Have you run this system through a couple of grows or is it new?

That reducer is going to really cut the flow in that leg. Why do you need it?

-SomeoneYouKnow

Thx for the response Some1. I planned to use two fans in the cab.

The 6" S&P TD Series 293/218 CFM with speed controller would be used to control light temp (intake-light-fan-exhaust) with intake from the top of the cab and then out the right side.

The 4" S&P TD Series 101/97 CFM with speed controller and a 4" pre-fab carbon filter would be used for ventilation/odor control (filter-fan-exhaust) with exhaust vent out of the top. Two "6 passive intakes at the bottom right side. I could upgrade this fan to the 6" model w/filter and 8" passive intake if I need the extra power to vent/filter the cab.

This has to be a stealth cab, thats why I can only place visible holes on the top and right side.

Some1uKnoOf said:

Buddy ,

You forgot the important parts.

What size lighting are in each tent?
What is your intake temperatures?
What problems (if any) are you having now?
Have you run this system through a couple of grows or is it new?

That reducer is going to really cut the flow in that leg. Why do you need it?

-SomeoneYouKnow

Click to expand...

I am running two 600 in the flower. I cool lights on a seperate line and have no temp problems the last few runs. Well, none that I couldn't sort out!

Just want to exhaust veg through a filter for odor control. I would like to run the veg filter line into my existing flower filter line.

I figure move the fan out of tent so it can pull through Y connector that splits veg/flower.

The reason I was thinking I have to reduce veg line to 4" is because it is shorter then the flower filter run and I'm not sure if the fan will pull equally through both filters???

How effective are dark room louvers? Are they restrictive on air flow?

JBlaze said:

How effective are dark room louvers? Are they restrictive on air flow?

Click to expand...

JBlaze:im not sure how restrictive darkroom louvers are but if you're wanting a compact light trap intake check out Scrub Ninjas diy light trap here.

Sirus said:

I planned to use two fans in the cab.

The 6" S&P TD Series 293/218 CFM with speed controller would be used to control light temp (intake-light-fan-exhaust) with intake from the top of the cab and then out the right side.

Click to expand...

I don't really see the purpose for the speed controller on the big fan. If you are venting the the light, there is no reason why you would want to slow the fan down. You aren't trying to hit a specific temperature like 80*F, you are trying to remove as much heat as possible before it gets into the grow zone. That means as much air as possible. Unless there is a noise or stealth issue, turn it up full and let it run!!

The other thing I'm not so sure about is the need for a 300CFM fan on the light. I definately agree that you need a fan but putting the largest up there seems like a bit of a waste of money, space, and noise. I would think you would need only about 100 CFM to cool that, not 300. The light will cause lots of resistance to airflow and probably doesn't have a 6 inch intake and exhaust hole that your S&P 300 fan will need. That's just going to mean lots of reducers, smaller duct work, etc. Just pick a duct size that goes with the fan. Even four inch diameter is probably going to be large for what you have in mind. Probably something more like 2 inches. If you can make something bigger work, then by all means do so. Computers use only about 40 CFM to cool their internals when you have two fans going. They normally don't use 400 watts continuous, though.
[/quote]

Sirus said:

The 4" S&P TD Series 101/97 CFM with speed controller and a 4" pre-fab carbon filter would be used for ventilation/odor control (filter-fan-exhaust) with exhaust vent out of the top. Two "6 passive intakes at the bottom right side. I could upgrade this fan to the 6" model w/filter and 8" passive intake if I need the extra power to vent/filter the cab.

This has to be a stealth cab, thats why I can only place visible holes on the top and right side.

Click to expand...

This gets into the whole coolTube problem. I have never been able to figure a good model for knowing how much heat you can capture when you have the light in one enclosed area (like a coolTube or your setup) and the plants in another, separated by a clear partition. Some of the heat will radiate through the glass, a bit will conduct through the glass, and the rest will get sucked away by venting on the bulb as described above.

The portion of heat that radiates or conducts through the glass is the part you deal with using the second fan and speed controller. If you can get 50% of the heat energy to go out the light fan, that means you only have to deal with 50% of the heat in the grow zone. That's a huge difference in fan power and related noise. Maybe it's only 30% or maybe it's 60%. I just don't really know. This will have a huge impact on the size of fan you need in the grow zone.

I know how to figure out the capture amount experimentally, but this means you need to build the box and run it while measuring some temperatures. I can tell you how to do this, but you won't really know what size fan to purchase for certain. I don't know the return policy of S&P. If you have a fan or two laying about or could borrow, we could work with that to figure out a decent idea of what you need.

Call me dumb, but I don't really see the purpose of the S&P 101/97 fan. Those are the low and high speed values. In my book, those are pretty much the same number. You aren't going to save much in noise between the two settings. The speed difference in those settings is not even 100 RPM. Pardon me, but it looks like a dumb product. They should have the slower setting be about 75CFM to make sense. The next size up is the 135/100 and this seems much more reasonable to me. Is there a big cost or noise difference? The bigger fan weighs twice as much but both use a 4 inch duct. The bigger fan can also deal with more static pressure. This is the link I am looking at:

http://www.solerpalau-usa.com/brochures/Residential_Light_Comm/TD_Extended_Brochure.pdf


It seems like you have a reasonably tall area. It is 5 feet, right? Some of that is going to be the light, but there is stll a large area remaining where you can put the fan and filter combination. Is that your plan?

At this point, I would say to build your cabinet but don't plant any seeds just yet. Get a 100CFM fan and vent the light to see if everything works. You can put some computer fan or something to vent the main space just to get some air movement and get an idea of fan placement, noise levels, vibration/rumble control, etc. Close the box up and turn the light on for a couple hours at steady state to see how hot things get. Use a digi-thermometer to monitor the temps remotely.

Once you can run for 45 minutes with the temperature in a narrow zone of a few degrees with a constant intake temperature, then you can start to play. Put another standard lightbulb (60 or 75 or 100 watts should be about right) like a trouble light inside the box with the plug coming out so you can turn it on and off remotely. Let the box run up to steady temperatures, then plug in the extra light to create more heat load. If you see a 10*F rise with just the HPS and then you turn on the new light and see it go up to 15*F with no other changes, you know the heat from the HPS is going to be twice as much as the new light. Do the math to figure out the heat load coming from the HPS. You can then size the fan you need for the main zone and buy the right one.

Instead of a bigger fan for the grow zone, I would think you might be better using two filters that operate in parallel. This gives you twice the surface area and half the air resistance. I think the filter is going to give you more airflow loss than just about any other part, if it is doing a reasonable job at controlling odor.

FYI - The extra lightbulb is used as a heat source of known wattage. We use it to get a temperature rise that we can measure, then use ratios to figure out what the unknown heat wattage from the HPS must be. This is about the only purpose I can think of for using standard incandescent bulbs in a growing environment

If you decide to do this experiment, let me know so we can walk through it in more detail to get it right. I don't really know of any other way to know for sure how big a fan you would need.

The other thing I would recommend for you to think about is to have the fan cooling the light set up to push air through the light, not pull it. This has two purposes. The first purpose is to keep from running really hot air through the fan. It's one thing to run 85*F air through the fan, but you need to be careful when the air gets about 100*F. The small S&P fans are only rated to a maximum of 104*F and you want to avoid that. Heat reduces the life of any moving part. The second benefit to pushing air through the light is that you have a high pressure inside the light. This is going to keep smells from leaking around the glass and getting out before hitting the filter. I can't see that you will be able to really seal the glass barrier totally, so this ensures you don't have to worry about some stupid leak. It is still a good idea to vent the light exhaust into some place where smells would be hard to notice.

Well, enough for me now. This is already way too long.

-SomeoneYouKnow

buddydro said:

I am running two 600 in the flower. I cool lights on a seperate line and have no temp problems the last few runs. Well, none that I couldn't sort out!

Click to expand...

I need all the numbers requested to know about anything. I still don't know the light size in the veg room, the intake temperatures, etc.

The fact that you have no temp problems means you are satisfied, I think.

buddydro said:

The reason I was thinking I have to reduce veg line to 4" is because it is shorter then the flower filter run and I'm not sure if the fan will pull equally through both filters???

Click to expand...

As best I can figure, you are getting about the same amount of air flow through each leg. The smaller diameter/shorter distance for Veg has about 5 or 10% less airflow than the 6" eight foot run to the flower zone. I don't know if you have any bends or not in duct work but you didnt' mention them so I assume not. If you are running the same light wattage in the veg side and you are pulling intake air for both zones from the same temperature, you should have just about equal temperatures in each. If light wattages or intake temperatures (or intake sizes) are different, this can affect the result.

Cooling the lights directly with a separate line is probably really helping your heat budget. It makes the 300CFM S&P actually work about right for you. I would also guess that your intake temperatures relatively cool, probably below 70*F. I can't really guess how much but I would say it is probably somewhere in the range of 62 to 68*F for the numbers to work out. I'm making lots of assumptions here, so I could be wrong. More info could yield better answers.


-SomeoneYouKnow

Once again thx for the input on this... I see your point of just letting the fan cooling my light to stay on high all the time. There is a huge stealth componet to this cab but the inlines can always be shut down if needed.

The reason why I opted for the 6" was based off the CFM/temp chart. I am aiming to keep my box temps at 75-78ish and based off that chart I would need 250CFM and 150CFM respectivly. The little extra was to compensate for static pressure from the insulated ducting curves. The reflector is air cooled with a 6" flange, cord out the top of the reflector. I didn't even think about the heat from the lamp damaging my fan, good lookin out

I agree with you on that low-end S&P fan, I will be getting the next size up for sure. I am hopeing that the 4" S&P will be able to generate the necessary CFM to circulate the box while pulling through a 4" pre-fab carbon filter. I do plan to keep it the fan/filter in the cab, venting out the right side above the light exhaust vent. I plan to also pick up a couple of the 6" Air King Clip-On fans for added cooling in the cab.

So thats the general plan, headed to Lowes this weekend for lumber and will start on the frame early next week...cant wait to get my 400W up'n runnin. When I get to the stage for temp testing I will be in touch. By chance to you know which is quieter, the S&P series or the Panasonic WhisperLine? The sone rating for the 6" whisper line is 1.4 which isn't bad but I can't find any stats for the S&P's.

Thanks again for all the input

Red, what size intake did you use on your DIY Clone/Drying box, when you were running lights in it? And what was your rise over ambient? I just made a nice box very similar to yours, but I need to make sure I get the passive intake right for it. Thanks for any help. Cheers.

I've always set my bottom tubs up to handle a 4" Fan in the top tub. With some lights stuck in the lid and a fan or a tru aire filter it runs into a small veg box. With a lid and a tru aire filter it becomes a drying box.

For a 4" fan, it has 12 sqin of exhaust area that needs 25 sqin of intake. One 5x5 intake hole is all you need.

The temps were fine with 4 x 26 lights and a tru aire filter. My super stacker works the same way.