I would like some help with an idea in The Workshop Book by Scott Landis on Page 106. In the section on installing a central dust collector they show using a low voltage circuit (using a 12v or 24v transformer) with switches on the the blastgates to turn the collector on or off. The circuit is tied into a standard magnetic switch. My question is HOW is it connected inside the magnetic switch?
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Mr. Landis failed to clearly explain, and probably didn't realize, is that to use a low voltage system, as he has it drawn, you need a magnetic switch that has a low voltage coil in it. Standard magnetic switches use line voltage coils, 110 or 240 volts typically, because they are simpler and less expensive.
If your switch does have 24 volt coils, the switch's labeling will clearly say so. The labeling should also indicate how to wire the magnetic switch to be controlled by an outside circuit, but the wiring diagrams are drawn using a system of electrician's hieroglyphics that can be baffling to even experienced electricians.
On some switches it is possible to replace the line voltage coil with a low voltage coil, and, of course, you could replace the entire switch with one that has a low voltage coil, but this will cost $150 to $200.
A third alternative, and probably the least expensive, in terms of parts, would be to use a separate relay operated by the low voltage circuit to switch the line voltage coils in the existing magnetic switch. For an industrial electrician this would be a straight forward job, but it would be a challenge, and a bit risky, for an amateur to tackle.
Sorry that I couldn't supply a simple way to do what the book suggested.
John White
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