6" or 8" cool tubes with a 12" inline fan?

I'm trying to decide between 6" and 8" cool tubes/venting for my flowering room. I'm worried that using the smaller 6" will reduce flow if I stick a 12" 1100CFM fan on the end of it.

Some people say that using the smaller 6" cool tubes make for more air pressure? I figure it just leads to more resistance but I'm not sure.

I should bust out my science book.

JohnQPub said:

I'm trying to decide between 6" and 8" cool tubes/venting for my flowering room. I'm worried that using the smaller 6" will reduce flow if I stick a 12" 1100CFM fan on the end of it.

Some people say that using the smaller 6" cool tubes make for more air pressure? I figure it just leads to more resistance but I'm not sure.

I should bust out my science book.

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I'm building out my room right now. 2x1000w with big 8" hoods. Ducting from the wall (fresh air in) runs through both hoods. At the other side of the room (12ft fun) is a 435cfm Votex style fan. It's a 6" and will litterally suck your balls off. That 12 fan is over kill. I would do 8" ducting and use a reducer to fit the 8" ducting to the 6" fan. The 6" fan is like $130 vs $190 for the 8". Both will work fine.

A 12" fan with that CFM rating is for very long runs. It would be killer to see in action but I don't think it's necessary.

johnq said:

Some people say that using the smaller 6" cool tubes make for more air pressure? I figure it just leads to more resistance but I'm not sure.

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Whoever told you that - I want you to take away their smoking device and slap them very hard, at least a dozen times. Drawing blood is acceptable here.

Certainly reducing the size of the tubing will increase the pressure - the back-pressure on the fan - which will then of course reduce the airflow.

So here "pressure" is bad. "Flow" is good.

The fluid dynamics aside,

dubsfan said:

Ducting from the wall (fresh air in) runs through both hoods. At the other side of the room (12ft fun) is a 435cfm Votex style fan. It's a 6" and will litterally suck your balls off. That 12 fan is over kill. I would do 8" ducting and use a reducer to fit the 8" ducting to the 6" fan. The 6" fan is like $130 vs $190 for the 8". Both will work fine.

Click to expand...

This is certainly correct - a 6" fan for a couple of cool tubes is more than adequete for any install I've ever seen.

You'll be fine with the 6" fan.