Timer contactor wiring diagram. In this circuit, we use a TP MCB ( Tripple Pole Miniature Circuit Breaker ), a timer, an SPST Switch, a magnetic contactor, and an overload relay. First, we need to connect the TP MCB with the power source, then connect the timer with TP MCB, then connect the SPST Switch the timer, then connect the magnetic contactor with the timer and then connect the overload. Now this circuit is ready for use.