Air-Cooling HPS Hood With Outside Air?

Discussion in 'Growing Marijuana Indoors' started by yerbamate, Sep 28, 2009.

  1. My current setup has me running a 400w HPS (external ballast) in an unfortunately quite small cabinet (36"w x 18"D x 40"H) and I am obviously running quite warm, which is my own stupidity. It's just been set up and the exhaust is an EcoPlus 180cfm blower with passive intakes from the room via drilled holes. I have to keep the door open with a box fan blowin in to keep it in the 80's.

    I am considering building an exhaust and passive intake into a window that would allow me to pull in outside air while the 180cfm EcoPlus blower is pushing warm air out the window.

    Would it be feasible to pull a large amount of heat from the sealed hood using this method? Would very cold outside air (as the temperatures drop this winter) cause any issues with the bulb or hood?

    I am hoping to move this to a larger space right now, but for the time being I need to make do with the metal cabinet. If I have to I'll get a 265 or 465 EcoPlus as well and use one for the hood and one for the box. But I'm curious about the cooling efficiency of a sealed hood and how much of a difference it makes in the overall heat buildup if most of the effort is going into pulling heat away from that bulb as it's generated.

  2. 1. Does anyone know if cooling a bulb with air that is considerably colder than the surrounding air will cause any problems? Obviously the air and bulb would need to both come on together so that extremely cold air wasn't introduced to an extremely hot bulb instantaneously (glass doesn't like sudden temperature changes). But if I've already got the fan pulling winter (near freezing) air from outside as the bulb is warming up and firing on, I wouldn't think there would be any negative effect.

    2. Can anyone tell me how much of an overall reduction in temperature they experienced by trying to pull as much heat as possible out of the reflector? Is it possible to just have the bulb very efficiently cooled and have the internal temperature of a relatively small space remain relatively stable?

    3. Has anyone successfully run a 400w HPS in a small enclosure (anything in the neighborhood of my 36" x 18" x 40") and not gone insane doing it? :)
  3. so right now you're just running the bulb open in a reflector while exhausting only the cabinet? if that's the case just run a cool tube setup instead, the temperatures are going to be a night and day difference. A passive intake through a cool-tube then exhausting out should be sufficient enough without running ice cold air through it. At any rate, that is a mighty confined space for a 400 watt setup.

    I wouldn't exhaust the hot air directly outside the window, but maybe to an attic or other room. It could help with winter heating bills, just make sure you carbon filter it first. I rant about this all the time, if you need another blower fan, try a stanley blower or a lasko blower, they're cheap and powerful, easily modded, and quiet.
  4. The bulb is running in a Sun Systems Super Sun I reflector. It's glassed in and currently has one flange, which is connected to the EcoPlus, pulling air from the reflector and exhausting it straight outside. The goal was to get the second flange (they don't make the reflector anymore so I'm having to hunt it down) and have the passive come from outside, through 4" duct to the hood, out the other side and back out the window.

    The exhaust to the outside is a box I built that has vertical ports for input and exhaust which are separated from each other. There's an exterior flat panel that hides the in/out and makes it look like just a nice wood panel in the window frame. That window is on the fairly secluded second story backside of my house.

    I don't partake much, really just for insomnia and to turn the brain off in the evenings, so growing is more for light personal use and more so simply to be self sufficient, so I figured going low tech and growing mostly during the cold season using the cold air to cool the bulb would be nifty.
  5. exhausting air into the attic in the winter is not a good idea. Unless your house is really new, and was built properly. (which it most likely wasn't) Never had any experience with it but, in theory, it is bad for your roof.
  6. So for the record, I figured out how to make a cabinet of this size work. Because I was able to place it with its back against a deep silled window, I created an intake/exhaust box that the window closes down on top of. There are two holes in the back of the cabinet - one is attached to a 180cfm blower pushing outside air into the box, and one is attached to a 265cfm blower pulling air through the now glass-sealed hood from inside the box, and exhausting it back out the window. The temp at the surface of the plants with the light fourteen inches away and the doors closed is in the mid to high 70's day and night.

    So that's how you run 400w HPS in 4.5 square feet with 40" height to work with. This should at least get me through autumn/winter/early spring :)

  7. thx for the update. +rep
  8. Aww, my first rep. woOt!

    I just realized I could attach photos so I've provided two - one of the cabinet itself showing two of the three plants, the reflector and exhaust fan. The other photo showing the back of the cab with the intake fan, and the ducting between the window box and the cabinet in that deep window sill. There is a 'T' shaped piece of ply which covers the top of the cabinet and the gap between it and the exhaust box, and that's what the window closes down on. Makes a great shelf and the cats dig it cause it's warm up there :)

    For scale, the pots are 12" across and the light, although at a weird angle in the shot, is between 14-16" away from the leaves.

    The plants themselves are just shy of 4wks and have been lst'd since seedling, so all of the veg pointing up is side branches. I am going to continue to veg & lst for part of October and switch to 12/12 while continuing to tie down through the growth spurt.

    Attached Files:

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