Should I wire the limit switch to the remote control or to the contactor?
A limit switch must always be wired in series into the power circuit, that is, into the contactor coil line. The order is: receiver relay output, then the normally closed contact of the limit switch, then the contactor coil. That way limit protection works independently of the radio link and of the receiver's state; when the limit switch opens, the contactor cannot pull in under any circumstances.
The basic principle of limit protection is that the protection must not depend on communication. Wiring the limit switch to the receiver input and expecting a software cut removes the protection as well when the radio link or the receiver fails.
The correct wiring order:
- The receiver relay contact closes.
- The current passes through the normally closed contact of the limit switch for that direction.
- The contactor coil is energised and the motor turns.
- When the limit position is reached, the NC contact opens, the coil drops out and the movement stops.
In this arrangement a separate limit switch is used for each direction: the upper limit switch cuts only the hoisting direction and the lower limit switch only the lowering direction; movement in the opposite direction stays free, otherwise the machine reaches the limit and locks up.
Additional notes: using an NC contact also keeps you on the safe side when a cable breaks. The limit switch must be adjusted correctly mechanically and tested periodically. Limit protection and the machine's hard-wired emergency stop circuit are different functions; one does not replace the other.
The full topic: Wireless remote control installation: pairing, relays, safety