HPS Ventilation Setup Revised

After moving things around several times, and taking some needed ILGM moderator advice on ventilation setup, I think this is better and the temps dropped 10 degrees. Any thoughts or constructive criticism?

AC unit set to turn on at 71 F which is keeping the canopy temp range at 70-81 F. Two oscillating fans are blowing across the canopy 24/7, the 6" inline fan blows across the bulb 24/7 now at half speed (for noise purposes). Humidifiers are keeping RH range at 33%-46%.

Six inch inline fan is now moved to canopy level sucking in any additional cold air from the AC (if it’s on), blows across the hot HPS bulb and vents out to the attic in a separate duct line from the AC exhaust to keep the hot air from mixing and blowing back into the room. There is no second fan sucking air out at the attic level.

Thanks everyone for their input so far. It’s a little complicated. :v::v::v:


@spacey my only question is the plaid curtain is that the window :window: by chance and how are you going to control your dark hours manually ?


Yes, it’s covering a window that faces the street, it took that to block out the bright 1000 watts from outside view.

I know a white reflective board or foil would reflect light more, but it’s a room that’s also used for other things, the light is pretty bright as it is in the room.

The light will be controlled by a timer and the room’s door will be shut while the room is dark and won’t be disturbed.

I’m into your ac venting. I’m trying to figure out how to exhaust my AC hot air out without also exhausting the smell. What is the fan/exhaust (by the chair) in the 3rd pic doing?

Are you just directing the ac exhaust into the attic without any filtering? Do you get a lot of smell in the attic?

If you exhaust out your window you’ll be sending out the smell too. I used to use large activated carbon filters you can buy on Amazon with a 6" size that fits the ducting when I was using a tent in my closet because I didn’t want my clothes to smell. It impedes the ventilation process and creates more heat I believe but it did a great job of creating no smell outside of the tent if it was zipped up.

I doubt there is any detectable smell in the attic with a moderate sized house, heat rises so will the hot hair carrying the smell and it will exit out of your vents on the sides of the house. No one would smell it that high up. I’ve read about how some cops look for no snow on a roof to look for grow houses while all other houses in the area have snow but it didn’t happen that way here this winter, then again it’s only one 1000 watt light and not an entire house being used for that purpose.

The small fan on the chair seat is just a simple oscillating fan to lower the temp on that corner of the canopy since that’s where it gets the hottest since it’s furthest away from the A/C unit.

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Are you pulling the hot air from the light through the fan , back through the hot :fire: light into the attic? Than you sending your fresh cool air to the acttic too ? Why ?
I dont think that one light would melt snow on the roof through the insulation .
You ac should be blowing cool fresh air on the plants :potted_plant:, and you suck the hot air from the light and blow that air threw the carbon scrubber . Instead of using your scrubber as a vaccum , put it on the blowing out side so the smell can blow threw the scrubber verses being sucked into it , reverse it & you should get a more stable temperture !

No, the system is currently setup to pull air at canopy level through a six inch inline fan which is pointed towards the AC unit and receives any excess cold air, it blows across the HPS bulb and then exits into the attic. The AC unit has a separate exhaust that exits into the attic through a separate hole in the ceiling. That way there is no co-mingling of high temp exhaust.

The AC is blowing cool air across the canopy as needed to stay in a 10 degree range, there is no scrubber and is not needed. Smell is not an issue as both exhausts enter the attic.

Also I never said this light would melt snow on my roof, another poster mentioned that scenario.

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Okay :ok_hand: now i understand but the co2 will make them grow faster you think :thinking:?
I think it will work great , now thats a grander 4000k bulb and whats the light hieght 42 inches maybe or lower , 48 will be a good hieght for that grander !

I’m not really focused on CO2 this grow because I’m trying to get the ventilation and nutrients down first. I do have CO2 tanks ready for next time.

The bulb is a 1000 watt HPS. I love it but it puts out a LOT of heat even in an open room with no tent.

Raise it to 48 inches it will not heat stress the plants to drink water so much and they wont have that wax leather look to them.
Better coverage too at 42- 48 if its a grander hood !

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That height seems a little too far away. If the canopy temperature is 71-81 F, there won’t be heat stress. With 24" they get more light and more energy to grow in veg stage and flower in flowering stage.

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Thats for Led , HPS has high UV output , i bet you its hot :fire: on the back of your hand under that light for 10 minutes , if you can feel the heat , the plants can , it shoukd be cool and tropical not hot ! So on average in veg with HPS you might can flower at that hieght , but if they stretch to 80 inches which they might still , they will stress !

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I’m doing SCROG, stretching is a good thing. 80F is not too hot.

@spacey if you raised to 42 inches just for 3 days ?
You can always lower it back right and just see the different in the plants growth for yourself . You only raising it 20 more inches :crazy_face:, they will literally start to grow much more aggressively.

Height is not the goal with SCROG. It’s bud site numbers per square footage. You have two accounts don’t you? :grin::joy::grin:

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