The Ventelation 101 thread and other question.

[weeeduh]

So I have a cabinet that I am going to get cut out this week.

The inside dimensions are exactly 22"x43.5"x69"

This puts me at just over 38CF of volume of scrubbed air that I will need to move out of my cab once every 5 minutes.

This means I only need to push out 7CFM in my fan filter combo (assuming I have heat under control).

Now I haven't quite figured out the calculation yet, but this is what I am looking at getting.

http://www.htgsupply.com/viewproduct.asp?productID=52531

4" fan/filter 170cfm @ 80w.

That sounds like it will destroy my plants inside of 38CF! Something like swapping the air out over 4 TIMES a minute!

So I am thinking I can still use this, as long as I get one of these to change the speed of the fan.

http://www.htgsupply.com/viewproduct.asp?productID=53142


Sounds good right?

 

[FreezerBoy]

While you may want to control fan speed for sound purposes, 170 cfm in that space will do no harm. Are you sure 170 is enough?

 

[weeeduh]

I think the 170cfm with filter attached will be too much. I am not exactly sure how those ventilation numbers work, but just thinking about it, my main concerns for ventilation are 2 fold.

1st being the heat put off by the lights in such a small place as well as my ambient temps likely to be hitting the mid 80's.

2nd is cleaning the air. If I can control my temps with either cfl and lowering ambient temps with ac OR control with a high intensity independent aircooled hood the I am sure the 170cfm is way too much I will be growing in a 38cf cab, that means 170 cfm will exchange the air more than 4 times per minute.

If I can run the cab with lights at 5 degrees over ambient, then I will need to run ac during the day in the middle of summer, which I don't see as a problem. Just were I am setting up has no ambient ac duct.

So assuming that I am able to pull that off, with flouro's or unrestricted air cooled lights, then my next concern really is how big to make the intake holes.

I really am not sure if the 170cfm is what I am really going to get out of the combo. From what I can tell, as long as I keep my temps under control I only need to exchange the air in the cab at the cab cubic feet, which is 38cu, once ever 4-5 minutes. So I only need to push out 7-8cfm to keep the air fresh both inside and outside the cab. So I am not sure how a 170cfm rated fan/filter combo can get knocked all the way down to 8cfm.

I am also a little concerned that if I go with such an oversized solution and don't regulate the airflow, either by restricting the intake holes or slowing down the fan, that I will stunt my plants potential.

I think my math is right here, and I really hope that a combination of restricting intake and slowing down the fan will solve the oversized problem.

Thanks for the feedback FreezerBoy. I assume when you say it will do no harm you mean that I won't be creating a wind tunnel that will shock the plants. If that's the case, I'm going to just go with it, and if I have to adjust, I am sure I can adjust.

I am eager to get started, and you can only plan so much. The old saying, you study long, you study wrong comes to mind. Sooner or later, just gotta do it.

 

[FlaDankster]

I purchased the same unit from HTG.Just hooked it up and got all squared away yesterday.It to my surprise is doing what i wanted but my space is larger than yours,4x7x8 with a 600 as my source of light.I have central a/c to my room but without the a/c runnin temps are stayin at 78.

A bit of overkill is kinda a good thing incase you need more air flow.For your space you will def need the speed control.I can't find all my paper work i got with the fan but i beleive the 4 inch scrubber cfm is between like 145-230 or so.Maby you could use that filter with a smaller fan??.And i will say this,the fan is not very quiet so if stealth is a concern your gonna have to do some extra work to hide your noise like i did.Call HTG and speak with them,GOOD customer service they have,they will help.

 

[LunaShadow]

As you have a small space shouldn't you get a smaller fan?

Using that speed controller you might find you have to reduce the speed of the fan to such an extent that you get a motor humm.

Getting a smaller fan to start with or using a variac speed controller will eliminate these possible issues.

atb

 

[FlaDankster]

As you have a small space shouldn't you get a smaller fan?

Using that speed controller you might find you have to reduce the speed of the fan to such an extent that you get a motor humm.

Getting a smaller fan to start with or using a variac speed controller will eliminate these possible issues.

atb

Another thing.These fans are on the cheaper side of things so ya gotta ? how long this thing would last being turned all the way down for the majority of it's use i would assume>

 

[FreezerBoy]

1st being the heat put off by the lights in such a small place as well as my ambient temps likely to be hitting the mid 80's.

Mid 80s won't kill you but, it's not optimal. Dropping temps another 10º would be better for you and that means a bigger fan. HOWEVER, bigger fans mean more noise and noise raises questions. Questions, bad. Very, very bad.

Blasting directly on the plants would be bad but, 170 cfm flowing through the cab is nothing to worry about unless it's too little air flow or too loud for the surroundings.

 

[weeeduh]

I purchased the same unit from HTG.Just hooked it up and got all squared away yesterday.It to my surprise is doing what i wanted but my space is larger than yours,4x7x8 with a 600 as my source of light.I have central a/c to my room but without the a/c runnin temps are stayin at 78.

A bit of overkill is kinda a good thing incase you need more air flow.For your space you will def need the speed control.I can't find all my paper work i got with the fan but i beleive the 4 inch scrubber cfm is between like 145-230 or so.Maby you could use that filter with a smaller fan??.And i will say this,the fan is not very quiet so if stealth is a concern your gonna have to do some extra work to hide your noise like i did.Call HTG and speak with them,GOOD customer service they have,they will help.

Thanks for the feedback, on this. Are you cooling your light and scrubbing your air in the same duct? I was thinking that if I decided to go with HID in cooltube or hood that I would go with the 6" in line duct fan from htg. Now that I think about it, that probably is a better solution!

I can get this 4" filter by itself http://www.htgsupply.com/viewproduct.asp?productID=49749

with this 4" in line duct fan at 80cfm. http://www.htgsupply.com/viewproduct.asp?productID=46434

For that matter, I don't think I would need the variable speed as at most I am looking at 2 air exchanges per minute. I could restrict this by choking off the holes if it gets to be to much air moving around. But it sounds like that is not even going to be a problem.

As far as noise, yes that is definitely a concern as well when thinking about the security of the grow. I put noise and fresh air together under security concerns.

I am pretty good with acoustics. The cab I am building is already being designed for noise insulation, so i should be good.

Thanks all for feedback, this really gives me confidence that I am going down the right track for indoor growing.

 

[FlaDankster]

What up weeeduh.....

Yes i am scrubbing and cooling with the same line.

For your cab bro 6 inch would be waaayy over kill just because of an HID light i think.Like i said,i'm scrubbin and cooling a 600 watt hps in a 4x7x8 space.So far it is doing fine.? is would that 4 inch scrubber(that is rated at a higher cfm than the booster fan your lookin at)going to work properly???To my understanding for things to work right the fan and filter cfm have ta go kinda hand in hand.I feel the combo you posted would do fine for you,cfl,HID don't matter.But i'm tellin ya....it's a bit loud.

 

[FreezerBoy]

with this 4" in line duct fan at 80cfm.

That's a duct booster, meant to work as an aid to your real fan. Without a real fan doing all the work, it's pretty useless.

 

[2Lazy]

I don't think you've gotten very much good advice here.

You cannot have too much ventilation. Nature's CFM is in the trillions, so don't think that moving air around your plants is going to hurt them, it won't.

I use that exact fan in my 2x4 grow tent and it does the job perfectly. My temperature in the tent stays constantly about 2 degrees warmer than the intake (closet room temperature). So I just keep my place in the low to mid 70's and the fan takes care of the rest of the work.

I only use an exhaust fan. I used to use a 4" axial intake fan but it was extremely loud and turned out to be needed elsewhere in my grow area.

Get that fan and attach some ducting to it. It will get much quieter with the ducting.

 

[FlaDankster]

I don't think you've gotten very much good advice here.

You cannot have too much ventilation. Nature's CFM is in the trillions, so don't think that moving air around your plants is going to hurt them, it won't.

I use that exact fan in my 2x4 grow tent and it does the job perfectly. My temperature in the tent stays constantly about 2 degrees warmer than the intake (closet room temperature). So I just keep my place in the low to mid 70's and the fan takes care of the rest of the work.

I only use an exhaust fan. I used to use a 4" axial intake fan but it was extremely loud and turned out to be needed elsewhere in my grow area.

Get that fan and attach some ducting to it. It will get much quieter with the ducting.

I would agree yes.....you can't really have too much ventilation but,going anymore than what he is lookin at would be over kill...on the pocket on the work to do to cover more noise ect...no need to have more just cause it won't hurt.K.I.S.S.

Umm....where is YOUR good advice??You pretty much said what the rest of us did.

FD

 

[RugerBaby]

I took some advice form the ventilation thread and used some axial fans. They are freaking loud! I ended up buying a 6 in active air centrifugal fan. Now the room is a lot quieter.

 

[2Lazy]

Umm....where is YOUR good advice??You pretty much said what the rest of us did.

FD

I was going to justify that with a public retort.

But then I realized you're trying to act a troll.

Whatever dude. I don't care that you care.

 

[FlaDankster]

I was going to justify that with a public retort.

But then I realized you're trying to act a troll.

Whatever dude. I don't care that you care.

Uhh.....no need to be negative bro.It's good that you don't care,so please.......your public retort would be much better for the rest of the viewers and ME.But to just say dude you ain't gettin good advice and to just put up the same thing everyone else has was kinda dumb in my book....but thats my book.Me ain't tryin to start no shit bro......here to learn dude.So please.....you got GOOD advice to post please do.

Troll?........eat a dick bruddah!Had to get that in there sorry.But like i said,you got good info i would like to hear some.

Have a good day and stay safe dude.

FD

 

[THCforus]

I was going to justify that with a public retort.

But then I realized you're trying to act a troll.

Whatever dude. I don't care that you care.

Fladankster makes a valid point.
If your going to make a statement like that it really should be followed by some very useful advice.
You might want to get a better understanding of what trolling is.

 

[weeeduh]

Just wanted to follow up with some filter research I have been doing. This is on the CAN Labeled filters as they seem to be popular and reputable. Here is the link.

http://www.planetnatural.com/site/xdpy/kb/can-filter.html

What I found extremely helpful was the detailed specs. For instance, this seems to be a popular choice over on ebay..

I will point out what I thought was important after the specs.

Can-Filter-33

Specifications:
Max cfm: 200/350 m3/h @ 0.1 sec contact time
Recommended Min Airflow: 100 cfm
Prefilter: Yes
Flange: 6 & 8"
Dimensions: (with pre-filter)
·Outside Diameter: 305mm/12"
·Height: 330mm/13"
·Weight: 7kg/15.4lbs.
·Carbon Bed Depth: 50mm/2"
Max Operating Temp: 80ºC
Pressure drop at max cfm: 180pa/. 75wg

Recommended Can-Fan:
FAN Filtered Air CFM
RS6HO 219
RS6 156
RS4HO 137

*Note* These specs interchange metric/standard standard/metric somewhat haphazardly.

First of, there is a minimum and maximum CFM for each filter to work properly. For this one, the minimum is 100CFM and maximum is 200CFM. I am pretty sure this is the airflow at the surface of the filter. I don't think it matters whether you are pushing or pulling.

Next, what I realized after studying these data, we don't see the CFM on the other side of the filter and there is a very logical and sound reason for this that did not hit me until after I found these specs. See, the purpose of the air filter is to trap particles in the air. When the filter is brand new, the CFM AFTER the filter is going to be higher than it will be the next day or even the next minute of use. That's cause as soon as you start pushing air through the filter its going to start clogging up.

I don't know why I didn't realize this sooner. I have worked on cars all my life and changed tons of oil filters. They are always heavy when the get old because of all the crap they trapped. This is why they have to be changed because the pressure builds up on the "high side" or pump side of the filter.

Anyways, I though it was pretty awesome to realize this because it helped me to understand what I was missing.

Ok, so next important thing I realize was the MAX operating temperature. This one is 80 degrees! Wow! I was actually wondering about how heat impacts the ability of the filter to clean the air. Heat causes particles in the air and the air itself to expand. This means less particles hitting the surface area of the filter. But, wow 80 degrees! This pretty much rules out putting the filter at the end of the chain if using one fan to cool and scrub the light and the air, respectively. I see folks here write it up like so..

Fan -> Light -> Filter.
Filter -> Fan -> Light.
Light -> Filter -> Fan.

Etc, 6 different ways to do this. The vent101 thread recommends cooling the light by itself for many reasons. I didn't recall reading this as one of those reasons.

Anyways, so it looks like the best way I see to set up would be..

Filter -> Fan -> Light

I suppose you could also go

Filter -> Light -> Fan

But I imagine the same issue would come up with the fans minimum operating temp.

The next thing I realized was that dang these filters are pretty heavy! This one is like hanging up a friggin' bowling ball! almost 16 POUNDS!

Well, this is a pretty good template for filter specifications and is exactly what I needed to know to help me shop.

I hope this information is useful, oh and as you can see, a fan with a higher CFM than the fan's max is recommended, but not by much. I am certain now that if you were to by a fan much bigger than your filter, you would burn up your fan pretty quick. A little back pressure isn't too bad, because you'll get that anyways as the filter gets older day by day. And for the minimum, you would end up having the same problem because the filter would clog really quickly since there isn't enough pressure to overcome the density of the filter.

So I conclude, it is probably best to find a fan that is slightly less than the rated max CFM. This will make sure the filter works, and make sure your fan doesn't spend the filters entire lifespan working harder than it has to.

Oh yeah, and one more thing, for the vent calculations, it probably a good idea to divide the filters max CFM by 2 to determine how much air exchange will be going on inside your space. This way you will make your intake and exhaust holes the right size according to your airflow.

 

[FlaDankster]

Just wanted to follow up with some filter research I have been doing. This is on the CAN Labeled filters as they seem to be popular and reputable. Here is the link.

http://www.planetnatural.com/site/xdpy/kb/can-filter.html

What I found extremely helpful was the detailed specs. For instance, this seems to be a popular choice over on ebay..

I will point out what I thought was important after the specs.

Can-Filter-33

Specifications:
Max cfm: 200/350 m3/h @ 0.1 sec contact time
Recommended Min Airflow: 100 cfm
Prefilter: Yes
Flange: 6 & 8"
Dimensions: (with pre-filter)
·Outside Diameter: 305mm/12"
·Height: 330mm/13"
·Weight: 7kg/15.4lbs.
·Carbon Bed Depth: 50mm/2"
Max Operating Temp: 80ºC
Pressure drop at max cfm: 180pa/. 75wg

Recommended Can-Fan:
FAN Filtered Air CFM
RS6HO 219
RS6 156
RS4HO 137

*Note* These specs interchange metric/standard standard/metric somewhat haphazardly.

First of, there is a minimum and maximum CFM for each filter to work properly. For this one, the minimum is 100CFM and maximum is 200CFM. I am pretty sure this is the airflow at the surface of the filter. I don't think it matters whether you are pushing or pulling.

Next, what I realized after studying these data, we don't see the CFM on the other side of the filter and there is a very logical and sound reason for this that did not hit me until after I found these specs. See, the purpose of the air filter is to trap particles in the air. When the filter is brand new, the CFM AFTER the filter is going to be higher than it will be the next day or even the next minute of use. That's cause as soon as you start pushing air through the filter its going to start clogging up.

I don't know why I didn't realize this sooner. I have worked on cars all my life and changed tons of oil filters. They are always heavy when the get old because of all the crap they trapped. This is why they have to be changed because the pressure builds up on the "high side" or pump side of the filter.

Anyways, I though it was pretty awesome to realize this because it helped me to understand what I was missing.

Ok, so next important thing I realize was the MAX operating temperature. This one is 80 degrees! Wow! I was actually wondering about how heat impacts the ability of the filter to clean the air. Heat causes particles in the air and the air itself to expand. This means less particles hitting the surface area of the filter. But, wow 80 degrees! This pretty much rules out putting the filter at the end of the chain if using one fan to cool and scrub the light and the air, respectively. I see folks here write it up like so..

Fan -> Light -> Filter.
Filter -> Fan -> Light.
Light -> Filter -> Fan.

Etc, 6 different ways to do this. The vent101 thread recommends cooling the light by itself for many reasons. I didn't recall reading this as one of those reasons.

Anyways, so it looks like the best way I see to set up would be..

Filter -> Fan -> Light

I suppose you could also go

Filter -> Light -> Fan

But I imagine the same issue would come up with the fans minimum operating temp.

The next thing I realized was that dang these filters are pretty heavy! This one is like hanging up a friggin' bowling ball! almost 16 POUNDS!

Well, this is a pretty good template for filter specifications and is exactly what I needed to know to help me shop.

I hope this information is useful, oh and as you can see, a fan with a higher CFM than the fan's max is recommended, but not by much. I am certain now that if you were to by a fan much bigger than your filter, you would burn up your fan pretty quick. A little back pressure isn't too bad, because you'll get that anyways as the filter gets older day by day. And for the minimum, you would end up having the same problem because the filter would clog really quickly since there isn't enough pressure to overcome the density of the filter.

So I conclude, it is probably best to find a fan that is slightly less than the rated max CFM. This will make sure the filter works, and make sure your fan doesn't spend the filters entire lifespan working harder than it has to.

Oh yeah, and one more thing, for the vent calculations, it probably a good idea to divide the filters max CFM by 2 to determine how much air exchange will be going on inside your space. This way you will make your intake and exhaust holes the right size according to your airflow.

Good post weeed

Did notice though your posted specs give your degrees in celsius on the filter bro........Put da joint down dude.
That would be bout 175 degrees i think?

 

[weeeduh]

Good post weeed

Did notice though your posted specs give your degrees in celsius on the filter bro........Put da joint down dude.
That would be bout 175 degrees i think?

Oh dang heh, nice catch! And I looked at that several times thinking that I might get problems keeping temps at 80 F with no A/C.

well, I still wonder then its probably better to keep that filter in front of the light instead of blowing hot air onto the filter.

But yeah I had to stare at those specs for a while especially the CFM cause that is cubic FEET per minute, but the metric version is m3/h or cubic meter per hour. Seemed like they would just put metric on one side and standard on the other, but noo they mixed it all up, and when I only saw the temp I guess I just assumed it was in Fahrenheit cause that is what I am used to. That big ole C after it wasn't there when I posted I swear to you!