New Grow Room Ventilation/Fans & Cooling, Please Help!?!

Discussion in 'Growing Marijuana Indoors' started by newtogrowing, May 18, 2010.

  1. Hi there.

    Am VERY new to all of this, and was hoping someone may be able to give me some advice relating to my current issues & concerns, re: indoor growing...

    Okay. I am creating my first grow room at the moment. Currently, what I have is:

    250W HPs (w/ ballast, etc)
    Mylar Grow Tent (45x80x160cm) or roughly, 1.5x2.5x6ft (very rough) with black casing. The tent is completely light proof.

    Now, my concerns come in relation to the ventilation system, and heating/cooling...

    With a grow tent of this size, and a 250W HPS, what sort of ventilation and cooling should I be looking at? The tent has a 150-200mm opening at the bottom left for Air Intake, and another at the top right, for Exhaust...

    What I was considering, and wanted to see if this would be suitable - getting a 21W 150mm inlet fan and installing this as the exhaust fan... Then, I was thinking I could just leave the intake hole empty, for passive intake. The intake hole would face the centre of the bedroom - with window open... Would this be okay, or would I need to have the same fan there for intake, as I put for exhaust?

    Also, if I were to do this, would it remove any problems I may have regarding heat, as a result of using the light???

    And also, if I were to install just the exhaust fan, and ducting, and were to run the ducting over the top of the tent, and position it to blow directly out my window, through a fly screen, would this work?

    I am hoping someone may be able to assist me with this... And also, in regards to air movement, within the tent... Would the exhaust fan take care of all of this, or would I need other fans inside the tent as well??? A few ppl have told me that by only putting an exhaust fan of this size, at the top, it will suck the 'used' air out, and blow it (wherever i direct it), whilst, at the same time, sucking fresh and cool air through the intake hole (without the need for an intake fan)... Is this correct? And if so (and again, if not) will I need smaller fans inside the room to circulate air & create movement, or will the suction from the exhaust fan simply drag the fresh air across the plants (as the holes are on opposite sides of the room)??? If I do need fans for inside the tent, will the small, crappy PC fans work sufficiently (perhaps, 2 in there; in the sides/corners not already used by the intake/exhaust holes???

    Ultimately - I have the 2.5ft X 1.5ft X 6ft Mylar Grow Tent & the 250w HPS with ballast, etc... I am trying to make it as stealthy as possible, and hoping to minimise electricity costs (as much as possible, anyway)... So, simply put - what do you guys (the experts) recommend in regards to controlling the airflow, odour & temperature of the tent? Primarily being the airflow/ventilation... I am hoping that, by solving the intake/exhaust problem (or knowing what to do) I may be able to reduce, or even better, remove, the need for cooling, or fans inside...

    If it helps, or affects your recommendations & advice, it is currently winter here, and (probably) averaging about 14-22 degrees Celsius (and perhaps a little lower at night)...

    Any help would be most appreciated... I know there are other feeds & posts explaining some of the things I have asked, but none seem to apply for a room of this size, or Australian Winter temps, etc...

    Thanks in advance.
  2. 250w wont be too much of a heat issue.

    Here is my setup. My tent is 2'x3'x5', roughly.

    4" Carbon scrubber -->>> 4" inline fan-->>4" to 6" coupler -->> ducting to light hood-->> 400w HPS inside of easy cool 6 hood-->> out of hood--->>> out of tent ---->>> out the window.

    in case that's not clear, the ducting is 4" between the carbon and the fan and then it goes to 6",

    You will have to convert that yourself, they dont teach us metric here, especially when it comes to distances/lengths.
  3. I have a 2.8' x 2.8' x 5.3' grow tent. Using a 15 yr old non cooled 400W HPS inside of it. I am using a 265 cfm squirrel cage fan with a 2 ft duct. I actually have the exhaust fan sitting on top (outside) of the tent, with the duct hole sitting right on top of the tent exhaust hole, with the 2 ft ducting going downward into the tent. I could not find a good way to install the squirrel cage fan inside the tent. So I ran it like described as a test.

    I also have a high velocity mini floor fan sitting outside one of the intakes. And an oscillating fan inside.

    With that setup, and the air conditioner in my room keeping temps at 67 - 68 (tent is in closet) my tent temps are averaging 76 - 78 degrees constant. I have a humidifier sitting outside the tent as well for when I need a little boost of humidity. Keeping my humidity at 45 - 60 depending on the weather.

    Just giving you my setup and numbers for reference. I do not have a typical setup, but what I have is working for me for now. Will adjust if necessary. I have not added my carbon filter yet, (I will be pushing into the carbon filter. I know its better to pull through, but again, with my current setup, I can not. So I will put the prefilter in the other end, and push air into the filter. Should work for my measley 2 plants. :) plants are only in there 2nd week.

    Good Luck. Peace Love, and Pot.
  4. Given the low temperatures here lately, what I was considering... What if I were to just start with the 250W HPS & the tent, then get a 21W fan for exhaust...? And simply leave the vent at the bottom open for air intake??

    Then, if I set BOTH the lights & exhaust fan up to an 18/6 timer, running from, say, 4pm till 10am? That way, between 10am & 4pm (during the majority of daylight hours) the lamp & exhaust fan will remain off, with only the intake open... Then, from 4pm to 10am, during the cooler hours, the light & exhaust fan would turn on, to minimise temperature problems (too hot with the light on OR too cold at night)... Do you think this would work???

    It seems pretty crucial that I have an oscilating fan in there as well, from what I have read. Given that its not such a large space, what size fan should I be looking at? I cant find smaller oscilating fans anywhere... Could I take one designed to be plugged into a Car Cigarette lighter & somehow convert it to plug into an Australian powerpoint??

    As im only starting out, naturally, the plants are gonna be tiny - just sprouting still... At what height should the light be hanging, and when does this need to be adjusted? And where should I be positioning the fans in relation to the plants, themselves??

    What if i were to simply get two of those little computer fans? If we say the front/bottom left corner is where the intake valve, the exhaust will be at the back/top right... Doesnt this mean the air will be 'dragged' over the plants, from the intake to the exhaust?? And in that case, what if instead, i used 2 small computer fans - 1 at the back left corner, 1/3 of the way up, then another in the front right corner 1/3 of the way down (from the top, that is, a bit below the light)....

    That way (id have thought) the air would come in passively, through the bottom left intake hole... Then be sucked up, through the tent, and across it virtually diagonally, to the top-ack-right, where the exhaust fan is... That way, at the same time, the fan 1/3 of the way up from the floor will blow some of that air in the opposite direction its being drawn, by the exhaust... Then, the fan 1/3 of the way down, will do the same thing, but higher up... And this fan would only be a little below the lamp - that way it could be redirecting the heat...

    That would create circulation throughout the tent, would it not???

    The intake valve would only ever be taking in ordinary air from my bedroom. Which would obviously have to remain locked, etc, with window open... Then, the exhaust ducting would run from the exhaust fan at the top of the grow tent, up, and be positioned at the top of my bedroom window, blowing diagonally upward - outside... Is this sorta smell likely to become terribly noticeable, if im in a 2nd floor bedroom, with only 2 neighbours?
  5. my intake is passive through the mesh vent in the bottom back of the tent.

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