I have a 3000 square foot shop with 2 10-foot sliding table saws at one end using 1000 square feet. My ceiling is 12 feet high. I would like to use a ceiling mounted unit to clean secondary dust that the dust collectors miss. Any advice on what type of unit to get and what size?
I built one from a piece of house heating duct, mounted 2 barrel fans (from a side-by-side fridge) on a piece of plywood with exhaust holes cut. Stacked 3 furnace filters on the other end. It collects dust big time--I need to change filters monthly. I am moving into a shop the same size as yours soon and will be installing 6 units. I found some small blowers at a surplus store, 600CFM, $10. They are from a large IBM computer.
Curt Corum, forum technical advisor
I have a 20' X 24' garage and designed and built a 1,200 cfm dust filter for under $100. The main part of the advertised filters is a squirrel cage blower powered by a small electric motor. The same blowers operate forced air furnaces where the first thing to fail is the firebox. The minimum sized furnace blower is 1,200 cfm. When furnaces are replaced, the case and blower are scrapped. A local furnace dealer gave me the blower and wiring if I would remove it from the furnace carcass.
I designed a plywood case to hold the blower, which takes in air from both sides, so a clearance on each side of about 3" does the trick. Most blowers can be any side up (check the name plate) and run on 110V. There is a 1" space between the blower case and the extended bag filter. The bag filter is held in place by a channel made of 3/8" strips glued around the inside, on both sides of the bag filter sheet metal frame. A third row of strips holds the pre-filter just inside the inlet opening. The case is 40" long X 21" wide, 14" high at the filer end and 19" high at the blower end. Of course a filter has to be dimensioned to fit the blower and the filters.
The following purchases completed the project:
1. 5/8" 5 ply plywood, hinges and a latch for a double hung window.
2. A bag filter (removes 98% of particles 3 microns or larger) and a pre-filter from Penn State Industries for $35.00
3. A rotary one-hour manual switch from Home Depot. This allows you to run the filter after you have left the shop to really clean the air, plus a 3 wire cord and plug.
4. Screw eyes for the filter and screw hooks for the ceiling.
5. A 7 1/2" X 9" adjustable louver for the outlet end of the blower from Home Depot.
The box was glued together using biscuit joints to make it reasonably airtight. A door was hung on the side to allow the filters to be removed and cleaned or replaced. The exhaust end was screwed to the case to allow for blower removal if it ever wears out. The filter should be placed close to the ceiling and close to a wall-near the middle to do the best job of cleaning all the air in the shop. It works great, there is no fine layer of dust on my car, and no noticeable draft while working.