? about ventilation

A 4" will work very well. @ about 150 CFM, you'll be exchanging the air in the Cabinet (180CuFt) every 70 seconds or so, provided you're providing adequate intake area. AMPLE .... hth

Sinc.
SlackerBee

 

Couldnt agree more, +rep

 

The above poster is quite wrong. You want a fan with a CFM rating 4-5 times greater(3 times greater at a bare minumum) than the cubic feet of your room. To find the cubic feet you multiply the dimensions. Your box is 150 cubic feet so you will want a fan with a CFM rating of atleast 450. You didnt say how strong your fan is but i have seen very few 4" which top 180 cfm. Assuming yours is that strong you would have just enough to vent your box. However pulling through a filter and any bends in your duct will decrease the power of your fan. In other words, unless you have your fan pulling in a straight line and exhausting through a filter(not intaking) it wont work, youll need more power. I would recommend the hydrofarm blowers from Indoor Plant Care, Hydroponics, Grow Lights, Natural Pest Control and more... they are the cheapest on the market and they work amazing. Do any research on exhausting a grow room and it will say the same thing i am now. Plus i use a 2x2 secret jardin darkroom with a 400 watt digital ballast and an aircooled reflector(both of which greatly reduce heat) and my 180 cfm fan barely gets temps to 80*. Even in my other 2x4x7 box a 265 blower gets temps to about 77*. you can try your 4" in a 6x6 room but its not going work. Youre going to have even bigger things to worry about though cause theres no way a 400 watt bulb is going to cover that big of a space. You need either a smaller box, or a bigger light, in either case you need to take this bag to the drawing board imo.

 

If you are supplying enough cool air in, your cfm's wont need to b as high, but he is correct in a sense that if your ventilation is your cooling system, higher CFM's will reduce humidity and temperature faster. Make sure your puling air out from the top and feeding cool air in from the bottom. Heat rises ;-)

You can effectively flower 4-5 plants under 1 400w lamp.

 

Exccuse me Buddha88, but my recommendation is right on the money. BGHydro suggest exchanging the air in the room every 3 minutes minimum. Furthermore, my experience tells me the same ... What temp air are YOU pulling into your box??? How large are your intakes? Ventiliation Explained - Part 1 | BGHydro

CapeCodKid, You can get away with a passive intake but Buddha88 was quite right in regard to intake restrictions. Bends will limit your intake significantly. Two 18x18 (or better) electrostatic furnace filters will do you right

sinc.
SlackerBee

 

See here bro you really have to look at the wording here. every 3 minutes minimum. Lets do some math. Assuming his 4" is one of the best on the market it pulls 180cfm. This means he exchanges the air every 50 seconds. Pulling through a filter however reduces your cfm by 10-20% depending on the size of your fan in relation to the filter. Odds are youll cheap out on the filter so your fan will probably be too strong and the drag will only be 10%. Youre now pulling at 162 cfm. Now if you have any 90* angles that will reduce your cfm by 50% for EACH one. Most setups have atleast one since the boxes are usually vented through the top. So now youre pulling at a stiff 81 cfm. Remember that any other bends will reduce it even more and if you buy a quality filter youre cfm actually decreases more as well. So lets recap. Assuming you have one of the best 4"(you probably dont) and you follow an average vent setup, youre fan is pulling at 81 cfm. But lets be realistic, your fan probably pulls in the market average of 140-160 cfm. In which case youre realistic cfm is 63-72. 63-72 cfm for a 150 cubic foot box is not exactly great. However growing is all about trial and error. Feel free to try and error. I will leave you with this last bit of information which i took as well from the bghydro website. Thank you slackerbee

Step 3 – Additional factors
Unfortunately, the minimum cfm needed to ventilate a grow room is never quite that simple. Once the grower has calculated the minimum cfm required for their grow room the following additional factors need to be considered:

Number of HID lights – add 5% per air cooled light or 10-15% per non-air cooled light.


CO2 – add 5% for rooms with CO2 enrichment


Filters – if a carbon filter is to be used with the exhaust system then add 20%


Ambient temperature – for hot climates (such as Southern California) add 25%, for hot and humid climates (such as Florida) add up to 40%.

 

Buddha88,
I appreciate your detailed approach and agree that aggravating circumstances may require additional measures. Engineering via "worst case scenario" may be fitting for a mass marketed idea, but given over-sized intakes and quality filters, the 4" inline fan should do a fine job, easily achieving over 100 cfm with a little forethought. Of course, if you're sucking Hot-Humid air in, there is little that makes sense beyond investing in an A/C. Peace

sinc.
SlackerBee

 

BTW: Buddha88 ... No need to PM me with your snide comments. If you have anything to say, say it here.


Sinc.
SlackerBee

 

best thing you could do IMO is make sure you have a ducted hood for your light that isolates any air that cools the light from the air in the tent.

i have a 400watt mh/hps switchable in a 4x4x6.5ft enclosure in a daystar AC hood that is hooked up to a fan that does 170cfm. i have another can fan that's the exact same as the one that is one light except for this other one is just sucking out the air from the tent and blowing it into the room. i run it with a fan speed controller at like half speed and the tent stays the same temp as the room its in.

The KEY part is that the hot hot hot air that touches the bulb never mixes with the air in the tent because the hood is ducted on both sides. the intake is from the outside of the tent, and the exhaust is also outside the tent. the hood has a glass lens, too.

good luck

 

Hey I'm just reviewing the thread, are you 2 really arguing about something when it does not really matter?

The reality is, you need intake, and exhaust, you want the fan to be strong enough that it can exchange the air at least a few times a day. He is obviously a newer grower and probably does not care to hear some arguing about correct CFM measurements according to the square or cubic feet measurements. Get yourself a cheap fan, inline preferably, vent the exhaust at the top and intake at the bottom, flip the switch and LETS GROW SOME POT kid, not build a 16 page thesis on why my fan is better than the one you mentioned.

 

that site is the most expenive i have seen for supplys 200 dollars for a 4' fan ebay ftw

6' inline fan, great deals on Home Garden, Business Industrial on eBay!

 

I have 2 of them linux, they are awesome, but start up loud. They move some SERIOUS air, and work well over 440 CFM IMO w/ no pre-filter

 

Grow room ventilation - squirrel cage fans, whisper fans - - * The original, proven, high performance EcoPlus® fans._br_ * Very powerful

I bought this for my 5 x 5 grow room, I would suggest at LEAST this much Cfm for pulling air through a light and out of your room. and you might want just a small axial fan ( 4 inch ) as high as possible on the door to sweep air from the top of the room out, and just a passive 4 inch hole at the bottom of the door will be fine for Intake.

This works well for me, I started with much less and could not keep temps down

 

well i plan to make a sound proof box so that should help alot or does the noise travel through the duct more then out of the sides?

 

You know what worked well for me? You know how there is a metal mounting rail on the fan, what I did to keep the sound inside of my place was to just put a rubber damper between the metal and where I mounted it. I got my rubber washers from the automotive junkyard. On car's axles and suspension there are rubber bearings that prevent the metal from rubbing on the strut. They are about 3 dollars and stop the sound from traveling through the walls just as I wanted. making a sound proof box is fine and all, but it would need to be air tight, and that would require sealant. If the fan breaks or needs maintenance, you have to deconstruct everything to get to it. Try using a padding between the mounting rail and whatever its mounted too. There will be no vibration or loud start rolling through the walls.

 

Pieces of Dynamat can also be used to help deaden sound emanating from hard surfaces. hth


Sinc.
SlackerBee

BTW: A passive air intake for a 6" fan should be closer to 12" dia or 10"x10" to realize it's potential.

 

I wish I would have thought of that!