Running HPS without venting the hood?

Discussion in 'First Time Marijuana Growers' started by Ill420, Sep 25, 2009.

  1. Im trying to find out if I need to pay the extra money to air cool the hood for a 400W HPS in a grow tent(4'X4'X8'). Won't the exhaust fan for the whole tent take care of the heat? I've been seeing a lot of posts about having to exhaust the hood as well because of how much heat HID's give off. Buying another fan to blow air into the hood and another to exhaust the hood seems like a lot of redundancy, especially if you could just achieve the same results by exhausting the tent as a whole which I know I would have to do whether or not I vent the hood. Any help would be appreciated. Thanks
  2. Well my tent is about 4x2x6 and I have a hooded 400w HPS with no venting right now. Just keeping my tent door open (still early in veg) but my point was, with that setup and a 9in. household fan blowing over them on high at all times, the lights raise my temp anywhere between 5-10 degrees sometimes.

    I feel like if you had a good intake/exhaust going through your vent that actually venting the hood may be overkill if your on a budget or something.
  3. thanks for the reply. i would not be able to keep the tent open as I need some stealth. are you saying the light raises the temp in the entire room 5-10 degrees or do you have a thermometer in your tent? I also wanted to know if having the tempered glass in the hood would be hazardous to the bulb or the whole setup since it would probobably get really hot in the hood?
  4. You really need to vent when using anything other than CFL. HPS and MH produce alot of heat. If the light did not need to be vented more than likely the hood wont have vents for the light. If the hood has vents for the light rule of thumb is you need to vent the light. If you was using something like 100w or 75w you probabley wouldnt need much but using 400w I suggest you vent or run ac in the room to keep the temp down. I am not too sure if anyone has ever told you but growing/flowering plants above like 83 or 85 you run a chance of getting a hermaphrodite.

    If you want to keep your geow stealth just get yourself like 5 or so CFL bulbs 3500k for veg 2700k for flower. They produce little to no heat and they wont run up your light bill.

    Good Luck
  5. My space is 4x4x5 and I tried to run my 600 watt un cooled and temps went up above 90. I have to leave one side open even when venting the hood with an 80 CFM fan. I also have another 80 CFM fan bring in outside air and a 9" fan cirulating air. My temp gets up about 80f to 83f when its 90f outside. The weather is supposed to start cooling or I would upgrade my exhaust fam to 250 cfm.

    What I would liek to know is about the glass lens and how to tell how much CFM to cool a hood? I can't find anything to tell me if I use the lens how much CFM to have running through the hood so the thing does not burn up.

  6. i run a 400 watt HPS in the closet with the door open, and have a fan blowing right under the light.
    it raises the temp at least 10 degrees but i can still keep my space cool enough

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