All Replies on Dust Collection related: square to round..loss of CFM?

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Dust Collection related: square to round..loss of CFM?

by Holbs
posted 11-08-2018 01:42 AM

4 replies so far

View Fred Hargis's profile

Fred Hargis

6437 posts in 3351 days

#1 posted 11-08-2018 11:43 AM

Man, it would take some serious lab testing to verify that one way or another. I think you have no problem…but even if it caused some loss there’s not much you can do. Filters are round and your outlet isn’t, I think you’ll have to judge whether you have adequate performance after you’re set up. I’ll say this: there are a lot of DCs that go from square to round on one side or the other (mine does that on both the inlet and the outlet) so I wouldn’t think it’s a big problem or that might not be so common.

-- Our village hasn't lost it's idiot, he was elected to congress.

View Scap's profile


128 posts in 785 days

#2 posted 11-08-2018 12:47 PM

As long as the cross section area is similar, and you’re not introducing a rough or corrugated round pipe to the system, they should flow similarly.

View Manitario's profile


2816 posts in 3741 days

#3 posted 11-08-2018 07:51 PM

It appears that round ducting is actually a bit more efficient, ie. you have to have slightly larger square ducting area to get the same CFM:

-- Sometimes the creative process requires foul language. -- Charles Neil

View Holbs's profile


2366 posts in 2887 days

#4 posted 11-09-2018 02:49 AM

I talked to a HVAC guy today about this. He said yes, for home HVAC purposes, there is 50-70 CFM loss from going square to round due to the initial turbulence of the transition (if taken from a snaplock 6” duct and making one end square while leaving other end round). But he said for dust collection purposes of high CFM, not to worry about it.
Either Fred says above, gotta do what we gotta do with it, as is.

-- The Carpenter Bee is derived from the Ancient Greek word wood-cutter "xylokopos/ξυλοκὀπος"

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