| STEP 1 - How to Layout your Shop |
The example above illustrates a simple 3 machine layout. In laying out your shop, try to follow these basic guidelines:Typical CFM ratings for woodworking equipment:
- Place machines requiring the highest CFM (air flow in cubic feet per minute) closest to the dust collector (see chart below)
- Try to keep runs as short as possible
- Try to kep all duct work at the same height as the dust ports on the machines
- Try to keep directional change fittings (T's and Y's and Elbows) to a minimum
Machine CFM Required 12" Planers 350 13"+ Planers 400 Shapers 400 Bandsaws 400 Radial Arm Saws 350 Tablesaws 350 Disc Sanders 300 Belt Sanders 300 Floor Sweeps 350 Jointers 350 Drill Presses 300 Scroll Saws 300
NOTE:
We recommend installing a blast gate for every tool to help direct all of the air flow to the tool being used.
| STEP 2 - Determining the Duct Diameter Needed |
Find the tools you will be using tht require the most CFM from the chart above. If you will be running more than one tool at a time, ass the CFM numbers of those tools together. Using the chart below, determine the duct diameter that will be required for your system. We do not recommend using duct smaller than 4" in diameter.
250 - 400 CFM 4" DUCT 400 - 650 CFM 5" DUCT 650 - 800 CFM 6" DUCT
If you determine that your system will require greater than 800 CFM, you can calculate the appropriate duct diameter usinf the following equation below:
Duct Diameter = (CFM * 183) / 350
| STEP 3 - Determining Static Pressure Loss |
Determine the length of stright duct work in your layout from the duct collector to each tool. Count the number of each type of directional change fittings to each tool: Y-fittings, T-fittings, and Elbow Fittings. Each type of fitting is equivalent to a specific lenth of stright duct in the amount of Status Pressure Loss it causes. Refer to the following chart for reference:
Duct Dia. 90º Elbow 
30º Y-Fitting 
90º T-Fitting 
4" 6 feet 3 feet 7 feet 5" 9 feet 4 feet 10 feet 6" 12 feet 5 feet 13 feet 7" 13 feet 6 feet 14 feet
Determine and add up the equivalent number of duct feet for all of the directional change fittings for each tool. Add this number to the total length of straight line duct from the dust collector to each tool. Once you have determined the total length of duct to each tool, (straight line duct plus fittings), you can then calculate the Statis Pressure Loss for each tool based on the chart below. Static Pressure Loss is measured in inches.
Duct Diameter Static Pressure Loss
per foot of duct4" Duct .055 in./ft. 5" Duct .042 in./ft. 6" Duct .035 in./ft. 7" Duct .026 in./ft. 8" Duct .022 in./ft.
Example
In our sample layout, the system consists of 3 tools: a jointer, a planer and a tablesaw. The calculations for this system looks like:
Jointer Planer Tablesaw 4" Dia. Duct 15 ft. 11.5 ft. 22 ft. 90º Elbow 1=6 ft. 0 1=6 ft. 30º Y-Fitting 0 1=3 ft. 0 90º T-Fitting 1=7 ft. 1=7 ft. 1=7 ft. TOTAL FEET 28 ft. 21.5 ft. 35 ft.
To determine the Statis Pressure Loss for each tool, multiply your total feet by .055" (4" diamter duct)
Jointer Planer Tablesaw Statis Pressure Loss 1.54 1.182 1.925
We recommend adding 1" of Static Pressure Loss to compensate for a dirty filter bag. The highest Static Pressure Loss for this system would be 1.925" for the tablesaw plus 1" for a dirty filter bag resulting in a total Static Pressure loss of 2.925".
| STEP 4 - Determining which Duct Collector is Needed |
Use the tool with the greatest Static Pressure Loss and the tool requiring the greatest CFM to determine the size of dust collector you needed for your system. If you will be running more than one tool at a time, you must add the CFM's and Static Pressure Loss of these tools. In our example, the tool with the greatest CFM is the planer at 400 CFM. Therefore, we must purchase a dust collector with a Static Pressure Loss rating of 8.5" and a CFM rating of at least 650. It would be wise in this circumstance to consider a larger Dust Collector such as the JET DC-1200CK.
| STEP 5 - Preventing Static Electricity Build-up |
There is always the danger of static electricity building up in the duct system and causing a flash explosion of fire. To prevent this, run ground wires through both the inside and around the outside of all the piping. Use stranded aluminum or copper, or solid copper wire for the inside and aluminum antenna guy wire for the outside. The JET Dust Collection Grounding Kit contains all of the necessary components to safely ground your system.
At directional change fittings, you can solder the wires on the inside of the fitting. Wires in Y-Joint fittings must be soldered facing away from the aire flow, or you can drill a small hole in each branch of the fitting—bring the wires out of the fitting and connect them with a wire nut. You must do this for all Blast Gates so you can completely close the gate. Seal the holes with caulk after the system is put together to prevent air leaks.
Wrap a wire around the outside of the hose and fittings to remove any static electricity that might build up on the outside of the ducts. Ground both the inside and outside wires to a metal part on each woodworking machine—including the Dust Collector. You may need to use a screw or bolt with a lock washer to ensure a complete ground connection.