Should I connect the relay output directly to the motor or to a contactor?
On small DC motors, the LF100R's 2x10A relay output has the capacity to handle forward/reverse direction control without a contactor. On large motors, however, the correct method is to drive the contactor coil with the relay contact and let the contactor carry the motor current. This approach protects the relay contact, makes the part to be replaced in the event of a fault cheaper, and makes it possible to add thermal protection.
The decision is given by the motor current and the load type.
Driving directly. As stated in the product description, the LF100R's 2x10A relay output has the capacity to handle the forward/reverse direction control of a DC motor without a contactor. This noticeably simplifies wiring on low-current actuators, small hoists and similar loads.
Driving through a contactor. As the load grows, driving directly becomes risky. On inductive AC loads an inrush current of up to roughly 10 times the operating current arises at the first instant; this current wears the relay contact out early. On large motors:
- The relay contact drives only the contactor coil.
- The contactor carries the motor current, and a thermal overload relay comes into play against overload.
- When a contact burns, the part replaced is a cheap contactor, not the receiver.
In both cases use mechanical and electrical interlocking between the forward and reverse contactors, and suppress the arc with a reverse diode on DC coils and an RC snubber on AC coils. Connect the limit switches in series with the contactor coil circuit, not with the remote control.
The full topic: Wireless remote control installation: pairing, relays, safety