1.2m grow tent overheating with 6" extracton and 4" intake fans

Hi there.

I have recently decided to try my luck growing. However I have encountered a big problem, would be highly appreciated if some experienced growers could point me in the right direction..

My grow tent is experiencing insanely high temperatures right now. My friends warned me about the heat 600w HPS lights emit so I purchased a 6" RVK A1 and a 4" intake fan. But the temps are still touching 85-90F [ at night, with the tent door open and a fan blowing on the light!!! ]. The tent is only 1.2m, so the 6" RVK should be overkill right? I have 2 windows in the grow room where the tent is kept, so I pull air from one and extract out of the other. I have 3 digital thermometers in different locations of the tent so it's not a faulty reading. Really confused about this one... I even bought a fancy SMSCOM fan controller, but even with the settings maxed out it does nothing.


Thanks for your time, Josh.

What is the temp of the air you're pulling in?

It's pretty cold mate. I live in england soo.. You think it could be a intake problem?

I live in Florida. It hits 105F frequently. So A/C is kind of a necessity. If the tent is open, you're cooling with the room air, not the outside air.. Your duct work may be too long or too many bends, or both. A air cooled hood or cool tube does wonders. A pic of your whole grow area would help us see the problem. Intake should be as big as or bigger than exhaust. A 6" fan should cool a 600w bulb in a hood or tube easily, assuming your ducts aren't restricting it too much. If you have a bare bulb you will have heat problems unless you put some massive A/C in there.

Thanks for your quick reply Red. 105F outside?? Wow.. I thought I had problems haha.. Yes I think you're right. I had no idea how much heat these lights put out.. I'm going to buy a cooltube with a 6" fan as you suggested, hopefully that will bring down the temps 10F or so..

I will check back if i'm still having problems once I get the tube. Grateful for your help man. Josh.

A 600w HPS is like having a 500w heater in there.

4x4 tent, 600w HPS, cold intake air... you must not be pulling air out of your tent quick enough.
If your exhaust fan is up to scratch, which it should be, then your little 4" fan is restricting the intake.
Make sure you have a small fan to circulate the air around the tent and be sure to have your exhaust duct right at the top of the tent (hot air rises)

*Remove the 4" fan and run the 4" intake ducting out the window (passive intake)
If the 6" fan pulls well and there are no air leaks, you should see the tent suck in.
If it sucks in a lot, change your passive intake ducting to 6" as well if possible.

Matching intake and exhaust fans is not as simple as most people make out.

Let us know how you go

Cheers Jimmy.