6” duct reduction

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@bobthebricklayer

Member
Hey I’m setting up a new 4x4 with a 6” ac infinity inline fan. I know this topic has been discussed here before but I didn’t find any answers specific to my situation. I can’t find a 6” duct vent hood for outside my house anywhere plus I would need to buy a $40+ 6” hole saw so I was planning on running everything 6” up until the point that I hook the duct to the 4” outside vent hood and reducing it to 4” there. Is this okay just being at the end of the duct run or will it decrease performance of the fan?
 
@bobthebricklayer said:
Hey I’m setting up a new 4x4 with a 6” ac infinity inline fan. I know this topic has been discussed here before but I didn’t find any answers specific to my situation. I can’t find a 6” duct vent hood for outside my house anywhere plus I would need to buy a $40+ 6” hole saw so I was planning on running everything 6” up until the point that I hook the duct to the 4” outside vent hood and reducing it to 4” there. Is this okay just being at the end of the duct run or will it decrease performance of the fan?
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Yes, it will slightly decrease the efficiency/performance of the fan and my be a Lil louder. Sawzall, jigsaw, drill a bunch n knock out will work. Cheep whole saws available too.
 
@bobthebricklayer said:
Hey I’m setting up a new 4x4 with a 6” ac infinity inline fan. I know this topic has been discussed here before but I didn’t find any answers specific to my situation. I can’t find a 6” duct vent hood for outside my house anywhere plus I would need to buy a $40+ 6” hole saw so I was planning on running everything 6” up until the point that I hook the duct to the 4” outside vent hood and reducing it to 4” there. Is this okay just being at the end of the duct run or will it decrease performance of the fan?
Click to expand...

As others have said there are other options than a hole saw. A 6" hole saw is hard to handle with a light drill too. I just used a jig saw for most of it but couldn't cut close to the ceiling so used a drywall saw to do part of it. Use a compass to mark your hole area and make sure there's not a wall stud behind it before starting the cut.

Lining up the outside hole with the inside one can be tricky. I have some long smaller drills so once I had my centre inside drilled thru that centre to mark my centre on the outside wall. 6" thick walls too.

I also found a 6" aluminum dryer vent at the local farm supply and a plastic one at Home Hardware. Any building supply or HVAC place should carry them and the 6" hose to hook things up. Online for insulated hose if noise is an issue. Speed control helps cut down on the noise too. I also have a temp/RH controller on my exhaust fan so it only runs when it's needed.

For a 4x4' tent a 4" fan running half speed is good enough really.

:peace:
 
I don't think it will impact performance much at all. It all depends on a lot of factors that we can't see in your setup. I run a 6 in fan through 2 cool tubes with HID and multiple 90° turns and I can still keep my temps in line. Is it ideal? No. But it works.


I say try it and see. Worst that can happen is after a couple hours your temps skyrocket and you have to pivot. But a reducer is like a $7 gamble.
 
As long as you don't have a lot of bends, elbows & long runs you'll be fine. I've always run my 6" inline fan reduced to a 4" outside thru-wall vent because the thru-wall vent was already in-place and enlarging it to 6" is not practical in this situation. I've had no problems. Keep it simple.
 
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