Flickering Fluorescent Tubes and Buzzing Ballasts

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Flickering Fluorescent Tubes and Buzzing Ballasts

If you've ever had to work for 16 months in an office with overhead fluorescent tubes that flicker or buzz, you know how annoying they can be. If you work in an office with flickering lights AND buzzing ballasts, you may have a permanent headache (in addition to your boss).

While the effects are headache-inducing for some people, you may wonder why no one has called the maintenance manager to replace what appears to be equipment ready to fail?

Unfortunately, don't expect someone to come change your office lights anytime soon just because of complaints about buzz and flicker. Even if maintenance does show up, unless there is an upgrade of the ballast and a close look at minimum lamp operating temperatures, the annoying buzz and flicker is likely to continue.

Buzzing Ballasts

Older magnetic ballasts are the chief cause of buzzing from fluorescent fixtures. Make Magazine explains how this happens:

An inductor [i.e., magnetic ballast] will certainly limit the rate at which current can travel to the light, however it does so by absorbing magnetic fields into its core. This absorption, which causes magnetostriction, is probably the source of your hum- it literally causes the inductor to expand and contract at twice the AC frequency, which creates an audible sound wave

Changing the ballast is the best solution here, replacing the magnetic one with an electronic ballast that will not hum and operates at a lower wattage to regulate the voltage going to the fluorescent bulb itself.

Alternatively, buzzing can increase or decrease based on a number of other factors. One large lighting manufacturer explains that these include the following:

  • How the ballast is mounted in the fixture
  • The overall design of the fixture
  • Reverberation from the walls, floors, and ceiling
  • The size of the ballast -- larger ones have the capacity to generate more buzzing than smaller versions

The good news is that many T12 lamps and magnetic ballasts have been legislated out of existence, so your headache may eventually go away when the bulb finally fails. The bad news is that you may be waiting a long time: T12 bulbs haven't completely disappeared yet and can last 10-20,000 hours, while magnetic ballasts are designed to operate for an average of 50,000 hours.

Flickering Fluorescent Lamps

Flickering lights are another issue entirely. Known as "striation," the light coming from a fluorescent bulb may appear as if it is traveling in waves from one end of the bulb to the other. Striations do not indicate an electrical problem. Common causes of striation are fluorescent bulbs filled with heavy gases like Krypton, excessive airflow across the bulb (unlikely inside a fixture) or, most commonly, lower air temperatures than recommended by the lamp manufacturer.

In fact, striation is one of the reasons why fluorescent bulbs have recommended minimum operating temperatures. Newer energy-saving, reduced wattage fluorescent lamps are more prone to striation, according to Philips Advance (PDF), due to the their greater sensitivity to low temperatures.

For example, a 32 watt T8 lamp paired to an electronic ballast can be upgraded to energy saving 30 watt, 28 watt and 25 watt versions (each with a compatible electronic ballast). These lower wattage replacements save energy, but, if operated below 59 degrees F, striations may result. In most office environments, temperatures this low are not likely during working hours.

Even "full wattage" fluorescent lamps (eg. F32T8) can sometimes exhibit striations. Assuming sufficiently high operating temperatures and optimal ballast pairing, the exact cause may be difficult to identify.

Prevention is the best solution for minimizing flicker. According to lighting experts, all fluorescent fixtures placed in offices, classrooms, and spaces occupied for any length of time, should include the appropriate lamp/ballast system and follow the minimum recommended room temperatures during occupancy.

Special attention to these factors apply when using energy saving lamps.

One final note: even if the bulbs are upgraded from fluorescent to linear LED tubes, buzzing can still occur if the LEDs are ballast compatible. However, with ballast-bypass or external driver LED tubes, a failing, buzzing ballast no longer factors into the lighting system, so should no longer be a problem.

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