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Fluorescent tubes require a ballast to operate. A fluorescent tube circuit includes a ballast, wires, lampholders, and the tubes.
Electricians usually refer to a light bulb as a lamp. Light bulb manufacturers use the term “lamp” when referring to fluorescent lights. On this page, we will refer to a fluorescent light bulb as a lamp or tube.
Individual vs Common Ballast Wires
Individual ballast wires each connect to a lampholder on one side of each tube. The common wire(s) connect to the lampholders on the other side of the tubes.
Wire colors for individual and common connections on fluorescent ballasts will vary depending on ballast type, brand, and the number of lamps they support. Ballasts have certain colors for individual wires to lampholders, and other colors for common wires to holders.
Older magnetic fluorescent ballasts are usually wired in series. Newer electronic ballasts are usually wired in parallel, except for rapid start, programmed start, and dimmable ballasts.
Series vs Parallel Ballasts and Wiring
When a series ballast operates multiple lamps and one lamp fails, the circuit is opened and the other lamps will not light.
When a parallel ballast operates multiple lamps in a circuit, the lamps operate independently of each other. If one lamp fails, the others can keep operating as the circuit between them and the ballast remains unbroken.
With some 3 and 4-
1 Lamp Series Ballast
1 Lamp Parallel Ballast