See BoD agenda item for details: https://dallasmakerspace.org/wiki/Board_of_Directors_Meeting_20180223#Purchase_Dust_Collection_System_for_the_Woodshop_.28Andrew_Zalaket.29
Felder info page: https://www.felder-group.com/us-us/products/dust-extractors/clean-air-dust-extractor-rl-350--350-mm.html
From the Felder page, the proposed unit has a nominal capacity of 4090 CFM at 2630 Pa (10.5" WC) with a 350 mm (13.7 inch) inlet.
This is a list from long ago, but will work for reference:
That’s 5800 cfm. That 5800 cfm is the total at the collection port on the tool. I also think the manufacturer recommended collection volume for the table saws is low. This is my first concern: the unit will not collect enough for the peak use periods.
My second concern is that the stated 4090 CFM in a 14" duct does not produce sufficient velocity in the duct to keep the particles suspended. 4090 CFM yields 3826 feet per minute (fpm) linear velocity. Guidelines for wood dust and chip collection vary between 4200 to 5200 fpm to maintain suspension. As dust settles in the duct, you decrease flow area – thereby decreasing flow rate. Dust settling in the duct also creates a fire hazard. The velocity required to resuspend the particles (called scour) is higher. This is why ducts should be accessible and regularly cleaned.
The flow rate of fans is a curve dependent on pressure. The harder is it to push (or pull in this case) air through the system the lower the flowrate is. As you close gates in the system, say at 2 AM when one guy is building a cabinet, the pressure increases because the system is trying to suck all 4090 cfm through the 1 dust collection port. Except it can’t suck that hard and ends up churning. This heats up the fan and motor dramatically.
I guess it comes down to what the goal is. If the goal is to appease the Fire Marshall, I hope we have in writing his concurrence that this system will fulfill his requirements. If the goal is to purchase a long term solution, I don’t think this fits. Commence discussion
p.s. this is a great reference for duct data: http://www.spiralmfg.com/wp-content/uploads/2015/09/engineering_data-1.pdf