Grow box too damn hot!

Hey guys so I have an old dresser I converted to a grow box, it's 48"h 30"w and 18"d and I'm using a 150 watt hps and I have a 95cfm exhaust fan with a 4" carbon scrubber and a passive intake system. Inside I have 2 6" clamp on fans to move air around. Anyways I just flipped to flower and before when I was using cfl for veg I could keep temps around the 82f mark but now that I have the hps in there it gets up to 91f! Way too hot! What can I do to cool down my box like 10 degrees? The room it's in is around 76 on average. Hard to control the temp around it because it's in a wide open undeveloped basement so I don't think ac is an option for me...any help would be appreciated guys! Thanks.

LED or the CFL bulb...? Id go a 200w CFL at 2700k, if thats too cold add another 200w cfl at 2700k

Thanks but I think I want to try and find a solution to make the hps work before I resort back to cfl. I already spent the money on it and it'll give me a better yield. Anyone else?

get a better fan, 95 cfm isnt enough you want more air changes per minute with that size of dresser.

How do you figure out how big of fan ill need? I was told that 3x per minute is more than enough and to add a bit more for the scrubber and at 15cf in my box that's 45 so I have double that to compensate for the scrubber. I guess I was misinformed.

How is you 95 cfm fan venting the room? Does it attach to the top of the 150hps? I use a 150hps in a grow box and had similar issues. I took dryer venting and attached it on top of the light. I have a 50 cfm that attaches to the light and another 50cfm beside the light. These fans connect together and vent outside my box to my carbon filtration. I also added yet another 50 cfm fan at the floor of the box as powered intake and added 6 3" holes on the back for added passive intake. I now run with a 150 hps and a 100 t5 at the same time and my temps are hanging at 82 with the lights on and room temp with them off. I just started a journal today on this box on, check out if you like I have some good pics that may help you, but I have solved my heat issue... Peace..

https://www.rollitup.org/blogs/blog33253-new-ams-grow.html

i had this same problem of too much heat after switching from CFL's to HID. The solution? Vent more air! That's what worked for me.

Straighten the duct if there are turns in it. But most importantly, get a more powerful fan (if needed). Make sure intake air enters at the bottom of the grow chamber and the outtake air exits at the top (heat rises duh). Also, how close is the light to the plants? HID's put off infrared and need to be kept a lot farther away from the plants than CFL's.

m3d1c1n3man said:

i had this same problem of too much heat after switching from CFL's to HID. The solution? Vent more air! That's what worked for me.

Straighten the duct if there are turns in it. But most importantly, get a more powerful fan (if needed). Make sure intake air enters at the bottom of the grow chamber and the outtake air exits at the top (heat rises duh). Also, how close is the light to the plants? HID's put off infrared and need to be kept a lot farther away from the plants than CFL's.

Click to expand...

I found after adding duct work right to the top of my 150hps I could have the buds 6" from the light (mature plant, younger plant will tolerate 12" with proper venting) with no problems which increased the density dramatically.

yes. the scrubber will take 25 % away from airflow. 90 degree bends in ducting will take another 25%..

frizzlegooch said:

yes. the scrubber will take 25 % away from airflow. 90 degree bends in ducting will take another 25%..

Click to expand...

So if I have a fan, and 3 90 degree bends there will be 0 airlflow? lol ok, how do people come up with this stuff?

Lazyeyes12345 said:

How do you figure out how big of fan ill need? I was told that 3x per minute is more than enough and to add a bit more for the scrubber and at 15cf in my box that's 45 so I have double that to compensate for the scrubber. I guess I was misinformed.

Click to expand...

That's how much ventilation your plants need. HPS and MH lights need a lot more air to cool them. I have a 440cfm fan cooling my 600w HPS, but I use a speed controller and keep it between 20% (when my light is turned down) and 40-50%. The speed controller controls how much power is going to your fan, not how much air it's moving, by the way.

You're going to need a 4" 170cfm inline centrifugal from a hydro shop.Bathroom fans and cheap HD/Lowes duct booster fans suck.and din't handle pressure losses for shit.Also you need to vent the exhaust to another room or out a window so that hot exhaust air isn't heating up the room your dresser growbox pulls it's fresh intake air from.

Lol..Mr2shim you are right..I think what he meant to say was that a fan can only push air so many feet. A 90 degree bend is the same as adding an additional 10 foot of straight duct.

mr2shim said:

So if I have a fan, and 3 90 degree bends there will be 0 airlflow? lol ok, how do people come up with this stuff?

Click to expand...

Ummm...no the air flow interruptions are incremental thus 100% to first bend, 75% to second bend, 56.25% to third bend, 42.18% to fan....31.63% of original power reaches the other end. Give or take.

All good advice. If you have a 150w HPS it may have the attached ballast and no way to air cool the reflector. I have this setup. It's a pain. I could probably run 250 with a better lamp and still have less heat. When I add in cfl side lighting things get warm.

I find that by increasing the draw of my fan by using a fan speed controller that it makes no difference in my temps.The most success I have had was by venting my fan through a wall and into another room. I also blow a fan into my closet from a separate room. I'll try to make this more clear...My tent is in my walkin bedroom closet. I vent the warm air into the kitchen through the back of my closet and I keep another fan blowing into the closet from my bedroom with a window open to keep temps around 72f.

Everyone says cfl's are cool. They really aren't that cool. I find that running a fan across my cfls helps dissipate the heat.

All in all it's a balancing act. Start by venting to a different room if you haven't already and keep the ducting as short as possible and in a straight line if you can.

Best of luck.