I have a Delta radial arm saw (208 volt) and a Milwaukee panel saw (120 Volt)connected to a Delta dust collector (120 Volt) and I'd like to be able to just turn on either the panel saw or the radial arm saw and have the dust collector come on automatically.
Currently I have to turn on a switch that turns on the dust collector in order to be able to turn on the radial arm saw or the panel saw. This works but I'd like to simplify the process.
Any suggestions on how to make this work? I have a metal enclosure and a couple of relays to use but am stuck on the exact wiring. I'll try to include a drawing of how I thought I could wire it but it did not work.
Thanks,
I need to figure out how to post pictures/attachments.

Here is the way I had it wired and the dust collector would come on if you turned onn either switch but the saws didn't run.

Anyone?

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Sorry, got busy.

The coils of the relays, as shown in drawing, are in series with the load, and should be connected in parallel.

The coil for the panel saw needs to be rated 120 volts, the other coil needs to be 208 volt.

HK, could you draw the circles connected to both lines, instead of in series? Much appreciated if you can.

Sorry, I really don't want to rain on your parade, but assuming that this is a home work shop and not an industrial environment, there appears to be something you have not considered.
Typically, with the home work shop sawdust collection system, you have blast gates at each machine that have to be opened and closed manually as each machine is used.
It would be simpler to used a low voltage contacts at each blast gate to turn the central vacuum on and off.

Even simpler would be to use a electronic remote control. One common brand is the Lone Ranger Dust Control sold by PSI.

To automate everything as you would like would probably require fabrication of automated blast gates with servo motors and modification of electrical circuitry of each saw.

I can't argue with that.

Quote:

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Originally Posted by hkstroud

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HK, I'll modify the drawing and label the contacts and relays.

Quote:

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Originally Posted by tkrussell

Sorry, got busy.

The coils of the relays, as shown in drawing, are in series with the load, and should be connected in parallel.

The coil for the panel saw needs to be rated 120 volts, the other coil needs to be 208 volt.

HK, could you draw the circles connected to both lines, instead of in series? Much appreciated if you can.

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TK, I see what you mean. I'll see how I can put the two loads in parallel. I have 2 separate relays. 1 is 120v coil and the other is 240v coil.

I'll try to modify the drawing to get your approval. :) I appreciate the help.

I bought this equipment at an auction and he just had it set up the way I described earlier.
My problem with wiring the relay coils and motors in parallel is that the saws just have cords that plug into the wall and the switch is located on the saw.
I might just have to disable the switch on the saw and use an externet switch mounted close by.
Thanks

HK, the saws are connected by separate hoses to the dust collector and there are plastic inline slide gates to isolate each saw but they are both just always left open since the smaller hose won't draw very well unless the larger hose gate is open some. And closing the gate to the small hose doesn't really effect the larger hose suction so they just stay wide open and it works.

Hi Dave,
OK, if you shop vacuum works with both ports open that's good.

With the wiring diagram you have in the box, as TK noted, you appear to have the coils to the relays connected in a series with the saws. Apparently there is enough of a voltage drop across the relay coils to cause the relays pick the points and turn on the vacuum when you turn the saw switch on. However, the coils are also acting like a resistor and limiting the amperage to the saw motor. Thus the saw will not run. The relay coils must be connected in parallel, that is between the hot and the neutral or between the two hots in the case of the arm saw.

That's easy enough to do, but the connection must be made after the switch that turns the saw on. That means running wire back from the saw to where the relays are located.

I can think of no way making it work the way you have it designed, with everything in the box, no additional wires back to the box and no modification to saw internal wiring, unless you can find some amperage sensing device to signal the relays to turn the vacuum on.

Think about it like this. Right now you are using voltage to signal when to turn the vacuum on. Since voltage is always present on the line up to the saw switch, you must connect after the switch. The only way, inside the box, to sense when the saw is running, is to measure the amperage. Whether such a device exist, I don't know.

I was looking at it some yesterday and looking for the easiest way to wire the motor and relay in parallel. I'll just have to think some more. I might put a small box with a relay out on the saws and run a cord back to the j-box.

You might want to consider a current sensing relay such as this.
Aprilaire 50 24V Current Sensing Relay.
This appears to be designed to be used with a furnace fan motor wiring to turn on a low voltage humidifier. Doubt that the points would be capable of passing the amperage of shop vac at 120V. Might have to use it to pick another high voltage relay to turn on shop vac. There may be a version for high voltage.

Suggestion,

Install small sub panel sized to supply the greater of, radial arm saw and shop vac or the panel saw and shop vac.

Install double breaker for radial arm saw, install breaker for shop vac on one leg. Install breaker for panel saw on the other leg. Install current sensor on the same leg as panel saw, before breaker for radial arm saw.

If current sensor relay is capable of passing amperage of shop vac, run shop vac line through sensor relay. If current sensor relay not capable of passing amperage of shop vac install low voltage transformer on same leg as shop vac. Use low voltage from transformer through current sensor to pick low voltage line relay and turn shop vac on.