Operation and Repair of Fluorescent Lamps

There are a number of reasons why homeowners might consider voluntarily replacing incandescent fixtures with fluorescent lamps. Fluorescent lamps offer:

• More even and “shadow-free” illumination, and
• Improved energy efficiency as a significant amount of the electricity in an incandescent bulb is discharged as heat rather than light, where as a fluorescent bulb remains cool.

Operation of Fluorescent Fixtures

A typical fluorescent fixture consists of the bulb, ballast, and starter:

• The current passes from the plug (left hand prong) through the ballast (a magnetic coil that adjusts the amount of current flowing through the tube, causing an initial surge of current when the starter initially opens and then maintaining the current flow at a rate commensurate to the specified level of required glow),
• Through one of the two lamp filaments,
• Through the closed switch in an automatic starter,
• Through the other filament in the lamp, and
• Back to the plug (right hand prong)

The current heats the two elements in the ends of the fluorescent tube, forcing the starter to open, and enabling the current to flow through the lamp. The starter will remain open until the fixture is de-energized.

Requirements for added light often result in fluorescent fixtures with more than one tube, requiring a starter and ballast for each tube. The ballasts and starters are often built into cases and cannot be individually replaced.

Repair of Fluorescent Fixtures

Defective starters, incorrect wiring, or poorly functioning ballast are the more common causes of fluorescent light malfunction. And, given that there are only three elements to a fluorescent lamp, repairs are generally simple:

• The initial indications of a failing fluorescent light fixture are a noticeable decrease in light (fluorescent lamps typically dim with age), and even a slight flicker or flash during operation.
• A dim tube should be replaced as soon as possible as it can strain the other parts of the fixture.
• Flickering or flashing will ultimately wear out the starter. So, again, immediate replacement of the tube is warranted.
• Similarly the actual fixtures (starter and ballast) can be replaced as well.

But, based on cost, there is a recommended sequence and method:

• Start with the fluorescent tube. If not sure that the tube is the problem, simply test the tube in another fixture. And if deemed to be the problem, perform a like-for-like replacement.
• If not the tube, then change the starter, ensuring the proper wattage rating for the replacement starter. The old starter can be removed by twisting it out of the socket in the fixture; and the new starter need only be inserted into the socket and locked in place.
• If the initial symptoms of a failing fluorescent fixture persist, then replace the ballast, again ensuring the proper wattage rating is applied. This is the least likely part to fail, but the most difficult to replace, requiring the de-energizing of the circuit, disassembly of the fixture, transfer of wiring to the new ballast and then reassembly of the fixture.

If the problem is not as simple as merely replacing the bulb, it is simpler, and often less expensive to replace the entire fixture in total.

There may still be challenges with the fixture. Then it will be necessary to determine if the light switch itself is defective, which will also require replacement, after de-energizing the circuit by removing the fuse or tipping the circuit breaker:

• The switch is normally screwed into a threaded mounting nut inside the lamp where 2 wires (from the switch) are connected to 4 wires from the tube.
• Disassemble the fixture to the extent necessary to make the back of the switch accessible.
• Screw in the new switch and transfer the 2 wires from the old switch to the new one.
• Reassemble the fixture and re-energize.

If there is still a problem, it may then be necessary to call in a licensed electrician.