Overheating Grow Box

I have a problem and though I have some ideas, I'm hoping to find some help on here...

I'm just about done constructing my grow box but after a test run, I've found that with the lights on, it is running at just above 100 degrees (F). Here are the specs:

- Grow box is 3' x 2' x 4.5' (h)
- One 4" computer exhaust fan (65 CFM) at top
- One 250W HPS light
- Four 23W CFLs
- Three passive intake holes at bottom
- Homemade ghetto-fabulous reflector made out of 4" duct

I've put some time and spent the money on the HPS lighting system and after all this work, this is the last thing I wanted to happen. From reading through a lot of threads on here, I'm contemplating:

- Making a ghetto-fabulous light exhaust with some 4" exhausting tubing I have laying around
- Adding another grow box exhaust using either a computer fan or a conventional house fan that I already have lying around
- Removing the CFLs... though I really don't want to do this, nor do I think it will make a big difference

Anyone have any suggestions? Thanks in advance for your help.

i have problem with heat as well......

bummppp!

Make sure the area of your intake is atleast 1.5x-2x the area of your exhaust. If that doesn't work, then try adding more exhaust. And when you add more exhaust, you'll need more intake. Keep going until you find your happy zone.

i had the same problem..i just put a fan in and my temps are fine now

there are many ways to drop your temps, some more effective then others. you can throw in a couple jugs of water, some of the heat energy will go to heat the water and keep it a constant temp, this is only good for slight temp changes nothing major. you can also put some box fans or oscillating fans, get an intake fan to push in cool outside air, get a bigger/secondary exhaust fan, get a cooltube reflector or custom make a piece of glass or plexiglass to cover your light and add a fan and some ducting to pull out the hot air from your light.

Here's an article from the RollItUp FAQ. It should help.

https://www.rollitup.org/view.php?pg=faq&cmd=article&id=684

My flowering box is the exact same dimensions as yours and I use a 250 watt HPS with this fan: http://www.hydrofarm.com/pb_detail.php?itemid=8092
My temps are perfect so I suggest that you get a nice inline fan similar to the one I linked and you will be good to go. You should check out my journal to compare since we have very similar setups

tom__420 said:

My flowering box is the exact same dimensions as yours and I use a 250 watt HPS with this fan: http://www.hydrofarm.com/pb_detail.php?itemid=8092
My temps are perfect so I suggest that you get a nice inline fan similar to the one I linked and you will be good to go. You should check out my journal to compare since we have very similar setups

Click to expand...

Holy S&@%! I have the same type of fan but 125cfm.. how loud is yours? because mine sounds like a powerful vacuum cleaner :S

skybike said:

Holy S&@%! I have the same type of fan but 125cfm.. how loud is yours? because mine sounds like a powerful vacuum cleaner :S

Click to expand...

build a box like I did for my 424cfm....cut down the noise 50%

Thanks for all the feedback. Going to use a little bit of all of your suggestions. Going to start my increasing the area of my passive intake. If that doesn't work, I will also add more exhaust. Using the info at https://www.rollitup.org/view.php?pg=...article&id=684 (provided by beginningbotanist420 - thanks), I've figured out that the current CFM of my exhaust fan is well under what I need.

skybike said:

Holy S&@%! I have the same type of fan but 125cfm.. how loud is yours? because mine sounds like a powerful vacuum cleaner :S

Click to expand...

my 85 cfm fan isn't too loud at all... in fact, you can barely hear mine. but then again, looks like i may need to add another one so my two fans combined could start sounding a little more like yours... lol

They might be quiet but they don't put out enough air to cool your box. Trust me you can't cheap out on the ventilation. My inline fan is loud as shit

Flo Grow said:

Just use the chart below and you'll be fine !

Click to expand...

Isn't this a bit misleading? Things like cooltubes and more efficient ducting could change these numbers...

Although, thanks for the info. I guess it's pretty useful as a general guideline.

MrJoshC said:

Isn't this a bit misleading? Things like cooltubes and more efficient ducting could change these numbers...

Although, thanks for the info. I guess it's pretty useful as a general guideline.

Click to expand...

The chart is for basic ventilation. It doesn't take into account any air-cooled reflectors b/c not everyone starts off that way. MOST growers don't run air-cooling reflectors, especially the micro growers and those using CFL's.

If a person is running air-cooled and something happens to where they can no longer do so, this chart will help.