Experienced Cab Growers, Need Some Light Advice.

Hey Guys and Girls,

I have recently started construction of a grow cabinet, It measures (LxWxH) 600mmx600mmx1200mm. I was hoping to run a 250w HPS inside of it, however, due to the width and depth of my cab using a cool tube isnt really an option. I was planning on running a neg pressure cooling system consisting of 4x 120mm pc fans mounted on the top back of the cab, extracting hot air, with some venting on the front bottom of the cab to let in fresh air. In your experiences would this allow some appropriate temperatures in the cab? I will also be adding a small oscillating fan for some airflow when i can find a suitably sized/priced one. My 1st run is to grow out 4 of my onyx autoflower seeds, so il probably run an 18/6 light schedule. I know its vague, but im hoping I can get some rough advice from some more experienced growers... Especially when ive only ever grown outdoors, which in Tasmania never gives you heat issues lol. Oh i probably should add, the grow box is constructed with a light wooden frame, and 4mm thick mdf walls. Also, the outside temp (which will be drawn in) this time of the year is a max of about 15deg celcius.

Cheers, Dirty1

I would go with a 64k 130watt cfl
they run cooler than the hps which is really only good for flower

That was going to be my next question lol. Ive been looking at those 130w cfl's lately, but havent heard much about them... but surely one would not be enough for a decent yeild? i had thoughts about running four of them, but that would probably end up just as hot lol.

I should probably add, there will be no filter etc as smell is no issue... the cab will be locked away in a shed, which is only accessed by myself and another, and the shed has plenty of airflow through it (it is not sealed). I think im going to go with a 250w hps, and four 120mm fans to see how i go... Money isnt a huge issue so if it runs too hot il just run a 6inch inline fan (i can source them cheap).

dirty1 said:

I should probably add, there will be no filter etc as smell is no issue... the cab will be locked away in a shed, which is only accessed by myself and another, and the shed has plenty of airflow through it (it is not sealed). I think im going to go with a 250w hps, and four 120mm fans to see how i go... Money isnt a huge issue so if it runs too hot il just run a 6inch inline fan (i can source them cheap).

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Sounds like you have a good base plan, check the grow in my sig if you want to see how small an area you can fit a 250w HPS into... Though instead of PC fans I'd run a 4" exhaust and have a passive intake, just drill some 2" holes in the bottom or low down on the side, I had to drill about 30, 1" holes in the floor of my cab to be enough for the fan. Passive works a lot better than forcing air in with fans, you just get cleaner airflow imo and it's a bit cheaper 'cause you have less fans (plus if you have a hefty exhaust fan and little intake PC fans, the exhaust can make them spin backwards lol).

OH and make sure your cab is pretty much airtight, this is easy with the right application of duct tape, and draft excluder strips.

cheers mate, i purchased the 4 pc fans last night, gonna run them all as exhaust with holes in the floor for intake as you stated, see how i go with light leaks, i may make some simple light traps for them with some pvc 90deg bends... my brother works for a large company which specialises in ducting and air con etc so if the pc fans dont work to a satisfactory level il run an inline fan for sure.

Im really kinda kicking myself for not looking into cooltubes before constructing the cab, as i would have made it 3ft wide instead of two so i could fit a cooltube and ducting... but oh well lol.

the cab should end up being pretty airtight, i might chuck a few pics up when i pick up the mdf sheeting for the panels (apart from the light, fans and hygrometer/thermometer its all im waiting for to complete the cabs construction, would have got it ages ago, but my car is off the road due to a power tripping cop and the car im using in the meantime is a struggle to fit anything in lol), im planning on sealing all pannels to the frame by using some form of silicon etc on all joins after construction...

cheers for the advice mate, il have a looksi at your grow

yeah screws and silicone that'll keep it tight... I wouldn't worry about the lack of cool tube, but without one I reckon you'll need more than the PC fans but hey you'll see if you do when you get that far!

Try to use OSB or plywood if you can, MDF has a nasty habit of warping like a bitch when you paint it, and/or get any water on it!

Lol i think you're probably right too... Was a bit of an impulse buy for the 4 pc fans but only cost me $12 for all 4 off ebay so no biggie lol.


Ahh thats a good point actually... might grab some thin plywood instead. Plus i guess ply always feels more sturdy too at that thickness...

If you do end up getting a 4-6" fan just use the PC fans in the cab as circulation, more airflow never hurts