Turn the power off for the entire system. Switch it off from the system’s circuit breaker. Put on electrical gloves and use other safety precautions necessary to prevent any accidents from happening because lighting circuits operate under heavy electric loads.

Find and open the service box that relays electricity to the lights. This box is normally fitted at a location near the lights and contains a transformer and wires connecting the lights to their switches and the circuit breaker. Use a screwdriver to mount and screw the contactor into the service box.

Use a screwdriver to loosen the terminal screws on the mounted contactor. There are a total of six terminals on lighting contactors; two for low voltages and four for high voltage. The low voltage terminals are also termed as “control”, the high voltage output as “load” and the high voltage input as “line."

Connect the wire from the switch to one of the low voltage terminals of the transformer. Join another wire from the second low voltage terminal of the transformer to one of the control terminals of the contactor. Take the second wire from the switch and insert it into the second control slot on the contactor.

Insert the neutral wire from the circuit breaker and one of the high voltage wires on the transformers to the contactor line terminal marked “L1”. Put the live/hot wire from the circuit breaker and the other high voltage wire on the transformer to the line terminal marked “L2”. The Live wire is either black or red while the Neutral wire is white in color.

Connect the Neutral wire that leads to the lights to the load terminal marked “L1” and the live/hot wire to the terminal marked “L2” on the contactor. Close the service box after all the connections are properly made.