I'm in the final stages of getting my first grow room set up and I am struggling to keep the temperature down. Let me start out by saying I know this is a very common issue and I have read just about everything I could find of heat control ventilation ect. over the past few months and I honestly thought I wasn't going to have a problem with it.
This is my set up: I have a 4x4x6.5 grow tent inside a room that is approx. 8x12x8. Knowing heat was going to be an issue I went with a bigger fan than I thought I would need, a Tjurlund 6" inline rated at 500cfm. This is my only ventilation fan and it set up like this; 6x24" Phat filter -> Inline fan (pulling through filter) -> 600w HPS 6" air cooled reflector (Xtrasun) ->out of the tent and out a nearby window through a 6" louvered dryer vent. The window I exhaust out of is the type that swing out on hinges kind of like a door, I have the window cracked about 2-3" and its about 30" tall. For intake into the tent I am relying on two passive vents, one 6" duct and one 14x10 vent. Intake into the room that the tent is in is also passive, with just the gap under the door (approx. 3/4"x24") and the a heat vent in the room. I also have a nice size circulating fan in the tent.
I finally ran the light and fan for a few hours yesterday for the first time and was shocked at how hot it got under the light. I was taking the temp in two ways, with a digital thermometer and a IR thermo. The air temp in the tent up by the ceiling leveled off at about 74-76F, but directly under the light got a LOT hotter. The digital thermo was reading about 80-84 directly below the light with a 18-24" gap between the light and the probe. Using the IR thermo I was getting reading as high as 90F on a green t-shirt that I was using to simulate a plant at about 18". Not what I wanted to see. The air temp in the room that the tent is in is around 70F but got up to 74 with everything running for a few hours.
So now the real question, why is it getting so damn hot under the light, and what can I do to get the temp down 5 or so degrees? I honestly am not sure what the problem is at this point. I thought my fan would have plenty of CFM for my set up, at its rated CFM it would exchange the air in my room like 4x a minute, but maybe with all of the obstructions, turns, and lack of active intake. Am I just not getting enough CFM to cool the light? I have seen some people who claim they can put there air cooled 600w as close as 4-6" from there plants, how is that possible? Is it just a matter of having enough CFM through the light? It seems like my problem is the radiant heat from the actual light, not the actual air temp (convection) in the tent, will more air flow be able to do much with that kind of heat? Two possible solutions I can think of would be to add another fan for an intake into the tent, or possibly swap out the Xtrasun hood for a Cooltube. If there is a cheaper solution that would obviously be ideal. I am a renter and I don't want to have to make any major alterations to the house itself, so cutting a whole in the door and things like that are not options for me.
The first thing I tried was to remove a piece of white speaker cloth that I had over the duct behind the louvered exhaust vent. The speaker cloth made the vent less noticeable visually from the outside, but removing it did seem to noticeably increase air flow. Unfortunately not enough to have much effect on the temp. The temp probably went down a degree or two, but its still in the 80s under the light. Any thought/advice/tips would be awesome, I was hoping to have some girls in the room within the next couple weeks. Thanks!
This is my set up: I have a 4x4x6.5 grow tent inside a room that is approx. 8x12x8. Knowing heat was going to be an issue I went with a bigger fan than I thought I would need, a Tjurlund 6" inline rated at 500cfm. This is my only ventilation fan and it set up like this; 6x24" Phat filter -> Inline fan (pulling through filter) -> 600w HPS 6" air cooled reflector (Xtrasun) ->out of the tent and out a nearby window through a 6" louvered dryer vent. The window I exhaust out of is the type that swing out on hinges kind of like a door, I have the window cracked about 2-3" and its about 30" tall. For intake into the tent I am relying on two passive vents, one 6" duct and one 14x10 vent. Intake into the room that the tent is in is also passive, with just the gap under the door (approx. 3/4"x24") and the a heat vent in the room. I also have a nice size circulating fan in the tent.
I finally ran the light and fan for a few hours yesterday for the first time and was shocked at how hot it got under the light. I was taking the temp in two ways, with a digital thermometer and a IR thermo. The air temp in the tent up by the ceiling leveled off at about 74-76F, but directly under the light got a LOT hotter. The digital thermo was reading about 80-84 directly below the light with a 18-24" gap between the light and the probe. Using the IR thermo I was getting reading as high as 90F on a green t-shirt that I was using to simulate a plant at about 18". Not what I wanted to see. The air temp in the room that the tent is in is around 70F but got up to 74 with everything running for a few hours.
So now the real question, why is it getting so damn hot under the light, and what can I do to get the temp down 5 or so degrees? I honestly am not sure what the problem is at this point. I thought my fan would have plenty of CFM for my set up, at its rated CFM it would exchange the air in my room like 4x a minute, but maybe with all of the obstructions, turns, and lack of active intake. Am I just not getting enough CFM to cool the light? I have seen some people who claim they can put there air cooled 600w as close as 4-6" from there plants, how is that possible? Is it just a matter of having enough CFM through the light? It seems like my problem is the radiant heat from the actual light, not the actual air temp (convection) in the tent, will more air flow be able to do much with that kind of heat? Two possible solutions I can think of would be to add another fan for an intake into the tent, or possibly swap out the Xtrasun hood for a Cooltube. If there is a cheaper solution that would obviously be ideal. I am a renter and I don't want to have to make any major alterations to the house itself, so cutting a whole in the door and things like that are not options for me.
The first thing I tried was to remove a piece of white speaker cloth that I had over the duct behind the louvered exhaust vent. The speaker cloth made the vent less noticeable visually from the outside, but removing it did seem to noticeably increase air flow. Unfortunately not enough to have much effect on the temp. The temp probably went down a degree or two, but its still in the 80s under the light. Any thought/advice/tips would be awesome, I was hoping to have some girls in the room within the next couple weeks. Thanks!
^^^
Never know till you try.