Problem with ventilation!!?? please help

I have other posts going around about extremely high temps and dry soil in my grow tent. What is the cheapest way to ventilate a 5x2x4 grow tent with a 400w hps in it? Would those little computer fans work, and where would the cheapest place to order them from be?> all i have now are two 6in desk fans, and they are NOT working!!!

desk fans will move the air around your tent but not have much in the way of cooling your tent,
you need to get a exhaust fan preferably with filter, the bigger the better.
ideally some thing like this:

I'm using a 400 hps in my dr100 and use what azman posted works great recomend 5"/6" but I also have a cooltube that helps alot
good luck

dam, how can I pick up that exhaust fan for cheap, u guys kno?

and how many cfm will i need in the fan for the 400w hps in a closed mylar grow tent? thanks tho!!

PC Fans will not work for you application. definatley not. Look at the cfm of some pc fans most are between 20 and 40. I have 40 35cfm pc fans in my 2'6"x1'x3'4" cab and still not doing quite a good enough job. still a little to hot at the top.

Mines 170cfm I think but I have cooltube you may need a larger fan without.

Cooltubes are gonna be the best bang for your buck in a tent or closed space...along with a centrifugal fan and a charcoal filter for stealth. Check amazon.com....there are some fan/filter combos that are matched well and will definitely help keep your temp down....

Def, go cool tube. Those work really well. Even the cheaperish ones work well. Was at my local Hydro shop the other day and they had a name brand one with excellent airflow. This ones also a reflector and comes pre equipped with a socket. All you need is a light and a ballast, which you already have. They wanted $100-$120 depending on size.

check ebay for em
I was lucky a friend gave me his 6" cooltube for £25

ok how do i know what tube will fit my light if its not preattached to the fixture and reflector? and would you all recommend an inline fan or a cooltube first to keep temps down, im leanin towards the fan but old u sound convinced. goodlookin every1 +reps

A cooltube cant run without a inline fan so get your self a filter kit like this> http://cgi.ebay.co.uk/125mm-5-VENTS-CARBON-FILTER-FAN-KIT-HYDRO-GROW-LIGHT-/280575153641?pt=UK_HomeGarden_Garden_PlantsSeedsBulbs_JN&hash=item41539515e9 < then eventually get a cooltube

MH.Hps and 250-200 watt cfls bulbs fit into E40 light fittings I think Any thing smaller than a 200 cfl fits into E27.
You could buy as a whole kit to save worrying just plug a grow.

ok thanks inline first. Ebay got 400cfm inlines for 99 without a filter, I was wondering if the filter is just for the smell, or is it also helping keep the plants sterile? cuz with just that inline i could lead the duct to blow right out the window so I wouldn't worry bout smell, i live on the 3rd floor

I run a 1K in a 2x4x7.5 using a cooltube and one of these: http://www.rewci.com/panwhisfvven1.html (You can find them cheaper, just look aorund) if sound is an issue you should look into them probably the quietest fan you will find. I also ran a 2x2x2.5 cab with 400W with that fan and no cooltube. The 1K is probably about the limit of what you can do with it (I have a pretty cool room to start with) that it runs in and temps are in (the high 70's with smaller plants and slightly cooler when she's full), but it should pretty easily take care of a 600W.

The filter is just for the smell. PPL will smell it if they are anywhere near you and they open their window, so its not a bad idea.

ok i gotcha, but now if I get the filter and one inline fan, I would have to have the filter attached to the fan pulling air into the tent, and then and open duct to allow air to leave, right? I cant think how else to set it up with only 1 intake fan and no exhaust fan.

I hang my filter near the top of the tent to suck hot smelly air out. Dont need a inlet fan for my 170cfm just open the vent flap things near the bottom.