do i need 2 separate exhausts?

Currently planning out my grow room. Gonna be using 400 hps cooltube.

Now do i need 2 exhausts(1 for cooltube, 1 for growroom) like in the first pic? (dont pay attention to the intake fans, i can use passive intake right?)

or....

can i just use the 1 exhaust from the cooltube and take off the other ducting(exhausting air through the cooltube, with a passive intake) ex: pic 2


im sure u could do it both ways. it seems like it would work better with separate exhausts, but is it that much of advantage have 2 exhausts?

please lemme know

p.s. the room is 4 x 3 x 8ft

I might not be an expert but i am pretty sure you do. THe cool tube should be run on a separate exhaust to suck out the heat the light is putting out. The second exhaust for the air exchange with in the grow itself.

Pic two will work if you want to exhaust the room all the time. But if you dont want to exhaust the room at all times or plan on doing co2, you will need two fans. One for exhausting the room when you like and the other dedicated to the cool tube.

works either way naturally if your fan is strong enough. I like seperate cooling for lights in small grow rooms & tents 'cause if you add CO2 you can still run your fan that's cooling your cool tube whilst shutting down your cabs intake/exhaust during CO2 release

anybody ever tried this with 1 exhaust through the cooltube?

the only problem i see is the exhaust is drawing warm air instead of cool air arcoss the tube, which would probably mean less cooling. but does it still cool it a little or not at all?

great point about the co2. thank you both.

I am debating the same issue. I think I am going to go with one fan to vent the room and cool the light. I am going to test temps tomorrow, hopefully I will be able to post the results for you. I have a 4x5x6 grow room. What are you doing about smell?

Seaweed11 said:

I am debating the same issue. I think I am going to go with one fan to vent the room and cool the light. I am going to test temps tomorrow, hopefully I will be able to post the results for you. I have a 4x5x6 grow room. What are you doing about smell?

Click to expand...

Seaweed please get back to me on your temps. are you only having to cut 1 hole if your room for exhaust?

As for smell if i get carbon filter, can u attach it directly on the cooltube. (this is if your only using the 1 exhaust idea)

tyler666 said:

Seaweed please get back to me on your temps. are you only having to cut 1 hole if your room for exhaust?

As for smell if i get carbon filter, can u attach it directly on the cooltube. (this is if your only using the 1 exhaust idea)

Click to expand...

I will be testing the temperatures tonight in a relatively small closet (2' x 3.8' x 7'). I plan on venting the whole space through the cool tube (Leaving one end open and pulling the room air through). I am using a Can Fan 4" HO model which is rated at 178CFM (overkill for this space), so I am hoping it's more than enough.

I will report back with temps.

I have a post showing the room itself and the "DIY Light Trap" intake I made out of carboard.

Keenan said:

I will be testing the temperatures tonight in a relatively small closet (2' x 3.8' x 7'). I plan on venting the whole space through the cool tube (Leaving one end open and pulling the room air through). I am using a Can Fan 4" HO model which is rated at 178CFM (overkill for this space), so I am hoping it's more than enough.

I will report back with temps.

I have a post showing the room itself and the "DIY Light Trap" intake I made out of carboard.

Click to expand...

keenen you have almost identical dimensions and set-up as mine minus the diy intake. please lemme know temp and if your fan is suffient. p.s your ducting seems awful long. did you have to shorten it?, or did your fan give you plenty of cooling and venting, even with the excess tubing

tyler666 said:

keenen you have almost identical dimensions and set-up as mine minus the diy intake. please lemme know temp and if your fan is suffient. p.s your ducting seems awful long. did you have to shorten it?, or did your fan give you plenty of cooling and venting, even with the excess tubing

Click to expand...

Yeah, well I have a fairly decent inline fan mounted above in the attic. I will put a picture of it below.

I do have a bit of excess tubing, but I wanted enough to raise and lower the lights. I could probably cut maybe a foot or two off, but I am getting plenty of airflow considering the entire length of vent from start to finish is only 25'. The fan is meant for this type of application and is even rated "under load" so I will eventually be able to put a carbon filter on the other side.

I need to find a nice cheap thermometer tonight and I will run the whole setup for a few hours and try to determine the peak temperature. Unfortunately I don't know how much this can really tell you as it's going to greatly depend on the ambient temperature outside the closet. Maybe I can get a indoor/outdoor thermometer for cheap enough and give you both readings.


[Smokes just so you can gauge size. The fan is actually larger than I thought it would be.]

So I hooked up the 1000w just to see what kind of heat it put off, it raised the temp of the room from 70 to 84 in 20 minutes, and 2 ft under the light the temp was raised to 96. I am not sure at what point the temp stabilizes, but we are definitely going to have to pull air off of these things. I am thinking based on this that I will be able to cut just one hole to exhaust the hot air off of the 1000w and circulate the air.
I have cut another hole for a passive air intake at the bottom of the room diagonally across from where the 1000w will be pulling air.
So 2 holes, one for passive intake, one to exhaust the room and pull the air off the 1000w.
I have seen setups where people go: Carbon filter-->ducting--> 1000w-->ducting--> fan-->exhaust out of room.

Ok, as of about 45 minutes ago my room has been on. I got a nice indoor/outdoor (wire probe for outdoor) digital thermometer for $10 at lowes. So, I should be able to give you the temperature inside and outside the closet in a few hours. Keep in mind I'm a newbie, so I'm not really sure how many hours I should wait before checking on temps. I assume it'll take quite some time to hit 'max' temps.

The other thing I neglected to mention is I do have a standing oscillating fan running in the room, which I hope at least moves air around (not sure if that has any effect on temps).

Will post tonight or tomorrow whatever I find out.

Just as a FYI, my room pics here: Grow Closet 400 Watt HPS, Cool Tube, DIY Cardboard Light Trap Intake.



EDIT: 4-ish hours of run time.... 84 inside the closet and 73 right outside the door.