Exhaust duct reducer @ fan vs 2ft.

[Beanfish]

I have an 8" inline fan the i need to reduce to 6". I think I read somewhere years ago that it's best to run a duct 2-4 feet away from the fan before adding a reducer. I just can't remember if it was pertaining to fan efficiency, noise level or both.

Can anyone confirm?

 

[Guest]

Hi Bean,

Try it both ways, and you got your self a bonafide experiment! Let us know your results. I am not sure, and wouldn't just rely on what someone says. Test it yourself, and then you can be the someone who knows from experience!

Thanks in advance

 

[Beanfish]

Well..... That's plan B.

Those of you that use reducers, do you reduce at the fan or do you have say 2-4ft of duct before reducing?

I was just hoping that it was already common knowledge. I'm still setting up/upgrading my room and the time can be better spent building a new veg system and veg/mom cab.

 

[smurfin'herb]

i would like to know this also.

 

[smurfin'herb]

Ok heres my take, I would say that its better to put it further away. Reason being, cfm's are lost thru ducting runs, so if you have a 8 inch 700 cfm fan and are reducing it to a 6 inch, your goal is to try to find a spot further down on the 8 inch duct that the cfm's are significantly less than that of where the 8 inch fan sits. At this spot you are hoping that the cfm's are at least equal to or less than about half of the cfm's on the rating of the 8 inch fan. So hopefully about 350cfm or less which would be about equal to the cfm rating of a six inch fan of the same brand. So there would be no restrcition really, since at that "special spot" on the duct run already is only able to move as much or less than a 6 inch reduced duct would allow.. Thats my opinion, im no havc, but from my exp. thats what i would say.