T8 LED Tube Lights
Plug and Play vs Bypass Ballast T8 LED Tubes
LED retrofit T8 bulbs can be wired and installed two different ways. The first installation option is the ballast compatible plug and play LED tube lamp. Plug and play T8 bulbs are used as direct replacement without having to take out the existing fluorescent ballast. These lamps are double ended and connect both wires to the electronic ballast for power. Ballast compatible LED tubes may work with instant start, program start and dimming fluorescent ballasts. Manufacturers provide a ballast compatibility list as a guide for using plug and play LED tube lights.
The second option is through direct wire or bypass ballast installation. Direct wiring requires the fluorescent ballast to be removed and the LED lamp is wired directly to the 120-277V line voltage from the sockets. Bypass ballast T8 LED tubes can either be single ended or double ended. Single ended T8 lamps get power only from one end using a non-shunted socket and none from the other. Double ended T8 tubes are wired at both sides and the electricity flows through both sockets.
A special kind of installation is for hybrid LED tube bulbs. These bulbs are compatible with both direct wire and ballast compatible installations. Hybrid T8 lamps have the option of an easy installation by plugging into the electronic ballast, and once the ballast dies out the LED lamp can be wired directly to the line voltage with no ballast to maintain.
External Driver LED T8 Tubes
A recent trend in retroffitng fluorescent fixtures to LED is using the LED T8 lamps in conjunction with external LED drivers. The fluorescent electronic ballast is removed and replaced by the LED driver, and the LED tube is then wired double ended to the driver. The advantage of using an external driver is to provide a dimming compatibility since most LED drivers can work with LED dimmers. Having a programmable external driver also controls the output level of the lamp and allows it to be set at high output, normal output or low output.