Reducing a 8" centrifugal fan to 6" duct

I've tried google and I'm going to continue my research. Hoping someone can chime in on this though.

1. Does pulling air through a 6" duct with an 8" fan make the fan work harder? Is the output of the fan reduced?

2. Does pushing air through a 6" duct with an 8" fan make the fan work harder? Is the output of the fan reduced?



Thanks in advance.

What you are looking for is called a "transition". Search for 6" to 4" transition. The fan will only improve its performance.

i think the answer is yes to both but think a speed controller would help this....peace

their will deffinetly be a lower cfm. your fan will spin just as fast but you won't have quite as much power either way you do it.

no chance. somebody is pulling your leg.

try it by mouth.

get a straw and suck it through a pint glass it wnt fucking matter.

the 6 inch to 8 inch effect will cause the rush of air through the 6 inch to make a lot more noise and friction, producing heat and louder noise.
you are thinking that if you blow harder through something it will cool better, this is true, but your fan is only blowing harder because you are reducing the duct size.
the amount of air the fan will push or pull will never be more than the cfm that is written on the side of it.

why dont you reduce it from 8 inch to 1 inch then you can take off to the dominican republic on holiday on the jet power, LOL.

this is how a vacuum cleaner works but with a reverse effect.

the fan wont pull any more air through itself it will just concentrate the suck on a smaller area because of the small hose size.

and listen to how loud it is, and feel how hot the motor is after 10 minutes as it struggles to draw the air through the small bore hose..

It's going to work harder ether way. It's like the old saying. Your trying to cram 10 pounds of shit in a 2 pound bag. You fan will be stressed out eather way.
Take a straw suck and blow through it as hard as you can./ Takes to long and not efficient.
Now do the same thing with a garden hose. It's easier, takes less time and energy to get the same amount of air.
If your going to put a 6" fan in duct it with 6" piping.

The reduction will create a venturi with a resultant venturi effect. As the passage narrows the pressure (atmospheric) along the walls of the venturi decreases resulting in increased velocity.

Read about it sometime. They talk about it in skule.

IMO, frictional losses would come into effect. Otherwise, they would be selling tents with 1" holes for extraction.