T8 Lighting and Sockets

Anyone who has a fluorescent light should know how to replace the bulb and, occasionally, the socket. The light bulb slips in and out of two sockets, one on each end. When replacing a T8 socket for a tubular lamp, knowing which socket you need for is important. Using the incorrect socket will void the Underwriters Laboratories (UL) listing, shorten the lifespan of the light, damage the sockets or tubes, and even create a fire hazard.

T8 socket is used with linear fluorescent bulbs to attach the bulb to the ballast. They are commonly used in commercial installations. The “T” in T8 stands “tubular,” and the “8” is the diameter of the lamp in 1/8″ increments. A T8 lamp is a 1″ diameter lamp which requires a T8 size socket. T8 sockets are available as shunted and non-shunted sockets. Which type to used depends on the size of the lamp and the ballasts.

Shunted sockets join two points on a circuit with a conductor. There is a single track for the electrical current to travel from the ballast through the socket to the lamp pins. These sockets are designed to be only used with instant-start ballasts.

Non-shunted sockets are not joined and have two separate points of entry for the wires. This creates two tracks for the electrical current to travel. These sockets are designed to be used for programmed-start ballasts.

Sometimes it is not easy to determine the difference, so it is best to use a voltage meter to check if the electrical contacts are joined.

Before replacing the socket use proper safety. Ensure the power is cut off to the light at the circuit breaker. After shutting off the power, use a voltage meter to check that there is no power to the unit.

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