(12-03-2019, 05:33 PM)Wayne G. Wrote: Currently have a Delta 50-589 1.5 hp motor and fan only. I've used 6 inch duct with this for years with 4 inch drops and its done well. Recently I was thinking of upgrading to a 2 hp motor and fan on the same trunk lines. It looks like its only 200 cfm more. I'm looking at roughly $350 to get the Pennstate unit but I'm questioning if 200 cfm makes much difference at all.
Those are based on marketing air flow values, which are typically about twice what you could expect in service, though with no filters, you're probably getting more than half the published value. Depends on what it's connected to, of course.
Have you even put an ammeter on the line to see how close to rated power that motor is working? Most small DC's, with bags/filters, don't get very close to the motor's rated current when connected with a 4" flex to a tool or machine. This is where the fan curve makes a difference, as one with a higher max static pressure will pull more air through the same piping network than one with a lower value. Usually. Helps to see the fan curves for both, which are usually not available to the public for these small commodity type DC's.
But I agree with the others - if you're going to upsize, start at 3 hp and go up from there if you can. Restricting the air flow won't hurt the motor, as it actually
unloads the motor, like a vacuum cleaner (universal motor) that speeds up when you block the air. So going big has no downside in that respect.
Four inch hose, especially corrugated, will present a lot of flow resistance, by the way, so you can increase air flow by going up in size if you can and/or going to smooth hose.