Give me your thoughts on this idea. 4’x4’ tent 1000 watt hid in an air cooled hood. How effective would ducting the light on one side to the fan as an exhaust and leaving the other side open to draw from the tent to double as an exhaust fan and keep temps down in the space
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Works good that’s how most people run vented tents for cooling.
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With fans make sure to go big. Two fans won’t push as much as one big one.
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I think you will struggle to keep it cool enough for the plants, unless the air you are drawing in comes from an air conditioner at a fairly low temp. Normal ambient air temps will affect the ability to cool especially in summer.
I used to use a squirrel cage fan pushing air across the cool tube and out of the space. This will work better than pulling the air through the fixture.
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I pull from filter, push through tube vent to outside. And actually blow some exhaust to mix with my intake air…
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Ambient temp 72-74 constant. No fan after 2 hours with hps bulb on it was 100deg. I’m wondering if pulling through a filter in the space through the fixture avid then out would keep temps down enough with possibly a smaller fan pushing ambient air in or should I try for a negative pressure in the space
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I have a 4x4 veg tent, I struggled to keep temps below 85f with a 1000w HPS. Using air-conditioning in the room the tent was in.
I struggled to keep it below 80f with a 600w HPS, with no air-conditioning, and just a 6 inch extraction fan.
Best bet would be get a 1000w LED light, that will produce the same heat as a 600w HPS.
What size is the extraction fan, you may have negative pressure whether you want it or not, while the fan is running.
Even with my bottom 2 vents fully open as well as 2 x 6 inch, duct openings, open, I have negative pressure, when the fan comes on, set on the lowest speed. If you run the fan hard, it will suck the sides into the middle, I had to put braces across mine so I didn’t lose 30% of my space in the tent.
Haven’t gotten the fan yet but was thinking about an 8" inline fan. Was also thinking about running 2 6" inline fans meant to boost air flow in ac vents to feed cool air into the tent to keep it from sucking in. I’d love to go led but budget isn’t good enough for decent led lights so I’m havingto use what I have. Will be a dwc setup in the tent and wondering if a fine mist to folar feed would help keep temps down as well. I know it will increase humidity but with the fan on it shouldn’t get out of control
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Water in the air will hold the heat more, that’s why air conditioning takes water out of the air. Unless you cool the air in the room, you will always be only able to cool the tent to a few degrees below ambient air temps.
8 inch fan will be way too strong, even with a controller on its lowest setting and forcing air in the tent.
I think without air-conditioning, or a smaller light, you will be really struggling, to keep a useable environment. Your other option is a sealed room with extra CO2, but if your money is tight, that’s out as well.
I made the same mistake bought a 1000w light then couldn’t use it without cooking the plants, even in my 8x8ft flower room I need air-conditioning in the summer to keep it below 80f.
For a 4x4 tent a 400w hid and HPS is adequate, 600w is the upper limit.
Your next problem will be plant height, with a 1000w light you will need at least 20 inches underneath the light, to the top of the canopy, or the plants will get damaged from light intensity. You will probably have at least 8 inches above the light so that’s 28 inches of growth height you have lost. Pots will lift the plants about a foot, so now you have about 36 inches on the average tent height, for your plants to grow up in. When they hit the stretch, you may have to bend a lot of tops over or do some LST before flipping them.
How tall is the tent?
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4’x4’x80" tall the room is air conditioned stays about 74 constantly in there
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Hood is about 8" tall and have it set up to where i only have about 2" above it when at the top.
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Yep, scrubber -> light shade -> out of room.
Your room is ~120 cubic feet, so a fan pulling say 400cfm should exchange the room 3 times a minute which is plenty.
Keep in mind if you’re dumping the warm air into the same room you’re intaking from it won’t stay 74° for long! Best to dump the hot air somewhere else.
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With the room cooled with aircon @ a constant 74, you have a chance, as Beacher said though, you will have to exhaust out of the room.
ATM my 4x4 is in a 7x13 room with 8ft ceilings, ambient temp outside is +4 atm, in the room 63F with a small window in the back door open 3 inches. I have about 1100w of LED lights and 2 fans in the tent that are creating heat. My exhaust fan comes on when the temps hit 80F and off at 74F which is fine for veg. The exhaust fan is running every 9 minutes for 2 minutes then cycles again. So I am getting a 1 degree F rise every 90 seconds, doesn’t take long to build up the heat. Once summer hits, I will put a vent in the door window, and attach ducting to it so the hot air goes outside. This time of year, winter and late fall is the cheapest time for growing for me, using ambient air temps.
Also if you are doing DWC you need to keep the reservoir under 70F if possible, from what I have read, not tried it myself. So you may need to chill your res.
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I’m in same boat. My ballast is dimmable so i have dialed it down to 750 watts. Sucks
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My ballast is the same 50% and 75% so i could if need be dial it back a bit because I’m well over the 33 wts per sqft
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Yeah kills me to do it.
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Mine lights do the same but when you reduce the wattage you change the light spectrum, from what I have read the heat the bulb produces, is what is required for the gasses to create the right spectrum. When wattage is reduced the spectrum narrows. So you are producing less heat but not a good spectrum.
There is always a catch. I am Scrooge with money, always looking for a cheaper option, to get around these problems, and be more efficient.
I did what you are doing now, trying to make it work, it will be very frustrating for you, everything is connected, when you change one thing, you change others as well, it’s collateral damage 
I hope it works for you bud.
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Hps spectrum change is negligible when dialing down 1000 to 750
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That brings up the question could I dial it back to 50% and run a 600w bulb? Have to make sure it doesn’t get turned up by mistake though
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