by mannytheseacow » Thu Nov 13, 2014 5:09 pm
It would vary with system size. You'll want to keep a consistent volume throughout the system, so you'll have to measure the outside dimensions of your riser and inner dimensions of your barrel or outer covering and subtract the area of the riser from the barrel. That remaining area will need to be at least your CSA, and the larger the better. Or more simply, probably the same as the top gap, so minimum 1.5" for a 6" core and 2" for an 8" core. Again, the bigger the better.
Obviously, the opening to the plenum can't be 360* around the core, so the gap will have to accomodate that area, too.
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