I wish Id read Bill Pentzs site BEFORE I bought my Grizzly 0861 2HP cyclone dust collector, but now I must do the best I can with what I have.
According to Bill Pentz, either:
a) I use 7 duct thereby getting my 1000 cfm and fine dust removal, but worry about dust piles in the line OR
b) I go with 6 duct and leave the fine dust in the air.
Hmmmm, burn down the house or get lung cancer what a choice!!
So, Im trying to figure out two specific issues:
1) What size should my main duct line be (6 or 7)(see detailed questions below), and
2) Confirmation of my belief that one should never downsize at a tool, but instead modify the tools outlet using wyes so that the sum of the tools outlets equals the area of the duct line.
1a) Main duct line. Bill Pentz says that on todays dust collectors the 7 duct line will not have enough pressure to generate the air speed needed to keep vertical lines from plugging. He recommends a minimum of 4000 fpm. Grizzly says the 7 inlet of my collector has about 3500 FPM, moving 1023 cfm with 1.2 static pressure.
So my question is, if I decided not to run my duct line up to the ceiling with down drops, but instead, roll my tools over to very short lines that have a maximum vertical drop of 3' can I use the 7 duct without getting dust accumulation in the line? If so, I could get my 1000 cfm without burning down the house.
1b) If I have to decrease to 6 pipe to increase velocity, at which point should I reduce? Right at the inlet to the dust collector using a 6 main? Use a 7 main and reduce at my branches? Use 7 main and branches and reduce at the tool? Im guessing this will all depend on the resistance in the lines of the various options and theres no simple answer.
2) According to Bill Pentz, theres never a reason to reduce a port at a tool below the duct line, right?
This is my first post and my first dust collection plan for my shop, so please forgive any mistakes.
Thanks so much,
Maureen