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Fluorescent Ballasts

What is a Fluorescent Ballast?

A fluorescent light system requires a ballast to operate. The ballast regulates the current that travels to the fluorescent lamps and provides the necessary amount of voltage that the lamps require to start. A fluorescent lamp cannot be directly connected to a power source, because the high voltage would cause the lamp to immediately burn out. Instead, the ballast supplies high voltage briefly to create an arc between the lampís two electrodes. After the arc appears, it reduces the voltage to regulate the electrical current, producing a fixed, steady output of light.

Different Types of Ballasts

For the optimal rated light output and lamp life from a fluorescent light system, the characteristics of the ballast must match the requirements of the connected lamps. Ballasts are usually made to operate a certain number of lamps (typically 1 to 4), a type of lamp (for example, a 4-foot T8 bulb) and a start method at a particular line voltage. In the U.S., itís usually either 120 or 277 volts (though others are possible). Therefore, itís important to know the lamp type, lamp quantity, start method, and line voltage of your lighting fixtures.

Ballast Start Types

  • Instant Start Ballasts light up the lamp the second you flip the switch, making them an energy efficient choice. However, this may be somewhat more damaging to the bulb, so itís best for lights that are left on or off for longer spans of time.
  • Rapid Start Ballasts turn on lamps quickly, but not instantly. They use more watts and reduce the life of the bulb. Programmed Start Ballasts are replacing rapid start ballasts, as theyíre more efficient and better for lamp life. They take a little longer to start, but theyíre the best option for lights that are frequently turned on and off, such as for hallways, bathrooms, utility rooms, and rooms with sensors that detect occupancy.
  • Emergency Backup Ballasts are typically used in hospitals, schools, and offices where emergency lighting is required. These require an additional primary ballast for everyday use.
  • Low Temperature Ballasts are used in freezers and other locations that require stable, reliable performance in very cold temperatures.


Choosing the proper ballast for your fixtures will help control noise and flickering, in addition to ensuring the most energy efficient operation and longest lifespan out of your fluorescent light fixtures.