Ventalation Question->?

[igrowwitmatches]

Ok, im tryin to set up some decent ventalation in a small tent.. and my temps r stilll running alittle high... im using 1 fan to pull through a cooltube and a carbon filter... is it more important to suck the air from the top of the tent.. or keep the ducting strait/short

any comments, suggestions appriciated.. thnx
any questions let me know

also anyone that knows anything about lights ->heat... does efficiency effect heat output of diffrent types of bulbs.. or is 100 watts of Mh Hps Cfl FLoro Cmh all emit the same amount of heat

 

[FreezerBoy]

What type of lamp? What size fan? How many intakes?

 

[igrowwitmatches]

i have an 250 w hps/mh fan is an inline s+p alittle over 100 cfm no fan intake... since the tent is very small and in part of a closet.... its alittle hard to regulate the temp especially since the cooltube hardly fits in the tent.. much less with ducting on each side and a filter attached... so i need to compromise between putting some 90 degree bends or putting the filter on the floor..

 

[Jnugg]

the problem lies in this.

You are using one fan to both air-cool the light and to ventilate and de odorize the hot air being exhuasted.The fan is rated for 100cfm.

Once that fan has had a carbon filter added to it it's airflow is reduced...dramaticly.Slap some ducting and some bends in the ducting in there and the airflow has been reduced even more.

Either A) Get another fan so that you have one dedicated to just cooling the light and the other is dedicated to ventilation and de odorizing of the exhuast air.

What are your ambient temps (air temperature of the room the grow tent sits in)?

Is there any way for that air to enter the closet that houses the grow tent?

Where are you exhuasting to?

Try running your exhuast to the attic or another room.If you are just exhuasting out the top of the tent and allow the exhuast air to interact with the air outside the tent then you are just heating things up as you are recirculating hot air.

I would say you need at least 150cfm if not more.

in a 2.5' x 2' x 5.5' cab using a 400w HPS in an air-ccoled hood I use only 1x 4" 172cfm inline centrifugal to both cool the light and to ventilate the grow (no carbon filter) and in the summer temps in the cab can get up above 82f if I don't keep my central a/c at 68-72f.

I usually have a 5-8f t-diif over ambient temps so cab usually sits at 73/77f - 76/80f lights on....in the winter temps in cab stay at 72-75f.

Had I bought a 6" 392-440cfm inline centrifugal my temps would always be 2-5f above ambient...even in summer.

 

[igrowwitmatches]

yea im trying to deal with those problems... most of the heat gets exausted but like you said i dont have much of an intake system... which is part of the problem... and yea i may need to get a second fan... but ill have to cut holes in the tent for the second fan... which i wouldent prefer to do but may need to... ambient temps around 68-71 .... when i run a 100 watt cfl like i have on now it stabalize's around 82 and doesnt go any higher... if i run the hps/mh then temps will stay 82 or under for about half the day... but it wont stabalize and will continue to rise (prolly due to some recirculating heat) and will rise to
90+ ...

 

[Jnugg]

im using 1 fan to pull through a cooltube and a carbon filter... is it more important to suck the air from the top of the tent.. or keep the ducting strait/short

The best thing to do is place the exhuast fan at the top of the grow tent/box/can/room as heat rises.It is also a good idea to keep the duct runs as short and straight as possible.If you need to make bends in your run of ducting try to use 45 degree angle bends over 90 degree bends.This allows for better airflow and less static pressure on the fan.



What kind of exhuast fan are you using? blower/squirrel cage ie; dayton,panasonic etc.,Mixed Vent (Soler & Palau),Inline centrifugal (Can Fan,Elicent,Eco Plus,Vortex etc.)?

Axial/PC fans move alot of air,but when you add static pressure to the mix via ducting,bends in ducting,reflectors,carbon filters.


Inline centrifugal fans move alot of air too only this style of fan holds up best in environments where static pressure is presesnt,some inline centrifugal fans can handle static pressures as high as 2.5" while still having some sort of airflow.Inline centrifugals are also known to be loud and scream like a mini scaled jet engine when starting up,especially with no ducting attached to either end (the exhuast side is loudest).There are many things you can do to help reduce the noise caused by inline centrifugals.You can:

Build an insulated fan box out of MDF and acoustical foam to reduce the noise of the fans motor.

Use insulated ducting to the heat from radiating out from the ducting and to help silence the air going into/coming out of the fan itself and the sound of the air wooshing around inside the ducting.If you can use oversized ducting (4" fan gets 6" ducting,6" fan gets 8" ducting and so on) to allow for better airflow and less noise.

Once you install a carbon filter this will also reduce the noise of your ventilation system,especially if you exhuast into te carbon filter.

Buy or make a duct muffler.They add no unwanted static pressures and cut the percieved noise by atleas 50%

Mixed Vent inline fans (Soler & Palau) are a hybrid between axial/pc fans and inline centrifugals.They move a decent amout of air and handle static pressures much better then axial/pc fans but but not quite as good as inline centrifugals.

One key thing to think about when planning you ventilation is going overkill on the exhuast fan.When you get a fan that moves way more air then your design needs this is a good thing.It allows you to use a solid state speed controller which allows you to slow down the RPM's of the fans motor which in turn reduces fan noise while still moving plenty of air.

Usually when one adds a carbon filter to an inline centrifugal they can expect to see a 0.5" to .75" pressure drop and that's just from attaching the fan to the filter.This does not account for ducting,reflectors,bends in the duct runs etc.

I base all my fan/filter decisions by comparing the specs to Can Fan's specs.

You can find their fan specs here

You can find the specs for each individual carbon filter here

I always compare to the 4" HO and the 6" HO from can fan.

Here is the Spec Sheet for Can Fans -



And here is the S&P Technical Spec Sheet -



If we look at the Can Fan 6"HO we see it is rated 392cfm @ 0" static pressure.

Now lets look at the 6" S&P TD-150,it is rated 293cfm @ 0" static pressure....so far so good,only 99cfm less then the Can Fan 6"HO!

Now lets look at the Can Filter 50.There are two ways to set up a carbon filter.

1 = inside the tent so the fan is pulling/sucking air through the filter.This is called scrubbing.

2 = outside the tent so the fan is pushing/blowing the air into the filter.This is called exhuast.

Each can filter is rated for a maximum cfm/airflow rating for both scrubbing and.or exhuasting.

The can 50 set up to scrub has a max cfm/airflow rating of 840cfm,and set up for exhuast a maximum cfm/airflow rating of 420cfm.What does this mean?

It means when setting up your can filter for scrubbing to not use a fan that will exceed 840cfm,when setting up your filter for exhuast do not use a fan that will exceed 420cfm.

Each can filter also has a recommended minimum cfm/airflow rating.What this means is do not use a fan with a lower cfm/airflow rating then the filters minimum cfm rating.If we look we see that the Can Filter 50 has a minimum airflow/cfm rating of 210cfm therefore we would need to use a fan that atleast does 210cfm as a bare minimum.

Can Fan also helps us out in deciding which fan to which filter.Each filter has a recoomended fans list.

If we look at athe Can 50 the recomended fans to use with said filter are the Can Fan 6"HO,Can Fan 8",and the Can Fan 10".Can Fan also helps us out again by telling us what the expected airflow of said combo would be after attaching fan and filter.With the Can Fan 6" HO attached to a Can 50 filter we can expect an effective airflow of 300cfm,meaning a 0.5" pressure drop (attaching just the fan to just the filter add's 0.5" static pressure)....more then enough to cool a 400w or 600w and quite possibly a 1000w grow (depending on ambient temps and point of exhuast etc.).

My guess is if you bought a 6" S&P TD-150 and ran it at full speed you'dd see a similar pressure drop and effective airflow of just fan and filter should be around 131-206cfm...add ducting and hypotheticlly we'll say another .25" or so of pressure drops so about 131 cfm.

I have not done the testing this was all the sum of comparison and a little guestimation.

When it comes to ventilation as with most things there are many variables.

Are we using the fan to just exhuast through a carbon filter or no carbon filter...are we using the fan to cool the light and ventilate/deodorize etc. etc.

With The S&P mix vent fans I think the best route is two fans.One dedicated solely to ventilation/exhuast and deodorization of the exhuast air.The other fan dedicated solely to air-cooling of the light.They are cheap ($,and efficient as the 6" S&P TD-150 uses only a meager 65w of power at full speed and only 54w on low speed settings.The Can Fan 6" HO has a max. wattage of 149w.

You can get the S&P TD fans at HVACQuick.com.The TD-150 sells for $127 each.

 

[igrowwitmatches]

thanks for the information... im gonna read that alittle slower in a bit... my computer had some serious issues.... had to compleatly reformat and install everything over reset my internet and update everything... i read through really quickly and looks like some great information.... right now i have a small s+p fan... i reajusted the ventalation and i think i can keep it under 85 degreez .... i doubled the exaust hole size to another room... still no intake... aside from what it pulls through cracks.... so i still need to work on it alittle... im gonna try to use some of that information to fine tune... right now its lookin up though thanks for the help +Rep'd you

 

[BLUNToPOTomuss]

Great info in your last couple of posts Jnugg! Its posters like you that make IC great! you take the time to explain what may be a complex issue to some but simple to others!

Im able to use a single 265 activeair blower to exhaust my cab, cool my cooltubed 400 HPS, and push through a Durban Poison DIY scrubber. Oh my cab is 16 cuft.

Igrow- check my journal it may give you some ideas. I did a few easy things and dropped my temps 20 degrees!!!!! If you have any specific questions fire away!!

good luck!

EDIT-- did I read right....... Igrow, do you have ZERO intake other than cracks? A little more info on my cab.... I have ONE 4'' and THREE 2'' passive intakes for a 6'' exhaust hole. I cant get my cab above ambient unless I turn off the AC. It runs at -2 ambient! with a VERY MINOR suck to the door when closed.

 

[FreezerBoy]

Three 2" holes combined are 1/3 the area of one 6" hole. A=∏r².

 

[BLUNToPOTomuss]

Totally freezer! Thats why I have a 4'' passive also!

Now come to think about it! my cooltube is reduced from 6'' to 4'' as soon as the reducer leaves the cab! So I gues I would have to say Im exhauting out of a 4'' hole right?

Thanks for bring that up! I gotta change how I descride my cab to be more accurate!

 

[FreezerBoy]

Adding the 4" still leaves you shy. I'd junk the reducer and add another 6" intake.

 

[Jnugg]

igrowwitmatches - You need to seal up any cracks in the cab and make a passive intake near the bottom of the cab.Intake area should be 3x+ the area of your exhuast.

A 4" fan has an area of 12.56",multiply by 3.14 and we get 39.4384" needed for passive intake area.

Basiclly out if using a 4" fan and using 2" PVC as intakes you would need atleast eight of them.

I like the louvered darkroom vents for passive intake(s).They are light tight so there are no unwanted light leaks in or out of the grow,and even though they are louvered still allow good airflow.

You can buy an 8" x 8" louvered darkroom vent for $20+ shipping or you can buy two 8" x 8" louvered darkroom vents for $38+ shipping.If a grower needs alot of intake area due to a larger grow/fan etc. they also make 12" x 12" and 12" x 24" louvered darkroom vents.

 

[igrowwitmatches]

has 3 built in intakes about 4-5'' x 12'' ?? ish?? with flaps over them built into the tent.... but there are no intakes into the closet