420 Magazine Background

Help with my grow box!


New Member
Hello all, thank you to anyone reading this :thumb:

I have been having serious difficulties with my Medicine grow box -- mostly because of choices that I have made! But I am stuck with those choices now, and still trying to march onward. Originally this project was to help save me money in the long run, and it is turning into a huge money-pit with no bottom! Heeeeelp :)

Here is what I am working with.

Garage - temps in the winter time inside the garage can/may reach as low as the mid 50's I am guessing. Perhaps even lower if it a very cold winter.

I have a 2' x 4' x 4' wooden box I constructed. Inside it is caulked air tight. I then laid 2" styro insulation throughout all sides. This was then covered with mylar reflective film. Weatherstripping around the doors, and it is indeed air tight and thoroughly insulated.

AdvancedLED Diamond series full spectrum grow light

Ceramic Heat Emitter, 60 watt (From pet store)

Exhaust Fan: (my problem..)
VenTech IF4 4" inline duct fan, 190 CFM's

Intake: (2) 4" holes, with grating.
Exhaust: (1) 4" hole, attached to exhaust fan + DIY carbon filter.

Filter - > Fan -> exhaust (PULLING the air through the filter.)


So here is my problem. Heat. I went and bought this super duper expensive state of the art LED light, cause I was impressed with the lack of heat it made and the efficiency of it's energy use and durability and years of life. I thought to myself "man, how great is it that i won't have to worry about exhausting all that excess light/lamp heat!".... but to my unhappiness, I then realized "oh yeah, I won't have ANY heat now... in a garage-based box." ... then the forehead slapping began.

Currently my garage ambient temperature is around 65 degrees in the daytime.
Inside-box temperature with the exhaust running, is the same, 65 degrees.

So i added the CHE for heat... this did not add any noticable heat. Maybe 1 degree.

So then i did an experiment, and turned the fan off. My box quickly heated up into the 80's and even hit 90 degrees! .... So this told me right away, "ok genius, you got WAY too much fan... and it is sucking all your hot air right out of your box." --- this was confirmed as, when i turned the exhaust on, the temperature dropped 20 degrees in literally a few minutes, settling down to the same temp as the ambient garage temperature.

I would like some ideas and feedback and heeeeelllppp on what I should do to fix this problem. It is such a sweet box, it is paining me to have these heat problems.

Obvious answer: New fan? -- I just ordered a 100CFM in-line-duct-booster type fan.. and am going to try this..
Another answer: Bleed/dump excess air out the exhaust? .... would this work? Perhaps use a backdraft dampener and a Y connector.. and dump air out back into the box, and only allow part of it to go out the actual exhaust? ..... or....... maybe poke holes in the exhaust duct itself, bleeding air out that way before it leaves the box?

I have read in multiple forums that connecting an AC motor/fan like I have to a typical "dimmer switch" to adjust the speed of the fan is a fire hazzard and just asking to break your fan... and my fan only has 1 speed.

So i do not know how to control this problem. I am fairly positive I have too much exhaust, and it is pulling all the heat out of my box. What is every ones suggestion to solving this problem.. any work-around or advice is welcome. This has been wracking my brain.


-SMILES :peace:


New Member
So, re-vamp my carbon filter to allow less air to be pulled through it into the fan.. this does make sense.. i was shying away from that, because I thought it might be bad for the fan to allow it to work full-steam, but then not have ample air running through it. I take it I am wrong in this belief? Because you are right, this would be a much easier fix..

Or are you saying make my 2, 4" holes i made for intake smaller? say.. cover one of them up.


New Member
like this


New Member
Thanks for the replies guys!
I will do some more hardware store shopping and constructing over next few days and give updates... hopefully this solves my problem outright :) I may need to get another CHE regardless though, or at least a higher wattage one.. I got the 60, think they make a 75 and 150 also. They seem to be a good choice to add heat, since they don't emit any light of their own..


New Member
Just an update, I haven't found exactly what I am looking for... I will continue looking. BUT, I already had slitted dryer vent gratings over the intakes.. so I just left one alone, and I duct taped the other one up air-tight. Good ole duct tape. Anyways, This has completely solved my heat problem -- as now my super fan isn't sucking all the hot air out. The CHE seems to be working fantastic for the LED set up I have to add that extra heat. Oh, I also rebuilt my carbon filter a bit.. which restricted air flow a lil bit, which also helped with my fan/heat problem. Overall, temps are maintaining ~77degrees, and 85 inside a humidity/clone dome w/heating pad... really, can't ask for much more than that. Great help canabinerd, Thank you!


Active Member
For the future you could possibly build another room,box, etc around your box, possibly a heavy tarp(as insulated as possible) completely surrounding your grow box. in this you could have a small electric heater set on a thermostat. if your pulling in the air temp you want then you will maintain temps and a consant flow of fresh carbon dioxide laden air! Especially with the low heat LED. Look to the future, if heat will be a problem in summer then look at a reverse cycle a/c in that area. A/C's and heaters can burn a lot of electricity but not if they are on thermostat in a small area. As I use HID in my tent I put an A/C in a room, my tent in the room and set the a/c to 22c to maintain 25-26c in the tent.


New Member
I'm not sure I would go the route to restricting air-flow, as that will put a lot of strain on your fan, and -will- burn it out quicker than normal.

I had something approaching the same problem just a week ago. I have my box in an, otherwise, unheated basement, and the temps inside the box never got above 50F. (I use a big CFL.)

What I did was put a small heater (one of those which looks like a portable radiator) on low right outside the intake holes to the box. Now I have pinpoint accuracy when it comes to temps. I feel it's a little bit of a waste, but if it helps me grow dank bud, then I'm okay with it.


Well-Known Member
Thread, rise from the grave! LOL

Okay, it's probably way too late for this info, but maybe some other poor sucker will benefit. The answer is to modulate the speed of the fan with a controller.

You can get a cheapo fan speed controller for less than $20, but those may be flakey and shorten the life of your fan. I've heard that if you want total control over your fan speed in a way that won't damage it, you need one of these:

3 Amp Variac Variable Transformer SC-3M

They're around $60, you can get 'em on Amazon and elsewhere. You can just dial down the power until the fan is running enough so that you're getting some air exchange, but not so much that you're losing all your heat. Plus, your fan will be WAY quieter!

I've got one on my to-buy list along with the exact same fan you're using. SO I don't have personal experience with using the stuff yet, this is just what my research has uncovered so far. So take my info with a grain of salt and do your own research, but I've read a few user reviews that indicate this will work exactly as advertised.


Well-Known Member
I've read that those work fine with some fans but can cause noise and heat problems with others. Here's the info I found online:

Review for a Speedster type speed control:
"I bought this product and plugged it in and it worked as stated. But it slows the engine speed by changing the sine wave of your Alternating Current (A/C) current into a Square Wave. Why is this bad? A/C appliances are made to run with a smooth ramp up and a smooth ramp down. By changing this into a square wave, it's 100% plus, then zero, then 100% minus, without a ramp. This produced an immediate hum in my fan as soon as I slowed the engine with this device. It will also reduce the efficiency and shorten the bearing life of your fan. Electronic equipment nearby may suffer from electrical noise such as lines on your TV or hum in your sound system.
I suggest this product as an alternative: Variac Variable Transformer
3 Amp Variac Variable Transformer, 300va Max, 0-130 Volt Output
It costs more, but it will last much longer. And it can be used on many other things in your house. You can actually dim Compact Fluorescent Light Bulbs (CFLs) with this product. I have one of these that was made in the 1970s and it still works today. It slows your fan by reducing the voltage. A Variac does not change the A/C sine wave."

And Also:

"Some fans that are considered "brushless motors" or "magnetic motors" are Permanent Split-Phase Capacitor motors and require a solid state motor control of the Triac variety. (Vortex, CanFan, Fantech are some)
A Triac type controller sends out specific wavelengths of current to prevent the current from rising and possibly damaging the motor windings.
A variac is a variable transformer that lowers the voltage to the motor, but a lower voltage results in a higher current and can potentially be a problem at very low speeds (under 30%) because of the reduced cooling and higher amperage.
Always check with a fan manufacturer to find out their motor type and if they require a solid state controller."

So it sounds like the Speedster is def useful with the right type of fan. :)


Well-Known Member
Um, o.k. Just saying. I used mine continuously for a 3 month grow and not an issue. No doubt your mileage may vary, but I got mine at my local hydro store as well as the fan and if they'd have gone wonky, I would have taken them back and gotten my money back.

I will say this, even with an inline fan advertised as "quiet" and installed into my cabinet with foam rubber gaskets, there was still some noise. It was dampened though and my primary goal was to gain definitive control over the cabinet environment THEN address noise last which is what I did. I may actually invest in something a bit more efficient with an emphasis on silent operation, but that would merely be an upgrade as, functionally, it worked perfectly.
Top Bottom