does the length of a passive are duct matter

  • Thread starter biggerbud420
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biggerbud420

biggerbud420

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i have a 6 inch exhaust fan taking air out of my tent . i have 4 4 inch passive intake ducts bringing air into the tent. i want to run at least 2 of those into another room with air conditioning and those ducting would have to be 8 to 10 feet long would that length matter ?
 
Madmax

Madmax

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And the correct size hole for air coming in.the norm is to have the hole bigger than the exhaust fan size as to not restrict the fan.but i have a 6 inch with 6 hole in small room works fine.but in flower room i have 2 6' holes to the 8'extraction fan.bends do restrict airflow and when considering cfm its been said to go 25-30% bigger than the cfm needed..
 
ThatRapperWeed

ThatRapperWeed

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i have a 6 inch exhaust fan taking air out of my tent . i have 4 4 inch passive intake ducts bringing air into the tent. i want to run at least 2 of those into another room with air conditioning and those ducting would have to be 8 to 10 feet long would that length matter ?
Keep in mind a bend in the ducting can reduce airflow from 20-40% depending on the angle.
 
coherent

coherent

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Type, length and bends in any duct affect airflow. HVAC installers calculate duct requirements based on specific CFM output/input and requirements of a given unit and based on the area/room. The calculations get pretty in depth so while your question is basic compared to an AC install no one can give you a specific answer with the basic info you provided. For your purposes I'd simply assemble your setup and see if it meets your needs. If not, turn the fan up higher or add a bigger (or another) inline fan to meet your CFM requirements.
 
RippedTorn

RippedTorn

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No one needs 400cfm in a tent. No one needs 24 square inches of intake in a tent. You wouldn't need that much intake even if you did run 400cfm. The only thing stressing your fan is when you try hooking up a duct booster to a tiny little Cannabis carbon scrubber that's sucking humid air neem oil and spider shit all day. 50-100 cfm is plenty for a tent. A 4" hole can move that just fine. The ducting will have like a 5%-10% higher demand
 
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