Help design our ventalation system...

[Seedtoweed]

Hi there;
We're excited to get our first grow on our way but we're running into a few "first timer" problems... We ordered a 250W HPS system that we ran for the first time today and the tempature skyrocketed from about 70 degrees to about 94.4 after about five to ten minutes. For ventalation, all we had was a 7 inch oscalating fan that was blowing towards the light... which was enough to keep our small wattage CFL (40w; planted a bit too early too...) cool.

So, I have two elbow PVC peices that have a three inch diameter that I could use for passive intakes at the bottom of the cab. I plan on going to Lowes and Wal-Mart, our only two options for supplies (small town) and purchase things needed to greatly improve our ventalation problem...

The cab is a Black N Decker Utility type closet from Lowes ($80)... its made of (sturdy) plastic. The dimensions are 71 inches tall by 25.6 inches wide by 17.7 inches deep.

So, with this information what should we get and do as far as greatly improving our ventlation.

We have a $40 budget, give or take a few dollars.

I was thinking of getting two five inch or greater fans from Wal-Mart and place them side by side at the base of the plants, with one blowing in and the other out...

Or having two fans ontop blowing air in a sort of ducting that is aimed more towards the plants, so airflow is more concentrated. With one blowing in, one blowing out.

And we're up for suggestions; this is our first grow so we dont know what will work the best. Gotta ask the pro's

 

[Jnugg]

Your cab measures about 6' tall by about 2 feet wide by about 1.5' deep so a total of 18 cubic feet.

Normally you want an exhuast fan that can remove the air in the cab and replaceit with fresh air 3 times per minute (ie, cab is 18cf so a fan that can exhuast 54cfm (CFM = cubic feet per minute).

Now since your temps in the cab with the 250w on rises from 70F to 94F-95F you'd probably want o go head and step your exhuast fan up to remove hot air and replace with cool air 5+ times a minute (ie;90cfm+)

Sorry this will be over your budget and seeing as you probably don't want to spend the money ona centrifugal go abd get a 265cfm Dayton blower for $100 U.S although I think you would be better off with an inline centrifygal that does about 170cfm especially if you plan on connecting a carbon scrubber.

General rule of thumb when it comes to passive intakes is you want the area (totl area of intake) to be about 3.3 times the size of your exhuast fan (ie;4" exhuast fan = 13" of passive intakes but you can get away with 8"-10" of passive intake surface area (ie;four to five 2" O.D. PVC tubing with 90 degree elbows for a light trap on either end of the tubing or both ends).

 

[Seedtoweed]

Hi, thanks for the informed reply.

How about if we use a large vent for the passive intake, we want to place this about a foot above the plants.

The fans need to be mounted UNDER the light, seeing as the reflector to the light only allows a few inches on either side of it... so airflow would be very hard to maintain or get around the reflector. It would be impossible to run ducting around it; but ducting may not be needed.

WHAT IF... we get a vent like said above, use our 8 inch fan for intake air... perhaps another one for outtake aswell, and a Stanley blower unit and mount it inside the cab blowing air at the actual light? I also have two PC fans wired up that could be used to help circulate the air aswell...

We encountered our first big mistake on our first grow... never start too early. We should of had all this taken care of first, but the problem was overlooked.

Have a nice day.

 

[Jnugg]

Seriously just go out and get a 265cfm Dayton or a 170cfm Inline cetrifugal/

Do you have a Batwing/gull wing reflecto (two open ends)?

Place the exhuast fan (not a crappy 8" home fan either) in one corner of the cab at the top (prefferably outside of the cab).There you go,you have proper exhuast.

Geta darkroom vent (8" x8") or the cheaper route which is 2" outer diameter pvc/abs pipe that has a 2" 90 degree elbow attached to atleast one end of each pvc/abs tube for light traps.

I'll take pics of my cab in a little while and maybe you'll get a better understanding although I run an air cooled hood if I were to take the ducting off it would be just like I told you to do yours.

Sit tight,pics in an hour or two,

 

[Guest]

DIY wiring with sicors oh my!!! light leaks!! heat!!! disturbed during sleep!!!! oh my. look out hermis here we come.. fire department please have a fire truck ready....

 

[bostrom155]

The stanley is good, I use it to exhaust off the light. I'd get more intake too.

 

[Laxpunker]

For fourty bucks you could get two of those window fans, you know the nice big rectangular jobbies. Mount them on the sides opposite of each other, run the cords through the inside and then out the back (or into your outlett if you put it inside your cab. Just dremel out a hole of appropriate size, set the fan in and epoxy/caulk/duct tape it in. If your cab is supposed to look discreet then this may not be the solution, but it would move quite a bit of air through the cab for probably under 40 bucks.