DC duct length question

[Jack Porter]

I have a 2hp cyclone (air suction capacity 1550cfm, SP at max CFM 11", exhausts outside) and am upgrading the ducting for a new jointer and bandsaw (woohoo, darn MS cashback got me;)). I am running 6" metal snap lock and the max run would either be 40ft for the easy ducting solution or 32 ft for the pain in the butt ducting solution to the farthest machine, both runs would have 3 long radius 90 degree bends. The system has blast gates at each machine and would only need to serve a single machine at a time. I'm just trying to decide if going through the hassle of having 8ft of duct would make a significant difference in performance.

Does anyone have a similar setup?

I know we can all run static pressure loss estimates, but I am looking for some as-built performance recommendations.

Any input is appreciated, thanks.

[Jeff Miller]

I have a 2 hp. cyclone exhausted to the outside with this setup. I have about 60 to 70' of 6" and probably another 60' of 4" .

First picture is before I added the planer and sander to the system.

I think you would be OK with the 40' easy route.



http://i44.photobucket.com/albums/f32/woodfarmer/New%20Shop%20Pictures/newshop026.jpg




http://i44.photobucket.com/albums/f32/woodfarmer/performax/owwm086.jpg



JEFF:D

[Jack Porter]

thanks Jeff, this will make the next few nights in the shop a little easier.

I must say I'm jealous of all the open space you have, just another reason to buy a few more tools.

[Jim Becker]

Jack, while length certainly adds to the friction equation, turns are far worse. If you plan out your duct work to have the most efficient routing (not necessarily the most aesthetically pleasing, of course) you'll end up with better performance, despite the distances that need to be traveled. In general, you want to avoid "perimeter" designs as they generally increase the total duct length. Oneida has (as far as I know it's still there) a very nice duct planning guide document on their web site that helps to explain this in a graphical way.

[Scott Wigginton]

The extra 8' will only result in an additional 0.36" SP (4.5" per 100 ft of 6" pipe)

Each of your 90deg turns for 6" pipe is the equiv of 12' (or 0.5" SP), so if you can minimize these you will be better off.