Replacing Interior Light Fixtures

When working with electricity always: Turn off the power. Test the wires to ensure the power is off. Lock out the panel box, so no one can accidentally turn the power back on while you are working. Check with local authorities to see if a permit is required. Have your work checked by an inspector. Wear eye goggles and a dust mask. To avoid overloading the circuit, consult a licensed electrician.

You don't have to be an electrician to replace a light fixture. Many homeowners are afraid to tackle electrical projects—and rightly so. If improperly handled, electricity poses electrocution and fire hazards. But simple jobs like light fixture replacements are easy and safe if you follow a few simple rules.

The most basic principles of the wiring in your home are simple. The following is elementary information from which every homeowner can benefit.

In contemporary wiring, individual wires run in a sheathed cable. "Two-wire with ground" and "three-wire with ground" cables are available. Two-wire with ground cables have a black wire, a white wire and an uninsulated ground. Three-wire with ground cables (used when installing three-way and four-way switches) have a black wire, a white wire, a red wire and an uninsulated ground. Older houses may have "knob and tube" wiring—a two-wire system. With this system, individual wires are insulated with white or black treated fabric.

Regardless of the type of wiring in your home, the white wire is usually the neutral wire, the black wire is "hot," and the exposed copper wires are ground wires. The white wire is sometimes used as a hot wire because some wiring installations require it. In this case, the white wire should be coded black with paint or electrical tape. Note, however, that it is possible that whomever did the wiring may not have coded the wire. If a red wire is present, it should also be hot.

If only a single cable enters the box (or one set of black and white wires), the fixture is at the end of the circuit. This is usually, but not always, the situation with ceiling light fixtures. If two cables enter the box (or two sets of black and white wires in older "knob and tube" installations), the fixture is in the middle of a circuit. A third cable (or set of black and white wires) may also enter the fixture, depending upon the installation. The placement of the fixture within the circuit affects how it is wired.

It is easy to tell if your home has aluminum wiring—the metal under the insulation is almost white instead of copper colored. Aluminum and copper wires should be connected with a wire connector specifically rated for this purpose. Otherwise, copper and aluminum will react with each other, possibly leading to a loose connection and creating a fire hazard.

Before removing the old light fixture, be sure to observe the first rule of electrical work—Turn off the power to the circuit on which you plan to work! Do this at the service panel (breaker box), and check the circuit to make sure it is off. Inexpensive circuit testers are available that are, essentially, a light with two probes designed to handle house current. They are very useful for testing ground and hot wires, as well as for determining whether a light fixture is carrying current.

Unless the fixture you are replacing is broken and doesn't work, it is possible to use a less elegant method to check the circuit. The light will quit working when its circuit is turned off at the breaker. It will come on again when the breaker is turned back on. (This proves that it is not the light itself that has quit working!). To test, turn the circuit breaker off and on and off again, double-checking the light to confirm that it is indeed the lack of electricity that is causing it to quit working, and not some coincidental failure that could mislead you into getting shocked.

Once the circuit has been turned off at the breaker and has been checked, there is no need to fear working with the wiring on that particular circuit.

The second rule to remember when replacing fixtures is: Wire the new one back in the same way the old one came out! It really can be that simple. Most of the time when replacing light fixtures you will simply be connecting white wires to white wires, and black wires to black. If several wires are involved, however, or if the wiring seems more complicated and perhaps even includes a red wire, take note of the connections before you disconnect them. Make yourself a sketch of how the fixture is wired (index the sketch by wire color) or mark the wires themselves with masking tape and a pencil so you will know how to put them back.

Now that you know how the new fixture must be incorporated into the existing wiring, you may remove the old fixture. Since the physical installation of your new fixture will depend upon the fixture itself, refer to the manufacturer's instructions for directions on this part of the process.

Make your electrical connections by "tying in" to the home wiring using plastic connectors, often called "wire nuts." Install the connector by twisting it onto the wires.

If the new fixture includes a ground wire (bare or green insulated wire), it should be connected to any other ground wires that may already be in place, and to grounding screws in metal electrical boxes when metal boxes are used to support the fixture.

Finish installing the fixture as indicated in your manufacturer's instructions. Then, you're ready to install the recommended bulbs, turn on the breaker and try out the new light.

If you've wired the new fixture just like the old, it should work fine. But people do sometimes make mistakes. If you make one, it's probably not as big a deal as you may suspect. If you have miswired the fixture, one of two things will happen. Either the breaker will trip when you turn on the light switch—or else it simply won't work.

Double check to see that the breaker is off. If the breaker has indeed tripped, look again at your sketch or your masking tape tags to see where you made the mistake. Double check your wire connections to see that the wires are properly connected and insulated by the wire nuts.

If the breaker hasn't tripped, but the fixture doesn't work, don't forget to test the bulb—more than one bulb has chosen to fail just as someone was testing a light fixture. If the bulb is fine but the fixture still won't work, turn off the breaker and perform the checks listed above.