I need help to lower temp in grow cabinet

I just finished building my grow cabinet. It is 6'H x 3'W x 2'D. I have a 400 watt MH on a digital ballast, that is air cooled. The light is air cooled with 2 inline fans. I also have a inlet and exhaust fan in the grow area, with a fan blowing above the plants for circulation. I have a electronic temp/humidity gage in the cabinet. When I have my light on I can't get the temp below 94 degrees. I cant put a inlet in for the ac to blow cold air in. I'm starting to think that my only option in to get a smaller light. Does anyone have any suggestions as to how I could get the temp lower? I would really like to stay with the 400 watts, to get the best possible buds from my garden. Any help is greatly appreciated. If I didn't post this in the right area sorry. I'm pretty new to the sight.

Hey there,

You should post some pics if possible, I just finished a nice cabinet myself, really no heat issues, after a lot of work.

One question: Is your ballast INSIDE the cabinet?

what kind of inline fans do you have and whats their cfm?

arss said:

what kind of inline fans do you have and whats their cfm?

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That was my next question. If you're using those booster fans you can get at a hareware store, they will not work. Even with two running.

You need a super high velocity fan, the fan needs to totally inundate the reflector with fresh, cool air.

Punk said:

That was my next question. If you're using those booster fans you can get at a hareware store, they will not work. Even with two running.

You need a super high velocity fan, the fan needs to totally inundate the reflector with fresh, cool air.

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Yeah, those booster fans are shit. check out s&p inline-fans (http://www.hvacquick.com/spfnconfig.php?fm=td). they're very quite and relatively cheap, i have a 4in and a 6in and am very happy with them.

Punk said:

That was my next question. If you're using those booster fans you can get at a hareware store, they will not work. Even with two running.

You need a super high velocity fan, the fan needs to totally inundate the reflector with fresh, cool air.

Click to expand...

See this cabinet. It's 3ft tall, 3ft wide, 1.5ft deep. That light is a 250mh.

See the exhaust fan on the right. $14 online purchase through home depot. Intake was passive. Just a hole...

One question, where is your thermometer?

Also, a previous question asked was where is your ballast?

I'm running 250 watts of watts of old school power. Granted 400 is a big leap from 250, but you're running cool tubes too? Your cabinet size versus mine and the wattage difference tells me, in my head, that we should easily be at the same temps.

You're 5ft high?

I'm using a 50cfm exhaust in a much smaller space. Something isn't adding up.

We need pics dude.

ah we're gonna show off cabinets now, eh?

Punk said:

ah we're gonna show off cabinets now, eh?

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My set up with lamp was under $100. I don't show off. In fact this cabinet isn't even running right now. If I were to show off I'd show you photos of my Brazilian chica

Looks nice though.

Just playing bro.

Punk said:

Just playing bro.

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I know. Looks nice though. I think we both agree that white paint is the best reflective material. Mine was just for veg...very simple

Questions to the man with the heat problem appear to be:

Where is your thermometer?

Where is your ballast?

What is the CFM rating of your exhaust fans?

Where are they located?

When can you post pics.

Pretty much dead in the water without pics dude.

DubsFan said:

I know. Looks nice though. I think we both agree that white paint is the best reflective material. Mine was just for veg...very simple

Questions to the man with the heat problem appear to be:

Where is your thermometer?

Where is your ballast?

What is the CFM rating of your exhaust fans?

Where are they located?

When can you post pics.

Pretty much dead in the water without pics dude.

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Thanks for all of your replies so far. My thermometer is mounted on the side of my receiver about an inch lower than the top of my pots. The ballast is mounted to the back of the box on the outside, near the very top of the box. I don't know what the CFM rating is on my fans, I built them myself from small 4" house fans. I have a fan mounted to the side of the box at the beginning of the inlet duct, and another mounted to the other side of the box at the end of the outlet duct. I'll try to post some pictures tomorrow. I have the light hanging 3 feet above the plants. For right now so I don't stress my seedlings to much, I turned of the 400 and put in 104 watts of 6500k cfl about 6 inches above the plants. I think I need to go buy 2 high CFM fans and mount them closer to the light. My plants seem to be ok though. They just went into the box this evening, and U can all ready see new growth.

Medic3829 said:

Thanks for all of your replies so far. My thermometer is mounted on the side of my receiver about an inch lower than the top of my pots. The ballast is mounted to the back of the box on the outside, near the very top of the box. I don't know what the CFM rating is on my fans, I built them myself from small 4" house fans. I have a fan mounted to the side of the box at the beginning of the inlet duct, and another mounted to the other side of the box at the end of the outlet duct. I'll try to post some pictures tomorrow. I have the light hanging 3 feet above the plants. For right now so I don't stress my seedlings to much, I turned of the 400 and put in 104 watts of 6500k cfl about 6 inches above the plants. I think I need to go buy 2 high CFM fans and mount them closer to the light. My plants seem to be ok though. They just went into the box this evening, and U can all ready see new growth.

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Subtraction by addition...if you have added ducting to route your exhaust take your CFM rating and throw it in the trash.

See that little white vent on the inside of my small cabinet. It's just screwed into a 4" hole. I wanted my work to look clean. Well, the resistance of three plastic vent blades inhibited the fresh air intake of my cabinet by almost 3 degrees. Plus I had one on the exhaust.

Two fucking super light weight vents with zero ducting cost me about 5 to 7 degrees. Now think about ducting....then think about ducting plus vents, then ducting plus bends in the ducting plus vents.

This may not apply to your scenario cause I don't have pics. But it's something to consider.

How long is your exhaust ducting from the exhaust fan?

If you have intake ducting how long is that?

Haveing limited indoor experience I have noticed that in order to properly ventilate and use ducting you need massive exhaust. If it's rated at 100cfm, after all the ducting and a vent I put it at less than 50% of it's rated cfm. Maybe lower. My little fan straight out of my cabinet with a hole in the bottom rocks. And that's with 60% of your power in 50% of the space. Don't know if heat/ventilation and exhaust works in those percentages but it's worth considering.

I have 1 foot of inlet duct and 1 foot of exhaust duct. I going to make a few changes to my ducting, and exhaust tonight. Hopefully I can get this under controll soon so I can turn the MH 400 back on. But at least I had the CFL's laying around to use in the mean time. Thanks for your help. And I'll try to get some pictures up tomorrow.

Medic3829 said:

I have 1 foot of inlet duct and 1 foot of exhaust duct. I going to make a few changes to my ducting, and exhaust tonight. Hopefully I can get this under controll soon so I can turn the MH 400 back on. But at least I had the CFL's laying around to use in the mean time. Thanks for your help. And I'll try to get some pictures up tomorrow.

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Sweet. That would help.

Judging by what you've described, its a simple matter of your light fan(s) not being strong enough.

You really need to flood the reflector with that cool air, what you're doing right now is more of a trickle. The hot air isn't being swept away fast enough and its causing the heat to emit into the cabinet.

Actually, that pic of my cabinet is with my old fan, can't find the other pic, but your cabinet size is very close to mine, and I use a 400 watt system as well, with that old fan, my temps were in the 90s as well, but when I got the new fan, it keeps my temps below 84, usually around 81.

My grow is in a tent and I had a problem with temps being too high also. I had great results with an air cooled unit called the Cool Tube. Ducting and a fan draw air across the lamp which is enclosed in heat proof glass. I was able to lower my tent temp by 10 degrees. For me the only trouble is the dam thing is too small for the the 3'9" x 3'9" x 7' tent. I bought it from HTG.com for about $75. Here is a link to another site that shows the unit. http://www.4hydroponics.com/lighting/rsuntube.asp
It works great be it is best for a small area, like yours.
I agree with the other postings that you need evacuate the lamp heat with as little transfer to the grow area as possible. Cool Tube might work for you. Here is a link to a build your own you might want to try.. http://www.greenpassion.org/f39/build-your-own-cool-tube-under-30-00-a-686/

I am getting rid of mine after my grow ends. But I need it for another 4-6 weeks.

I'm thinking you need a solid 100+ cfm fan. 1ft of ducting shouldn't deminish its effectiveness.

Jaybo said:

My grow is in a tent and I had a problem with temps being too high also. I had great results with an air cooled unit called the Cool Tube. Ducting and a fan draw air across the lamp which is enclosed in heat proof glass. I was able to lower my tent temp by 10 degrees. For me the only trouble is the dam thing is too small for the the 3'9" x 3'9" x 7' tent. I bought it from HTG.com for about $75. Here is a link to another site that shows the unit. http://www.4hydroponics.com/lighting/rsuntube.asp
It works great be it is best for a small area, like yours.
I agree with the other postings that you need evacuate the lamp heat with as little transfer to the grow area as possible. Cool Tube might work for you. Here is a link to a build your own you might want to try.. http://www.greenpassion.org/f39/build-your-own-cool-tube-under-30-00-a-686/

I am getting rid of mine after my grow ends. But I need it for another 4-6 weeks.

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Thanks for your suggestion, but I'm going to stay with the light that I currently have since it is only 3 days old. I changed out the fans on my light today. I bought 2 170 cfm inline blowers. They mounted right to the air cooling inlet and outlet on my light. They are quieter than the fans that I built and had on the light. And they are moving at least 10 times more air through the light than before. Since I put them in this afternoon, the temps have came down nicely. The last time I check about an hour ago the temp was 79. Which is much better than 95+. And the humidity is running at 42 to 47. Now if I can get my seedlings to perk-up everything will be great. Thanks everyone for all of your help.

Medic3829 said:

Thanks for your suggestion, but I'm going to stay with the light that I currently have since it is only 3 days old. I changed out the fans on my light today. I bought 2 170 cfm inline blowers. They mounted right to the air cooling inlet and outlet on my light. They are quieter than the fans that I built and had on the light. And they are moving at least 10 times more air through the light than before. Since I put them in this afternoon, the temps have came down nicely. The last time I check about an hour ago the temp was 79. Which is much better than 95+. And the humidity is running at 42 to 47. Now if I can get my seedlings to perk-up everything will be great. Thanks everyone for all of your help.

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if your plants rebound as they should, those numbers say you are rolling. Pics bro...let us see

I'll get pics up as soon as I can. I am saving to get a new camera, or Iphone. I normally just use the camera on my Iphone, but I broke it last week. I'm not sure that a couplof my seedlings are going to make it. I'm going to start a new thread called seedling root rot, and I'll explain what is going on in there.