1 Fan, 2 filters

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AlexHarryy

Member
So i have 2 tents and 2 HPS 400W each so it is 1600W in total. Both tents have 2 Sputnik reflectors with cool tubes conected in line. Would the temp be good if i put on the both ends carbon filters 350 cfm each and 1 fan outside of the tents 700 connected to both pipes? And can somebody suggest best way how to connect 2 pipes with one fan pipe?
 
coreywebster

coreywebster

Well-Known Member
2 ducts with one fan, you want a Y piece duct bracket
Problem is if your not careful you could end up with one filter working better than the other. The fan will pull the air through the path of least resistance, so if your ducting isn't even length and even amount of bends there will be more resistance in one part than the other and the one with the least will pull more air through than the other.
Keep it as close to identical and you should be ok.
 
Ryry94

Ryry94

Well-Known Member
Here is what works for me...I pull air from two 4x4, 600w hid tents through duct connected to one side of each each light, then out of the tent and connect to a Y connected to the 6” 450cfm can fan which sits on top of one 6x24 can lite filter. No smell unless the tent is open, temps are room temp and RH with lights off and 6-8 degrees above room temp with lights on. I keep the tents on opposing schedules, therefore running only one light at a time in flower. I usually have one tent in flower and the other in veg, in that case I overlap the schedules in the middle of the night when the temps are coolest. Highest temp I’ve seen is 83 during the heat of the summer. This set up is in a basement with no ac.

Length of the duct and route should be nearly identical to reduce “path of least resistance” that Cory mentioned. Monitor the temps and you will quickly know if you have an imbalance. I think you only need one filter.
 
A

AlexHarryy

Member
Thanks guys for answering,

coreywebster said:
2 ducts with one fan, you want a Y piece duct bracket
Problem is if your not careful you could end up with one filter working better than the other. The fan will pull the air through the path of least resistance, so if your ducting isn't even length and even amount of bends there will be more resistance in one part than the other and the one with the least will pull more air through than the other.
Keep it as close to identical and you should be ok.
Click to expand...
Does couple cm differece be a serious problem?

Ryry94 said:
Here is what works for me...I pull air from two 4x4, 600w hid tents through duct connected to one side of each each light, then out of the tent and connect to a Y connected to the 6” 450cfm can fan which sits on top of one 6x24 can lite filter. No smell unless the tent is open, temps are room temp and RH with lights off and 6-8 degrees above room temp with lights on. I keep the tents on opposing schedules, therefore running only one light at a time in flower. I usually have one tent in flower and the other in veg, in that case I overlap the schedules in the middle of the night when the temps are coolest. Highest temp I’ve seen is 83 during the heat of the summer. This set up is in a basement with no ac.

Length of the duct and route should be nearly identical to reduce “path of least resistance” that Cory mentioned. Monitor the temps and you will quickly know if you have an imbalance. I think you only need one filter.
Click to expand...
Thats a good idea but i already have two :(

But does 700 cfm fan would be enouth for 4 HPS 400W
 
Ryry94

Ryry94

Well-Known Member
Sorry, I didn't read your original post carefully enough. My set up will not work for you because your fan CFM is double what each your filters can handle on their own.

I'm sure there is a general guideline for CFM in a grow tent or room, but I don't know what it is. 700 CFM seems to be in the ballpark, consider this example... each tents is 5x5x7.5 or 187.5 cubic feet, x 2 tents = 375 cubic feet giving you 1.87 complete air changes in the tent per minute. So if you farted in the tent, the stink would be gone in 32 seconds.
 
coreywebster

coreywebster

Well-Known Member
Alex, providing you try and stay as equal in duct length as possible I don't see it been a massive problem. Just making you aware of it so you don't end up having a set up with 1m of straight ducting and another length 3m long with several bends.
 
X

XipXipXoom

Active Member
I believe the rule of thumb from the overgrow FAQ was 1 airchange per minute for low temps, 2-3 changes per min in normal temps, and 3-5 in high temps.

Also, while fans are generally better at pulling through resistance than pushing, I don't believe the difference is that huge. Consider putting a single filter on your exhaust. Some say this keeps charcoal dust off your bulbs anyway.
 
fn217

fn217

Active Member
XipXipXoom said:
I believe the rule of thumb from the overgrow FAQ was 1 airchange per minute for low temps, 2-3 changes per min in normal temps, and 3-5 in high temps.

Also, while fans are generally better at pulling through resistance than pushing, I don't believe the difference is that huge. Consider putting a single filter on your exhaust. Some say this keeps charcoal dust off your bulbs anyway.
Click to expand...
I second this. Rather than filter the air at the beginning of the exhaust, you should pull the air out with your inline fan, and pushed out through your carbon filter. That is, if you're not exhausting straight to a window or something.
 
A

AlexHarryy

Member
fn217 said:
I second this. Rather than filter the air at the beginning of the exhaust, you should pull the air out with your inline fan, and pushed out through your carbon filter. That is, if you're not exhausting straight to a window or something.
Click to expand...
I didnt quite got what you write, my english is bad :(... You think one filter will be ok too?
 
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