As I saw on another thread,
Dust Collector Remote Switch for 16A Extractor several people having similar needs thought this may prove useful.
Please do not attempt this unless you are happy with some wiring, Switch off before starting, you are responsible for your own safety, not me. Also, see note below about fusing.
QIACHIP 2 channel remote as posted above, mount in a suitable enclosure, I used a double socket mattress box and blanking lid. Mounted somewhere sensible, not sure if it would work in a metal box.
Relay A is used to remote start, so you push the 'A' button the relay switches the contactor on and it latches, Relay B for remote stop, (push B and the contactor drops out, both relays in momentary mode. The relays are just switching the starter contactor and NOT the motor, so could use this for larger loads than the relays are rated for. If you use the relays to directly switch the load make sure they can handle it and consider what sort of protection is in place. I wished to keep the DOL starter as it has overload protection and didn't want the relay to be handling motor starter currents, and be permanently energised whilst the extractor is running. Apart from anything else you'll struggle to get a larger cable in the terminals of the controller.
Controls on front of the DOL starter also continue to work. (which is handy cos I always seem to leave the remote at the other side of the workshop!)
Excuse the crude drawing.
Relay A is in parallel with the start button on the DOL starter, Grey and black wires.
Relay B is in series with the stop button, blue and brown wires, you are replacing the red wire in the first diagram with the normally closed contact of relay B. (yes I know I could have used less cores, but wasn't 100% on the way the controller worked)
Bear in mind that your starter labelling maybe different (it used to be a standard configuration, but I've been out of the industry for a while now)
Optional fuse: If you take 240V power to the controller from the DOL starter whatever is protecting the starter also protects the small cabling that you have put in and the controller circuit board. If your machine is on a 16 amp (or larger) plug and socket, then please put an inline fuse (or feed the the controller from a plug top with an appropriately sized fuse (suggest 3 or 5 amp)
Hope that helps, and makes sense, any questions then please ask.