two dust collectors–parallel,serial, se
I have two dust collectors. One is “stationary” with two bags, a 4″ Tee on the suction side and about 1,000 cfm with two bags; the other portable with just one bag about 600 cfm.
I have only one garbage can lid (cyclone) for a two-stage setup.
What should I set up?
There are three ways: parallel, serial and separate.
I think parallel would give the most suction. I would connect the suction end of the portable to one side of the suction tee of the larger one. The whole system would be two-stage.
Serial would be connecting the suction of one to the exhaust of the other. I think there is less suction this way, even though I can still have all two-stage.
Separate would be one two-stage and one single-stage. This setup has its merits, but the footprint would be a bit more.
What are your opinions? I think it is quite OK to use single-stage for machines, like jointer and planer, that produce finer dusts, while table saw with large chips should have two-stage.
Replies
I'd go for separate. Put the separator on the static system, and use the mobile one to supplement the other where you need better collection (say one above and one below on your tablesaw) or where the tool is too far away to easily connect to the system.
The only way serial would be useful would be if your ducts were too small, and a DC normally effective was not because of flow resistance over the long distance. That's because serial will increase suction pressure difference, but not flow rate above that you'd get without resistance.
Parallel might be helpful, but if you have small ducts (4") the extra flow is likely not to be as much as all that, since increased flow will cause increased pressure difference, which the DC likely can't overcome. So the flow will be less than the sum of the flows when separate. It may even be that your small DC can't pull at the operating pressure differential of the large one, in which case the parallel setup would be almost the same as the large one by itself. If your ducts are large, you will get increased flow of alsmost the sum of the two separate machine's flow, and that will likely empty out your trashcan separator.
That's why I think separate is best. It's easiest too.
I've got two HF DC's hooked up in parallel on a Pentz style cyclone and it works really good. As Alan mentioned above, be sure you are using big enough ducting (5" or 6") or you will be wasting your time.
Government's view of the economy could be summed up in a few short phrases: If it moves, tax it. If it keeps moving, regulate it. And if it stops moving, subsidize it.
Ronald Reagan, August 15, 1986
You should probably look at http://billpentz.com//woodworking/cyclone/index.cfm for information on the impacts of hooking those up in series. This page has a lot of information and one of the points that Bill makes is that the motors on a DC work hardest when they are moving the most air. If you hook those up in series you run a real risk of overloading the downstream motor and burning it out.
Another big point that Bill makes here is that 4" is not enough to move the kind of air you need to do the job right. The CFM numbers that most manufacturers put out are based on their units run with no ducting on them at all. If your machine can move the air with the proper velocities, you should opt for 6" ducting all the way to your machines.
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