Electrical 101

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3 Lamp Instant Start Two Ballasts Diagram

Factory wiring

Light Fixtures with Two Ballasts

Fluorescent tube light fixtures with two ballasts are typically wired in the same manner. Individual wires of one ballast connect to the one side of the fixture, individual wires from the other ballast connect to the other side of the fixture. The common wires of each ballast are connected to the other side of the fixture from each of the individual wires.

As seen below on ballast 1, the individual wire is connected to the lampholder of lamp 2 on the left side, and the common wire on the right side.

On ballast 2, the individual wires are connected to the lampholders of lamps 1 and 3 on the right side, and the common wires to lamps 1 and 3 on the left.

How to Replace 3 Lamp Two Instant Start Ballasts with One Instant Start

A 3 lamp fixture with two instant start ballasts can be replaced with one 3 lamp instant start. The wiring of the new 3 lamp ballast is fairly simple because the wire colors match the old ballasts. As you can see below on the 3 lamp ballast, an individual wire is connected to the lampholder of lamp 2 on the left side, and the common wire on the right side.

The other two individual wires are connected to the lampholders of lamps 1 and 3 on the right side, and the common wires to lamps on the left.

Connect each of the individual blue wires from the new 3 lamp ballast to each of the lampholder individual blue wires of the three lamps.
Connect each of the common red wires from the new 3 lamp ballast to each of the lampholder common red wires of the three lamps.