Ducting Question

[Keith Winter]

I'm putting in another 3hp dust collector blower. Problem is there is an obstruction approximate 2.5 feet from the intake. I cannot move the obstruction and the blower could be moved elsewhere, but it would then run into another obstruction. So the first obstruction is 1.4 foot tall so the 8" vent pipe has to clear it.

I've read you're supposed to have 3 feet of straight pipe into the intake of a dust collector for it to perform best. Unfortunately that doesn't look like it's going to happen.

I'm wondering what you guys think is the better of the two evils?
1) Angle it right off the bat to clear the obstruction.
OR
2) Go straight for 2 foot then do a 90 degree then another 90 degree
(see attached diagrams of the options)

Second question, how much of a performance hit am I going to take?

[Chris Padilla]

An elbow is worth something like 3-5' of duct in terms of loss.

I'd go with Scenario #1 as it is the lower loss of the two.

[David G. Jones]

Can you do a couple of 22.5 degree fittings to ease into the turn?

[Terry Hatfield]

Scenario #1 is a much better configuration. It should not adversely effect performance vs the 90's in Scenario #2 right before the blower. I have a 22.5 degree fitting tight at the blower intake and it doesn't seem to make any difference.

[David Kumm]

#1 but can't the cyclone be turned a little to avoid some of the bend? Dave

[Keith Winter]

Thank you all. I was thinking #1 wouldn't cause too much of an issue. Glad to hear you agree. Thanks again!

[Wade Lippman]

If you are only planning on using one tool at a time you can afford a lot of hits on a 3hp machine before it will matter.

[Ole Anderson]

Rather than using fittings, use 8" aluminum flex so you can use a smooth transition to fit. I found my 7" at HD. Probably smoother than all of the little segments needed in several fittings. My duct approach to the collector is far from ideal, but it still gets the job done.