While we know the ballast is an important part of light fixtures, what exactly does it do?

Just like the heart pumps blood throughout the body, a ballast sends energy through the lamp by providing the correct amount of voltage to start the lamps and regulates the amount of current that flows to them once they are on. Without a ballast, fluorescent lighting systems would uncontrollably increase their draw of electrical current at a rapid rate from the power source. This would cause the lamp to overheat and burn out within a couple of seconds. Ballasts are designed to operate with a specific number of lamps of a specific type at a specific voltage. This means, not all ballasts are compatible with all fluorescent lamps.

There are 2 types of ballasts: magnetic and electronic. Magnetic ballasts are an older technology that generally comes in either preheat start or rapid start methods. These ballasts tend to be less expensive than others but have the tendency to hum and flicker. The preheat and rapid start methods heat the lamp's cathodes before the ballast provides the voltage to start the lamp. Electronic ballasts operate quietly, eliminating the flicker that is common in magnetic ballasts, and are more energy efficient. This type of ballast can be instant start, programmed start, or rapid start methods.

Instant start ballasts are the quickest to turn on the lights. However, they are designed to stay on or off for longer cycles. Frequently switching them on and off can shorten the lamp life in the long run. They are called instant start because they start the lamp instantly by sending about 600 volts through the lamp to kick start the cathodes. Programmed start, or programmed rapid start, ballasts are slower to start, but don't have the damaging effects of an instant start ballast when used with more frequent on/off cycles. This type of ballast is typically a smart rapid start ballast. This type of ballast senses the temperature of the lamp cathodes and uses just enough power needed to ignite them. Since cold cathodes take more power to ignite, these ballasts are more energy efficient than other ballasts. They are designed for rooms with frequent on/off cycles like stairwells, hallways, or bathrooms fitted with occupancy/vacancy sensors.

Some LED replacements for fluorescent lights are compatible with the ballasts and some are not. Bulbs that are not ballast compatible require the LED replacement to be re-wired and retrofit into the existing lighting fixture.

Plug & Play are linear lamp LEDs (shaped like a fluorescent light tube) that snap into place as easily as replacing a regular light bulb. They cost more but don't require the ballast to be removed for the new LED to be wired into the power source.

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