Replies

1. 
   BruceT999 | Jun 16, 2007 09:42pm | #1

   I'm in the same boat you are.

   Rick Peters' "Controlling Dust in the Workshop" says "For systems under 3HP, 24ga or 26ga is the way to go."
   "Woodshop Dust Control" from Taunton Press says that 26ga is too thin for 5" or greater because it could buckle if you mistakenly start up with all blast gates closed.

   Elbows are stiffer due to the adjustable joints, so I'd guess that they should not be a problem.

   Penn State is the least expensive source I have found online.
   Long-radius elbows greatly reduce static pressure loss, but they are expensive. I think I may stack two adjustable elbows together ($5 ea. at http://www.kencraftcompany.com/sheet_metal_adjustable_elbows.htm) instead of $25 for a fixed long-radius.

   I contacted a local HVAC contractor and asked where to get heavier gauge pipe. He said that his supplier won't sell to anyone without a contractor's license, but he was willing to add my parts on next time he orders materials.

   You asked, "Would it be OK to put the DC unit at the "bottom" of the U and run two separate main ducts, one up each side?"
   Certainly. You will use only one machine at a time and closed ducting puts no load on the blower. Size the main line to carry the volume of air of the largest branch and still maintain 3500 FPM velocity (V = CFM divided by duct cross section area)

   You asked, "I was wondering if I could include 3 or 4 air intake hoods in my system to circulate and clean the shop air."
   If you put a hood at each end of your "U", air flow at each hood with a 1 1/2hp system would probably be at best about 300 CFM. Of course, those hoods could only be used when you aren't working. A dedicated air filter, because it doesn't have to pull through long ducts, can move more air with less hp and it can run while you are working.

   BruceT
2. 
   woodwish | Jun 17, 2007 12:05am | #2

   I did all the duct work for my DC with 4" PVC drain pipe.  Regular 4" PVC will cost a fortune, but the drain pipe is reasonable.  I bought mine at Home Depot and it's usually outside near where they keep the septic tank pipes.  Cuts easily on with a chop saw, elbows are cheap and since it is drain pipe you dan get long sweeps, glues together easy, 4" blast gates fit right in the pipe tightly (put some thin foam tape on the gate first for a tighter fit), inset a cleanout on the end, wonderful stuff.

3. 
   SARGEgrinder47 | Jun 17, 2007 06:19pm | #3

   Morning Quesne...

   The 26 guage Bruce metioned will be fine with a 4" piped system. The 4" drain woodwish metioned will be fine also as neither have much chance of collapse with a 1 1/2 HP DC.

   But.... if I had any suspicions that down the road I would be adding a Cyclone and knew it would be postioned where the current DC would sit, I would opt for the more expensive stuff now instead of replacing it latter. Kind of like running 10 gauge wire on a 220 V 20 A circuit where 12 guage would suffice. An addition of a 30 A down the road is allowed for latter if necessary and the correct guage is already in place.

   Just a few Sunday morning thoughts...

   Sarge.. jt

4. 
   alanplanesaw | Jun 18, 2007 04:10am | #4

   quesne,

   Disclaimer -  I am not a DC expert.

   Reality - I have a Jet DC-1200, so we have similar machines.  I used 4" ductwork with a leg to left and one to the right, sort of like your idea of being at the bottom of the U. 

   I added a gate on each leg, in addition to a gate at each machine.  That way, if I am using a machine on the left leg, I close the gate on the right leg.

   ALSO - wherever I turned a 90 degree corner, I used at least 2 adjustable 90 degree elbows (45 degrees each).  On the mainline of each leg, I used three.  That made the turns very gentle and didn't slow the airflow down as much.

   Been working successfully for about 8 years.

   Alan - planesaw