—If the CFM for your static pressure loss is above the requirement of the woodworking machine, then the line will most likely be successful.
—If the CFM for your static pressure loss is below the requirement of the machine, then that line will not effectively collect dust. You must modify some of the factors in that line to reduce the static pressure loss. Some of the ways to do this include installing larger duct, reducing amount of flexible duct used, increasing machine dust port size, moving machine closer to dust collector to eliminate duct length, and reducing 90˚ elbows or replacing them with 45˚ elbows.
System Grounding
Since plastic hose is abundant, relatively inexpen- sive, easily assembled and air tight, it is a very popular ducting material. We recommend using flexible hose (flex-hose) to connect the wood- working machine to the dust collector. However, plastic flex-hose and plastic duct can create a static electrical build up, which will build until it discharges to a ground. If a grounding medium is not available to prevent static electrical build up, the electrical charge will arc to the nearest grounded source. This electrical discharge may cause an explosion and fire inside the system.
To protect against static electrical build up inside
anon-conducting duct, a bare copper wire should be placed inside the duct along its length and grounded to the dust collector. You must also confirm that the dust collector is continuously grounded through the electrical circuit.
If you connect the dust collector to more than one machine by way of a non-conducting branching duct system and blast gates, the system must still be grounded via copper wiring as above, with the wire attached to each grounded machine and dust collector.
Be sure that you extend the bare copper wire down all branches of the system. Do not forget to connect the wires to each other with wire nuts when two branches meet at a “Y” or “T” connec- tion. If using plastic blast gates to direct air flow, the grounding wire must be jumped (Figure 25) around the blast gate without interruption to the grounding system.
Plastic
Blast
Gate
Copper | |
Ground | Metal Duct |
Wire |
Figure 25. Ground jumper wire when using
plastic blast gates and metal duct.
We also recommend wrapping the outside of all plastic ducts with bare copper wire to ground the outside of the system against static electrical build up. Wire connections at Y’s and T’s should be made with wire nuts.
Attach the bare ground wire to each stationary woodworking machine and attach to the dust collector frame with a ground screw as shown in Figure 26. Ensure that each machine is continu- ously grounded to the grounding terminal in your electric service panel.
| | External |
| | Ground |
| | Wire |
| Internal | Ground |
| Ground |
| Screw |
| Wire |
| |
| Flex-Hose | |
| Figure 26. Flex-hose grounded to machine. |
