Can I switch to wireless control without removing my existing pushbutton wiring?
The receiver relay contact is wired in parallel with the existing button contact; nothing is removed. Interlocks, limits and wired e-stop stay in place.
Yes, you can. The method is simple: the relay contact of the receiver is wired in parallel with the existing pushbutton contact. The same contactor coil is energised whether the button closes or the relay closes; you do not have to remove the existing wiring.
Wiring order
- Isolate the panel and note down the existing button cables together with their terminal numbers. Taking a photograph is not enough; write down which end goes where.
- Power the receiver. A panel-mount receiver can be powered from 12/24V DC or 220V AC; check first which voltage is available.
- Run the relay contact in parallel to the same two points as the contact of the button concerned.
- Before switching on, measure every direction by hand, then disconnect the motor and try it with no load.
Points to watch in practice
- The interlock must not be broken: the mechanical and electrical interlock that prevents the forward and reverse directions being energised at the same time has to stay valid for the relay side as well as the button side.
- Limit switches must stay in circuit: the limit switches belong in series inside the contactor coil circuit, not inside the remote control. That way the limit is preserved independently of the radio link; where the limit switch is to be wired is dealt with separately.
- Emergency stop: the wired emergency stop circuit of the machine is not removed; the wireless remote control does not take its place. Whether an emergency stop given over the wireless link is sufficient is a separate question.
- Labelling: mark in the panel which terminal comes from the RF receiver; it shortens fault finding later. Put the current version of the diagram in the panel file as well, because once the parallel connection is made the original diagram no longer describes the wiring fully.
Where the parallel connection does not fit
The method does not work identically in every panel. In three situations the arrangement changes:
| Existing circuit | Result | What to do |
|---|---|---|
| Momentary (press-to-run) button circuit | A direct parallel connection fits | Run the relay contact in parallel with the button |
| Latching (start-stop hold-in) circuit | The parallel connection may latch the movement on | Review the latching logic, convert it to a momentary arrangement if needed |
| Button going to a PLC input | If the contact is paralleled the PLC logic may be bypassed | Take the relay to the PLC input and drive the output through the PLC |
Whether the relay contact will drive the motor or the coil is settled here as well; connecting the contact directly to the motor is not suitable in most applications.
What to verify during commissioning
Once the wiring is complete, make three trials separately: first with the button alone, then with the remote control alone, and last by pressing both at the same time. The third one is critical; if the contactor chatters when the two commands clash, or opposite directions try to be energised together, it shows the interlocking is incomplete. Trigger the limit switches by hand as well and see that the movement really is cut: a switch that looks to be in series on the diagram may have been bridged out on site. Make the trials with the motor disconnected or with no load, then repeat them at low load.
A phased changeover
This parallel working approach allows a phased changeover, particularly in plants that cannot stop production: the receiver is connected and tested first, then once the site operator has got used to it wireless working becomes the main method and the buttons stay as a backup. On the ST100 and SF100 sets, using the manual button together with the RF remote control is foreseen for this scenario; on other variants confirm the same possibility from the product page. Do not remove the buttons during the changeover and show the operator both methods; the real gain of this approach is that the plant does not stop while the remote control is on charge or when it fails.
The full topic: Wireless remote control installation: pairing, relays, safety