Connecting a two-wire light fixture to a three-wire power supply cable is not an ordinary occurrence. Three wire supply cables generally carry red and black hot wires of 110- to 120-volts each with a single white neutral wire. The lighting could be added to the three-wire cable provided that the circuit breaker is no more than 15-amps and the wire size is no greater than 14-gauge. You can do the work with the proper tools, materials and electrical circuit knowledge.
Turn off the circuit breaker at the main panel that supplies power to the three-wire cable intended for the light fixture. Tag or otherwise mark the breaker to alert others of the work being done.
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Test the wires to verify that no power exists using a voltage tester. Place one probe of the tester on the white neutral wire and the other probe on the black wire. Also test the red wire with the white neutral.
Cut any exposed copper from the red wire with wire cutters. Place a wire nut over the end of the wire and tighten clockwise by hand. Wrap a few layers of electrical tape clockwise around the wire nut overlapping the tape onto the red insulation.
Strip 1/2-inch of insulation from each of the remaining wires using wire stripping pliers.
Connect the black hot wire to the black wire of the light fixture with a wire nut. Tighten clockwise by hand.
Connect the white neutral wire to the white wire on the light fixture using a wire nut.
Wrap each of the wire nuts with electrical tape. Be sure to overlap the tape from the nuts onto the wire in a clockwise direction.
Place the wiring into the box and secure the fixture.
Restore power to the circuit and remove all tags and markings from the panel.