Outside Exhaust Vent Size

[Andrew Kertesz]

Would there be any advantage to go to a 6" exhaust if I am venting outside or would 4" be sufficient? I will be running a HF DC through a Super Dust Deputy, one machine at a time being a hose dragger. Usage would be: TS, Performax 16-32, BS, jointer and planer. Dust Deputy will sit on an airtight 35 gallon drum.

Thanks for your input...

[Peter Aeschliman]

My non-scientific answer would be to go bigger to reduce back pressure. If you look at Clearvue cyclones, for example, they have a 6" inlet and an 8" outlet.

But I'm sure there will be more scientific answers.

[Jim Becker]

Any venting post impeller is generally larger than what's in front of the impeller...you don't want any pressure back there from the duct work, other than what you can't avoid if you are filtering. With a direct vent, go larger rather than smaller. Be sure you consider that "some" material may get by the cyclone and plan for it accordingly as well as keeping "creatures" out.

[Jim Andrew]

My system is 6", and when I ducted it outside, used an 8" outside vent. Built it myself like a dryer vent. It still forces some air back out the filter, so bigger would be better. Might just be the back pressure caused by the flapper, although it is only 1/4" plywood.

[Robert Engel]

If, for example the exhaust housing is 4" this is the point of restriction.

Going to a larger duct would only help if the exhaust run is more than a few feet long.