In article .net,
says...
The famous website on dust collection is adamant that you should use 6"
ducts from the collector all the way up to your tools, then reduce down to
4" to get into the tool. He says this allows you to get the full capacity
of a dust collector, if its 1.5 hp or greater. My dealer swears I should
use all 4" ducts and it will be fine with a Jet DC1100 or greater. My shop
is 3 car garage and he's been out here and has some idea of the pipe network
I would need for dust collection.


Take a look at the spreadsheet on that site, then do some computations
with your setup. Be sure to use the dust collector volume vs. static
pressure drop curve for your dust collector. I have a 2 HP system, and
5" pipe is the optimal size for the pipes, 4" has too much static
pressure drop, 6" doesn't get the flow rate up high enough. I used to
have the system hooked up with 4" flex duct -- I never had a clog and it
always sucked up the chips, but... When testing my 5" system, I
understand now what static pressure drop really does to a system;
although my 4" system on the table saw would clean up the chips, I could
actually see the system pulling in dust through the blade insert with
the 5" system -- it looked like one of those Jenn-aire range hood
commercials. When you use the curve I indicated above, the process on
that spreadsheet will be iterative, you will have to find flow volume,
check the pressure drop, then adjust the volume input until the volume
and drop intersect on the chart.

The jet book on dust collection recommends a 6" main pipe with 4" branches
going to the tools.

I'd like to hear the real-world experience from some of you that are running
1.5 - 2 hp dust collectors.

By the way, can anyone tell me what difference I might observe between the
jet 1.5 hp and 2 hp collectors? The published specs are 1100 cfm and 1200
cfm. I would suspect the larger collector could achieve its capacity
through a more complex or restrictive pipe system.

Are there any other brands you might recommend? The Jet models seem to be
the most for the money in the $400-$500 price range. Others that use
cartridges seem to be in the $800 up price range.

Bob