Exhaust fan for grow room help please!

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Purplehaze01

Member
Not too sure what you mean by open fixture or air cooled my friend.. I have 2 holes at the bottom for passive air intake and I do have a fan attached to a hole (so I guess that's an active intake). How should I cool the room down more? Does it really matter? I havn't installed the exhaust fan yet.. would'nt that lower the temperature?
 
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Purplehaze01

Member
Also how do I attach the exhaust fan to my grow tent hole in the ceiling? Duct tape or something? Not sure if that's going to work..
 
Bubblin

Bubblin

Well-Known Member
Purplehaze01 said:
Not too sure what you mean by open fixture or air cooled my friend.. I have 2 holes at the bottom for passive air intake and I do have a fan attached to a hole (so I guess that's an active intake). How should I cool the room down more? Does it really matter? I havn't installed the exhaust fan yet.. would'nt that lower the temperature?
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He's talking about a cooled hood or cooltube for the bulb. They're a godsend.
https://www.amazon.com/s/ref=nb_sb_noss?url=search-alias=aps&field-keywords=cooled+hood

If your ambient is 82.4f you're gonna need a cooled hood or cooltube minimum. Probably an air conditioner as well. I try and shoot for 76-80 max in my area but my indicas don't like the heat.

Best bet is run a test with the light on asap and figure out how hot it's gonna get in there.
Imo don't waste money on anything until you decide if you're gonna get a cooled hood / cooltube, It will probably change what you purchase because you're building a ducting system rather than just cooling an area.
 
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Purplehaze01

Member
They're pretty expensive.. Do I really need them? I already bought a reflector.. Would'nt the exhaust lower the temp? Is a 120 cfm exhaust fan okay?
 
Bubblin

Bubblin

Well-Known Member
Purplehaze01 said:
They're pretty expensive.. Do I really need them? I already bought a reflector.. Would'nt the exhaust lower the temp? Is a 120 cfm exhaust fan okay?
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If your ambient is 82.4f then you're going to need one. You can find a cheap one for like $40.

Just go flip on your light.
 
Bubblin

Bubblin

Well-Known Member
Purplehaze01 said:
My bulb smashed so I'm waiting for my new one, should get here tomorrow. Should I still buy the exhaust fan with 120cfm?
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Don't waste your money on a 120cfm fan. Go 6" and 220-240cfm minimum.

Purplehaze01 said:
How much will the cooltube lower my temperature by?
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With a decent vent setup and good fan, a metric shit ton. A lot compared to without one, like seriously a lot.

The reality is you're ambient temps are close to max temperature without a light running. So wait for your bulb to come in, flip it on and cross your fingers lol. in a 19" x 19" space, it's gonna get hot af.



This.
Mount said:
To high IMO.. especially without the light on. With the light it is sure to climb, and I did not see if you said it was an open fixture or air cooled?

A few places for light reading:
http://www.theweedblog.com/what-is-the-best-temperature-for-a-marijuana-grow-room/

http://www.growweedeasy.com/temperature

http://www.growweedeasy.com/humidity
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Olive Drab Green

Olive Drab Green

Well-Known Member
Purplehaze01 said:
Hi I have a grow tent which is Width 50cm x Length 50cm x Height 100cm and will use a 250watt HPS light

I will have 2 fans below and above my plant and I'm pretty sure i'll need an exhaust fan at the top of my grow tent. My room outside the tent is pretty warm but hopefully that's not a problem? I would like to know how much CFM I'll need my exhaust fan to be and if the setup will be okay

Thanks!
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Stop growing with HID in small tents. Problem solved.
 
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Purplehaze01

Member
Niceee okay I guess I gotta buy one of those then.. I really hope this all works lol. But when I did the calculations of room size and the watts of my bulb It works out for me to only need to use like 120cfm.. Isint over exhaustion bad? and would I need to vent it out the room or something? I can't vent it out the window, I;m hoping I don't need to vent it outside my room
 
Bubblin

Bubblin

Well-Known Member
Purplehaze01 said:
So do you think I'll need an air cooled hood or just a cool tube?
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Cooltube is fine, just check the measurements of the tube you get. You're in a small space and most of them are 20"+. Might end up needing to run it diagonally / corner to corner or something. And you'll need room to hook up the ducting.

Purplehaze01 said:
I heard the cool tubes weaken the light ray..
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From what I've read it's in the 300-500 lumen range if the glass is decent. I have no way to test this though. But HID + small space = cooled hoods or tubes. Tbh it might be easier and cheaper in the long run to just get a COB led setup lol. Dealing with HID heat is a royal pain in the ass.

Just wait for your bulb to come in and test it ;)
 
squishbox

squishbox

Member
GuyLeDuche said:
Worth noting that though fans say things like "200cfm" that refers to perfect conditions, often a 200cfm inline booster will only run about 80-100 actual cfm IME, so it's worth going bigger, but 400 cfm does sound like alot to me for that space...
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So, if a 200cfm booster usually runs about 100 (half strength without perfect conditions), wouldn't a 400 be the logical choice, since without perfect conditions it would be running at 200?

I run a similar sized tent (plus or minus a 1/2") with a 400w HID open fixture, and 400cfm is perfect. I have a tiny bit of overhead, and my temps hover right around 76-78f all day.
 
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Purplehaze01

Member
Yeah that does make sense actually.. Do you know if I can use a regular fan as an intake fan and/or a regular fan pointing out my room as an exhaust fan?
 
tyke1973

tyke1973

Well-Known Member
All ways go bigger than you need ,i use a 12" out let and a 8" inlet with 2 x 600 hps lights cool hoods, temps never get above 25 even on the warmest day's,But sometimes i have friends that need money,so i have a other set up bang same has i use and we run 4 x 600 hps lights ,we also use a swinger a 600 hps light with no hood we can drop around the room,with a 12 " out let and 8" inlet with 6 plants,in the room.Tenps hit around 28 and the amount is all ways good,we pull around 5 1/2 lb to 6 lb
 
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