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Changing Light Bulbs

It takes only one do-it-yourselfer to change a light bulb. Changing a light bulb is usually easy, but choosing the right replacement bulb calls for some thought.
      Check the label on the lamp or light fixture that shows the wattage limit for bulbs. If you install a standard bulb of a higher wattage than recommended, the fixture or lamp will overheat. This probably will not start immediate fire, but it will likely damage the wire insulation or light sockets, possibly causing problems later. If you need more illumination, consider a screw-in fluorescent or a halogen bulb, each of which delivers more light for less wattage. Or install a new fixture.

Light Bulbs To Choose

Standard incandescent bulbs cost the least and certainly do the job. Bulbs labeled “long life” will more than pay for themselves. However, incandescent are not very energy efficient. Consider purchasing fluorescents that can be screwed into regular sockets. They will last longer and use far less energy. Most take a few seconds to become bright. If that is a problem, consider a halogen bulb, which is nearly as energy efficient but lights up immediately.

      Most household fixtures and lamps take standard light bulbs with a medium base. Decorative fixtures or lamps may require bulbs with different size bases.
For track and recessed lighting choose a flood bulb for wide illumination or a spot bulb when you want to highlight a small area.

      Halogen fixtures use low voltage, and only halogen bulbs will work in them. Flood and spot bulbs are available for halogens. Be aware that halogen bulbs get very hot.

Light Bulb Burnout

A typical incandescent light bulb has a life span of approximately 900 to 1000 hours. At roughly five hours per day, that’s about six months. If your light bulbs seem to have a shorter life span, the problem may be with the fixture. Some fixtures have loose contacts. A loose center contact on a lamp can overheat, melting the lead weld on the glass filament support. If the fixture doesn’t appear to be the problem, check the light bulb for the following:

An Overheated Light bulb. If bulb wattage is too high and there’s too little space around the fixture, the bulb will burn out due to improper air circulation.

Vibration. Bulbs can vibrate in loose fixtures or a wall that bounces.

Excessive Line Voltage. If the line voltage equals or exceeds 135 volts, have it checked out by your power company.

Light bulbs Rated 130 volts are superior to standard light bulbs but may not last as long as a commercial grade bulb.

The plastic coating on a rough service light bulb will contain the glass shards should it explode.

If none of these is the cause of your bulb burnout the bulb may be inferior. Be sure to purchase the best bulbs you can. Look for commercial or industrial grade light bulbs because they last much longer than standard light bulbs. Bulbs rated at 130 volts are better than standard light bulbs but do not necessarily last longer. This is also true of rough service bulbs that have a plastic coating on the surface and are designed to withstand vibration and will prevent shattering if the bulb explodes.

Troubleshooting Incandescent Light Fixtures

Problem	Diagnosis	Solution
Bulb Doesn’t Light	Plug has been pulled from receptacle.	Push plug back into receptacle.
	Bulb is loose; isn’t making contact with socket.	Tighten bulb.
	Bulb is burned out.	Replace bulb.
	Cord is damaged.	Replace cord.
	Switch is defective.	Replace switch.
	Receptacle is defective.	Replace receptacle.
Bulb Flickers	Bulb is loose; barely makes contact with socket.	Tighten bulb.
	Loose wire at socket terminal.	Turn off power to circuit or unplug fixture; then secure wire.
	Switch is defective	Replace switch.
	Receptacle is intermittent.	Replace receptacle.
	Receptacle wire is loose.	Reconnect or splice wires.
	Socket contact is dirty or corroded.	Turn off power; clean contact.
Fixture Blows a Fuse or Trips Circuit Breaker	Short circuit in cord.	Replace cord.
	Plug is defective.	Replace plug.
	Socket is defective.	Replace socket.

Fluorescent
In a fluorescent tube, electrical current jumps from an electrode at one end of the tube and flows through the tube and flows through the tube to an electrode at the other end. This current flow causes mercury and argon gases in the tube to emit ultraviolet (UV) light, which is not visible to the human eye. To make the ultraviolet light visible, the tube is coated with a phosphor powder that glows, or fluoresces, when it is struck by the light. When the fixture is turned off, the mercury/gas mixture within the tube does not conduct electricity. When power is first applied, several hundred volts are emitted form the ballast to initiate the release of electrical energy. Once this occurs, however, a much lower voltage is all that is required to maintain power-usually less than 100 volts for fluorescent tubes under 30 watts and 100 to 175 volts for tubes of 30 watts or more. When the higher voltage breaks down the gas and current begins to flow through it, the gas emits a great quantity of ultraviolet light but not much visible light. Only when the UV light hits the phosphor coating does the tube begin to glow. Different phosphors are used to achieve the light spectrum required for the fluorescent tube’s intended designation-cool white, warm white, colored, or black light.

Fluorescent bulbs are about two to four times more efficient at light production than incandescent bulbs. They also last a lot longer- 10,000 to 20,000 hours vs. 900-1000 hours for a typical incandescent. However, this does not take into account the expense of replacing fluorescent light ballast when one fails. Nevertheless, not all fluorescent bulbs require ballasts, and they are more energy-efficient than incandescent, providing two to four times more light per watt and using fewer watts than standard bulbs. They are also fairly maintenance-free.

One way to start a fluorescent light is to use a starter switch, sometimes known as a glow switch. The switch turns on when it is activated by an electric current. Inside it is a contact and a bimetal strip that provides the initial current surge that warms the bulb’s cathode (electron-emitting electrode). After the initial warm-up, the starter permits the electrical current to energize the gases in the tube. There are three types of starters: preheat rapid start, and instant start. In preheat starters; the electrodes are heated before high voltage is affected to the bulb. This type of starter is a replaceable twist-in module. Rapid start fixtures have electrodes that are constantly heated by low-voltage coiled wires (windings), and instant-start bulbs rely on step-up transformers for a short burst of high voltage to start up. The latter two types of starters are built into the ballast and cannot be independently replaced. The ballast is an enclosed component that governs the electric current-holding it to the level required to operate a fluorescent light properly. There are two types of ballasts: choke and therma-protected. Choke ballasts limit the amount of current flowing through the fluorescent tube. Fixtures that hold long fluorescent tubes use thermal-protected ballasts that include transformers as well as choke coils. With this type of ballast, when the light is turned on, a transformer momentarily steps up the voltage.

Another important aspect of florescent tubes is their pin configuration. The pins are the protrusions on each end that hold the tube in the fixture and transfer power to the tube. Fluorescent light fixtures commonly installed in homes use 4-foot-long bi-pin (two-pin) lamps. The two narrow pins on each end make these lamps difficult to install but easy to be loosened by normal vibrations. Once the base pins become loosened, the tube contacts disconnect, causing the light to flicker or go out.

A more reliable configuration is found on 8-foot-long tubes. These have a large pin on each end, and one is spring-loaded. They are equipped with an instant starter. They are easy to install and present few problems. Having one large connection on each end of the lamp eliminates the light flickering and corrosive tendencies of the smaller bi-pin tubes. In areas needing even more light, special fixtures with high-output tubes can be used.

Troubleshooting Fluorescent Light Fixtures

Problem	Diagnosis	Solution
Bulb Doesn’t Light	Bulb is loose; pins aren’t making contact with fixture terminals.	Reinstall lamp.
	Bulb is burned out.	Replace bulb.
	Terminals are corroded.	Clean terminals.
	Lamps are dirty.	Remove lamps and wash them.
	Bulb is cold.	Remove old ballast and install cold-rated ballast.
	End pins are broken or bent.	Replace bulb.
	Starter/ballast is defective.	Replace starter/ballast.
Bulb Flickers	Bulb is loose; pins aren’t making contact with fixture terminals.	Reinstall lamp.
	Bulb is cold.	Allow enough time for ballast.
	Starter/ballast is defective.	Replace starter/ballast.
Bulb Discoloration	Bulb is worn out.	Replace bulb.
	Starter/ballast is defective.	Replace starter/ballast.
Humming	Loose ballast wires.	Secure wire connectors.
	Ballast is incorrect.	Replace with correct ballast type.

Loose bulbs or connections are common problems with fluorescent fixtures. Test a fixture using a bulb known to be working. Inspect connection terminals, and clean off dirt or corrosion. Typical fluorescent lights are designed for warm areas, and their ballasts may not function below 50 degrees Fahrenheit. For unheated spaces it’s best to install cold-rated ballasts. Another common problem is a broken or bent tube pin or fixture terminal. Also, dirt and dust affects the phosphorous coating and may cause the lamps not to work. Excessively dirty lamps should be removed, washed with soapy water, rinsed, dried, and reinstalled about every 6 months. Inspect ballasts and starters, too. If a bulb flickers or won’t turn on, the ballast may be defective or the starter module may have failed. In either case, replace the defective part.

How to: Replace a Fluorescent Ballast

Difficulty Level:

Tools and Materials

• Ballast replacement
• Insulated screwdriver
• Diagonal-cutting pliers
• Electrical tape
• Neon circuit tester
• Wrench (optional)
• Wire connectors

Remove the Defective Ballast. Disconnect power to the circuit at the main panel.  Remove the light diffuser, fluorescent bulb or bulbs, and the metal fixture cover. Using a neon circuit tester, verify that the power is turned off. Disconnect or cut the ballast wires at the fixture sockets. Carefully supporting the ballast, use a screwdriver or wrench to loosen the locking nuts that hold it in place. Make certain that the replacement ballast matches the one removed.

Install the New Ballast. Support the replacement ballast with one hand, while leaving your other hand free to fasten it in place. Line up the new ballast so it will be positioned in the same location as was the old ballast. Once the ballast is accurately positioned, tighten the locking nuts. Using appropriately-sized wire connectors, splice together the ballast and socket wires, making certain to twist-connect the like-color wires. For added safety, wrap the wire connectors with electrical tape. Also tape the wires securely in place inadvertently pinned beneath the cover when it is put back in place. Nest, reattach the cover, install the fluorescent tube, and then replace the light diffuser. As a final step, turn on the power to the circuit, and test the light fixture.

How to: Replace a Fluorescent Fixture

Difficulty Level:

• Fluorescent fixture replacement
• Long-nose pliers
• Wire connectors
• Insulated screwdriver
• Neon circuit tester
• Multipurpose tool

Remove the Old Fixture. Turn off the circuit and switch to the existing fluorescent light fixture. Remove the light diffuser and fluorescent tube, and take off the fixture cover. Using a neon circuit tester, verify that the power is off. Disconnect the fixture wiring, and unscrew the cable clamp. Loosen the fasteners holding the fixture in place, and carefully remove the fixture form it’s mounting.

Install the New fixture. Locate the new fixture over the mounting, and pull the branch-circuit cable through the center hole. Mount the fixture securely to the mounting bracket or structural framing. Connect the fixture wires to the branch-circuit wires, following the manufacturer’s instructions. Be sure that like-color wires are properly matched and spliced, using wire connectors. Reattach the cover, replace the fluorescent bulbs and light diffuser, and turn on the power. Patch the ceiling, if necessary, and test the circuit.

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Troubleshooting

Panel Upgrades

Code Corrections

New Outlets & Circuits

Working with Inspectors

Additional Switches and Dimmers

Wires and Cables

Evaluating Curcuits for Safe Capacity

Planning New Electrical Service

Understanding Electricty

Glossary

Installation Price