My DC is an old Delta canister, model 50-179. The motor is 3/4 HP. All ducting is 4" with the joints taped with reinforced foil tape.
According to what I've found online, the CFM is 650. There is nothing about CFM in the original manual. When I converted it to a cyclone, it seemed to increase CFM output. I don't have anything to get an accurate CFM reading.
I'd like to tap into the existing output, which is ducted to the outside, and install a canister filter, preferably a HEPA, MERV 16 so I can switch between outside ducting and the interior filter. Plans are to cool the garage in the summer, thus the interior filter.
The question is how to determine the correctly sized filter based on CFM. Any suggestions?